Employment 8. Topographical Anatomy and Operative Surgery of Forearm and Shoulder. Topographical Anatomy and Operative Surgery of Arm. Topographical Anatomy and Operative Surgery of Hand

 

SHOULDER

 

The shoulder is divided topographically into the axillary, the pectoral, the deltoid and

the scapular regions. The cutaneous nerve supply of this region is derived from the supraclavicular, the axillary, the medial antibrachial cutaneous, the medial brachial cutaneous and the intercostobrachial nerves.

AXILLARY AND PECTORAL REGIONS. AXILLA The axilla is an anatomic pyramid situated between the medial side of the upper arm and the upper lateral side of the chest wall. Since it is pyramidal in shape, it consists of 4 walls, an apex and a base. Walls. The four walls are the anterior, the posterior, the medial and the lateral. The anterior (pectoral) wall is composed of a superficial layer (pectoralis major muscle with its enveloping fascia) and an inner or deeper layer (pectoralis minor and subclavius muscles with their enveloping clavipectoral fascia). The posterior (scapular) wall is formed by the scapula, which is covered by the subscapularis, the latissimus

FIG. The cutaneous nerve supply of the shoulder: (A) anterior view; (B) posterior view.

 

FIG. The 4 walls of the axilla. The axilla is pyramidal in its shape; hence, it has an anterior (pectoral) wall, a posterior (scapular) wall, a medial (costal) wall and a lateral (humeral) wall. The various walls and views are depicted.

 

dorsi and the teres major muscles. The medial (costal) wall consists of the upper ribs (2nd to 6th) and the serratus anterior muscle; the lateral (humeral) wall is formed by the humerus (bicipital groove). This groove lodges the long head of the biceps tendon, and its lips give attachment to the muscles of the anterior and the posterior axillary walls. The long head of the biceps tendon is covered by the short head of the biceps and the coracobrachialis. Apex. The axillary apex is blunted and triangular and is bounded by 3 bones: anteriorly by the clavicle, posteriorly by the upper border of the scapula and medially by the first rib. Base. The base of the axilla is made up of skin, subcutaneous tissue and axillary fascia, the latter extending from the lower border of the pectoralis major muscle to the latissimus dorsi. Occasionally, a small strip of muscle extends from the latissimus dorsi to the structures deep to the pectoralis major; this forms the anomalous axillary arch.

PECTORAL REGION Fasciae. There are 2 fasciae in the pectoral

region, namely, the pectoral fascia proper and the clavipectoral fascia. The pectoral fascia proper is attached above to the anterior superior aspect of the clavicle; it passes down to ensheath the pectoralis major muscle and then blends with the axillary fascia in the floor of the axilla. Medially, it is attached to the sternum and is continuous below and medially with the serratus anterior and the external oblique muscles. Laterally, it blends with the fascia of the arm. The clavipectoral fascia lies deep to the

pectoral fascia proper. Vertically,

FIG. The axillary fascia.

 

FIG. The clavipectoral fascia. (A) Seen from in front after reflecting the pectoralis major muscle. (B) Sagittal section; the pectoral fascia is also shown.

 

 

FIG. The pectoralis minor muscle and its relations. The pectoralis major muscle has been reflected, and the clavipectoral fascia has been removed. The axillary vein lies medial to the axillary artery, and the brachial plexus appears to be wrapped around the artery.

 

it extends from the clavicle above to the dome of the axillary fascia below, thereby acting as a suspensory ligament for the axillary fascia. It is interrupted in its vertical path by the subclavius and the pectoralis minor muscles, both of which it separates and encloses. That portion of the clavipectoral fascia which lies between the subclavius and the pectoralis minor muscles is called the costocoracoid ligament (membrane); it is attached laterally to the coracoid process and medially to the 1st and the 2nd costal cartilages. The suspensory ligament is that part of the clavipectoral fascia which lies between the pectoralis minor and the axillary fascia. The costocoracoid ligament is pierced by the cephalic vein, which drains into the axillary vein; the thoraco-acromial artery, a branch of the axillary artery; the anterior thoracic nerves to the pectoral muscles; and lymph vessels from the upper outer quadrant of the breast. Muscles. The pectoralis minor muscle is the key structure to the axillary and the pectoral regions; its position and relations to the brachial plexus and the axillary vessels are important surgically. The pectoralis minor is a triangular muscle which has its origin from the 3rd, the 4th and the 5th ribs near their costochondral junctions, and its insertion on the medial border of the coracoid process of the scapula. The coracoid lies 1 inch below the clavicle, barely covered by the anterior border of the deltoid muscle. The pectoralis minor is covered by the pectoralis major, which lies on the same plane as the deltoid muscle. The deltopectoral groove is situated between

FIG. The axillary sheath. The prevertebral layer of deep cervical fascia gives off a fascial process which is continuous down the arm as the axillary sheath.

 

the deltoid and the pectoralis major muscles. The cephalic vein runs in this groove, crosses the anterior surface of the pectoralis minor muscle and pierces the costocoracoid membrane before emptying into the axillary vein. The cephalic vein is an important surgical guide to the axillary vein and the axillary artery, and it acts as a compensatory vein when the axillary can no longer function. Axillary Sheath. If the pectoralis minor muscle is severed and reflected downward with its clavipectoral fascia, the axillary vessels and the brachial plexus do riot immediately come into view because they are covered by a connective tissue layer known as the axillary sheath; this is a lateral prolongation of the prevertebral layer of fascia traveling down the arm as far as the elbow. The fascia passes over the scalenus muscles, the brachial plexus and the subclavian artery. On leaving the neck, on their way to the axilla, these vessels and nerves pierce this fascia and carry a tubular sheath of it along with them. VEINS The axillary vein is the first structure to appear following incision into the axillary sheath. It is formed by the junction of 3 veins of the superior extremity: the 2 vena comites of the brachial artery (the brachial veins) and the basilic vein, which pierces the deep fascia in the middle of the arm. The axillary vein begins at the lower border of the teres major muscle and continues to the outer border of the 1st rib, where it becomes the subclavian vein. The latter joins the internal jugular to form the innominate vein. Sometimes the union of the basilic and the brachial veins does not take place until the clavicle is reached; in such instances a single-trunk axillary vein may not exist or may be very short. When the arm is abducted, the vein covers the axillary artery and conceals it. This intimate relationship between the artery and the vein explains the not-too-infrequent appearance of arteriovenous aneurysms in this region. The tributaries of the axillary vein correspond to the branches of the axillary artery. ARTERIES The axillary artery is a continuation of the subclavian and is about 6 inches in length. It starts at the outer border of the 1st rib and ends at the lower border of the teres major muscle, where it becomes the brachial artery. The pectoralis minor muscle divides the axillary artery into 3 parts. The first part lies proximal to the pectoralis minor muscle under the costocoracoid membrane and has one branch, the highest or superior thoracic artery. The second part lies beTtindThepectoralis minor muscle, is the shortest part and has 2 branches, the thoraco-acromial and lateral thoracic arteries. The third part lies distal to the pectoralis minor muscle, is the longest part and has 3 branches: the subscapular, the anterior humeral circumflex and the posterior humeral circumflex arteries. It is well to remember that part one has one branch; part two has two branches and part three has three branches. The superior thoracic artery is the first branch of the axillary artery and the only branch of part one. It is usually small, runs medially and supplies the muscles of the first two intercostal spaces. The thoraco-acromial artery arises from the second part as a very short trunk but is of considerable size. Winding around the upper border of the pectoralis minor muscle, it pierces the costocoracoid membrane and divides into 4 branches: the pectoral, the acromial, the deltoid and the clavicular. The deltoid branch accompanies the cephalic vein in the deltopectoral groove. The lateral thoracic artery also arises from the second part of the axillary artery, but it follows the lower border of the pectoralis minor muscle to the chest wall. It does not accompany the long thoracic nerve, as is commonly thought. The latter is found with the terminal part of the subscapular artery. The subscapular artery is the largest branch of the axillary artery. It arises near the lower border of the subscapularis muscle, along which it descends accompanied by its venae comites. The subscapular artery supplies the posterior axillary wall (subscapularis, teres major and latissimus dorsi muscles). Although it is the vessel of the posterior wall, it terminates on the medial wall (serratus anterior muscle). Branches of this artery accompany the nerve supply to the subscapularis, the teres major and the latissimus dorsi muscles. The nerve to the latissimus dorsi muscle is the thoracodorsal; hence, that part of the subscapular artery which runs with it is called the thoracodorsal artery. The terminal branches of the subscapular artery send twigs to the serratus anterior muscle, and here the artery is accompanied by the nerve supply to that muscle (the long thoracic nerve). The subscapular artery also gives rise to the circumflex scapular artery, which passes through the triangular space on its way to the dorsum of the scapula. Anterior and posterior circumflex humeral arteries form an arterial ring around the surgical neck of the humerus. The anterior lies behind the biceps and the coracobrachialis muscles, and the posterior accompanies the axillary nerve through the quadrilateral space to reach the deep aspect of the deltoid muscle. The 3 branches of the third part of the axillary artery may arise from a common trunk.

BRACHIAL PLEXUS To visualize the brachial plexus as a whole, it must be followed from its origin in the neck, through the axilla and into the superior extremity. The following facts should be kept in mind to understand the brachial plexus: (1) It is made up of the anterior rami of the 5 th to the 8 th cervical nerves and the 1st thoracic nerve, with communications from the 4th cervical and the 2nd thoracic. (2) The plexus is arranged so that 5 rami (roots) = 3 trunks = 6 divisions = 3 cords = nerve supply (branches) to the upper extremity. (3) The roots and the trunks lie in the neck; the divisions are behind the clavicle, and the cords and the branches are in the axilla. (4) The roots and the trunks are in relation to the subclavian artery; the cords are in relation to the first and the second parts of the axillary artery. (5) The cords become branches at the lower border of the pectoralis minor muscle (third part of the axillary artery). The 5th and the 6th cervical roots join to form the upper trunk; the 7th cervical forms the middle trunk; and the 8th cervical and the 1st thoracic form the lower trunk. Each trunk divides into an anterior and a posterior division. The 3 posterior divisions join to form the posterior cord; the anterior divisions of the upper and the middle trunk unite to form the lateral cord; and the anterior division of the lower trunk continues alone as the medial cord. Branches arise from the roots, the trunks and the cords; no branches have their origin from the divisions. Branches. The branches arising from the roots are: dorsal scapular (to the rhomboids), C 5; long thoracic (to the serratus anterior), C 5, 6 and 7; muscular branches (to the 3 scalenii and longus coli muscles). The branches arising from the trunks are: suprascapular (to the supraspinatus and the infraspinatus), C 5 and 6; subclavius (to the subclavius), C 5 and 6. The branches arising from cords are as follows: from the lateral cord, the lateral anterior thoracic (to the pectoral muscles), C 5, 6 and 7; the musculocutaneous (to the biceps, the coracobrachialis and the greater part of the brachialis), C 5, 6 and 7; the lateral head of the median, C 5, 6 and 7. From the medial cord arise the medial anterior thoracic (to the pectoral muscles), C 8 and T 1; the medial head of the median, C 8 and T 1; the ulnar, C 8 and T 1; medial cutaneous nerve of the forearm, C 8 and T 1; medial cutaneous nerve of the arm, T 1.

FIG. The pectoralis minor muscle divides the axillary artery into 3 parts.

 

FIG. The brachial plexus. The "formula" for the plexus may be presented as follows: 5 rami (roots) = 3 trunks = 6 divisions = 3 cords = the nerve supply (branches) to the superior extremity

 

FIG. Diagram showing the construction of the brachial plexus.

 

FIG. Relations of the brachial plexus. The pectoralis minor muscle and the axillary vein have been removed; the lateral and the medial cords of the brachial plexus are retracted upward.

 

FIG. Three types of brachial plexus palsy.

 

From the posterior cord arise the radial, C 5, 6, 7 and 8 and T 1; axillary (to the deltoid and the teres minor), C 5 and 6; thoracodorsal (to the latissimus dorsi), C 6, 7 and 8; upper subscapular (to the subscapular), C 5 and 6; and lower subscapular (to the teres major), C 5 and 6.

Relation of Brachial Plexus to Axillary Artery. The brachial plexus arises in the neck and takes a downward course; the axillary artery travels upward from the chest. Therefore, the plexus lies lateral to the subclavian artery. The 3 cords of the plexus are placed around the second part of the axillary artery and in this way receive their names. Thus, the lateral cord lies lateral to the artery, the medial lies medial to the artery, and the posterior behind it. Since all the nerves lie lateral to the artery in the neck, it must follow that the medial cord crosses the artery to assume its medial position. This it does by running behind part one of the axillary artery. Most of the branches of the plexus are grouped around the third part of the artery. The musculocutaneous nerve lies lateral to the median nerve, and both of these lie lateral to the artery. In the groove between the axillary artery and vein 2 nerves are found: the medial cutaneous nerve of the forearm and the deeper lying ulnar nerve. Because of this arrangement these nerves usually are confused with each other. The medial cutaneous nerve of the arm passes along the medial border of the vein. The axillary and the radial nerves separate the axillary artery from the subscapular muscle, and the radial nerve alone separates the artery from the latissimus dorsi and the teres major muscles.

SURGICAL CONSIDERATIONS BRACHIAL PLEXUS PALSY Brachial plexus lesions are divided into those lesions which involve the entire plexus or only the upper, the middle or the lower portions. When the entire plexus is involved, either from injury or pressure, the following features are noted: complete anesthesia of the lower part of the arm, the forearm and the hand, and flaccid paralysis of the superior extremities, with eventual wasting of the muscles. Erb-Duchenne (upper arm) paralysis is the most common type of nerve injury occurring at birth; it involves the 5th and the 6th cervical nerves. It may occur during the course of a complicated delivery, with marked downward traction on the head, resulting in a widening of the angle between the head and the shoulder. The injury usually is located where the 5th and the 6th cervical nerves join to form the upper trunk of the plexus; this is known as Erb's point and is the spot where 6 nerves meet, namely, the 5th cervical root, the 6th cervical root, the anterior division of the upper trunk, the posterior division of the upper trunk, the suprascapular nerve and the nerve to the subclavius muscle. The hand hangs at the side in internal rotation with the forearm pronated and the fingers and the wrist flexed. This is referred to by some as the "headwaiter's tip hand." External rotation and abduction are lost at the shoulder, as are flexion and supination of the forearm. The clinical appearance is produced by a paralysis of the abductors and the lateral rotators of the shoulder (deltoid, supraspinatus and infraspinatus) plus a paralysis of the flexors of the elbow (biceps, brachialis and brachioradialis); a weakness of the adductors and the medial rotators of the shoulders (pectoralis major, teres major, latissimus dorsi, subscapularis) also results. The pronator teres, the supinator, the flexors of the wrist and the thenar muscles may be slightly involved. The middle arm type lesion (middle radicular syndrome) involves the 7th cervical nerve and produces a paralysis of the entire radial nerve except its branch to the brachioradialis; there is also a paralysis of the coracobrachialis. Klumpke (lower arm) paralysis is usually the result of upward traction on the shoulder. It also may result from injuries or during breech presentations when the arms are placed over the head. The lesion involves the 8th cervical and the 1st thoracic nerves. It results in a paralysis of the intrinsic muscles of the hand and a paralysis of the flexors of the digits. A "claw" hand results. There is also diminished sensation over the medial side of the arm, the forearm and the hand.

LlGATION OF THE AXILLARY ARTERY If the axillary artery is ligated above the origin of the thoraco-acromial, the collateral circulation is the same as that of the third part of the subclavian artery. When ligated at its lower limit, the following arteries are involved in the collateral supply: the subscapular, the transverse scapular, the transverse cervical, the internal mammary, the intercostal, the thoraco-acromial, the lateral thoracic and the anterior and the posterior humeral circumflex. The axillary artery may be ligated in its first part (above the pectoralis minor muscle) or in its third part (below the pectoralis minor muscle). Ligation of the first part can be accomplished by an incision extending just below the clavicle from the coracoid process to the sternoclavicular joint. The clavicular portion of the pectoralis major muscle is incised through its whole thickness, and the pectoralis minor is retracted downward. The costocoracoid membrane is divided along the upper border of the pectoralis minor, care being taken not to injure the axillary vein. The axillary artery is now exposed with the vein on its inner side and the cords of the brachial plexus

FIG. Ligation of the first part of the axillary artery.

 

outside and behind it. To accomplish the ligation it may be necessary to lower the arm, since the vein overlies and conceals the artery when the arm is abducted. The third part of the axillary artery is superficial and is easier to approach. The incision is an upward prolongation of an incision placed over the brachial artery. The coracobrachialis muscle is exposed and drawn outward with the musculocutaneous nerve. The basilic vein, which joins the brachial venae comites to form the axillary vein, is found on the inner side of the artery. The cords of the brachial plexus are disposed around all sides of the artery and must be identified and retracted out of the way.

DELTOID AND SCAPULAR REGIONS It is well to study the scapula in the discussion of the deltoid and the scapular regions, since this bone presents many bony surgical landmarks and gives attachment to the muscles in this region.

SCAPULA (SHOULDER BLADE) The scapula (shoulder blade) is a flat, triangular bone which lies on the posterolateral aspect of the thorax opposite the 2nd to the 7th ribs. It has 3 borders, 3 angles, 2 surfaces and 2 processes. Borders. The 3 borders are the superior, the medial and the lateral. The superior border is the shortest; it inclines laterally and downward from the superior angle, where the levator scapulae is inserted. The suprascapular notch is located at its lateral part and is converted by the suprascapular ligament into a foramen which transmits the nerve of the same name. Since this border gives attachment only to the small omohyoid muscle, it remains thin and sharp. The medial {vertebral) border is the longest and is quite thick; it gives insertion to the second layer of back muscles (rhomboid minor, rhomboid major and levator scapulae). The lateral {axillary) border is the thickest of the 3. It extends from the inferior angle upward, laterally and forward to the glenoid cavity; at its upper end is the triangular impression known as the infraglenoid tubercle for the attachment of the long head of the triceps. Angles. The 3 angles are the superior, the inferior and the lateral. The obtuse superior angle is situated between the superior and the medial borders. It is covered by the trapezius and, therefore, is difficult to feel. The acute inferior angle is located between the medial and the lateral borders and is an important anatomic and surgical landmark; fortunately, it is felt easily at the level of the 7th intercostal space when the extremity hangs at the side. The lateral angle, located between the superior and the lateral borders, forms the shallow glenoid cavity, which articulates with the head of the humerus and displays above its apex a slightly roughened area (the supraglenoid tubercle) for the origin of the long head of the biceps.

FIG. Muscle attachments to the scapula and the humerus (anterior view). Origins are represented in red, and insertions in blue.

 

FIG. Muscle attachments to the scapula and the humerus (posterior view). Origins are represented in red, and insertions in blue.

 

FIG. Cutaneous nerve supply of the deltoid region.

 

FIG. The deltoid muscle. (A) Origin and insertion of the muscle. (B) The supraspinatus muscle initiates abduction of the arm, and this is continued by the deltoid muscle. (C) With a torn supraspinatus muscle, abduction cannot be started by the deltoid unless at first the arm is pushed away from the body.

 

Surfaces. The 2 surfaces are the dorsal and the costal (ventral). The dorsal surface is unequally subdivided by the spine of the scapula into the smaller supraspinous and the larger infraspinous fossae. Transverse grooves for the circumflex scapular artery are noted over this surface. The costal surface is hollow and forms the floor of the subscapular fossa, which is deepest opposite the spine. This area is covered by the serratus anterior and the subscapularis muscles. Processes. The 2 processes are the coracoid and the acromion. The coracoid process projects from the lateral part of the superior border of the bone and sharply bends forward and laterally at a right angle. The lateral border of this process gives attachment to the coraco-acromial ligament, which helps the acromion form an arch above the head of the humerus. The tip of the coracoid gives origin to the coracobrachialis and the short head of the biceps muscles. Although this tip is covered by the anterior fibers of the deltoid, it can be felt on deep pressure through the lateral boundary of the infraclavicular fossa about 1 inch below the clavicle. Acromion Process. The spine of the scapular terminates laterally as the acromion process, which projects laterally at first and then bends sharply forward to form the acromial angle. The entire upper surface and borders of the acromion are palpable subcutaneously. Immediately in front of the shoulder joint it gives attachment to the lateral end of the coraco-acromial ligament. MUSCULAR ATTACHMENTS, VESSELS, NERVES AND BURSAE Deltoid Region. The skin over the deltoid region is thick. Fibrous septa extend from the skin into the fibrous investments of the deltoid muscle. This area is supplied above by the supraclavicular nerves and below by the cutaneous branches of the axillary nerve and the intercostal nerves. The deep fascia covering the deltoid invests the muscle and sends many septa between its fasciculi. In front it is continuous with the fascia covering the pectoralis major muscle, and it becomes thick posteriorly, where it is continuous with the fascia covering the infraspinatus muscle. It is continuous below with the deep fascia of the arm and is attached above to the clavicle, the acromion process and the spine of the scapula. The deltoid muscle is large, thick and triangular and covers the shoulder joint in front, behind and laterally. It has a wide V-shaped origin from the lateral third of the clavicle (anterior border), the acromion (tip and lateral border) and the crest of the spine of the scapula (lower border). The fibers converge and are inserted into a roughened area called the deltoid tuberosity, which is located about halfway down the lateral aspect of the humerus. It is the great abductor of the arm. Most authorities agree that the first 15° of abduction of the arm are effected by the supraspinatus muscle, but the deltoid continues and maintains it. The clavicular fibers aid in flexion and internal rotation, and the posterior fibers aid in extension and external rotation. The muscle is supplied by the axillary (circumflex) nerve from C 5 and 6. The subdeltoid (subacrominal) bursa is one large bursa with subacromial and subdeltoid subdivisions. The subacromial division lies between the deep surface of the acromion above and the tendon of the supraspinatus muscle below. The subdeltoid division lies between the deltoid muscle and the upper and lateral aspect of the humerus. These two subdivisions usually communicate but occasionally are separated by a thin partition. The bursa does not normally communicate with the shoulder joint

 

FIG. The subdeltoid bursa. (A) The bursa has 2 parts: a subacromial and a subdeltoid. (B) Surface projection of the subdeltoid part of the bursa.

 

FIG. The muscles of the scapular region. (A) The relations of the long head of the biceps and the long head of the triceps brachii muscles. (B) The supraspinatus, the infraspinatus and the teres minor muscle insert on the greater tuberosity.

 

but may do so when the bursal floor (supraspinatus tendon) is torn. The long head of the biceps muscle arises by a round tendon from the supraglenoid tubercle on the scapula and passes through the shoulder joint. Although it is intrascapular, it remains extrasynovial, since it receives a tubular sheath from the synovial membrane. The tendon and its acquired synovial sheath pass through the intertubercular sulcus (bicipital groove) and are held in this groove by a thickened part of the capsule, which is called the transverse humeral ligament and is attached to both tubercles. Should this ligament be torn, the tendon of the biceps becomes displaced to the medial side of the lesser tubercle. The tendon strengthens the upper part of the joint and keeps the head of the humerus against the glenoid cavity. The short head of the biceps and the coracobrachialis muscles arise together from the coracoid process of the scapula. The coracobrachialis is slender, descends along the medial margin of the biceps and is inserted into the medial part of the humerus. The short head of the biceps muscle is the medial and is discussed elsewhere. Scapular Region. Three muscles, the supraspinatus, the infraspinatus and the teres minor, are attached to the greater tuberosity. The shoulder joint is bounded above by the supraspinatus muscle, below by the long head of the triceps brachii, behind by the tendons of the infraspinatus and the teres minor, and in front by the tendon of the subscapularis. The supraspinatus muscle arises from the medial two thirds of the floor of the supraspinous fossa. The fibers pass laterally under the acromion and end in a short, stout tendon inserted into the top of the greater tuberosity of the humerus. The supraspinatus is covered by the trapezius, the coraco-acromial arch and the deltoid. Its tendon is closely adherent to the capsule of the shoulder joint. This muscle initiates the action of abduction, which is then continued by the deltoid. In cases of injury to the suprascapular nerve, the supraspinatus and the infraspinatus muscles are paralyzed; in such cases the patient cannot initiate abduction but can carry out this action if he starts it with the hand of the other arm or swings the arm away from the side of the body by a quick movement. The infraspinatus muscle arises from the whole of the floor of the infraspinous fossa and is inserted into the greater tuberosity a little behind the supraspinatus. Its tendon is closely adherent to the capsule of the shoulder joint, and its lateral part is covered by the deltoid. At times a small bursa is found between its tendon and the capsule of the shoulder joint; if present, it may communicate with the joint. This muscle is a lateral rotator of the arm. The teres minor muscle is small and lies along the lower border of the infraspinatus. It arises from an elongated flat impression on the dorsum of the scapula and is inserted into the back of the greater tuberosity of the humerus slightly behind the infraspinatus. As it approaches its insertion it is separated from the teres major by the long head of the triceps brachii. It is adherent to the capsule of the shoulder joint and acts as an abductor and a lateral rotator of the arm. The greater tuberosity of the humerus is reserved for the insertion of the three "SIT" muscles: the Supraspinatus on the anterior impression, the Infraspinatus on the middle impression and the Teres minor on the posterior impression. These muscles aid in lateral rotation of the arm. The subscapularis muscle is thick and wide and arises from the ventral

FIG. The subscapularis muscle.

 

surface of the scapula. It does not reach the vertebral border of the scapula because this is reserved for insertion of the serratus magnus muscle. Its fleshy fibers converge on a stout tendon which is closely adherent to the capsule of the shoulder joint and is inserted into the lesser tuberosity of the humerus; this tendon is seen when the joint is opened posteriorly. As the muscle proceeds to its insertion, it passes under an arch formed by the coracoid process and the conjoined origin of the short head of the biceps and the coracobrachialis muscles. The subscapularis is an adductor and internal rotator of the arm. If it is cut vertically, it will be noted that the muscle does not arise from the part of the subscapular fossa which is near the joint; the muscle only passes over this part and is separated from it by a loose tissue which contains the subscapularis bursa. At this site the bursal wall and the joint capsule are in contact. The bursa facilitates the movement of the subscapularis on the front of the head and the neck of the humerus. An opening between the bursa and the joint tends to weaken the capsule, and at this point the head of the humerus may burst through in dislocations. The tendons of the supraspinatus, the infraspinatus, the teres minor and the subscapularis converge and fuse with the capsule of the shoulder joint to form a common tendon, capsule "cuff". The subdeltoid (subacromial) bursa lies on this "cuff" and the greater tuberosity; it is covered by the deltoid muscle, the acromion process and the coraco-acromial ligament.

THE SHOULDER JOINT The shoulder joint is a ball-and-socket joint (enarthrodial). The ball is the head of the humerus, and the socket is the glenoid cavity of the scapula. In no other joint are the movements so free and varied. The ligaments do not maintain

FIG. Five ligaments surround the shoulder joint proper: (A) seen from in front; (B) lateral view with the humerus removed.

 

the joint surfaces in apposition; when only the ligaments remain, the humerus can be separated from the glenoid cavity for almost 1 inch. The joint is protected above by an arch formed by the coracoid process, the acromion and the coraco-acromial ligament; this prevents upward displacement of the joint. The ligaments of the shoulder joint proper are five in number: (1) the articular (capsular), (2) the coracohumeral, (3) the glenohumeral (superior, middle and inferior), (4) the transverse humeral and (5) the glenoidal labrum. The articular capsule (capsular ligament) completely encircles the shoulder joint and is attached above to the circumference of the glenoid cavity beyond the glenoid labrum; below, it is attached to the anatomic neck of the humerus. This capsule, or ligament, is so remarkably loose and lax that it has no action in keeping the bones in contact. It is strengthened above by the supraspinatus tendon, below by the long head of the triceps brachii, behind by the tendons of the infraspinatus and the teres minor, and in front by the tendon of the subscapularis. The weakest part of the capsule is its lower portion, this being partially due to the lax folds which are visible when the arm is adducted. Because of this weakness, dislocations of the head of the humerus take place through this inferior part of the capsule, downward and into the axilla. When such a dislocation occurs, the circumflex vessels and the nerves may be injured. There are usually 3 openings in the capsule: the first is anterior and below the coracoid process and establishes a communication between the joint and the bursa beneath the tendon of the subscapularis. When this aperture (subscapular bursa) is large, a dislocation may take place through it rather than the inferior aspect of the shoulder joint. The second aperture is not constant; if present, it is situated at the posterolateral part of the capsule and permits protrusion of the synovial membrane to form a bursa under cover of the infraspinatus muscle. The third aperture is in the groove between the tubercles of the humerus; this permits passage of the long tendon of the biceps brachii. The tendon is enclosed in a tubular prolongation of synovial membrane which surrounds it and lines the bicipital groove. The articular capsule cannot extend onto the lesser and the greater tuberosities because the subscapularis, the supraspinatus, the infraspinatus and the teres minor muscles insert here; however, it does extend inferiorly down to the surgical neck. The coracohumeral ligament is a broadband which strengthens the upper part of the articular capsule. It passes from the lateral border of the coracoid process to the front of the greater tubercle of the humerus, where it blends with the tendon of the supraspinatus. The ligament is connected intimately to the capsule by its hind and lower borders; its anterior and upper borders present a free edge which overlaps the capsule. The glenohumeral ligament consists of 3 parts. They constitute 3 bands which are thickenings of the anterior part of the capsular ligament and have been referred to as the superior, the middle, and the inferior glenohumeral ligaments. They may be thick enough to bulge into the joint and raise ridges on the synovial membrane. The transverse humeral ligament is a broad band which passes from the lesser to the greater tubercle of the humerus. It is limited to that portion of the bone which lies above the epiphyseal line and converts the intertubercular groove into an intertubercular canal in which the long head of the biceps brachii is located. The glenoid labrum is a dense fibrocartilaginous lip attached to the rim of the glenoid cavity; it aids in deepening the socket. It is somewhat triangular in shape and becomes continuous above with the tendon of the long head of the biceps brachii. The synovial membrane lines the capsular ligament and is prolonged onto the glenoid labrum and over the neck of the humerus to the articular margin. It supplies the long tendon of the biceps with a sheath which is prolonged into the bicipital groove. It becomes reflected upward and is continuous with the joint lining beneath the ligament to form bursae which have been described previously Relations Around the Shoulder Joint. Anteriorly, the subscapularis muscle and its bursa separate the axillary vessels and nerves from the joint. Above, the supraspinatus and the coraco-acromial ligament form an overhanging arch; the subacromial bursa is beneath this arch and the deltoid muscle. Posteriorly, there are the infraspinatus and the teres minor muscles. Inferiorly, there are the long head of the triceps, the posterior circumflex vessels and the circumflex nerve, which lie in the quadrilateral space, and that part of the subscapularis which arises alongside of the lateral margin of the scapula. The circumflex (axillary) nerve and the posterior circumflex vessels separate the teres major and the latissimus dorsi from the inferior portion of the subscapularis muscle. Passing through the joint and over the head of the humerus is the long tendon of the biceps, which is excluded from the joint cavity proper by its synovial sheath. The deltoid overlaps the joint anteriorly, posteriorly, laterally and above but does not come into contact with the capsule because it is separated by the coracoid process, the coracoacromial ligament, the subacromial bursa and the muscles which attach to the tuberosities. Scapular Anastomoses. Around large joints throughout the body there occur free arterial anastomoses; these are situated close to the bones which take part in the articulation. The shoulder joint is no exception to this rule. The anterior and the posterior circumflex humeral arteries form an anastomosing circle around the upper end of the humerus and a free anastomosis on both the costal and the dorsal surfaces of the scapula. The scapular anastomosis takes place in the following way: the suprascapular artery (transverse scapular) is distributed to both supraspinous and infraspinous fossae, and

FIG. Relations around the shoulder joint: (A) seen from the left side with the humerus removed; (B) the synovial sheath.

 

the deep branch of the transverse cervical artery passes downward along the medial border of the scapula. These two arteries are branches of the subclavian via the thyrocervical trunk. Both the subscapular artery, which passes downward along the lateral border of the scapula, and the circumflex scapular artery, which arises from the subscapular, are distributed to the infraspinous fossa; both are derived from the third part of the axillary. Since the suprascapular and the transverse cervical arteries are derived from the first part of the subclavian, and since the subscapular and the circumflex scapular are derived from the third part of the axillary, the scapular anastomosis connects these 2 widely separated vessels. On the thoracic wall the intercostal arteries anastomose with the transverse cervical, the highest thoracic, the lateral thoracic and the scapular arteries. Nerves and Movements. The nerve supply to the shoulder joint is derived from the suprascapular, the upper subscapular and the circumflex (axillary) nerves. Since the shoulder is a ball-and-socket joint, movements in every direction are permitted. Flexion (forward movement) is produced by the pectoralis major, the coracobrachialis, the anterior part of the deltoid and the biceps. Extension (backward movement) is produced by the latissimus dorsi, the teres major and minor, the posterior part of the deltoid, the infraspinatus and the long head of the triceps. Abduction is brought about by the deltoid and the supraspinatus; adduction by the subscapularis, the pectoralis major, the teres major and minor, the latissimus dorsi, the coracobrachialis and the long head of the triceps. The force of gravity aids this latter movement. Circumduction (a combination of movements) is accomplished by combining the 4 preceding movements. Medial rotation, which is much stronger than lateral rotation because of the number of muscles brought into play, is produced by the pectoralis major, the anterior part

FIG. The scapular anastomoses.

 

FIG. The anterior approach to the shoulder joint.

 

FIG. The posterior approach to the shoulder joint. (A) Incision. (B) Exposure.

 

of the deltoid, the subscapularis, the latissimus dorsi and the teres major. The lateral rotators are the infraspinatus, the teres minor and the posterior part of the deltoid.

SURGICAL CONSIDERATIONS

SURGICAL APPROACH TO THE SHOULDER JOINT Many approaches to the shoulder joint have been described, but the 3 used most frequently will be discussed here. The anterior approach is the method described by Oilier and is the most popular of the 3. It gives access to the subdeltoid bursa and the upper part of the humerus as well as the joint. The incision is made in the deltopectoral groove, beginning at the coracoid process and extending about 5 inches down the arm. The cephalic vein is exposed and retracted in a downward direction, and the deltoid muscle is retracted laterally. The joint capsule is hidden by the muscles which attach to the tuberosities: the subscapularis to the lesser tuberosity, and the "SIT" muscles (Supraspinatus, Infraspinatus and Teres minor) to the greater tuberosity. The capsule can be exposed by detaching the muscles from their respective tuberosities or by detaching the tuberosities themselves. Through this approach the vessels and the nerves are avoided. The posterior approach has been described by Kocher. Although it is more difficult than the anterior, some authorities state that it gives better exposure of the joint. The incision is curved and commences over the acromioclavicular joint; it extends backward along the inner border of the acromion, then over the junction of the acromion with the spine of the scapula and ends about 2 inches above the posterior axillary fold. A finger is inserted beneath the deltoid muscle, separating it from the deeper muscles. The deltoid is cut away from the spine of the scapula to the acromioclavicular joint, leaving about ¼ inch of muscle attached to the scapular spine. The cut deltoid is retracted laterally, and by gentle traction the circumflex vessels and the nerve can be exposed without injury. The infraspinatus, the teres minor, the teres major and the long and the lateral heads of the triceps are now visible, as is the upper posterior aspect of the humeral shaft. If further exposure of the posterior aspect of the shoulder capsule is desired, the supraspinatus, the infraspinatus and the teres minor are divided near their insertions and retracted medially. The superior approach is used rarely, being reserved for cases where bony union of the humerus with the scapula is desired. Through this method the action of the deltoid muscle usually is sacrificed.

FIG. Aspiration of the shoulder joint. A frontal section showing 2 routes of approach (anterior and lateral).

 

FIG. Dislocations of the shoulder. Primarily, a shoulder dislocation assumes a subglenoid position, but then it may pass anteriorly (subcoracoid or subclavicular) or posteriorly (subacromial or subspinous).

 

RUPTURE OF THE SUPRASPINATUS TENDON This usually takes place close to the greater tuberosity, and most authorities are of the opinion that it is the most common cause of traumatic subdeltoid bursitis. Codman has devised a saber-cut incision which affords the necessary exposure. It passes posteriorly from the acromioclavicular joint, over the top of the shoulder and continues through the superficial soft structures. The acromion and its attached deltoid are then retracted laterally, and the superior aspect of the shoulder joint comes to view. The tendons overlying the humeral head and the capsule can be inspected, and the extent of supraspinatus tendon injury determined. The arm is placed in abduction, and a groove is cut in the anatomic neck of the humerus in which the edge of the tendon will be placed. Drill holes are made through the lateral edge of this groove, and fascia lata or a similar type of suture laces the tendon in place. ASPIRATION OF THE SHOULDER JOINT It may become necessary to withdraw fluid from this joint for diagnostic or therapeutic purposes. There are 2 methods for aspirating this joint: anterior and lateral. The anterior method is accomplished by placing the needle just lateral to the tip of the coracoid process and passing it in a backward and outward direction. The lateral method is accomplished by placing the needle just lateral to the angle formed by the junction of the spine of the scapula with the acromion. The needle is then passed inward until the joint cavity is reached. Fluid in the shoulder joint can follow the long head of the biceps and present a swelling on the anterior surface of the arm, or it can communicate with the subacromial bursa; it may escape through the weak areas of the capsule. At times, effusions in this joint pass under the deltoid muscle and appear at either the anterior or the posterior border of the muscle.

DISLOCATIONS OF THE SHOULDER This is the most frequent of all dislocations because of the shallowness of the glenoid fossa and the disproportion between the head of the humerus and the glenoid cavity.

FIG. Fracture of the clavicle. (A) The usual displacement. (B) Reduction in the recumbent position.

 

The capsule is protected by muscles in front and in back, and above by the coracoacromial arch; below, the capsule remains unprotected. The latter is the weakest part, and here the head of the humerus leaves the joint. A primary subglenoid position results as the head tears through this weak point; the humeral head enters the axilla in front of the triceps. From this position it may pass either anterior or posterior and assume one of the following positions: Anterior. If anterior, a subcoracoid dislocation results, and the humeral head lies below the coracoid process and the pectoralis minor muscle; three fourths of all shoulder dislocations are of this type. In subclavicular (anterior) dislocations, the head lies under the clavicle and the pectoralis major muscle, a rare occurrence. Posterior. The posterior positions are: subacromial, where the head rests on the posterior angle of the acromion, the supraspinatus is stretched or torn, and the infraspinatus is relaxed; subspinous, in which the head travels from the subglenoid position in a posterior direction and comes to rest on the posterior aspect of the neck of the scapula, the subscapularis muscle usually being torn. Luxatio erecta is a rare form of dislocation in which the head of the humerus remains below the glenoid cavity, with the arm pointing in an upward direction along the side of the head. As the head continues to pass downward, it comes to lie on the serratus anterior muscle. Many methods and modifications for the treatment of dislocations of the shoulder have been described. One of the oldest and most widely used is Kocher's method. It is accomplished by 3 movements: the wrist is moved outward until the arm assumes a position of external rotation; external rotation and flexion at the elbow are maintained by moving the elbow forward and inward until the arm is nearly horizontal; the arm is rotated inward, and the hand is brought to the opposite shoulder. By external rotation, the first movement, tension is relieved on the posterior scapular muscles, and the rent in the capsule is widened; in the second movement, relaxation of the tense but untorn portion of the capsule is obtained, and the head of the humerus is permitted to enter the socket; in the third movement, the head of the humerus is brought into contact with the glenoid fossa. Recurrent (Habitual) Dislocation of the Shoulder Joint. Following a traumatic dislocation, a weak point is left; this might result in recurrent dislocation from trivial trauma. Other authorities are of the opinion that structural weaknesses besides those in the inferior aspect of the capsule are the cause, and that all shoulder dislocations, therefore, do not start originally as a subglenoid variety. NICOLA OPERATION An incision is made from the clavicle, above the coracoid, through the anterior border of the deltoid. The long head of the biceps is freed by dividing the transverse humeral ligament, below which the biceps is divided; the upper end is brought through a hole in the head of the humerus. This is united with the lower end. The capsule and other structures are repaired as the last stage of the operation. FRACTURED CLAVICLE The clavicle is fractured more frequently than any other bone in the body. The usual location of such a fracture is at the junction of the middle and outer thirds of the bone. The medial fragment is tilted upward by the contractions of the sternocleidomastoid and the trapezius muscles, and the lateral fragment is displaced downward by the contractions of the pectoralis, the teres major and the weight of the arm. Treatment of a fractured clavicle may be bothersome because direct splinting of the bone is difficult. All methods of closed reduction aim at pushing the shoulder backward until the 2 fragments are placed in apposition. The recumbent position aids such reduction because the muscles are relaxed, and the displacement due to the weight of the arm is relieved.

 

ARM (BRACHIAL REGION)

SURFACE ANATOMY The arm in the adult appears to be flattened from side to side because of grouping of the anterior and the posterior arm muscles. The fullness anteriorly is produced by the fleshy belly of the biceps brachii; this is lost under the deltoid muscle. Over the posterior aspect of the arm the fullness is produced by the triceps brachii muscle; this fades into a flattened distal appearance, produced by the triceps tendon. The medial bicipital sulcus (groove) commences in front of the posterior axillary fold and descends along the inner aspect of the arm to its lower third, where it bends obliquely forward to the center of the elbow. It separates the biceps and the coracobrachialis muscles in front from the triceps behind. The groove indicates the course of the brachial vessels, the median nerve and the basilic vein. The lateral bicipital sulcus (groove) does not stand out as well as the medial. It commences at the middle of the arm near the insertion of the deltoid muscle and ends at the bend of the elbow. In its lower part it separates the biceps muscle from the brachioradialis and the radial extensor muscles; the cephalic vein ascends in this sulcus. FASCIA The arm, or brachium, is completely invested by a deep fascia called the brachial aponeurosis. This is a sleeve of tough fascia which is continuous with that of the forearm. It is fixed at each side of the arm by the intermuscular septa, which are attached along the outer and the inner margins of the humerus. The lateral intermuscular septum extends from the lateral epicondyle to the deltoid tubercle; the medial extends from the medial epicondyle to the insertion of the coracobrachialis muscle (in the middle of the shaft of the humerus). This fascial arrangement divides the arm into anterior and posterior compartments, which also serve to limit inflammatory exudates and hemorrhagic effusions. However, it is possible for such fluids to pass from one compartment into another by following those structures which pierce the intermuscular septa. MUSCLES ANTERIOR COMPARTMENT In the anterior (flexor) compartment 3 muscles are found: the biceps, the coracobrachialis

and the brachialis. The biceps muscle (biceps brachii) arises by 2 tendinous heads: the long and the short. The long head is lateral and arises from the supraglenoid tubercle on the scapula. Its tendon passes through the cavity of the shoulder joint ensheathed by synovial membrane; it emerges from under the transverse ligament and occupies the bicipital groove. In the middle of the arm, the long head joins the belly of the short head, which arises from the tip of the coracoid process. This head shares its origin on the coracoid process with the coracobrachialis muscle. The tendon of the biceps is inserted into the posterior part of the radial tuberosity. The bicipital aponeurosis (lacertus fibrosis) has been discussed elsewhere. Since this 2-headed muscle crosses 2 joints, the shoulder and the elbow, it acts on both; at the shoulder joint its action holds the head of the humerus firmly in contact with the glenoid cavity, and at the elbow it is the strongest supinator of the forearm when the elbow is flexed. Since it is a flexor and a supinator, it may be stated that the biceps is the muscle that "puts a corkscrew in and pulls the cork out." The coracobrachialis muscle runs parallel

FIG. The arm. Multiple cross sections are shown, and to the side of these the surgical approaches to the neurovascular structures are indicated by arrows.

 

FIG. Surface anatomy and cutaneous nerve supply of the arm: (A) the anterior aspect; (B) the posterior aspect.

 

FIG. The deep fascia of the arm. The musculature has been removed. This fascia is known as the brachial aponeurosis; it divides the arm into the anterior (flexor) and the posterior (extensor) compartments.

 

with and medial to the short head of the biceps. As its name suggests, it originates from the coracoid process and inserts at about the middle of the medial side of the humerus. It aids in flexion and adduction of the arm. The brachialis muscle has its origin by means of 2 limbs which pass to either side of the deltoid tuberosity. The posterior limb passes up into the spiral groove; the anterior extends upward between the insertions of the deltoid and the coracobrachialis. The muscle crosses in front of the elbow joint and inserts into the anterior aspect of the coronoid process of the ulna. It is the most powerful flexor of the elbow joint. POSTERIOR COMPARTMENT The triceps muscle fills the posterior (extensor) compartment of the arm. As its name implies, it has 3 heads: lateral, medial and long. The lateral head arises from the posterior surface of the humerus, proximal to the radial groove, and from the lateral intermuscular septum. This head is covered at its upper and by the posterior fibers of the deltoid muscle, but the remainder is superficial. This head converts the spiral groove into a tunnel. The medial head arises from the posterior surface of the shaft of the humerus, distal to the radial groove, and from the median intermuscular septum. It is covered by the other 2 heads, except for its lower fibers which become superficial. The long head is tendinous and arises from a tubercle situated below the glenoid cavity (infraglenoid tubercle). This head is superficial throughout and passes between

FIG. The muscles of the flexor compartment of the arm: (A) seen from in front with the intact deltoid; (B) the deltoid has been removed; (C) the deep musculature.

 

the teres major and the teres minor muscles to form the triangular and the quadrangular spaces. The fibers of the triceps muscle are inserted by a common tendon into the proximal surface of the olecranon. It is separated from the posterior ligament of the elbow joint by a small bursa. This muscle is the powerful extensor of the forearm.

Quadrangular Space. This space does not actually exist, but its boundaries must be artificially separated before it can be visualized. As seen from behind, it is bounded by the teres minor muscle above, the teres major below, the long head of the triceps medially and the surgical neck of the humerus laterally. The boundaries of the space as seen from in front are the same with the exception of the teres minor, which is replaced by the subscapularis as the upper boundary. The circumflex (axillary) nerve and the posterior circumflex humeral vessels pass backward through the space immediately below the capsule. Triangular Space. This space is formed by the teres minor above and the teres major below; the long head of the triceps forms its base. Although of little importance, the space acts as a landmark for the circumflex scapular vessels which pass through it.

NERVES The circumflex (axillary) nerve supplies an articular twig to the capsule of the shoulder joint, muscular branches to the deltoid

FIG. The triceps muscle: (A) superficial view; (B) deep view.

 

to the skin over the lower half of the deltoid. It arises from the posterior cord of the brachial plexus and descends between the axillary artery and the subscapularis muscle. It winds around the lower border of the subscapularis muscle, passes backward with the posterior humeral circumflex vessels through the quadrangular space and divides into anterior and posterior branches. The articular twig originates from the trunk of the nerve in the quadrangular space and enters the joint from below. The posterior branch supplies the nerve to the teres minor, curves around the posterior border of the deltoid and supplies this muscle; it continues as the lateral cutaneous nerve of the arm. The anterior branch of the nerve continues around the humerus with the posterior circumflex artery and ends near

FIG. The quadrangular and the triangular spaces.

 

FIG. The radial nerve.

 

the anterior border of the deltoid, supplying this muscle. It also distributes a few fine twigs to the skin. The radial (musculospiral) nerve travels through the posterior compartment of the arm, the "tunnel," and the anterior compartment. The course of the nerve is more vertical than spiral, being spiral in only a small portion of its middle third; in its upper and lower thirds it is almost perpendicular. In the posterior compartment of the arm the nerve appears as a continuation of the posterior cord of the brachial plexus. It lies on the long head of the triceps and appears below the lower border of the teres major muscle with the profunda brachii artery which accompanies it. It then enters the fascial plane between the long and the lateral heads of the triceps. The so-called "tunnel" is the musculospiral groove; its roof is the lateral head of the triceps, and its floor is the humerus proper. The radial nerve in this part of its course is in contact with the humerus. In its almost vertical descent through the "tunnel," it separates the lateral from the medial head of the triceps and supplies both. The nerve gains access to the anterior compartment by piercing the lateral intermuscular septum at the junction of the lower and the middle thirds of the humerus. It then passes vertically between the supinator longus (brachioradialis) and the brachialis, where it descends vertically. In the region of the lateral epicondyle it divides into its 2 terminal branches: the posterior interosseous and the radial nerves.

SURGICAL CONSIDERATIONS OF THE RADIAL NERVE For exposure of the nerve in the posterior compartment, an incision is made 3 cm. below the acromion and is continued for 5 cm. past the middle of the humerus; this is in a line with the olecranon. The incision is carried through the deep fascia. At its upper end 3 muscular structures may be identified: the posterior border of the deltoid muscle, and the long and the lateral heads of the triceps. The deltoid muscle is retracted laterally, and the 2 heads of the triceps are separated in their fascial planes. It may be necessary to incise a small part of the deltoid for more adequate exposure. After separating the 2 heads of the triceps, a glistening aponeurosis (the teres major muscle) is exposed. Distal to this an incision is made in a loose areolar sheath which reveals the nerve and its accompanying vessels. For exposure of the nerve in its course through the "tunnel," an incision is made extending from a point 3 cm. above the level of the insertion of the deltoid directly downward for 12 cm. This incision is carried through the triceps, separating the fibers longitudinally until the aponeurosis on its deep surface is seen. This aponeurosis is incised, and the nerve is exposed beneath it. ARTERIES AND VEINS The posterior circumflex humeral artery arises from the axillary artery a short distance below the subscapular, passing backward through the quadrangular space with the circumflex nerve. Winding around the surgical neck of the humerus, it is distributed to the deep surface of the deltoid muscle. Some of its terminal branches are distributed to the surrounding muscles, the shoulder joint and the skin. The anterior circumflex humeral artery is smaller than the posterior circumflex humeral artery. It passes anteriorly around the surgical neck of the humerus and makes an arterial circle by joining the posterior humeral circumflex. The brachial artery is subject to striking variations as are other vessels in the body, particularly the arteries affecting the extremities. I must repeat that the description given herein is the most common and the most accepted pattern of the vessel under discussion. The brachial artery is considered to be a direct continuation of the axillary artery. It commences at the lower border of the teres major muscle and terminates about 1 inch below the transverse skin crease of the elbow, where it divides into 2 branches: a larger ulnar and a smaller radial. The pulsations of the artery can be felt along the medial bicipital groove throughout the length of the arm until the vessel disappears behind the lacertus fibrosus. The brachial artery lies successively on 3 muscles, gives 3 main branches, is in contact with 3 important nerves and is associated with 3 veins. The 3 muscles which constitute the floor upon which the brachial artery runs are (from above downward): the long head of the triceps, the coracobrachialis and the brachialis. To cross the muscles in the above order, the vessel must pass downward and laterally; this it does, its course corresponding to the inner border of the biceps muscle. The 3 main branches of the brachial artery are the profunda brachii, the superior ulnar collateral and the inferior ulnar collateral. The profunda brachii is a large vessel arising from the upper part of the brachial artery, sometimes as high as the teres major muscle. It passes downward, backward and outward between the long and the medial heads of the triceps muscle; it is the companion vessel of the radial nerve. An important ascending branch arises from the upper part of the vessel and anastomoses with the posterior humeral circumflex artery, thus connecting the axillary and the brachial vessels. Having traversed the musculospiral groove, the profunda brachii reaches the lateral intermuscular septum and divides into anterior and posterior branches. The anterior branch follows the radial nerve through the intermuscular septum, passes in front of the lateral epicondyles and anastomoses with the radial recurrent artery. The posterior branch continues downward behind the intermuscular septum, in back of the lateral epicondyle and anastomoses with the posterior interosseous recurrent artery. In this way a complete arterial circle is formed around the lateral epicondyle. The superior ulnar collateral artery has also been called the inferior profunda artery. It arises near the middle of the arm and is the companion vessel of the ulnar nerve. It pierces the medial intermuscular septum, enters the posterior compartment and passes behind the medial epicondyle. It anastomoses with the posterior ulnar recurrent artery. The inferior ulnar collateral artery has been called the anastomotica magna. It arises about 2 inches above the termination of the brachial artery and passes inward behind the median nerve. It passes in front of the medial epicondyle, anastomoses with the anterior ulnar recurrent artery and forms an arterial circle around the medial epicondyle. These 2 arterial circles of the epicondyles in turn are connected by a branch of the inferior ulnar collateral artery which passes transversely across the back of the humerus; hence its name "anastomotica magna." In this way the rich anastomoses are formed around the elbow joint. The 3 important nerves which are associated with the brachial artery are the radial, the ulnar and the median. The medial cutaneous nerve of the forearm lies to the medial side of the artery and, although not as important as the other 3, it still may cause annoying cutaneous manifestations if involved or injured. The radial nerve is associated with the artery only in its upper part immediately below the lower border of the teres major muscle. Here it lies behind the artery, separating it from the long head of the triceps muscle. The median nerve is related closely to the brachial artery throughout its entire course. In the upper arm it lies lateral to the vessel but, as it descends, it crosses in front of the artery in the region of the midarm. At times the nerve crosses behind the vessel. As it continues downward, it comes to lie on the medial side of the artery in the lower arm and elbow region. The ulnar nerve passes downward on the medial side of the brachial artery, lying between it and the basilic vein. In the middle of the arm the nerve pierces the medial intermuscular septum and leaves the vessel. It should be noted that the median and the ulnar nerves make a "nonstop trip" through the arm, giving off no branches. The 3 veins which are associated with the brachial artery are its 2 vena comites (brachial veins) and the basilic. The basilic vein ascends in the groove on the medial side of the biceps muscle superficial to the deep fascia and medial to the artery. Halfway up the arm the basilic vein pierces the deep fascia and becomes more intimately related to the brachial artery. At a variable point, it joins the 2 brachial veins to form the axillary. The brachial veins pass one on each side of the brachial artery and make many venous contacts around the artery as they ascend. Relationships Around the Brachial Artery. These relationships are best described in thirds. In the proximal third, the brachial artery lies medial to the humerus and can be compressed laterally against this bone. It is overlapped laterally by the coracobrachialis muscle, from which it is separated by the median nerve. Both the medial cutaneous nerve of the forearm and the ulnar nerve lie to its medial side and separate it from the basilic vein. Posterior to the artery is the radial nerve, which separates the vessel from the long head of the triceps muscle. The middle third of the artery may be compressed backward and laterally against the bone. The vessel is overlapped by the medial border of the biceps muscle and is crossed from lateral to medial by the median nerve. The ulnar nerve is medial, but about the middle of the arm it passes posteriorly to reach the posterior compartment of the arm. Posteriorly, the artery lies on the brachialis and the insertion of the coracobrachialis muscles. The

FIG. The brachial artery lies successively on 3 muscles, gives 3 main branches, is in contact with 3 important nerves and is associated with 3 veins.

 

FIG. Medial approach to the brachial artery.

 

basilic vein and the medial cutaneous nerve of the forearm are separated from the vessel by the deep fascia. In the distal third, the brachial artery lies in front of the humerus and can be compressed backward against it. The biceps tendon overlaps it. The median nerve is medial to it; the ulnar nerve has passed into the posterior compartment.

SURGICAL CONSIDERATIONS OF THE BRACHIAL ARTERY The bifurcation of the brachial artery is not constant and may take place at a high level in the arm. Such a bifurcation may be troublesome as well as embarrassing when attempting to ligate the vessel for hemorrhage distal to the bifurcation. Ligation. The usual indications for ligation of the brachial artery are wounds, secondary hemorrhage, and hemorrhage from the deep palmar arch. Ligation may be done either at the middle of the arm or at the bend of the elbow. Ligation at the middle of the arm is accomplished in the following way. The arm is placed in abduction, and the hand in supination. If the arm is allowed to lie on a flat surface, the triceps muscle may be pushed upward and be mistaken for the biceps. Dissection through this distorted area exposes the superior ulnar collateral artery and the ulnar nerve instead of the brachial artery and the median nerve. The incision is made in the line of the artery along the medial edge of the biceps muscle. The basilic vein and the medial cutaneous nerve of the forearm may be identified superficial to the deep fascia at this level. If seen, they are drawn to one side. The deep fascia is incised, and the inner fibers of the biceps muscle are identified and retracted upward. The artery is found lying on the triceps muscle, with the median nerve in front of it. The nerve is isolated and protected. The brachial artery with its 2 venae comites are exposed; the artery is isolated from its companion veins and ligated. The collateral circulation differs when the brachial artery is ligated above or below the profunda brachii. If ligated above the profunda brachii, the circumflex humeral vessels above anastomose with the profunda brachii below. If ligated below the profunda brachii, the profunda brachii above anastomoses with the vessels around the elbow joint below.

HUMERUS The humerus is a long cylindrical bone which articulates with the scapula above and with the radius and the ulna below.

FIG. The right humerus. (A) Seen from in front. The different shapes of the humerus are depicted in cross section taken at the various identified levels. (B) The posterior view.

 

The head of the humerus forms a third of a sphere. It is covered with cartilage which is thickest in its central part and thins toward the circumference. The head is directed medially, upward and a little backward. The anatomic neck is a constriction which surrounds the articular cartilage and gives attachment to the capsular ligament. Tuberosities. Projecting forward and laterally from the humeral head is a mass of bone which is divided into two unequal parts called the lesser and the greater tuberosities. The groove dividing this bony mass is the bicipital (intertubercular) sulcus; it lodges the long tendon of the biceps. To these two tuberosities attach the tendons of the muscles which hold the head of the humerus in its socket. The greater tuberosity is the more lateral of the two and has been called the "point of the shoulder." Although it is covered by the deltoid, it can be felt on deep pressure. It has depressions for insertion of the three "SIT" muscles (Supraspinatus, Infraspinatus and Teres minor. The tuberosity gradually fades and becomes continuous with the shaft of the humerus. The lesser tuberosity is located on the front of the shaft and immediately below the anatomic neck. It is also covered by the deltoid and can be felt on deep pressure, especially during rotation of the bone. It provides attachment for the subscapularis muscle. The surgical neck of the humerus is a fingerbreadth below the tuberosities. A region of surgical importance, it is a narrow zone encircled by the circumflex vessels and partially encircled by the circumflex (axillary) nerve. This neurovascular bundle hugs the bone and does not pierce the 4 muscles inserted into the greater and the lesser tuberosities or the 3 muscles (pectoralis major, teres major and latissimus dorsi) which insert into the medial and the lateral lips of the bicipital groove. These lips descend from the tuberosities and deepen the bicipital sulcus. Epiphyseal Line. The surgical and the anatomic necks meet medially in the region of the quadrangular space. Slightly above the level of the surgical neck is the epiphyseal line, which coincides with the lower margin of the humeral head on the medial side, but passes through the lowest part of the greater tuberosity on the lateral side. The deltoid tuberosity is a roughened inverted "delta" with its apex downward. It is located about halfway down the shaft of the bone over its lateral aspect. The shallow spiral (radial) groove lies immediately behind this tuberosity and contains the radial nerve and the profunda artery. The body or shaft of the humerus is almost cylindrical in its upper half and prismatic and flattened in its lower half. The humeral body has 3 borders: anterior, lateral and medial. The anterior border extends from the front of the greater tuberosity to the coronoid fossa, its proximal part forming the lateral lip of the bicipital groove and its middle part the anterior margin of the deltoid tuberosity. The lateral border extends from the back of the greater tuberosity to the lateral epicondyle. It is indistinct proximally where the lateral head of the triceps arises and it is interrupted in its midportion by the oblique groove for the radial nerve. Its distal part is the prominent lateral supracondylar ridge. The medial border extends from the lesser tuberosity to the medial epicondyle and forms the medial lip of the bicipital groove. It is roughened in the middle for the insertion of the coracobrachialis, and its distal part becomes the medial supracondylar ridge. The body of the humerus has three surfaces: anteromedial, anterolateral and posterior. The anteromedial surface is situated between the anterior and the medial margins; the bicipital groove forms its proximal part. The anterolateral surface is located between the anterior and the lateral margins, with the deltoid tuberosity slightly above its midportion. The posterior surface, situated between the medial and the lateral margins, is occupied by the origin of the medial head of the triceps. The spiral groove begins on the posterior surface, running obliquely downward between the origins of the medial and the lateral heads of the triceps and ending below the deltoid tuberosity. The radial nerve and

FIG. Capsular reflections, epiphyses and metaphyses of the upper and the lower ends of the humerus.

 

its accompanying profunda vessels lie in this groove. A nutrient foramen is situated near the middle of the medial border and another is found frequently in the spiral groove. The lower end of the humerus is divided into 2 areas: the capitellum, which receives the head of the radius, and the trochlea for the trochlear (semilunar) notch of the ulna. The capitellum is sphere-shaped, and the trochlea is spool-shaped. The radial fossa is located immediately above the capitellum and receives the head of the radius during full flexion. The coronoid fossa, situated immediately above the trochlea, receives the coronoid process of the ulna during flexion. The olecranon fossa, the largest of the three fossae, is also situated above the trochlea; posteriorly, it receives the olecranon during extension. The lateral epicondyle is placed immediately above and lateral to the capitellum; its posterior aspect is broad, smooth and easily felt subcutaneously. The medial condyle is large and is felt easily medial to and above the trochlea; its posterior aspect presents a groove in which the ulnar nerve can be felt and roiled about. The metaphysis represents the line of junction between the epiphysis and the diaphysis of a long bone; frequently it is the site of bone disease in the young. If part of the metaphysis is inside of the joint capsule, the disease is likely to involve the joint; conversely, joint disease may involve the shaft of the bone if the metaphysis is partly within the affected joint. Therefore, the relationship between epiphyseal lines and capsular reflections becomes clinically important. At the upper end of the humerus, the epiphyseal line passes around the bone at the level of the lowest part of the articular surface of the head. The capsule is attached to the anatomic neck above, but below it is attached to the shaft about 1 inch lower than the lowest part of the articular surface of the head. This arrangement places the metaphysis partly intracapsular. At the lower end of the bone, the epiphyseal line is represented by a horizontal line at the level of the lateral epicondyle, the medial epicondyle having a separate epiphysis. The capsule follows the coronoid and the radial fossae anteriorly, and the distal half of the olecranon fossa posteriorly. Medially and laterally, it attaches about ¼ inch from the articular margins. Therefore, the metaphysis is partly intracapsular. Attachments to the Humerus. The following are the attachments to the humerus: To the greater tuberosity – the "SIT" muscles (Supraspinatus, Infraspinatus and Teres minor). To the lesser tuberosity – the teres major and the subscapularis, both extending to the surgical neck. To the anatomic neck – above and about ½ inch from it below and medially, the capsular ligament of the shoulder; the coracohumeral ligament extends onto the anterior part of the greater tuberosity. To the bicipital groove – the transverse ligament, attached to both tuberosities, bridges across its proximal part; the pectoralis major to its lateral lip; the teres major to its medial lip; and the latissimus dorsi to the floor. To the lateral epicondyle—the common extensor tendon, the lateral ligament of the elbow, the supinator and the anconeus. To the medial epicondyle – the medial ligament, the common flexor tendon and the pronator teres. To the medial margin of the shaft – the coracobrachialis. To the lateral margin of the shaft – the lateral head of the triceps. To the medial supracondylar ridge – the medial intermuscular septum and the pronator teres. To the lateral supracondylar ridge – the lateral intermuscular septum, the brachio

FIG. Fracture of the surgical neck of the humerus. The arrows indicate the pull of the muscles which produces the deformity.

 

radialis and the extensor carpi radialis longus. To the deltoid tuberosity – the deltoid muscle. From the anteromedial and the anterolateral surfaces – the brachialis. From the posterior surface – the medial head of the triceps. To the radial and the coronoid fossae – the anterior ligament of the elbow; the posterior ligament attaches to the margins of the olecranon fossa on either side and to the back of the epicondyles.

SURGICAL CONSIDERATIONS FRACTURES Fractures of the humerus may occur at the upper end, at the shaft and at the lower end. Fracture of the anatomic neck is intracapsular, rare and occurs mainly in older people. At times the shaft may be driven into the head of the bone, producing marked impaction. It may become necessary to treat the condition surgically, so that function is improved; or it may be necessary to remove a loose fragment. Fractures of the surgical neck are extracapsular and usually result from direct violence; they occur mainly in young or

FIG. Separation of the upper humeral epiphysis.

 

middle-aged adults. The deformity, although it may vary depending upon the relationship of the site of fracture to the insertion of muscles, remains fairly constant. The upper end of the lower fragment is carried upward toward the axilla by the pull of the deltoid, the biceps, the coracobrachialis and the triceps muscles. It is drawn medially by the pectoralis major, the teres major and the latissimus dorsi. The upper fragment is abducted by the supraspinatus. In reducing the fracture, abduction of the arm should not be performed too forcefully or too rapidly because the pectoralis major acts as a fulcrum, and the upper end of the sharp lower fragment may injure the brachial plexus. Therefore, bringing the arm forward and making traction outward and forward will release the tension of the pectoralis major and allow the lower fragment to be brought into apposition. After complete reduction, the position should be maintained in abduction, usually by means of axial traction. Fracture of the greater tubercle can result from either direct violence or muscle pull from the attached supraspinatus, the infraspinatus and the teres minor. This type of fracture may accompany a fractured neck of the humerus or an anterior dislocation. The supraspinatus usually pulls the tuberosity upward and backward. The arm should be fixed in abduction and external rotation; if this fails, surgical correction becomes necessary.

FIG. Fractures of the shaft of the humerus: (A) above the insertion of the deltoid muscle; (B) below the insertion of the deltoid muscle.

 

FIG. Supracondylar fracture of the humerus. The close relations of the median nerve and the brachial artery to the sharp fractured fragments are shown.

 

Separation of the upper humeral epiphysis occurs up to the 20th year and usually is the result of the same type of injury as causes fractures of the surgical neck. Due to action of the supraspinatus, the infraspinatus and the teres minor, the upper fragment usually is abducted. Since the upper end of the diaphysis is conical, the epiphysis fits into this by a corresponding concavity. This results in a cup and cone arrangement which makes reduction difficult but immobilization easy. As the child grows older, the concavity of the epiphysis gradually becomes flattened so that this is altered. Reduction and immobilization in abduction are required. Fractures of the lesser tubercle are rare. The deformity is produced by the subscapularis, which pulls the fragments medially. Shaft fractures may occur in the upper third of the humerus above the deltoid attachment or, more commonly, in the middle of the shaft below the deltoid attachment; hence, the displacement and the deformity vary with the site of the fracture. If the fracture is situated above the insertion of the deltoid, the upper fragment is drawn medially by the muscles attached to the bicipital groove (pectoralis major, teres major and latissimus dorsi), and the lower fragment is drawn upward and laterally by the deltoid. If the fracture is below the insertion of the deltoid, the upper fragment is pulled laterally by the deltoid and the supraspinatus, and the lower fragment is displaced medially and upward. The relationship of the radial nerve to this fracture is important. At about the middle of the humerus and below the attachment of the deltoid muscle this nerve lies in direct contact with the bone, and a sharp bony fragment may injure it. The sensory branches of the radial nerve leave at a higher level than this site of injury; therefore, the nerve symptoms are entirely motor and will be manifested by a wrist drop. For proper reduction, normal relations between the external epicondyle and the greater tubercle should be maintained. Supracondylar (lower end) fractures occur frequently in children and at that point where the bone is thin (the anteroposterior diameter immediately above the condyle). The lower fragment is displaced upward and backward and may simulate a dislocation. However, the internal condyle, the olecranon and the external condyle remain in normal relations, which would not be true in posterior dislocation of the elbow. The median nerve and vessels in the cubital fossa may be injured, and the possibility of Volkmann's ischemic contracture must be kept in mind. The importance of incising the brachial fascia, following reduction and immobilization, has been stressed. Intercondylar fractures are supracondylar and extend into the joint between the condyles, forming a T- or Y-shaped fracture. They are difficult to reduce and maintain in position.

FIG. Exposure of the shaft of the humerus: (A) incision and position of the arm; (B) the relations of the exposed bone to the surrounding musculature.

 

FIG. Exposure of the neurovascular structures of the arm.

 

Fractures of the epicondyle may be caused by powerful abduction and extension of the elbow or by muscular action. Involvement of the ulnar nerve must be kept in mind when the medial epicondyle is fractured. The lateral epicondyle usually is fractured by a fall on the hand; this may involve the capitulum and the trochlear surface. Lower epiphyseal separation is usually seen in children between the ages of 5 to 10 years. The displacement is lateral and backward.

OPERATIONS ON THE SHAFT OF THE HUMERUS Exposure of the humeral shaft is difficult because this bone is not subcutaneous anywhere, and important vessels and nerves are closely related to it. The best approach is a lateral one. The lower two thirds of the shaft of the humerus is exposed through a skin incision which extends downward from the medial border of the deltoid, along the lateral border of the biceps almost to the lateral condyle of the humerus. The cephalic vein may be encountered. The deltoid is retracted laterally and the biceps medially, thus exposing the brachialis muscle. Flexion of the elbow will relax the brachialis tendon. The brachialis muscle is incised longitudinally to the bone, and the cut surfaces of the muscle are retracted laterally and medially. The radial nerve can be protected if it is retracted with the posterior part of the brachialis muscle. Thus the lower two thirds of the shaft of the humerus is exposed safely. The neurovascular structures in the arm are approached through a medial incision which is placed in the medial bicipital groove. The basilic vein is encountered and is retracted posteriorly. The medial border of the biceps muscle is elevated and retracted anterolaterally; thus the median and the ulnar nerves and the brachial artery, with its venae comites, are exposed.

 

ELBOW

ELBOW JOINT The elbow joint is the articulation of the humerus with the radius and the ulna; since it permits only flexion and extension, it belongs to the hinge or ginglymus variety. The trochlea and the capitellum of the humerus articulate respectively with the trochlear notch of the ulna and the head of the radius. The trochlea of the humerus is grasped by the trochlear (semilunar) notch of the ulna, and the capitellum of the humerus rests on the upper surface of the head of the radius. Some anatomists prefer to consider the elbow joint as the result of three separate joints having one synovial cavity: namely, the humero-ulnar, the humeroradial and the superior radio-ulnar joints. Here the elbow joint will be considered as having humeroulnar and humeroradial parts, and the superior radio-ulnar joint will be discussed as a separate joint communicating with the other two. Ligaments. The joint is surrounded by a capsular ligament, thickened and reinforced at the sides to form medial and lateral ligaments; the intervening portions are known as the anterior and the posterior ligaments of the elbow. The broad, thin anterior ligament is attached superiorly to the radial and the coronoid fossae and the epicondyles; inferiorly, it is attached to the anterior margin of the coronoid process and the annular ligament of the radius. The posterior ligament is placed medially and is thin and weak. Superiorly, it is attached to the floor and the medial and the lateral margins of the olecranon fossa and

FIG. Ligaments of the elbow joint: (A) the lateral aspect; (B) the medial aspect.

 

the epicondyles; inferiorly, it is attached to the anterior and the lateral margins of the olecranon. The medial ligament (ulnar collateral) consists of 3 bands which pass between the internal epicondyle, the coronoid process and the olecranon. The anterior band is strong and taut in extension. The posterior part is a weak (fan-shaped) portion which becomes taut in flexion; its oblique fibers, which also have been referred to as the ligament of Cooper, deepen the socket for the trochlea of the humerus. The ulnar nerve lies on the posterior and the middle parts of this ligament as it descends from the back of the medial epicondyle into the forearm. The lateral ligament (radial collateral) is fan-shaped and extends from the lateral epicondyle to the side of the annular ligament. It is a strong, short band, the superficial fibers of which may be continued onto the radius as the supinator. It is attached below to the annular ligament and not to the bone. The epiphyseal line of the humerus and the radius is almost entirely intracapsular; that of the ulna is extracapsular. The synovial membrane lines the deep surface of the capsular ligament but does not reach as high in the radial, the coronoid and the olecranon fossae as does the fibrous capsule. On the lateral side it is continuous with the synovial membrane of the superior radioulnar joint. The pads of fat which fill the coronoid, the radial and the olecranon fossae are intracapsular but extrasynovial. The anterior fat pad projects into the coronoid fossa during extension of the joint, and the posterior projects into the olecranon fossa during flexion. The synovial capsule bulges about ¼ inch below the lower margin of the annular ligament and surrounds the neck of the radius. The blood supply around the elbow joint is derived from anastomoses which constitute free communications between the brachial artery and the upper end of the radial and the ulnar arteries. This, like all other periarticular anastomoses, lies close to the bone. Branches of 9 arteries take part in its formation; they are: (1) the anterior branch of the profunda brachii; this anastomoses with (2) the radial recurrent on the front of the lateral epicondyle; (3) the posterior branch of the profunda brachii anastomoses with (4) the interosseous recurrent on the back of the lateral epicondyle. (5) The anterior branch of the supratrochlear anastomoses with (6) the anterior ulnar recurrent on the front of the medial epicondyle; (7) its posterior branch and (8) the ulnar collateral anastomose with (9) the posterior ulnar recurrent on the back of the medial epicondyle. The nerve supply of the joint is derived from the median, the ulnar, the radial, the musculocutaneous and the posterior interosseous nerves. Relations. Anteriorly, the brachialis muscle nearly covers the entire anterior ligament. It separates the joint proper from the brachial artery, its companion veins, the biceps tendon and the median nerve. Medial to the brachialis the anterior recurrent ulnar artery is found related to the anterior ligament. Under cover of the muscles is the radial nerve, with its posterior interosseous branch accompanied by the radial recurrent artery. Laterally, the common tendon of the extensors overlies the lateral ligament of the elbow, and the extensor carpi radialis brevis and the supinator arise from it. Medially, the common tendon of the flexors overlies the anterior band of the medial ligament of the elbow; the flexor sublimis arises from it. The flexor carpi ulnaris overlies the posterior band, and the ulnar nerve and the posterior ulnar recurrent artery lie directly on it. Posteriorly, the triceps and its bursa lie above the olecranon. The anconeus and the interosseous recurrent artery are at the lateral side of the olecranon. That part of the flexor carpi ulnaris which originates from the olecranon is found to its medial side. A fracture across the olecranon brings the bursa into direct communication with the joint. Movements at the elbow joint should not be confused with those that take place at thesuperior radio-ulnar joint. At the elbow joint there are two movements, namely, flexion and extension. The muscles which are chiefly concerned in flexing the forearm are the biceps, the brachialis, the brachioradialis and

FIG. Anastomoses around the elbow joint.

 

the pronator teres. Those which extend the forearm are the triceps and the anconeus; these are aided somewhat by the muscles arising from the lateral epicondyle. In extension, the forearm bones make an angle with the humerus. This is known as the "carrying angle" and is produced by the inner condyle of the humerus, which is set obliquely so that the axis of the elbow joint is transverse between the radius and the humerus but oblique between the ulna and the humerus. This angle disappears on full flexion, but in extension it is about 10 to 15°. The angle may be disturbed by fractures of the lower end of the humerus or by rupture of the collateral ligaments. If it is increased, the condition of cubitus valgus results; if. it is obliterated, the condition of cubitus varus ensues.

ELBOW REGION The cubital (antecubital) fossa is a triangular depression lying anterior to the elbow joint. The base of this triangle is formed by an imaginary line drawn between the humeral condyle; its converging borders are the pronator teres medially and the brachioradialis laterally. At the apex the brachioradialis overlaps the pronator teres; the floor is formed by the brachialis muscle, and the deep fascia forms its room. FASCIA, VESSELS AND NERVES The superficial veins of the cubital fossa lie in the superficial fascia. Although variable in their course and arrangement, a general plan usually can be adhered to. In this area 5 superficial veins are found: the cephalic, the basilic, the median cephalic, the median basilic and the median. The median basilic vein lies, as its name implies, medial to the basilic; the median cephalic lies medial to the cephalic, and the cephalic lies lateral to the basilic. The cephalic vein arises on the radial side of the hand, from the dorsal venous arch, passes upward and receives the median cephalic vein at the lateral epicondyle. It ascends over the lateral aspect of the biceps brachii and continues in the deltopectoral groove. It then pierces the costocoracoid membrane and terminates either in the axillary or the subclavian vein. The basilic vein arises on the ulnar side of the hand, from the dorsal venous arch, passes upward and receives the median basilic vein in front of the medial epicondyle. It ascends in the medial bicipital groove and pierces the deep fascia in the region of the middle of the arm. It continues as the axillary vein in conjunction with the two brachial veins. The median vein commences in the palmar venous plexus, ascends on the front of the forearm and divides at the apex of the cubital fossa into the median cephalic and the median basilic veins. This division takes place soon after the entrance of its chief tributary, the profunda vein, which drains the deeper structures of the forearm. The profunda vein drains into the median. It enters the median vein at the distal edge of the lacertus fibrosus and, in this location, may be compressed as a result of trauma or tight bandaging. Thus the vessel can become obliterated and the return venous flow from the deeper structures of the forearm

FIG. The relations around the elbow joint; (A) seen from behind; (B) cross-section.

 

FIG. The cubital fossa and its contents.

 

impaired. This, it is thought, is one of the contributing causes of Volkmann's contracture. For this reason, one of the treatments suggested for the condition is incision of the deep fascia to release pressure. Lacertus Fibrosus. The bicipital fascia, or, as it is more commonly called, the lacertus fibrosus, lies deep to the superficial veins of the elbow region. It is an excellent surgical landmark. The biceps brachii is inserted into the tuberosity of the radius by means of a flat tendon. However, some of the fibers of this muscle do not pass into the formation of this tendon but continue on as a flat tendinous expansion which passes medially and distally to fuse with and become lost in the fascia of the forearm. This flat tendinous expansion is called the lacertus fibrosus; it also has been referred to as the biciptal aponeurosis. It occupies the middle of the front of the elbow region and is about ¾ inch wide. The lacertus is the key structure of this region. The pulsations of the brachial artery can be felt immediately beneath its free medial margin. Full extension of the forearm facilitates the palpation of the artery by relaxing the bicipital fascia; the median nerve lies just medial to the brachial artery. The lateral antibrachial cutaneous nerve is the continuation of the musculocutaneous nerve; it pierces the lacertus fibrosus, runs under the median cephalic vein, becomes superficial and divides into anterior and posterior branches which supply the skin over the anterolateral and the posterolateral aspects of the forearm. The medial antibrachial cutaneous nerve, a branch of the medial cord of the brachial plexus, divides at the middle of the arm into a volar and an ulnar branch. The volar branch passes under the median basilic vein and supplies the skin of the ulnar half of the forearm as far as the wrist. Four structures are found on the lacertus fibrosus: the median cephalic vein, the median basilic vein, the lateral antibrachial cutaneous nerve and the medial antibrachial cutaneous nerve (or the branches of these nerves). When the lacertus fibrosus is cut and reflected, the underlying brachial artery and median nerve are exposed. The brachial artery and its venae comites are just medial to the biceps tendon, and the median nerve in turn is medial to the artery. The radial nerve can be found lateral to the biceps tendon in a compartment between the brachioradialis and the brachialis muscles. The groove between these muscles may be difficult to determine, owing to the absence of a well-marked septum. The usual

FIG. The cubital fossa and its contents after cutting the lacertus fibrosus.

 

error is to open the interval immediately between the brachialis and the biceps muscles, thereby exposing the musculocutaneous nerve instead of the radial. Therefore, it is advisable to hug the lateral border of the biceps tendon and seek the interval between the brachioradialis muscle and the biceps tendon. Lateral retraction of the brachioradialis will expose the radial nerve where it divides into superficial and deep branches. The brachial artery can be felt along the medial bicipital groove throughout the length of the arm until it disappears behind the lacertus fibrosus. It passes through the cubital fossa under the lacertus fibrosus and divides into a larger ulnar and a smaller radial artery. This division takes place at the level of the coronoid process of the ulna and the neck of the radius. These structures are located about 1 inch below the distal elbow crease. The ulnar and the median nerves give off no branches in the arm; they make a "nonstop" trip through it. The ulnar nerve lies medial to the brachial artery until it reaches the middle of the arm, where it pierces the medial intermuscular septum to reach the posterior compartment. The superior ulnar collateral artery accompanies it at this point. The nerve passes to the back of the medial epicondyle and then on into the forearm. The median nerve lies lateral to the brachial artery at its beginning but crosses it obliquely and then lies medial to it in the cubital fossa. This crossing usually takes place in front of the artery. POSTERIOR OR OLECRANON REGION The olecranon region includes the posterior soft parts of the elbow; the joint coverings are thin, and the articular extremities of the bones are felt easily. A knowledge of the surface landmarks in this region is essential. Both of the humeral epicondyles are subcutaneous and readily

FIG. The posterior or olecranon region: (A) bony and muscular landmarks; (B) the varying bony relationships in flexion and extension.

 

FIG. The posterior "U" approach to the elbow joint: (A) incision; (B) the resulting wide exposure of the joint following division of the olecranon.

 

palpable, but the medial epicondyle is the more prominent. A rather deep but narrow medial paraolecranon groove separates the medial epicondyle from the olecranon. The ulnar nerve can be felt passing through the posterior aspect of this groove. The lateral epicondyle is palpated most easily with the arm semiflexed, but when the arm is in full extension, this condyle is hidden in a small depression bounded by the anconeus muscle medially and the extensor carpi radialis muscle laterally. In the region of the paraolecranon groove the joint capsule and the synovia are nearest to the surface. When the forearm is extended, the intercondylar line is horizontal and passes through the proximal border of the olecranon. However, when the forearm is flexed, the olecranon becomes prominent and appears below the horizontal level of the intercondylar line. When the forearm is flexed to a right angle, the olecranon lies on the same plane as the posterior surface of the shaft of the humerus. In this last-mentioned position it forms the apex of an inverted triangle, the base of which is located at a line drawn between the epicondyles of the humerus. In full flexion of the forearm, the olecranon is carried downward and lies anterior to the articular end of the humerus. Distal to the lateral epicondyle and in a depression which marks the site of the humeroradial joint, the projecting head of the radius can be felt, especially on rotary movements produced through supination and pronation. With the forearm flexed, the head of the radius lies about 1 inch anterior to the lateral epicondyle, the interval separating them being occupied by the capitellum of the humerus. With the forearm in complete extension, a distinct depression appears immediately proximal to the head of the radius; this corresponds to the lateral and the posterior parts of the radiohumeral joint. An effusion in this joint obliterates this depression. The skin over the back of the elbow is thicker than that over the front; it moves with great freedom over the underlying parts. The olecranon bursa is situated between the dorsal surface of the olecranon process, the tendinous expansion of the triceps muscle and the skin. Enlargements or involvements of this bursa result in the condition known as "miner's elbow", which is associated with constant bruising as is produced when working in small and confined spaces. The tendon of the triceps brachii is situated proximal to the joint line where it inserts into the olecranon. The anconeus muscle is the only muscle which legitimately belongs to this posterior elbow region; throughout its extent it is palpable in the lateral olecranon groove. The flexor carpi ulnaris muscle arises from the medial epicondyle and the medial surface of the olecranon. The ulnar nerve reaches the elbow behind the medial intermuscular septum and can be palpated in the medial olecranon groove. It lies in contact with the periosteum under an expansion of the triceps tendon. The nerve leaves the para-olecranon region between the heads of origin of the flexor carpi ulnaris muscle. It may be drawn from its bed and brought around the medial epicondyle to a more protected position during surgery. The arteries of the back of the elbow are part of a network made up of the collateral branches of the brachial, the radial and the ulnar trunks which serve as a collateral anastomosis when the main brachial trunk is involved.

SURGICAL CONSIDERATIONS

SURGICAL APPROACH TO THE ELBOW JOINT There are many approaches to the elbow joint; each has its advantages and disadvantages. Some authorities believe that the lateral approach is the safest. The medial approach is hazardous. A posterolateral approach has also been used. Herein described is a posterior approach, using a U-shaped (MacAusland) incision. It begins at the external epicondyle of the humerus, extends downward and medially, crosses the ulna 2 inches distal to the dip of the olecranon and continues up to the medial epicondyle. The resulting flap is dissected upward, and the olecranon, with the attached triceps tendon, is exposed. The ulnar nerve is isolated and retracted medially, and the lateral expansions of the triceps tendon are divided transversely. The olecranon is divided with an osteotome and is retracted upward with its muscle attachment. The lateral and the medial muscles in this region are stripped subperiosteally and retracted. A wide exposure results. DISLOCATION OF THE ELBOW Dislocation of the elbow involves one or both bones of the forearm and may be backward, forward, lateral or medial. With these injuries, the ulnar and the radial collateral ligaments and the articular capsule usually are torn, and either condyle may be fractured. Posterior dislocation of both bones is the most common type; it usually results from a fall on the outstretched hand. The fibers of the brachialis muscle attaching to the coronoid process usually are torn. If the dislocation is complete, the head of the radius lies behind the lateral epicondyle, and the distal end of the humerus falls into the cubital fossa. As a result of this, the arm and the forearm are semiflexed and at an angle of about 120°. The olecranon projects

FIG. Posterior dislocation of both bones of the forearm.

 

posteriorly as a hump; the normal relations between the humeral condyle and the olecranon are changed, and the olecranon is found above and behind its normal line.Anterior dislocation of both bones is rare. It results from trauma to the olecranon when the elbow is flexed. The olecranon then lies anterior to the trochlea. Lateral and medial dislocations are also quite rare and occur from falls on the pronated and outstretched hand. ARTHROPLASTY OF THE ELBOW This operation forms an artificial joint and is indicated when an ankylosis is present in a poor position (complete extension). Two longitudinal posterior incisions are made, passing on each side of the olecranon. A single posterior incision also has been used. The 2 incisions are deepened down to the bony structure; the musculospiral nerve is located through the radial incision. The ulnar nerve is found behind the internal condyle of the humerus and is protected. The soft parts are retracted, and the ankylosed joint is exposed. The lower end of the humerus is removed in such a way that a convex rounded end results. The ulnar end is removed, but its end remains concave. It may or may not be necessary to include the radial head in the arthroplasty. Fascia and fat flaps are formed from the radial and the ulnar aspects of the arm and the forearm and are placed over the ends of the bones; these flaps are sutured to the capsule and the periosteum. If no capsule remains, or if it is destroyed, the flaps are sutured to the surrounding soft tissues. The wounds are closed,

 

FIG. Aspiration of the elbow joint.

 

and the elbow is immobilized at a right angle. Fascia lata transplants also have been used and sutured to the capsule. ASPIRATION OF THE ELBOW JOINT The part of the joint which is closest to the surface lies posteriorly between the head of the radius and the lateral condyle of the humerus. The joint should be flexed to a right angle and the forearm placed in a position of semipronation. The head of the radius is palpated, and the needle is inserted just proximal to it in a forward and anterior direction. If the joint is distended with fluid or pus, the capsule bulges to either side of the triceps and can be drained easily. FRACTURE OF THE OLECRANON PROCESS This injury results from direct or muscular violence and is characterized by a transverse type of fracture. The deformity is brought about by the triceps muscle, which pulls the olecranon upward. Flexion of the elbow further separates the fragments. The treatment of a fractured olecranon process may be nonoperative, with the arm in complete extension, or surgical, with the fragments held together by wire placed posterior to the long axis of the ulna.

 

FOREARM

 

The forearm is that part of the upper extremity which is between the elbow and the wrist. The anterior (volar) region contains those structures which are anterior to the plane of the radius and the ulna; these include the internal and the external muscle groups which arise from the medial and the lateral epicondyles, respectively. The posterior (dorsal) region contains the extensor muscle group, which composes the bulk of this region. When the forearm is in full supination, it appears as a cone which is flattened anteroposteriorly. Muscle masses which arise from the humeral epicondyles increase its transverse diameter near the elbow. Distally, the forearm loses its bulk because of the transition of the fleshy muscles into their respective tendons. The shafts of the radius and the ulna can be felt superficially in the distal part of the forearm. The cutaneous nerve supply to the forearm is derived from the lateral and the medial cutaneous nerves ventrally, and the lateral, the medial and the posterior nerves dorsally. The deep fascia of the forearm is a continuation of the deep fascia of the arm. It is strengthened around the olecranon by expansions from the triceps brachii and reinforced anteriorly by the lacertus fibrosus. At the wrist the deep fascia is continuous with the transverse and the dorsal carpal (annular) ligaments. From its deep surface arise intermuscular septa which extend to the radius and the ulna, and also form compartments for the various muscle groups which are to be described. ANTERIOR (VOLAR) REGION Muscles. The muscles of the volar aspect of the forearm occupy 3 planes or floors which, from above downward, are as follows: FIRST FLOOR (SUPERFICIAL). This consists of 4 muscles which have a common origin from the medial epicondyle of the humerus. They pass obliquely down the forearm, with the exception of the flexor carpi ulnaris, and are supplied by the median nerve. The pronator teres, although a powerful pronator of the forearm, is also a flexor. It is the most lateral and most obliquely placed muscle of the group. In addition to its origin from the medial epicondyle, it has a small deep head of origin from the coronoid process of the ulna. This deep head separates the median nerve from the ulnar artery; the nerve lies between the superficial and the deep heads, and the artery lies behind both heads. It inserts on the lateral surface of the middle of the radius. The flexor carpi radialis muscle becomes tendinous about the middle of the forearm; it is inserted into the bases of the 2nd and the 3rd metacarpals and produces flexion and radial deviation of the hand. The palmaris longus muscle becomes tendinous at about the middle of the forearm, but its tendon is longer and narrower than the tendon of the flexor carpi radialis. It passes anterior to the transverse carpal (anterior annular) ligament and inserts into the palmar fascia. Its contraction tenses the palmar fascia and flexes the hand. The flexor carpi ulnaris is placed most medially; the digitorum sublimis may be mistaken for it. It inserts onto the pisiform bone. Contraction of this muscle produces flexion and adduction (ulnar) of the hand. SECOND FLOOR. The second-floor muscle, the flexor digitorum sublimis, lies deep to the preceding muscle tendons and to their ulnar side. It has an extensive origin which is part humeral, part ulnar and part radial. The ulnar and the radial origins are bridged by a fibrous band through which the median

FIG. The right forearm. (A) Cross section study of the relations of the forearm. (B) The arrows indicate the proper surgical cleavage planes utilized in approaching the neurovascular structures.

 

FIG. The cutaneous nerve supply of the dorsal and the volar aspects of the forearm.

 

nerve and the ulnar artery pass to enter the space between the second-floor and the third-floor musculature. The individual tendons of this muscle start in the lower third of the forearm; they do not lie side by side but pass 2 above and 2 below. The 2 above travel to the 3rd and the 4th fingers, and the 2 below pass to the 2nd and the 5th fingers. The entire muscle is supplied by the median nerve. The splitting of these tendons and their insertions into the borders of the middle phalanges is discussed elsewhere. THIRD FLOOR. The third floor (deep) consists of 3 muscles: the flexor pollicis longus, the flexor digitorum profundus and the pronator quadratus. They form a covering for the radius and the ulna, and it is upon this that the nerves and the arteries of the front of the flexor region of the forearm travel. The flexor pollicis longus muscle arises from the anterior surface of the radius between the oblique line above and the pronator below. It inserts at the base of the terminal phalanx of the thumb. The flexor digitorum profundus muscle arises from the volar and the medial surfaces of the ulna between the pronator quadratus and the brachialis muscles. Unlike the sublimis, the tendons of the profundus lie alongside of the tendon of the flexor pollicis longus as they pass beneath the transverse carpal ligament to insert into the bases of the distal phalanges. The pronator quadratus lies at the distal end of the forearm but is behind the flexor tendons and sheaths, the median nerve and the radial vessels. It originates from the distal fourth of the anterior surface of the ulna, and inserts into the distal fourth of the anterior surface of the radius and a triangular area on the medial side of the radius in front of the interosseous membrane. It pronates the forearm. All of the muscles previously discussed are supplied by the median nerve with the exception of the flexor carpi ulnaris and the ulnar half of the flexor digitorum profundus (4th and 5th fingers); as the word "ulnaris" suggests, these muscles are supplied by the ulnar nerve. Nerves. The ulnar nerve enters the forearm by passing between the 2 heads of the flexor carpi ulnaris and continues downward on the flexor digitorum profundus. In the wrist it is overlapped by the tendon of the flexor carpi ulnaris. It supplies the ulnar half of the flexor digitorum profundus and the flexor carpi ulnaris. It descends vertically near the medial border of the flexor digitorum sublimis and can be exposed by splitting the septum between the sublimis and the flexor carpi ulnaris. The median nerve enters the forearm between the superficial and the deep heads of the pronator teres, passes through the sublimis arch and continues downward on the flexor digitorum profundus. It clings to the deep surface of the flexor digitorum sublimis and in the wrist is overlapped by the tendon of the palmaris longus. It supplies all the

FIG. The deep fascia of the right forearm. The section is taken at the middle of the forearm and shows the fascial spaces and compartments formed for the muscles, the vessels and the nerves.

 

FIG. The muscles of the volar aspect of the forearm. These muscles occupy 3 layers or floors, which can be divided into superficial, middle and deep groups.

 

forearm flexors except those already mentioned. That branch of the median nerve which supplies the deep flexors is called the anterior interosseous nerve. As the nerve descends, it clings to the undersurface of the flexor digitorum sublimis and appears at its lateral border. The radial nerve divides in the region of the lateral epicondyle into superficial and deep branches. The superficial (sensory) branch descends beneath the brachioradialis muscle; it approaches the radial artery in the middle of the forearm and then leaves it to pierce the deep fascia and supply the skin of the dorsum of the hand and the wrist. The deep (dorsal interosseous) branch is mainly motor and reaches the back of the forearm by winding around the neck of the radius through the supinator muscle, which makes a tunnel for it. At the lateral side of the shaft of the radius, the nerve passes between the superficial and the deep muscles of the back of the forearm and innervates them. Arteries. In the upper forearm, the ulnar artery is separated from the median nerve by the deep (ulnar) head of the pronator teres; in the mid-forearm, it descends obliquely behind the flexor digitorum sublimis and on the flexor digitorum profundus. At the wrist it is closely related to the ulnar nerve, which lies medial to it. Both the artery and the nerve are overlapped by the flexor carpi ulnaris. Its

 

FIG. The blood vessels and the nerves as related to the deep flexors of the right forearm.

 

 

FIG. The blood vessels and the nerves of the right forearm as related to the flexor digitorum sublimis.

 

branches are the anterior and the posterior ulnar recurrent arteries and, more distally, the common interosseous, which immediately divides into volar (anterior) and dorsal (posterior) branches. The radial artery is unique in that no muscle crosses it; therefore, it lies quite superficial and can be ligated almost anywhere in the forearm. However, it is true that in the upper forearm it is overlapped by the brachioradialis but, as it continues distally, it lies on the supinator, the pronator teres, the flexor digitorum sublimis, the flexor pollicis longus and the pronator quadratus in the order named. No motor nerve crosses it.

SURGICAL CONSIDERATIONS EXPOSURE OF THE RADIAL NERVE This nerve is injured easily because of its close relation to the humerus. A posterior approach usually is utilized. The incision begins about the middle of the posterior border of the deltoid muscle and extends almost to the olecranon. The deep fascia is incised, and the space between the long and the lateral heads of the triceps is identified. These are separated, and through this space the nerve with its accompanying profunda artery emerges from the axilla; it passes in the musculospiral (radial) groove. The lateral head of the triceps can be severed, and the nerve can be followed in its groove to the lateral region of the arm. LlGATION OF THE ULNAR ARTERY Ligation of the ulnar artery per se is rarely done. It may be ligated at any site along its course, but usually this is done in its lower two thirds. The course of the artery in its lower two thirds can be visualized along a line which corresponds to the lower two thirds of a line drawn from the medial epicondyle to the pisiform bone. The skin incision is placed along this imaginary line. The superficial veins are ligated, and the deep fascia is incised. The artery will be found under the flexor carpi ulnaris tendon, which can be drawn medially. The vessel is surrounded by its venae comites; the ulnar nerve is medial. This neurovascular bundle is covered by a layer of fascia which not only binds it down to the surface of the flexor digitorum profundus but also binds the structures to each other. Therefore, it is dangerous to place a hemostat without first identifying and dissecting the nerve. In the upper half of the forearm, the vessel lies more deeply, being placed beneath the muscle mass which consists of the flexor carpi ulnaris and the flexor digitorum sublimis. The intermuscular cleavage plane existing between these muscles should be opened. The vessel will be found here and can be followed proximally. LIGATION OF THE RADIAL ARTERY Ligation of the radial artery may be done anywhere along its course, which corresponds to a line drawn from the middle of the elbow fold (cubital fossa) to the inner side of the front of the styloid process of the radius. The lower two thirds of the radial artery may be exposed through a skin incision which is placed in the line of the artery and is of sufficient length for adequate exposure. The superficial veins are ligated, and the deep fascia is divided along the edge of the brachioradialis muscle. In the upper part of the forearm, the muscle is retracted laterally so that the artery is exposed with its venae comites as they pass over the pronator teres. The radial nerve approaches the vessels and lies close to them for a short distance in the middle of the forearm, but proximal to this there is a slight interval which separates them. The nerve should be guarded. In the lower part of the forearm the vessels are exposed immediately under the deep fascia.

POSTERIOR REGION The subcutaneous border of the ulna, which can be palpated from the olecranon to the wrist, separates the extensor muscles of the forearm from the flexors. Such a palpable bony ridge may be utilized as an excellent surgical landmark and guide. MUSCLES, NERVES AND VESSELS The muscles of the back of the forearm are divided into superficial and deep groups. The superficial group has 6 muscles, and the deep group has 5. The 2 muscles which belong to the superficial group which do not originate from the lateral epicondyle are the brachioradialis and the extensor carpi radialis longus; those which do originate from the lateral epicondyle are the extensor carpi radialis brevis, the extensor digitorum communis, the extensor digiti quinti proprius and the extensor carpi ulnaris. These latter 4 superficial muscles have a common origin by means of a tendon which is attached to the lateral epicondyle. The deep group of muscles consists of the supinator, the abductor pollicis longus, the extensor pollicis brevis, the extensor pollicis longus and the extensor indicis. The brachioradialis muscle (radial nerve) lies more toward the front of the forearm than on the back. It originates from the upper two thirds of the lateral supracondyo:

FIG. The muscles of the back of the right forearm. (A) The superficial group consists of 6 muscles. (B) The deep group consists of 5 muscles.

 

lar ridge, and about halfway down the forearm is converted into a flat tendon which inserts into the lateral surface of the distal end of the radius. Its fleshy part overlaps the brachialis and descends in front of the lateral epicondyle. It forms the lateral boundary of the cubital fossa. The principal action of the brachioradialis is to flex the forearm; it helps to initiate supination when the forearm is prone and helps to initiate pronation when the forearm is supine. The extensor carpi radialis longus muscle (radial nerve) is closely associated with the brachioradialis. It arises from the distal third of the lateral supracondylar ridge and, as it descends, it passes over the lateral epicondyle deep to the brachioradialis. At first it is lateral to the radius but it gains the dorsal surface about halfway down the forearm. It has a long tendon which is continued downward toward the wrist, where it passes under cover of the extensor retinaculum and inserts into the base of the 2nd metacarpal bone. It aids in extension and abduction of the hand at the wrist and is a slight flexor of the forearm. The extensor carpi radialis brevis muscle (posterior interosseous nerve) arises from the common extensor origin on the lateral epicondyle and passes downward; at first it is overlapped by the extensor carpi radialis longus but more distally is medial to it. Its tendon begins at the middle of the forearm and passes under cover of the extensor retinaculum through a compartment which it shares with the longus. It is inserted into the base of the 3rd metacarpal bone. Both radial extensors act as their names indicate: extension and abduction of the wrist. The extensor digitorum communis muscle (posterior interosseous nerve) arises from the common extensor origin at the lateral epicondyle; it passes downward medial to the extensor carpi radialis brevis. In the distal part of the forearm, its fleshy belly ends in a tendon which passes under cover of the extensor retinaculum and then divides into 4 tendons for the fingers. Over the dorsum of the hand the individual tendons diverge and proceed onward to the fingers, where they are inserted into the middle and the distal phalanges. These tendons are connected to each other by oblique bands. As a result of this, complete extension of an individual finger at the metacarpophalangeal joint is impossible so long as the other fingers are kept flexed. The manner of insertion of these tendons is discussed elsewhere. The extensor digiti minimi (quinti proprius) muscle (posterior interosseous nerve) is a slender muscle which arises in common with the extensor digitorum and at first seems to be part of it. It lies along the medial side of the extensor digitorum, but its tendon passes through a special compartment in the extensor retinaculum. The tendon splits into two parts, the lateral being joined by the tendon of the little finger from the extensor digitorum. It forms the dorsal extensor expansion for the little finger and is an extensor of all the joints of the little finger. The extensor carpi ulnaris muscle (posterior interosseous nerve) arises by means of the common extensor origin from the lateral epicondyle and remains fleshy until it reaches the wrist joint, where it becomes tendinous. It occupies the groove on the back of the distal end of the ulna, passes through the most medial compartment of the extensor retinaculum and inserts into the base of the 5th metacarpal. It is an extensor of the wrist and aids the flexor carpi ulnaris in adducting the hand. The anconeus muscle (radial nerve) does not really belong to the superficial group of extensor muscles, but it is convenient to consider it with this group. It originates from the posterior aspect of the lateral epicondyle and is narrow and tendinous; its fibers soon diverge and become inserted into the lateral aspect of the olecranon and the adjoining part of the posterior surface of the ulna. It covers the posterior aspect of the annular ligament of the radius, thus helping to separate the head of the bone from the surface. Its action assists the triceps in extension of the forearm. If the extensor digitorum communis and the extensor digiti minimi are divided transversely about their middle, the following structures are exposed: the posterior interosseous vessels, the posterior interosseous nerve and the deep muscles of the back of the forearm.

FIG. The dorsal aspect of the right forearm. (A) The extensor digitorum communis muscle has been retracted to expose the posterior interosseous nerve and artery. The anatomic "snuff box" is shown. (B) A cross section of the extensor retinaculum and the 6 compartments which it forms.

 

At a variable point in the region of the lateral epicondyle, the radial nerve divides into two branches: sensory (superficial) and motor nerves. Posterior Interosseous Nerve. The motor nerve is the posterior interosseous (deep radial) nerve. The level at which branches of nerves originate may be variable, but the side from which nerves originate is quite constant. A motor nerve leaves from that side of the nerve which is nearest the muscle to which it is distributed; hence, we may speak of "sides of safety" and "sides of danger." Since the radial nerve supplies the extensor muscles, its branches arise laterally, and, therefore, it is safe to dissect on the medial side of this nerve. The reverse is true of the median nerve. The posterior interosseous nerve winds around the radius in the substance of the supinator muscle, which creates a muscular tunnel for the nerve. The nerve emerges from the posterior surface of the supinator a little above its lower border and in this way gains access to the fascial plane between the superficial and the deep groups of extensor muscles of the forearm. In its course the nerve is accompanied by the posterior interosseous vessels; they pass across the dorsal surface of the abductor pollicis longus muscle and under cover of the extensor digitorum. At about the middle of the forearm the nerve reaches the extensor pollicis longus and at this point leaves the posterior interosseous vessels and descends over the back of the interosseous membrane. It is accompanied by the anterior interosseous vessels and passes under the extensor pollicis longus and the extensor indicis. The posterior interosseous nerve supplies all the muscles in this region with the exception of the brachioradialis, the extensor carpi radialis longus and the anconeus. The latter are innervated by the radial nerve itself. The nerve terminates on the back of the wrist joint in a slight elevation which sends branches to this joint and to the intercarpal joints. The posterior interosseous artery arises from the common interosseous artery near the upper border of the interosseous membrane. It passes backward between the radius and the ulna above the upper border of the membrane and appears on the back of the forearm between the supinator and the abductor pollicis longus. It travels in the fascial plane between the superficial and the deep group of extensor muscles with the posterior interosseous nerve and reaches the back of the wrist; its lower part is so slender that it seldom can be traced below the middle of the forearm. It ends by taking part in the anastomosis about the wrist joint. A recurrent branch (the interosseous recurrent artery) passes upward to take part in an anastomosis about the elbow joint. The supinator muscle (posterior interosseous nerve) should not be confused with the supinator longus muscle. The term "supinator muscle" means the supinator brevis; the term "supinator longus" has been used for the brachioradialis. The supinator (brevis) arises from the lateral epicondyle of the humerus and the supinator fossa of the ulna. Its fibers pass backward and laterally around the posterior and the lateral aspects of the upper part of the radius and are inserted into the anterior, the lateral and the posterior aspects of that bone. This muscle inserts as far down as the insertion of the pronator teres. The more the radius is pronated, the tighter and more twisted becomes the supinator. Its action is to untwist itself, and this it does by supination. The abductor pollicis longus muscle (posterior interosseous nerve) arises from the posterior surfaces of both bones of the forearm and from the interosseous membrane. This origin approximately covers the second quarter of the ulna and the middle third of the radius. At the junction of the middle and the lower thirds of the forearm, its tendon emerges between the extensor digitorum and the extensor carpi radialis brevis. Having come to the surface, it crosses the 2 radial extensors (extensor carpi radialis brevis and radialis longus) and is accompanied closely by the extensor pollicis brevis. It passes under the extensor retinaculum and is inserted into the radial side of the base of the metacarpal bone of the thumb. As its name suggests, it is an abductor of the thumb and also slightly assists in abduction of the hand. The extensor pollicis brevis muscle (posterior interosseous nerve) is placed along the distal border of the preceding muscle. It arises from a small area on the posterior surface of the radius and from the interosseous membrane. Its tendon is associated closely with that of the abductor pollicis longus and accompanies it under the extensor retinaculum. It is inserted by a delicate tendon to the dorsum of the base of the proximal phalanx of the thumb. It extends the proximal phalanx of the thumb; in a small number of cases it is absent. The extensor pollicis longus muscle (posterior interosseous nerve) arises from the ulna and the interosseous membrane, below the origin of the abductor pollicis longus, and takes an oblique course across the carpus. It is inserted into the base of the distal phalanx of the thumb. It is an extensor of all the joints of the thumb and plays a part in initiating supination of the forearm. The extensor indicis (proprius) muscle (posterior interosseous nerve) is a special extensor for the index finger, arising from the ulna and the interosseous membrane immediately below the preceding muscles. It passes downward and laterally to the extensor retinaculum, under which it travels in company with the tendons of the extensor digitorum. It terminates by joining the dorsal expansion of the index tendon of that muscle and it lies on the medial side of the most lateral tendon of the common extensor. Its action is to extend all the joints of the index finger.

EXTENSOR RETINACULUM LIGAMENT The extensor retinaculum (dorsal carpal or posterior annular) ligament is a specialized part of the deep fascia of the forearm which passes obliquely across the back of the limb. It is about 1 inch wide, has 4 borders and 2 surfaces and is longer than the flexor retinaculum but not as strong. The extensors are not able to spring away from the wrist as are the flexors. The ligament acts as a strap which binds the extensor tendons down and holds them in place and, being obliquely placed, does not interfere with pronation or supination at the wrist. Its inferior border is continuous with the deep fascia of the hand; the superior is continuous with the deep fascia of the forearm; the medial border is attached to the triquetrum (cuneiform) and pisiform; and the lateral is attached to the lower inch of the anterior border of the radius. In this way it forms an annular ligament for the head of the ulna. The retinaculum is not attached to the lower end of the ulna by its medial border; hence, there is no interference with the movements of the radius around the ulna. The dorsal or superficial surface of the extensor retinaculum is crossed by veins draining the dorsal carpal arch; this arch usually lies across the lower part of the back of the hand but is inconstant in position and shape. The arch gives origin to the basilic and the cephalic veins and receives tributaries from 3 dorsal metacarpal veins. Four cutaneous nerves cross superficial to the extensor retinaculum: the dorsal branch of the ulnar nerve, the superficial branch of the radial, and terminations of the posterior branches of the medial and the lateral cutaneous nerves of the forearm. Five septa, springing from the deep surface of the extensor retinaculum, are attached to the head of the ulna and to the ridges on the back of the lower end of the radius, thus forming 6 compartments for the extensor tendons. In this respect it is unlike the flexor retinaculum, which forms only one large compartment for the flexor tendons. Each compartment transmits 1 or 2 tendons and is lined with a synovial sheath which envelopes the tendon or tendons. Attached to the deep surface of the extensor retinaculum are the 6 compartments with their enclosed structures. The first compartment is located on the lateral side of the distal end of the radius; it contains the tendons of the abductor pollicis longus and the extensor pollicis brevis. The second compartment contains the extensors carpi radialis longus and brevis; compartment three contains the extensor pollicis longus. The fourth compartment lies over a rather wide but shallow groove at the medial part of the back of the distal end of the radius and contains the tendons of the extensor digitorum as well as the extensor indicis. Deep to these enclosed tendons this compartment also contains the terminal parts of the posterior interosseous nerve and the anterior interosseous artery. The fifth compartment is situated in the interval that exists between the distal ends of the radius and the ulna and it contains the tendon of the extensor digiti minimi. The sixth is the most medial compartment and is marked by a groove over the dorsum of the distal end of the ulna; it encloses the tendon of the extensor carpi ulnaris. Eight synovial sheaths surround 9 tendons, since each tendon has a synovial sheath of its own, with the exception of the extensor digitorum and the extensor indicis which have a common sheath. The proximal ends of the sheaths are deep to the extensor retinaculum or slightly proximal to it. The sheaths of the abductor pollicis longus and the 3 extensors of the carpus extend to the insertions of these muscles. The sheaths of the extensors of the digits usually end about midlength down the hand. At times the abductor pollicis and the extensor pollicis brevis may have a common sheath. Three oblique bands unite the 4 tendons proximal to the knuckles; hence, the independent action of the fingers is restricted. No one finger can be held in flexion while the others pass into extension. EXTENSOR (DORSAL) REGION OF THE FOREARM AND THE HAND (DORSUM) This entire area (muscular) is innervated by the radial nerve. No motor nerves are found on the dorsum of the hand. No muscles originate from the dorsum of the hand, and no tendons insert into the dorsum of the carpal bones. Skin. Over the lateral posterior aspect of the forearm, the skin is supplied by the lateral cutaneous nerve of the forearm; this is the terminal branch of the musculocutaneous nerve, which becomes cutaneous at the lateral border of the biceps about 1 inch above the elbow. It divides into anterior and posterior branches, which pass in front of the elbow; they then descend on the front and the back of the radial side of the forearm, the anterior reaching the thenar eminence and the posterior ending at the wrist joint. The medial cutaneous nerve of the forearm is a direct branch of the medial cord of the brachial plexus. Like the lateral, it too divides into anterior and posterior branches, which descend in front of the elbow and then on the front and the back of the ulnar side of the forearm to the wrist. The large strip of skin which passes down the middle of the back of the forearm is supplied by the posterior cutaneous nerve of the forearm, a branch of the radial; it becomes cutaneous about 2 inches above the lateral epicondyle, supplies the back of the forearm as far as the wrist and, in most instances, reaches the dorsum of the hand. The skin of the dorsum of the hand is supplied by the radial nerve and the dorsal branch of the ulnar nerve. The radial nerve winds around the radius, deep to the brachioradialis tendon, about 3 inches above the wrist, and continues downward superficial to the extensor retinaculum; it supplies the skin over the lateral two thirds of the dorsum and sends digital branches to the thumb, the index finger and the radial side of the middle finger. The dorsal branch of the ulnar nerve winds around the ulna about 3 inches above the wrist, descends superficial to the extensor retinaculum and supplies the rest of the skin, namely, that over the dorsum of the hand, the little and the ring fingers, and the ulnar side of the middle finger. The cutaneous patterns of distribution are variable. The dorsal digital nerves usually do not extend beyond the proximal interphalangeal joints; hence, the rest of the dorsum of each finger receives its nerve supply from the palmar digital nerves. Fascia. The superficial fascia contains an irregular dorsal venous arch which receives digital veins. From its ulnar and radial extremities, respectively, the basilic and the cephalic veins arise and continue upward in the superficial fascia. The deep fascia is part of a strong layer which forms a tubular investment around the muscles of the forearm. At the olecranon, at the posterior margin of the ulna and at the lateral distal end of the radius it is connected to the periosteum. It separates the extensor from the flexor muscles by a septum which passes along the posterior margin of the ulna. However, on the radial side the separation between extensors and flexors is not developed as definitely. Furthermore, it sends partitions between the individual muscles. At the dorsal aspect of the wrist the fascia is strengthened greatly by transverse fibers; this forms the dorsal carpal ligament (posterior annular or extensor retinaculum), which can be likened to a postage stamp, having 4 borders and 2 surfaces. The fascia over the dorsum of the hand reveals die superficial lamina, a thin layer under the superficial fascia and above the tendons of the extensor muscles; on both sides of the hand it blends with the fascia of the volar aspect. The intertendinous lamina is a connecting membrane which lies between the tendons of the extensor digitorum. It is very thin in the white race but thick in the Negro; it is a rudimentary tendon plate.

FIG. The subcutaneous and the subaponeurotic spaces of the dorsum of the hand. The drainage of these spaces is indicated.

 

The dorsal interosseous lamina lies above the dorsal interosseus muscles and dips down to fuse with the periosteum of each metacarpal bone.

Anatomic Snuffbox (La Tabatiere Anatomique of Cloquet). On the dorsum of the hand, the hollow at the base of the thumb is called the "anatomic snuffbox". It is bounded anteriorly by the abductor pollicis longus and the extensor pollicis brevis; posteriorly, by the extensor pollicis longus. Its floor is formed by the navicular (scaphoid), the trapezium and the articulation between the latter and the first metacarpal bones. The radial artery lies in this "box" on its way to the first interosseous space. A vein lies superficial to the artery and is called the cephalic vein of Treves; fine branches of the radial nerve are also found here. The vein is closer to the skin; the artery lies deeper and on the lateral ligament of the bones which form the floor. When ligating the radial artery it is best to avoid opening the sheath of the tendons to the thumb or the scaphoid trapezial joint.

FIG. The radius and the ulna: (A) in supination; (B) in pronation.

 

SURGICAL CONSIDERATIONS Infections of the dorsum of the hand may involve either the subcutaneous or the subaponeurotic spaces. The dorsal subcutaneous space may become involved in boils or carbuncles; diese infections are superficial to the extensor tendons and the aponeurosis. The dorsal subaponeurotic space infection is uncommon. It may result from perforating dorsal wounds which have pierced the dorsal aponeurosis or may follow an osteomyelitis of the metacarpal or carpal bones. Infections can reach this space from other spaces via the lumbrical sheath. The dorsum almost always becomes edematous in palmar infections because of the loose connective tissue on the back of the hand which is rich in lymphatics; actual suppuration and primary involvement of this space is rare. When pus collects here, it is limited proximally by fibrous partitions at the base of the metacarpals and distally by similar partitions at the metacarpophalangeal joints. Treatment consists of establishing drainage of the abscess through one or more incisions running parallel with the extensor tendons, on the dorsum. The hemostat which opens the space should be placed between the tendons.

RADIUS AND ULNA The radius and the ulna form the bony framework of the forearm, the radius lying to the lateral and the ulna to the medial side of the superior extremity. These 2 bones articulate above with the humerus and below with the carpal bones of the wrist. They also articulate with each other at their upper and lower extremities and are firmly united by the ligaments of the radio-ulnar joints and the interosseous membrane. They are so arranged that the radius supports the entire hand and can revolve on a longitudinal axis around the ulna. This action takes place at the radio-ulnar joints and provides the movements of pronation and supination. The ulna, which does not enter into the wrist joint, is the more important bone at the elbow joint; the radius has only a secondary role in the latter location. RADIUS The proximal end of the radius has a head, a neck and a radial tuberosity. The head of the bone is a cup-shaped disk, the upper surface of which is concave and articulates with the capitellum humeri. It is covered by hyaline cartilage, and its circumference articulates with the radial notch of the ulna. Although it is embraced by the annular ligament, the ligament is not attached to it. This disklike head can be felt easily from the posterior aspect of the limb. If the limb is passively extended, a depression becomes visible over the posterior aspect of the elbow on its lateral side. The radial head can be felt in the lower part of it and can be made to rotate within the annular ligament when the hand is alternatively pronated and supinated. In the upper part of this depression, the back of the lateral epicondyle of the humerus is palpable, and between these two bony projections the line of the radiohumeral joint is located. The neck is that constricted portion of the radius which supports the head; it marks the point at which the brachial artery divides into radial and ulnar arteries. The tuberosity is placed on the medial side below the neck; anteriorly, it is smooth, and a bursa is located here. It is rough posteriorly for the insertion of the biceps tendon. The shaft of the radius reveals a roughened area over its lateral aspect for the insertion of the pronator teres. The interosseous membrane is attached to the interosseous border of the shaft but does not extend as high as the radial tuberosity. The metaphysis of the upper end of the radius has the following relationships: since the epiphysis is formed by the head of the bone and the capsule is attached to the neck, the metaphysis or the joint may extend to one or the other very readily. The distal end of the radius, the widest and bulkiest part of the bone, presents 5 notches, a styloid process, a dorsal tubercle and an ulnar notch. The styloid process is present over the lateral aspect as a downward prolongation which is partially obscured in life by the tendons of the abductor pollicis longus and the extensor pollicis brevis. These tendons should be kept relaxed when the bone is being examined. The styloid processes are of great importance in the diagnosis of fractures of the radius; the radial styloid normally projects about ¼ inch distal to the ulnar styloid. The dorsal radial tubercle of Lister is the most prominent of the ridges over this area and usually can be felt, since it is grooved obliquely by the tendon of the extensor pollicis longus. The medial surface is concave and smooth and articulates with the head of the ulna. The lateral surface is about ½ inch wide and extends onto the ulna and to the styloid process. The posterior surface is convex and reaches farther down than the anterior; the dorsal tubercle is located about its center. Shallow grooves lateral to the tubercle lodge the tendons of the extensor carpi radialis longus and brevis, and a narrow oblique groove at the medial side of the tubercle marks the tendon of the extensor pollicis longus. A wide, shallow groove medial to this lodges the tendons of the extensor digitorum and the extensor indicis. The anterior surface is smooth and slightly concave, being limited distally by a thick ridge which can be felt above the wrist and laterally by a sharp edge which separates it from the lateral surface. The distal or carpal surface is concave, smooth and divided into a lateral and a medial area. The lateral area is triangular and articulates with the scaphoid bone, and the medial area is square and articulates with the lunate bone. The lower epiphyseal line passes around the bone on the level with the upper margin of the ulnar notch; it does not join the shaft until the 20th year. The metaphysis in this region has the following relationships: the epiphysis is represented by a horizontal line at the level of the upper part of the ulnar notch, and the capsule is attached very close to the articular margin all the way around. Therefore, the metaphysis is entirely extracapsular. Both bone and joint diseases are more limited than they would be if the upper metaphysis were involved. ULNA The ulna is the medial and longer bone of the forearm. Its proximal end presents an olecranon, a coronoid process and radial and trochlear notches. The olecranon is easily palpable posteriorly, and in extension the upper edge of this process is on the same level as the epicondyle of the humerus. It gives insertion to the tendon of the triceps. The coronoid process projects forward and ossifies with the shaft; its anterior aspect is covered by and gives insertion to the brachialis muscle. The radial notch is located over the lateral surface, is concave and articulates with the head of the radius. Its inferior and posterior borders give attachment to the annular ligament. The trochlear notch (incisura semilunaris) is a wide concavity bounded by the olecranon and the coronoid; it articulates with the trochlea. The shaft of the ulna tapers as it passes distally; the posterior border of the shaft is subcutaneous in its whole length from the posterior aspect of the olecranon to its styloid process. The distal end of the ulna presents a head and a styloid process. The head is small and rounded, and its distal surface articulates with the triangular articular disk. The head of the ulna can be grasped between the fingers and the thumb when the flexors and the extensors are relaxed, and in some individuals it presents a conspicuous prominence in full pronation. The styloid process projects downward from the posteromedial aspect of the head and is felt best when the hand is in full supination. The upper and the lower metaphyses have the following relations: at the upper end, the epiphysis may be variable but it usually is represented as a flake of bone on the upper surface over its whole extent. Therefore, this epiphysis is entirely extracapsular, so that the metaphysis and part of the diaphysis are related to the capsular line. At the lower end, the epiphysis is represented by a horizontal line at the level of the upper extremity of the articular surface for the radius; the capsule is attached to the margins of the articular surface, except laterally, where it is a little proximal to the radial articular surface. Therefore, the metaphysis in this location is partly intracapsular, and diseases of the bone or the joint may spread in either direction. RADIO-ULNAR JOINTS The radius and the ulnar are united at proximal and distal radio-ulnar joints. There is an intermediate "joint" where the bodies of the 2 bones are united by the oblique cord, the interosseous membrane, and the posterior layer of the fascia which covers the pronator quadratus. The interosseous membrane of the forearm is a fibrous sheath which stretches across the interval between the 2 bones of the forearm and is attached to the interosseous border of each. It begins about 1 inch below the radial tuberosity and extends to and blends with the capsule of the inferior radio-ulnar joint. Its fibers pass downward and mediad from the radius to the ulna, so that shocks transmitted to the radius from the hand are passed on to the ulna and then to the humerus. Over the anterior surface of this membrane and from its upper three quarters the flexor pollicis longus and the digitorum profundus arise; the anterior interosseous vessels lie between them and perforate the membrane near its lower end. The pronator quadratus lies on the lower one fourth. The posterior surface gives origin to the abductor pollicis longus, the extensors pollicis brevis and longus, and the extensor indicis. The

FIG. The superior and the inferior radio-ulnar joints.

 

supinator lies on its anterior part, the anterior interosseous vessels and the posterior interosseous nerve on its lower part. The oblique cord is a slender band arising from the tuberosity of the ulna and extending downward and laterally; it attaches to the radius immediately below its tuberosity. This cord crosses the open space between the bones of the forearm above the upper border of the interosseous membrane. The posterior interosseous vessels pass backward through the gap which exists between this cord and the interosseous membrane. Superior (Proximal) Radio-ulnar Joint. This joint is considered with the elbow joint because they have a common synovial cavity, and the lateral ligament of the elbow joint is connected to the annular ligament of the superior radio-ulnar joint. At this joint the medial part of the head of the radius

fits into the radial notch of the ulna. The annular ligament forms a collar for the head of the radius; this collar retains the radial head in the radial notch of the ulna. This ligament forms four fifths of a circle which is attached to the anterior and the posterior margins of the notch. It is narrower below than above; hence, the head of the radius cannot be pulled downward and out. The lower border of the ligament is free; this allows the head of the radius to rotate during pronation and supination. The synovial membrane of the joint lines the deep surface of the annular ligament and is continuous with that of the elbow joint, so that the joint cavities communicate freely. It lines the deep surface of the annular ligament and bulges slightly below it, producing a sacciform recess which encircles the neck of the radius. Inferior (Distal) Radio-ulnar Joint. This is a synovial joint formed by the head of the ulna where it articulates with the ulnar notch of the radius laterally and the articular disk inferiorly. Union is maintained by the articular disk and is aided by a weak capsular ligament passing between the margins of the articular surfaces. The articular disk is a thick triangular fibrocartilaginous plate. Its apex is related to the

FIG. Exposure of the shaft of the radius: (A) incision; (B) relations of the deep branch of the radial nerve (dorsal interosseous); (C) the exposed shaft of the radius.

 

depression at the base of the ulnar styloid process, and its base to the lower border of the ulnar notch of the radius. Its anterior and posterior margins blend with the corresponding ligament of the radiocarpal joint. Although it usually is a complete plate, it may be perforated. When this occurs, the joint cavities and the synovial membranes of the inferior radio-ulnar and the radiocarpal (wrist) joints become continuous. The capsular ligament is weak, possessing feeble anterior and posterior ligaments which invest the anterior, the posterior and the superior aspects of the joint. It is continuous with the capsular ligament of the wrist joint. The synovial membrane lines the capsular ligament and the upper surface of the articular disk. It projects upward to form a small cul-de-sac (recessus sacciformis) in front of the lower end of the interosseous membrane. The joint is supplied by the anterior and the posterior interosseous nerves and vessels. Movements of the Radio-ulnar Joints. The rotary movements of these joints take place around a vertical axis which passes through the center of the head of the radius above and the ulnar attachment of the triangular articular disk below. Supination, the position in which the bones of the forearm are parallel and the thumb points laterally, is produced mainly by the supinator, the biceps and the brachioradialis. In pronation the radius crosses in front of

FIG. Exposure of the distal fourth of the radius.

 

FIG. Exposure of the shaft of the ulna.

 

the ulna, the upper end remaining lateral and the thumb pointing medially. Supination is the strongest movement, due to the strength of the biceps. Starting from the supine position, the upper limb can be rotated so that the palm, originally directed forward, can be directed successively medially, backward and laterally, moving through an arc of 270°. However, the greater part of that movement is not pronation but medial rotation at the shoulder joint. Pronation alone can move through an arc of about 130°.

SURGICAL CONSIDERATIONS

EXPOSURE OF THE SHAFT OF THE RADIUS This is accomplished through an incision over the dorsal aspect of the forearm. The deep fascia is divided, and the extensor digitorum communis is retracted. This exposes the supinator muscle and the deep branch of the radial nerve (dorsal interosseous) piercing it. The supinator is divided longitudinally to the bone and retracted with the muscles of the thumb. The extensor carpi radialis brevis is retracted in the opposite direction, and the shaft of the radius is exposed. EXPOSURE OF THE DISTAL FOURTH OF THE RADIUS Exposure of the distal fourth of the radius is accomplished through an incision, about 3 or 4 inches long, extending upward and medially along the dorsal aspect of the bone. The deep fascia and the dorsal carpal ligament are incised, exposing the extensor digitorum communis muscle, the extensor pollicis longus tendon, the extensor pollicis brevis muscle, the abductor pollicis longus muscle and the tendon of the extensor carpi radialis brevis; a small part of the radius also is visible. The abductor pollicis longus, the extensor pollicis brevis and the tendon of the extensor carpi radialis brevis are retracted laterally, and the extensor digitorum communis and the tendon of the extensor pollicis longus are retracted medially. This will expose the distal fourth of the radial shaft. EXPOSURE OF THE SHAFT OF THE ULNA In the exposure of the shaft of the ulna, the location of the incision depends on the part of the bone requiring exposure. The incision is located somewhere on a line drawn between the olecranon and the ulnar styloid. The flexor carpi ulnaris is retracted medially, and the extensor carpi ulnaris and the anconeus are retracted laterally. These muscles must be stripped off of the bone with an osteotome. Thus the shaft of the ulna can be exposed in its entire length.

FIG. Fractures of the radius in relation to the pronator teres muscle: (A) fracture above the insertion of the pronator teres; (B) fracture below the insertion of the pronator teres.

FRACTURES OF THE FOREARM Fractures of the forearm present many problems in mechanics because of the complicated system of muscles which control movements of the hand and the ringers. For practical purposes some anatomists consider the ulna a downward extension of the arm which is associated with motion and strength of the elbow, and the radius an upward extension of the hand concerned with motions of the hand and the wrist. Therefore, the principal articulation of the ulna is with the humerus, and that of the radius is at the wrist. It is well known that the head of the radius may be removed from its articulation with the humerus without causing any disability to the elbow. The 2 forearm bones are joined by the interosseous membrane, the fibers of which run from the ulna to the radius in an upward direction. If both bones of the forearm are fractured, the membrane has a tendency to pull the ulna toward the radius. In the important motions of pronation and supination, the ulna remains fixed and the radius rotates around it so that when the hand is in full pronation the radius comes to lie immediately over the ulna, crossing it a little above its middle. The distance between the bones is greatest in semipronation. The pronator teres muscle is the important landmark in fractures of the forearm. It is located a little above the middle of the radius, and it must be determined whether the fracture is above or below its insertion. In a fracture of the radius above the insertion of the pronator teres, the upper fragment of the radius is pulled into supination by the supinator brevis and the biceps; the lower fragment is fully pronated. In such a fracture the biceps also will accomplish some flexion of the proximal fragment. In fractures below the attachment of the pronator teres, the supinator brevis and the pronator teres will equalize each other between pronation and supination in the upper fragment, and the lower fragment will be in full pronation. The correct position for a radius fractured above the insertion of the pronator teres is with the elbow flexed and the hand supinated. In fractures below the pronator teres, the thumb up (midprone) position is used with flexion at the elbow. In this position the palm of the hand faces the chest. The important rule in all fractures of the radius above the position of a Colles' fracture is to keep the elbow flexed, otherwise it will be impossible to maintain the forearm in any given position of rotation. Where both the radius and the ulna are fractured, the broken ends of bone are usually drawn together by the supinators and the pronators, and the interosseous space is narrowed. The lower fragments may be displaced laterally or anteroposteriorly with overriding. Shortening of the forearm results. The upper part of the shaft of the ulna may be fractured; this usually is associated with anterior dislocation of the head of the radius due to the fact that the annular (orbicular) ligament also may be torn. This is so common an occurrence that in all fractures of the upper part of the ulna, radial dislocation should be ruled out. Fractures along other parts of the ulnar shaft are usually transverse and occur in the distal third of the bone, where muscle masses are replaced by tendons. Marked displacement usually is absent because of the splinting effect of the intact radius. However, there is a tendency toward a narrowing of the interosseous space; this is brought about by a pull from the pronator quadratus muscle upon the lower fragment. FRACTURE OF THE HEAD AND THE NECK OF THE RADIUS This usually occurs in adults from indirect violence, such as a fall on the palm. Such a fracture produces interference with flexion and rotation of the forearm; these movements may produce crepitus. Reduction is brought about by pressure and flexion, and fixation is maintained in supination and flexion. Excision may be necessary. Fracture of the neck of the radius usually results from indirect violence, the fracture occurring between the head and the bicipital tuberosity. The treatment may be open or closed reduction. COLLES' FRACTURE Colles' fracture involves the lower end of the radius; it is nearly transverse and within 1 inch of the articular surface of the bone. It produces a deformity due to dorsal displacement of the distal fragment and volar displacement of the proximal. Usually it is due to a fall on the extended hand, and the typical sign is the "silver fork" deformity, in which there is a prominence on the back of the wrist and a lateral displacement of the hand toward the radial side. This is not present if the fracture is impacted or incomplete. If proper reduction has been accomplished, the surface markings can be made out even in the presence of swelling. Normal relations should exist between the styloid processes, and a uniform line should be present along the forearm through the wrist and to the hand. A reverse Colles' fracture is called Smith's fracture. This usually is produced by a fall on the back of the hand with the wrist flexed. Epiphyseal separation may be confused with a Colles' fracture. It is common in children and may occur at any time up to the 18th or the 20th year. Since the radius takes the brunt of the injury in falls on the outstretched hand, separation of the distal ulnar epiphysis is rare.

AMPUTATIONS The site of election in forearm amputations is at the junction of the lower and the middle thirds. However, any site above this junction to within 3 or 4 inches of the elbow will produce a good stump. A short forearm stump is difficult to fit because the biceps muscle pushes the limb socket when the elbow is flexed. In amputations of the forearm, anterior and posterior U-shaped incisions are made through the skin and the superficial fascia, thus outlining the flaps. The vertical incisions are carried through the muscles to the bone. The muscles on the anterior and the posterior aspects of the forearm are divided to the bone, and the periosteum is freed and retracted upward. The interosseous membrane is cut transversely at approximately the saw line, the soft parts are retracted, and the bones are sawed. Attempt is made to ligate separately the radial, the ulnar, and the anterior and the posterior interosseous arteries. The median, the ulnar and the radial nerves are cut short. The muscles and the deep fascia are closed over the bone ends, and the skin is closed with interrupted sutures.

FIG. Site of election in forearm amputations.

 

WRIST

 

The wrist is the link between the forearm and the hand. It contains the soft parts, the bones and the joints in that area which includes the carpus, the distal extremities of the radius and the ulna, and the bases of the metacarpals. The radiocarpal, the midcarpal and the carpometacarpal joints are located in the wrist, and it is in this region that the tendons of the forearm cross on their way to insert onto the carpus. The tendons are held close to the wrist bones by thickenings of the deep fascia which form ligaments. CARPAL BONES There are 8 small carpal bones which are arranged in 2 rows: proximal and distal. Each row consists of 4 bones which have received their names according to their general appearance. The proximal row, named from lateral to medial, consists of the navicular (scaphoid), the lunate (semilunar), the triquetrum (cuneiform) and the pisiform. The distal row, named from lateral to medial, presents the greater multangular (trapezium), the lesser multangular (trapezoid), the capitate (os magnum) and the hamate (unciform). These 8 bones are more or less cubical in shape and, therefore, have 6 surfaces: proximal, lateral, distal, medial, palmar and dorsal. Of these, only 2 surfaces, the anterior and the posterior, are roughened by the attachments of the ligaments. The remaining 4 surfaces, which articulate with adjacent bones, remain smooth and are entirely or partly covered with cartilage. The lateral surfaces of the lateral bones and the medial surfaces of the medial bones also receive ligamentous bands and are also roughened. The navicular (boat-shaped) bone does not withstand an indirect blow well. Such a blow may be received by falling on the palm of the hand in radial deviation. The bone is not adapted to receive such trauma because of its curved shape and obliquely curved axis. However, if the fall occurs, with the hand in ulnar deviation, only the proximal part of the bone is exposed to trauma. The navicular is the most commonly fractured of all the carpals.

FIG. The carpal bones: (A) seen from in front; (B) seen from the radial side; (C) seen from behind.

 

The tubercle of the scaphoid can be felt through the skin at the base of the thenar eminence and in line with the radial side of the middle finger. At times it forms a visible protrusion, but it usually is concealed by the tendon of the flexor carpi radialis, which inserts on it and can be felt when that muscle is relaxed. The distal transverse crease at the front of the wrist crosses this tubercle and the pisiform bone. The lunate (moon-shaped) is the middle bone of the proximal row; its distal articular surface, with a part of the distal scaphoid articular surface, lodges the head of the capitate bone. It is the carpal bone which is dislocated most frequently. The triquetrum (triangular-shaped) articulates with the articular disk, and by means of a specialized surface it also articulates with the ulnar collateral ligament. This arrangement permits the triquetrum, with the pisiform on its volar aspect, to glide toward the ulna in ulnar flexion. The remainder of the proximal surface of the bone is nonarticular. The scaphoid, the lunate and the triquetral bones form the carpal articular surface in the radiocarpal joint. The pisiform (pea-shaped) bone is located at the base of the hypothenar eminence on the medial side of the front of the wrist. Many anatomists consider it a sesamoid bone in the tendon of the flexor carpi ulnaris. When this tendon is relaxed, the bone can be moved about on the palmar surface of the triquetrum, thus revealing an isolated facet for the pisiform. The latter bone does not enter into the radiocarpal joint. The trapezium (greater multangular) is the most radially placed bone of the distal row. This and the scaphoid can be palpated in the "anatomic snuffbox," the hollow at the lateral side of the wrist which is situated between the styloid process of the radius proximally and the base of the metacarpal of the thumb distally. In this location the radial artery crosses these bones, and its pulsations can be felt here. The trapezoid and the trapezium are placed distally to the capitate. With the exception of the pisiform, the trapezoid is the smallest of the carpal bones, and it has been likened to a Chinese boot. The capitate (headlike) is the largest of the carpal bones; it is centrally placed and appears most prominent. It has a head, a neck and a body. The head occupies the deep concavity on the medial side of the first row of bones, and the body below supports the 2nd, the 3rd and the 4th metacarpal bones. It is the head of the capitate which transmits the force of a fall upon the hand to the radius through the navicular and the lunate bones. The hamate (hooklike) bone presents a projecting process, the hook of the hamate, which can be identified through the skin. It can be felt in the ball of the little finger about 1 inch below and lateral to the pisiform and in a line with the ulnar border of the ring finger. The interval between the hook and the pisiform allows the passage of the ulnar artery and nerve. The carpus is cartilaginous at birth. Complete ossification takes place between the 20th and the 25th years. The capitate, which is the largest of the carpal bones, begins to ossify during the 1st year; with the exception of the pisiform, which undergoes ossification about the 12th year, all the carpal bones are in the process of ossification by the 8th year. As a whole, the bones of the carpus are fitted closely together but permit a certain amount of movement, thereby giving a degree of flexibility to the wrist. The proximal surface of the carpus reveals that the pisiform has been placed in front of the triquetrum, leaving only 3 bones of the proximal row in the articulation with the wrist joint above and the distal row of carpal bones below. The widened

FIG. The distal skin crease of the wrist.

 

distal end of the scaphoid supports 2 bones: the trapezium and the trapezoid. The distal surface of the carpus, on the other hand, is quite irregular, since 5 metacarpal bones must articulate with 4 distal carpal bones. The 4th and the 5th metacarpals articulate with the hamate. The carpus as a whole forms a surface which is concave from side to side on its palmar aspect and convex over its dorsum; the extremities of this concavity give attachment to the flexor retinaculum (transverse carpal ligament). This ligament, plus its bony attachment, forms the osteofascial tunnel for the flexor tendons of the fingers. DISTAL SKIN CREASE The distal skin crease of the wrist is always visible and is an excellent landmark. It crosses the tip of the styloid process of the radius and the lower part of the lunate bone. It has the following features: it marks the proximal border of the transverse carpal ligament and the proximal row of the

FIG. The structures which are located proximal to the distal skin crease of the wrist. These structures are considered as lying in 3 layers.

 

carpal bones. It is bisected by the tendon of the palmaris longus (the clenched fist renders this tendon prominent). The median nerve lies immediately beneath the tendon of the palmaris longus; therefore, we may say that the median nerve bisects the crease. The flexor carpi radialis tendon crosses its lateral third, and the flexor carpi ulnaris is at the extreme medial end of the crease. It is interesting to flex the index finger and observe the wrist. Although the index is placed radially, the tendon produces movements on the ulnar side of the wrist. This illustrates the point that all the tendons of the flexor digitorum sublimis and the profundus lie on the ulnar side of the wrist; therefore, these tendons lie between the ulnar and the median nerves. Structures That Are Proximal to the Distal Skin Crease. These structures will be remembered more easily if they are discussed and visualized in layers or planes. The first layer of structures consists of, from lateral to medial: the radial artery, the flexor carpi radialis tendon, the palmaris longus tendon, the median nerve, the flexor carpi ulnaris and the ulnar artery and nerve. The radial artery, after crossing the pronator quadratus, comes in contact with the lower end of the radius. It then lies on the skeletal plane, and in this region it is covered only by skin, superficial and deep fascia. Therefore, this is the correct site to feel the pulse. The artery is no longer in relation to the major portion of the radial nerve, since the latter leaves it by winding around the radial border of the forearm deep to the brachioradialis tendon. The artery disappears deep to the abductor pollicis longus tendon. The flexor carpi radialis tendon lies between the radial artery and the median nerve. As it passes distally, it pierces the deep fascia (flexor retinaculum), making a private tunnel for itself. In its course it travels over the tubercle of the scaphoid bone and may be used as a guide to this latter structure. The palmaris longus tendon is not always present, but if it is, it crosses at a point which is in the middle of the wrist and, therefore, bisects the distal skin crease. It crosses in front of the flexor retinaculum and continues into the palm as the palmar aponeurosis; it lies immediately above the median nerve. If this tendon is absent, the nerve is more exposed to injury; hence, this tendon might be considered as the "roof" or "protector" of the median nerve. The median nerve is behind the flexor digitorum sublimis in the forearm, but in the region of the wrist it appears at the lateral border of and somewhat above this muscle. It is differentiated from the surrounding tendons by the fact that numerous small vessels (vaso nervorum) are noted distinctly on its surface. At the wrist it lies directly behind the palmaris longus tendon, the deep fascia intervening between the palmaris longus and the nerve; the latter usually clings to this deep fascia. At times a small "median artery" accompanies it. The flexor carpi ulnaris tendon lies at the medial extremity of the distal skin crease. It forms a "roof" and protection for the ulnar nerve and artery and acts as a guide to the pisiform bone. The muscle does not become entirely tendinous, but as far as the wrist, distinct muscular fibers of the flexor carpi ulnaris accompany the tendon, so that it is really half tendon and half muscle. The ulnar artery and nerve are both protected by the overlying flexor carpi ulnaris tendon. They are bound together

FIG. Deep dissection in the wrist, showing the arrangement of the tendons.

 

closely by connective tissue, and it is extremely difficult to ligate the artery in this region without incorporating the nerve.The second layer consists of the flexor digitorum sublimis. This group of 4 tendons lies between the median and the ulnar nerves, and, as they pass forward into the palm, the tendons of the middle and the ring fingers are placed somewhat in front of those for the index and the little fingers. The third layer consists of the flexor digitorum profundus and the flexor pollicis longus. The 4 tendons of the flexor digitorum profundus enter the hand by passing behind the sublimis. The tendon for the index finger separates from the remainder of the muscle about halfway down the forearm and represents a large structure. These 4 tendons do not lie 2 upon 2, as do the tendons of the flexor digitorum sublimis, but they all lie in the same plane. The flexor pollicis longus tendon lies in the same plane as the flexor digitorum profundus but is easily separated from it, since it travels in its own synovial sheath. It is found immediately beneath and lateral to the median nerve. At the extreme lateral (radial) margin of the wrist, the tendons of the abductor pollicis longus and the extensor pollicis brevis are found. They form the anterior margin of the "anatomic snuffbox". Structures That Are Distal to the Distal Skin Crease. The transverse carpal ligament has been referred to as the anterior annular ligament and the flexor retinaculum. It is a specialized portion of the deep fascia of the forearm which assumes the form of a tough

FIG. The flexor retinaculum (transverse carpal ligament). Its attachments to the 4 end bones of the carpus are shown.

 

fibrous band stretching across the arch formed by the carpal bones. It attaches to the 4 end bones of the carpus, namely, the navicular (scaphoid) and the greater multangular (trapezium) laterally, and the pisiform and the hamate medially. The arched carpal bones and the transverse carpal ligament form an osseofibrous tunnel called the carpal tunnel. Proximally, the ligament is continuous with the deep fascia of the forearm; distally, it merges with the palmar fascia. The structures superficial to the transverse carpal ligament are the palmaris longus tendon, the ulnar nerve and artery, the superficial branch of the radial artery and the cutaneous nerves and veins. The structures passing deep to the transverse carpal ligament are the median nerve, the flexor digitorum sublimis, the flexor digitorum profundus and the flexor pollicis longus. Unnecessary confusion seems to exist between the volar carpal ligament and the transverse carpal ligament. The volar carpal ligament is a fascial process which passes from the pisiform bone and the flexor carpi ulnaris medially to the palmar surface of the transverse carpal ligament laterally. In this way it forms the roof of a tunnel for the ulnar artery and nerve, the floor of the tunnel being formed by the medial border of the transverse carpal ligament. The median nerve, the flexor digitorum sublimis, the flexor digitorum profundus and the flexor pollicis longus cross under the ligament. The flexor carpi radialis goes through the ligament, creating in this way a fibrous tunnel for itself.

JOINTS. RADIOCARPAL (WRIST) JOINT This is the joint which exists between the forearm and the hand, the other joints in this region being known as the intercarpal joints. The proximal surface of the radiocarpal joint is formed by the concave lower articular surface of the radius and the articular disk. The distal surface is formed by the convex scaphoid, the lunate and the triquetral bones. Union is maintained by a capsular ligament which is strengthened by the anterior and the posterior radiocarpal, and the lateral and the medial ligaments of the wrist. The capsular ligament is of moderate strength and is attached close to the margins of the articular surfaces. The anterior and the posterior ligaments only moderately strengthen their respective aspects of the capsule. The fibers of these ligaments pass obliquely downward and medially from the front and the back of the proximal row of carpal bones and to the capitate. Therefore, during pronation and supination of the forearm, the radius drags the carpal bones after it. The lateral (radial collateral) ligament passes from the radial styloid process to the tuberosity of the navicular and the greater multangular. The radial artery crosses it. The medial (ulnar collateral) ligament extends from the styloid process of the ulna to the pisiform and the triquetrum. The synovial membrane lines the interior of the capsular ligament, the inferior surface of the articular disk and the 2 interosseous ligaments which complete the carpal surface. It does not communicate with the intercarpal joints. The blood supply is derived from the carpal branches of the radial, the ulnar and the interosseous arteries and the recurrent branches of the deep palmar arch. The nerve supply of the radiocarpal joint is derived from the anterior and the posterior interosseous nerves and the dorsal and the deep branches of the ulnar nerve. The active movements at the wrist joint are flexion, extension, abduction (radial deviation), adduction (ulnar deviation) and circumduction, the last being produced by a combination of the preceding movements. Rotation of the carpus and the hand around a vertical axis cannot be performed actively. Movements are checked in some cases by ligaments and tendons. When the fingers are flexed, the stretched extensor tendons do not allow full flexion of the wrist. Abduction is less free than adduction because the styloid of the radius meets the carpus. INTERCARPAL JOINTS In the carpus there are 2 joint cavities: the pisiform and the transverse carpal.

The pisiform joint is a small synovial joint which possesses a capsular ligament and a synovial membrane. Its cavity is shut off from the other joint cavities of the carpus.

FIG. The radiocarpal (wrist) joint, seen in frontal section.

 

The transverse carpal joint is a synovial joint which is common to the other intercarpal joints; it also has been referred to as the intercarpal or midcarpal joint. It is located between the bones of the proximal and distal rows of the wrist. These bones are connected to one another by palmar and dorsal ligaments, and at the radial and the ulnar extremities of the joint, by the lateral and the medial ligaments. The synovial membrane which lines this joint cavity is thin, not only between the two rows of bones, but also between the scaphoid and the lunate, between the lunate and the triquetral and downward between the bones of the distal row. Generally the cavity communicates with the joint cavities of the 4 medial carpometacarpal and the intermetacarpal joints. The opposed surfaces of the carpal bones, which are nonarticular, are connected to each other by interosseous ligaments. The intercarpal joints derive their nerve supply from the anterior and the posterior interosseous nerves and the dorsal and the deep branches of the ulnar nerve. The movements at these joints supplement those at the radiocarpal joints and increase the range of movements of the hand. Between the individual bones of each row the movements are of a gliding nature and are quite limited. CARPOMETACARPAL AND INTERMETACARPAL JOINTS The metacarpal bone of the thumb articulates with the os trapezium by a joint which is entirely separated from the other carpometacarpal joints. It is a synovial joint of the saddle variety and, because of its shape, permits a wide range of movements. The articular capsule which surrounds it is sufficiently lax to permit these movements. The medial 4 metacarpal bones are connected to the carpus by the palmar and the dorsal ligaments and by one interosseous ligament. A medial ligament is present also; this closes the medial side of the joint of the 5th metacarpal bone. The interosseous ligament arises from the contiguous distal margins of the capitate and the hamate bones and runs to the medial side of the base of the 3rd metacarpal bone. The metacarpal bones of the fingers are united by strong ligaments and articulate with each other at their bases. The ligaments which bind the medial 4 metacarpals together are: (1) a series of palmar and dorsal metacarpal ligaments which pass transversely between the palmar and the dorsal surfaces of the bases; (2) three interosseous ligaments which pass between the nonarticular parts of the sides of contiguous bases; (3) the deep transverse ligament of the palm, which indirectly connects the heads of the bones. Though the intercarpal, the carpometacarpal and the intermetacarpal joints are spoken of individually as having separate ligaments, these constitute one single ligament which surrounds a continuous joint cavity. (The pisiform joint and the carpometacarpal joint of the thumb possess separate capsules.) The synovial membrane lines all the ligaments and is prolonged over all the intra-articular parts of the bone that do not contain articular cartilage. METACARPOPHALANGEAL AND INTERPHALANGEAL JOINTS The metacarpophalangeal joints are synovial joints which form where the head of the metacarpal articulates distally with the base of the proximal phalanx and anteriorly with the palmar ligament.

FIG. The radiocarpal, the intercarpal and the carpometacarpal joints. Frontal section through the joints of the carpus.

 

FIG. The mechanism of injury to the navicular or lunate bone. The arrows indicate the direction of force following a fall on the outstretched hand.

 

Union is maintained by a capsular ligament which is greatly strengthened in front by the palmar ligament and at the sides by collateral ligaments. The capsular ligament is attached near the margin of the articular surfaces, but posteriorly it is defective, and its place is taken by the expanded extensor tendon. The collateral ligaments are strong oblique bands which pass downward and forward from the sides of the head of the proximal bone of the joint to the sides of the base of the distal bone. The palmar ligament is a dense fibrous plate which is the thickened palmar part of the capsular ligament. At the sides it fuses with the collateral ligaments and is connected with the deep transverse ligaments of the  palm. Distally, it is attached to the base of the phalanx; proximally, it is loosely connected with the palmar surface of the metacarpal immediately above the head. It forms part of the socket and articulates with the front of the head. Its palmar surface is smooth and is covered by the flexor tendons and their synovial sheaths. In a metacarpophalangeal joint of a finger, the margins of the palmar ligament give attachment to the deep transverse ligament of the palm and partial attachment to the processes of the palmar aponeurosis. The interphalangeal joints are similar in structure to the metacarpophalangeal joints. They are of the synovial variety and have capsular, collateral and palmar ligaments. The interphalangeal joints have ligaments corresponding to those of the metacarpophalangeal joints but, since they do not have rounded heads, they do not permit adduction or abduction

SURGICAL CONSIDERATIONS Injuries to the carpal bones result from falls on the outstretched palm, the force being directed from the 3rd metacarpal to the capitate and then to the navicular and the lunate. Any type of injury may result; the most common is fracture of the navicular, and the next most frequent is dislocation of the lunate. FRACTURE OF THE NAVICULAR (SCAPHOID) BONE This fracture is more frequent than had been suspected previously. As a result of a fall on the outstretched hand, the navicular is brought directly under the radius and is pinched between it and the capitate bone. Treatment is by reduction and immobilization. Excision of the navicular, either total or partial, should be avoided, if possible, since this leaves a permanent disability.

DISLOCATION OF THE LUNATE (SEMILUNAR) BONE Dislocation of this bone is caused by a fall on the outstretched hand which results in a momentary backward dislocation of the wrist. Since the lunate is attached more firmly to the radius and the ulna than are the other carpal bones, it does not take place in the backward dislocation; its ligamentous connection with the other carpals is torn. The backward wrist dislocation spontaneously reduces itself and, on returning, knocks the lunate forward. The proximity of the median nerve must be kept in mind, since an anteriorly dislocated lunate may produce signs of median nerve involvement. The dorsal ligament, which contains the important nutrient vessel to the bone, may be injured, and this may result in a progressive degeneration called Kienboch's disease. DISLOCATIONS OF THE WRIST Dislocations of the wrist are rare; they may be forward or backward, and their importance is mainly in their recognition, since they may resemble a Colles' or Smith's fracture. In dislocations the relationship between the styloid processes is preserved, but the relation of the carpal bones to these processes is altered. Dislocation usually involves the radiocarpal articulation; frequently, it is compound, and the articular edge of the radius may be fractured. True dislocation may occur from great violence, and the inferior end of the radius and the ulna then protrude, either to the dorsal or the volar surface of the wrist. In dorsal dislocation of the carpus, the deformity may resemble a Colles' fracture but it is closer to the hand. Dislocation of the inferior radio-ulnar joint is an extremely rare wrist dislocation, but it may complicate a fracture. Reduction should be accomplished by pressure on the displaced bone with supination. ARTHRODESIS OF THE WRIST JOINT A surgical bony ankylosis of the wrist joint

FIG. Arthrodesis of the wrist joint: (A) skin incision and division of the dorsal carpal ligament; (B) retraction of the extensor tendons and incision into the capsule; (C) the joint cavity is exposed, and the radius is curetted.

 

usually is created for flail wrist, ankylosis in a faulty position, wrist drop or arthritis. The position of choice (optimum position) for ankylosis should be sought; this is a 30° extension with some degree of ulnar deviation. In this position the flexors and the extensors are in proper balance. With the hand in pronation, a dorsal incision is begun opposite the center of the 2nd metacarpal; it is continued obliquely upward, bisecting a line drawn between the styloid processes and ending about 2 inches above the radial styloid. The dorsal carpal ligament is exposed and divided, and the extensor tendons are retracted. The capsule is opened so that the proximal row of carpal bones is exposed. A small wedge may be removed from the radius, the navicular and the lunate bones, or the bony surfaces may be curetted.

AMPUTATIONS AND DISARTICULATIONS Amputations and disarticulations at the wrist joint prevent the proper fitting of artificial hands; if possible, they should be avoided. However, there are times when carpometacarpal disarticulation is indicated; if possible, the thumb and a finger or other parts of the hand should be saved. A U-shaped incision is begun on the palmar side about ½ inch below the styloid process of the radius, passing down to the middle of the 2nd metacarpal, where it arches across the middle of the remaining metacarpals and ends about 1 inch below the styloid of the ulna. The dorsal incision is placed transversely across the carpal bones and connects with the palmar incision. The palmar flap is deepened to the flexor tendons and is reflected to the joint. The extensor tendons and ligaments are divided, the joint is traversed, and the flexor tendons and the remaining tissues are severed in similar fashion. Tendons and nerves are cut short. Some authorities advocate suturing the tendons together, but others permit them to retract. After careful hemostasis has been achieved, the wound is closed in layers.

 

HAND

The hand is an organ that is directed by the will and is capable of a great variety of complicated movements. These movements are possible because of the highly coordinated actions of its intrinsic and extrinsic muscles and its numerous joints. The thumb is all-important to the hand, since the property of apposition depends on it; without this, the functional capacity of the hand is reduced greatly. The hand can be divided conveniently into the palmar region, the dorsal region and the phalanges. PALMAR REGION This region is quadrilateral in shape and contains the soft parts in front of the metacarpal bones. The "hollow" of the hand is the triangular central part which is bounded on the radial side by the thenar eminence and on the ulnar side by the hypothenar eminence. These eminences approximate

FIG. Cross section through the right hand, showing the 9 layers in the center of the palmar region of the hand.

 

each other as they approach the wrist. It is helpful to consider the central part of the palmar region and then to discuss the thenar and the hypothenar eminences. The central part of the palm consists of the following 9 layers, from superficial to deep:

1. The skin

2. The subcutaneous tissue

3. The palmar aponeurosis

4. The superficial volar arch and the median nerve

5. The flexor tendons, their sheaths and the lumbrical muscles

6. The deep palmar spaces

7. The deep volar arch and the ulnar nerve

8. The adductor pollicis and the interosseus muscles

9. The metacarpal bones

Skin. The skin of the palm is thicker, coarser and more vascular than that of the dorsum of the hand. It is thin over the thenar eminence and especially thick over the heads of the metacarpals. It is free from hairs and sebaceous glands but is well supplied with sweat glands. Two transverse skin creases (proximal and distal) are present in the palm. The proximal crease accommodates movements of the index finger and approximately marks the convexity of the superficial volar arterial arch. The distal crease accommodates movements of the medial 3 digits and marks the heads of the 3rd, the 4th and the 5th metacarpals. A vertical palmar crease which limits the thenar eminence also is present. A series of longitudinal grooves extend from the roots of the fingers toward the palm; between these grooves are raised intervals of fatty tissue. The grooves correspond to the digital slips of palmar fascia, and the raised intervals mark the lumbrical spaces, which contain the digital vessels, the nerves and the lumbrical muscles. The palmar region of the hand receives its cutaneous nerve supply from the following nerve branches: the palmar cutaneous branch of the median nerve arises about 1 inch above the wrist, passes obliquely downward behind the flexor carpi radialis tendon and pierces the deep fascia between that tendon and the tendon

FIG. The skin creases and the cutaneous nerve supply of the palmar region.

 

of the palmaris longus. It then descends, branching as it goes, to supply the skin of the hollow of the palm. The palmar cutaneous branch of the ulnar nerve is very slender and at times is difficult to find. It arises at a variable point below the middle of the forearm and passes downward over the ulnar artery; it pierces the deep fascia near the wrist and supplies the skin over the medial third of the palm. The terminal part of the radial nerve pierces the deep fascia about 2 inches above the styloid process of the radius at the lateral border of the front of the forearm. It descends, crossing the tendons that overlie the lateral surface of the distal end of the radius, and supplies the skin over the thenar eminence. The palmar digital nerves are 7 in number; 2 arise from the ulnar nerve and are distributed to the little finger and the medial half of the ring finger. The others arise from the median nerve and are distributed to the outer 3 ½ digits. These nerves are accompanied by the palmar digital vessels, which are in front of them in the palm but behind them at the sides of the fingers. They supply the joints of the digits and the soft parts on the sides and the front of the fingers. Each nerve terminates at the end of the digit by dividing into 2 branches, one of which enters the pulp of the digit and the other the bed of the nail. Subcutaneous Tissue. The skin is bound to the palmar aponeurosis by fibrous septa, between which quantities of granular fat are present. This fat constitutes the subcutaneous tissue. Over the ball of the thumb (thenar eminence) and the ball of the 5th finger (hypothenar eminence) this fat is not so plentiful or granular. Where skin creases are found, subcutaneous fat is present in small amounts or is absent entirely; hence, perforating injuries are serious in these locations. The palmaris brevis muscle is a superficial sheet of muscle which arises from the flexor retinaculum and the ulnar margin of the palmar aponeurosis. It passes medially, superficial to the ulnar vessels and nerve, and inserts into the skin of the ulnar border of the hand. The superficial branch of the ulnar nerve supplies it. This muscle

FIG. The palmar aponeurosis. The triangular intermediate part is thick and strong, but the medial and the lateral parts are thin and weak.

 

raises the skin and the fascia over the hypothenar eminence when the fingers bend; this enables the hand to grasp more firmly. The webs of the fingers are present over the palm of the hand but are absent on the dorsum. In these webs transverse fibers (superficial transverse ligaments) are found. These should not be confused with the superficial transverse metacarpal ligaments, which are incomplete and pass across the webs just anterior to the digital vessels and nerves. The palmaris brevis muscle (ulnar nerve) is thin and subcutaneous and lies across the uppermost inch of the hypothenar eminence, hiding the termination of the ulnar artery and nerve. It arises from the flexor retinaculum and the palmar aponeurosis and is inserted into the skin of the ulnar border of the hand. If the palm of the hand is placed in the position of scooping up water, the skin over the hypothenar eminence is thrown into wrinkles caused by the action of the palmaris brevis. This muscle must be severed and reflected before the hypothenar fascia and muscles become visible. The Palmar Aponeurosis. This deep palmar fascia is divided into medial, lateral and intermediate parts. The medial and the lateral portions are thin and weak, and they extend over the hypothenar and the thenar eminences, respectively. The intermediate part is thick and strong and is the palmar aponeurosis proper. It is triangular in shape, with its apex placed proximally, where it becomes continuous with the palmaris longus tendon and the flexor retinaculum. Opposite the distal transverse palmar crease it divides into 4 slips, one going to each finger. Between these slips the digital vessels and nerves and the lumbrical muscles

FIG. The volar arches and the median and the ulnar nerves. The superficial volar arch is formed mainly by the ulnar artery and a small branch of the radial artery; the deep volar arch is formed mainly by the radial artery and a small branch of the ulnar artery.

 

are located. Each slip divides into 2 processes between which the flexor tendons pass. These processes diverge and attach along the inner and outer aspects of the proximal phalanges and to the proximal part of the second phalanges. They are continuous with the fibrous flexor sheath and assist in flexion; they also bind the flexor tendons to the front of the fingers. A spontaneous contracture of the palmar fascia results in a flexion of the fingers which is known as Dupuytren's contracture. At the base of the palmar fascia the diverging slips are connected to one another by transverse fibers called the superficial transverse metacarpal ligaments. In order to avoid confusion concerning these ligaments, it is wise to recapitulate: (1) The superficial transverse (palmar) ligament appears in the webs of the fingers as a thin band of transverse fibers. It stretches across the roots of the 4 fingers; however, at times it is incomplete. (2) The superficial transverse metacarpal ligament is a part of the palmar aponeurosis which connect the diverging slips of fascia. (3) The deep transverse metacarpal ligament holds the heads of the metacarpal bones together on their palmar surfaces. (4) The dorsal transverse metacarpal ligament holds the heads of the metacarpal bones together on their dorsal aspect. Between the 4 digital processes of the central portion of the palmar fascia are 3 intervals. These are occupied by fat in which is imbedded the digital arteries, the nerves and the lumbrical muscles. Corresponding to these intervals, in the distal part of the palm, are 3 slight elevations. If the palm is inspected, it is noticed that these elevations are bounded by 4 vertical depressions which mark the fusion of the digital processes of the palmar fascia with the fibrous sheath containing the flexor tendons. These elevations mark 3 intervals of surgical importance which have been referred to by such names as commissural spaces, lumbrical canals or web spaces. They are important because infections extending from the subcutaneous tissue of the finger to the subaponeurotic spaces of the palm must pass by way of these spaces. The space is bounded anteriorly by the superficial transverse palmar ligament, posteriorly by the deep transverse metacarpal ligament and laterally by the digital processes of the palmar fascia which fuse with the theca (fibrous tendon sheath). Their contents are fatty tissue, lumbrical muscle and the digital vessels and nerves. The superficial volar (palmar) arch lies immediately beneath the palmar aponeurosis and upon the branches of the median nerve. It is formed by a continuation of the ulnar artery and one of the 3 branches of the radial artery (superficial palmar, princeps pollicis or radial indicis). The anastomosis between the ulnar artery and the radial branch is so complete that both ends require ligation when the arch is cut. The arch lies superficial to the flexor tendons, the lumbrical muscles and the digital branches of the median nerve in the hand. These digital vessels and nerves cross each other in their trip through the palm: hence, in the fingers the nerve lies superficial to the vessels. The medial 3 ½ fingers are supplied by the arch through 4 digital vessels. The branch to the 5th finger does not bifurcate but travels along the ulnar border of this finger. The other 3 digital branches bifurcate in the 2nd, the 3rd and the 4th finger webs, each being distributed to its respective finger borders. The proximal transverse palmar skin crease marks the convexity of the arch.

The median nerve enters the palm behind the transverse carpal ligament, and at the distal border of the ligament it breaks up into lateral and medial divisions. The lateral division supplies the thenar muscles (recurrent branch), both sides of the thumb and the radial side of the index finger. The digital branch to the index finger supplies a branch which innervates the first lumbrical muscle. There are 2 medial divisions; both bifurcate to supply the adjacent sides of the index, the middle and the ring fingers. From the first of these divisions the nerve supply to the second lumbrical is derived. Therefore, the motor part of the median nerve supplies 5 muscles: the 3 thenar muscles (abductor pollicis brevis, opponens pollicis and flexor pollicis brevis) and the 2 lateral lumbricals (lumbricals 1 and 2). The sensory fibers of the median nerve supply the lateral 3 ½ fingers and the corresponding part of the palm. Flexor Tendons, Their Sheaths and the Lumbrical Muscles. As the flexor tendons (sublimis, profundus and pollicis) pass under the transverse carpal ligament and into the palm they are provided with 2 sheaths: a fibrous and a synovial. The fibrous sheaths of the thumb and the little finger are similar in construction to those of the middle 3 fingers. With the underlying bone, they form strong osteofascial tunnels which retain the tendons in place. A pair of tendons (sublimis and profundus) pass under each fibrous flexor sheath. The sheaths attach to the lateral and the medial borders of the phalanges. In front of the joints they are pliable and thin, but in front of the bodies of the proximal and the middle phalanges the fibers are curved transversely and are strong. These structures (flexor retinaculum, palmar aponeurosis and fibrous flexor sheaths) constitute a single continuous fibrous plate, the main function of which is to hold the tendons in position and to increase their efficiency. The arrangement of the fibrous flexor sheaths converts part of the tendon sheaths into cul-de-sacs. Directly beneath these resisting bands, the space is restricted greatly, so there is little or no room for pus. On the other hand, toward the finger end in front of the second joint and also in front of the metatarsophalangeal joint, dilatations in which pus may collect exist. In contradistinction to the arrangement in the foot, the palmar aponeurosis gives no fibrous extension to the thumb. The wide range of motion of the thumb is due to this fact and is characteristic of the human hand. The synovial or mucous sheath is a lubricating device in tubular form which ensheaths a tendon. These are necessary for the flexor tendons, since they rub on the back of the flexor retinaculum during flexion of the wrist, and during extension they rub against the carpal bones and the anterior margin of the lower end of the radius. Therefore, these tendon sheaths act as bursae. The sheath forms a sac which is closed at both ends and is made up of glistening, endothelial-lined membranes. Each within its sheath has or did have a mesotendon (which is a double layer of synovial membrane attaching the tendon to the wall of the sheath and carrying vessels to it. It is attached to the side of the tendon which has least friction. The flexor tendons (sublimis, profundus and pollicis) must have these sheaths, first, where they pass through the osseofibrous carpal tunnel and, then, where they pass through the osseofibrous digital tunnel. Therefore, there are carpal synovial and digital sheaths. However, in the thumb the sheath is always in continuity, but that of the 5th finger may fail to unite in about 10 per cent of the cases and thus be identical with that of the other fingers.

FIG. Distribution of the median nerve. The median nerve has both sensory and motor fibers. Its motor fibers supply 5 muscles of the hand, namely, the 3 thenar thumb muscles and the first 2 lumbricals.

 

The sheaths of the index, the middle and the ring fingers remain separate. The carpal sheaths of the 4 sublimis and the profundus tendons become one and are then known as the common flexor (carpal) sheath; this has a laterally placed mesotendon. The digital synovial sheaths of fingers 2, 3 and 4 extend from the neck of the metacarpal bone to the base of the third phalanx, where the profundus tendon ends. Over the middle third of these metacarpal bones the corresponding tendons have no sheaths. The common flexor synovial sheath extends for about ½ to 1 inch above and below the flexor retinaculum. The sheaths investing the tendons to the 5th finger as a rule continue proximally without interruption to join the common flexor sheath at the wrist. This common flexor sheath, with its extension along the little finger, is called the ulnar bursa. The tendon of the thumb has a sheath which extends from the base of the last phalanx to 1 inch beyond the proximal border of the wrist joint; this is called the radial bursa. These two bursae have been discussed elsewhere; they may be separate or they may communicate with each other. Should they communicate, an infection can spread easily from one sheath to the other. Thus, in a tenosynovitis of the thumb, the infection may extend along the sheath and infect the sheath of the little finger via such a communication. The radial and the ulnar bursae lie on the front of the carpus and are separated from the wrist and the intercarpal joints only by ligaments. Therefore, these joints may become infected from such suppurative processes. Certain portions of the original mesotendons of the flexors may remain as triangular folds, vincula, which pass between the tendons and the phalanx. The blood vessels run in the vincula to the tendons as they would in any mesentery. Scheldrup has described certain variations in tendon sheath patterns in the hand and has worked out their frequency statistically. It is his opinion that the generally accepted anatomic pattern is present in 71.4 per cent of cases. He has described 8 separate and different types of anastomoses. These are important to keep in mind, since they may alter the spread of infection in tenosynovitis. Opposite the base of the proximal phalanx the sublimis tendon divides so that the profundus tendon can pass to its insertion into the volar aspect of the base of the distal phalanx. The slips of the sublimis tendon insert into the volar surface of the base and the sides of the middle phalanx. The lumbrical muscles are 4 fleshy muscles that arise from the tendons of the flexor digitorum profundus and insert into the radial side of the tendinous expansions of the extensor digitorum communis of the medial 4 fingers. They are peculiar in that they arise from flexor tendons and insert into extensors. Each lumbrical muscle passes to the radial side of the corresponding finger and is accompanied by the digital vessels and nerves. They lie behind the vessels and the nerves and on the deep transverse metacarpal ligament; the interossei lie behind this ligament. The lateral 2 lumbricals arise by single heads from the radial sides and the volar surfaces of the deep tendons of the index and the middle fingers.

FIG. Arrangement of a tendon sheath.

 

FIG. The synovial sheaths.

 

FIG. Arrangement of the flexor tendon sheaths in the fingers, the hand and the wrist. The ulnar bursa has been divided into its 3 component parts.

 

FIG. Some of the variations in tendon sheath patterns and their statistical frequencies according to Scheldrup.

 

FIG. Insertion of the flexor tendons. The sublimis separates, and the profundus perforates.

 

The medial two each arise by 2 heads from adjacent sides of the tendons of the middle, the ring and the little fingers. These slender muscles end in delicate tendons which pass backward across the lateral surface of the metacarpophalangeal joint and connect with the expansion of the extensor tendon. It is inserted with the tendon of an interosseous muscle into the base of a terminal phalanx. They flex the finger at the metacarpophalangeal joints but extend them at the 2 interphalangeal joints through the medium of the extensor expansions. The action of the muscle is interesting, since in suppurative tenosynovitis of the flexor tendons and their sheaths, complete loss of function may result; yet often the patient can flex the metacarpophalangeal joint by means of the lumbrical muscles. The lateral 2 lumbricals are supplied on their superficial surface by the median nerve. The medial two are supplied on their deep surface by the deep branch of the ulnar nerve. The lateral two arise by single heads, and the medial lumbricals arise by double heads. This fact is important because it explains the formation of a fibrous septum which divides the palm into midpalmar and thenar spaces. Any fibrous septum (partition) which extends from the palmar aponeurosis deep into the palm is interrupted by the double-headed lumbricals which are associated with the 4th and the 5th fingers. However, such a lamina can be carried back on the lateral side of the belly of the 2nd lumbrical throughout its entire extent and insert onto the 3rd metacarpal bone. In this way a fibrous partition is formed which passes from the undersurface of the palmar aponeurosis to the 3rd metacarpal bone. This fibrous septum is the fascial investment of the 2nd lumbrical muscle. Such a partition also could be associated with the 1st lumbrical muscle, but because of the greater mobility of the 2nd digit, the fibrous tissue associated with its lumbrical is lax and thin and forms no barrier across the palm. In this way 2 spaces are formed: a middle palmar and a thenar.

FIG. The 4 lumbrical muscles.

 

FIG. Fascia of the lumbrical muscles. The fascia of the second lumbrical forms the fibrous septum which separates the thenar from the midpalmar space.

 

Deep Palmar Spaces. These spaces exist between the deep flexor tendons and the lumbrical muscles on the palmar side, and also between the interosseous fascia covering the metacarpal bones and the interosseous muscles dorsally. Localization of pus in this space and the spread of dyes when injected under pressure indicates that it is divided into two compartments. The work of Kanavel and Spaulding has shown that the lumbrical fascia of the second lumbrical passes to the lateral side of the muscle, thereby producing one complete anterposterior septum which passes from the palmar aponeurosis to the 3rd metacarpal bone.

FIG. The 2 palmar spaces. (A) The thenar space is laterally placed, and the midpalmar space is medial. (B) The posterior boundaries of the 2 spaces.

 

This septum divides the deep palmar space into two: a thenar space laterally and a midpalmar space medially. The thenar space lies under the outer half of the hollow of the palm; it has a roof, a floor and lateral and medial walls. The roof is made up of the flexor tendons, the lumbricals of the 2nd digit, and the thenar muscles. The floor is formed by the 2 heads of the adductor pollicis, particularly its transverse head. The medial wall is made up of the fibrous septum (fascia of the 2nd lumbrical muscle), and the lateral wall is formed by the flexor pollicis longus tendon and its synovial sheath. This space may be mapped out on the hand proximally from the distal border of the anterior annular ligament to the transverse palmar crease distally. The 1st lumbrical sheath extends as a distal diverticulum of the space. The midpalmar space lies in the inner half of the hollow of the hand; it has a roof, a floor and lateral and medial walls. The roof is made up of the flexor tendons and the lumbricals of the medial 3 digits. The floor consists of the dense fascia covering the medial 2 ½ metacarpal bones and their corresponding interosseous muscles. The lateral wall is made up of the fibrous septum described above and separates it from the thenar space. The medial wall is made up of the hypothenar muscles, which are separated from the midpalmar space by the attachment of the palmar aponeurosis, which passes to the 5th metacarpal bone. Distally, the space extends almost to the level of the distal palmar crease; proximally, it reaches the level of the distal margin of the transverse carpal ligament. The midpalmar space is connected potentially with the so-called Parona's retroflexor space. It has been referred to as the forearm space and has the following boundaries: anteriorly, the flexor digitorum profundus (ulnar bursa) and the flexor pollicis longus in its synovial sheath (radial bursa); posteriorly, the pronator quadratus and the interosseous membrane; proximally, it is continuous with the intermuscular spaces of the forearm; distally, it reaches the level of the wrist; and laterally, the space extends to the outer and the inner borders of the forearm. It is along these lateral borders that the space is drained by incisions. The Deep Volar Arch. Two arteries take part in the formation of the deep volar arch: the radial and the deep branch of the ulnar. The radial artery plays the chief part in its formation. On leaving the forearm, the radial artery winds around the radial side of the wrist and crosses the dorsal surface of the navicular and the trapezium (greater multangular). It then passes through the anatomic snuffbox (abductor pollicis longus, extensor pollicis brevis and extensor pollicis longus) to gain entrance to the proximal end of the first interosseous space. It continues medially and, in the palm, appears between the oblique and the transverse heads of the adductor pollicis. It turns medially and joins the deep branch of the ulnar artery at the base of the 5th metacarpal bone. The arch thus formed passes across the metacarpal bones immediately distal to their bases. The deep arch is about a fingerbreadth nearer the wrist than is the superficial; its convexity is directed toward the fingers. The deep branch of the ulnar nerve lies in its concavity. This arch lies deep to the flexor tendons and upon the volar interosseous muscles. Three arteries usually arise from the radial: the superficial palmar, which supplies the thenar eminence; the princeps pollicis to the thumb; and the radial indicis, which passes along the lateral aspect of the index finger.

FIG. The retroflexor space of Parona.

 

FIG. The adductor pollicis muscle. The radial artery divides its origin into 2 heads: a transverse and an oblique.

 

The deep arch usually supplies the 3 palmar metacarpal arteries, which pass between the fingers and unite with the digital branches of the superficial arch. The ulnar nerve enters the palm between the volar carpal and the transverse carpal ligaments. It divides into superficial and deep branches in the region of the hamate bone. The superficial branch supplies sensory fibers to the little finger and the ulnar side of the ring finger. The deep branch is motor; it supplies all the muscles of the palm of the hand, with the exception of the 5 supplied by the median nerve. Therefore, the deep branch of the ulnar nerve supplies the 3 hypothenar muscles, the 7 interosseous muscles, the medial 2 lumbricals (3 and 4) and the adductor pollicis. This branch passes to the medial side of the hook of the hamate bone and dips into the palm through the cleft between the abductor and the flexor of the little finger. It runs transversely across the palm and is accompanied by the deep volar arch. As it crosses, it lies behind the flexor tendons and on the interossei and it terminates in the adductor pollicis. Since it supplies most of the muscles of the hand which are responsible for the fine movements of the hand, it has been called the "musician's nerve."

Adductor Pollicis Muscle. The triangular adductor pollicis muscle lies in the depth of the palm and arises from the palmar border of the 3rd metacarpal and its corresponding carpal bone, the capitate. The radial artery divides the origin of the muscle into 2 heads: a transverse (distal) and an oblique (proximal) head. It inserts into the base of the 1st phalanx of the thumb. Although the muscle lies deep in the palm, its distal edge is subcutaneous and can be exposed by removing the skin and the fascia of the 1st interdigital web. It forms the floor of the thenar space. Its contraction draws the thumb across the palm and thus keeps the thumb and the palm approximated to each other. This action should not be confused with the action of the opponens, which approximates the tip of the thumb to the tip of the 5th finger. The interosseous muscles are 7 in number: 4 dorsal and 3 palmar. They are supplied by the deep branch of the ulnar nerve. The 4 dorsal interossei arise by double heads from the adjacent sides of the 5 metacarpals. On the palmar surface, the adductor pollicis arises from the 3rd metacarpal and inserts into the thumb. This leaves only the 2nd, the 4th and the 5th metacarpals free, and so it is that these give rise to the single heads of the 3 palmar interossei. The interossei insert into the bases of the proximal phlangeal and the extensor expansions.

FIG. The interossei: (A) the 3 palmar interossei; (B) the 4 dorsal interossei.

 

FIG. The metacarpal bones. The origins of the muscles are shown in red; the insertions, in blue.

 

 

FIG. The 3 thenar (thumb) muscles. These are the abductor pollicis brevis, the flexor pollicis brevis and the opponens pollicis. The last lies in a deeper plane than the other 2. The recurrent branch of the median nerve supplies this entire group.

 

Since their tendons pass backward and across the metacarpal joints to reach their insertions, they aid in flexing these joints. They are inserted by means of the extensor expansions into the bases of the terminal phalanges and aid in extending the interphalangeal joints. However, their main action is abduction and adduction. The dorsal interossei are abductors, and the palmar interossei are adductors. An injury to their nerve supply, the deep branch of the ulnar nerve, produces a characteristic deformity of the hand. When the interossei are paralyzed, they no longer can act as flexors of the metacarpophalangeal joints. Then the extensors are unopposed and bend the fingers backward at these joints; neither can the interossei act as extensors of the interphalangeal joints. Therefore, the flexors bend the fingers forward at these interphalangeal joints. The result is a typical main en griffe or "claw hand." The interossei pass dorsal to the deep transverse metacarpal ligament; this ligament separates them from the lumbricals. The dorsal metacarpal ligament joins the heads of the metacarpal bones of the fingers together posteriorly. With the deep transverse ligament it forms 3 osseofibrous tunnels between the 4 fingers in which the palmar and the dorsal interosseus muscles lie. Metacarpal Bones. The 5 metacarpal bones form the skeleton of the palm, articulate with the distal row of the carpus and diverge slightly as they extend distally to articulate with the phalanges; each has a base, a shaft and a head. The proximal ends (bases) are somewhat expanded and present articular surfaces; proximally, these articulate with the carpal bone, and at the sides there are one or more articular surfaces for articulation with each other. There are distinguishing features on the bases: the second is notched for the trapezoid, the medial margin of the notch articulates with the capitate, and the lateral boundary articulates with the trapezium. The base of the 3rd metacarpal articulates with the capitate; it has a short styloid process extending upward from its dorsolateral part. The fourth base is cuboidal and articlulates with the hamate and slightly with the capitate bones. The fifth has a tubercle on its medial side and a metacarpal facet on its lateral side. The shafts of the bones are 3-sided, each presenting a flat surface toward the dorsum and a smooth ridge toward the palm of the hand. Each shaft is curved longitudinally, with a palmar concavity and is prismatic on transverse section, revealing dorsal, lateral and medial surfaces. The anterior border of the 3rd metacarpal body is almost monopolized by the transverse head of the adductor pollicis. The 2nd, the 4th and the 5th bodies present the attachments of the 3 palmar interossei. The anteromedial and the anterolateral surfaces of the 5 digits give origin to the 2 heads of the 4 dorsal interossei. The heads of the medial 4 metacarpal bones are convex and smooth distally, and they articulate with the phalanges and the palmar ligaments which are attached to the shafts immediately above the heads. At these metacarpophalangeal joints the prominences of the knuckles are formed by the distal aspects of the heads of the metacarpal bones. The first metacarpal bone (thumb) is usually discussed alone because it is the shortest and most movable of all. Its dorsal surface is the same breadth throughout and shows no sign of the flattened triangular areas which differentiate the dorsal aspect of the shaft of the other metacarpal bones. The base of this bone is saddle-shaped and articulates with the trapezium. Thenar and Hypothenar Eminences. The 3 thenar {thumb) muscles are the abductor pollicis brevis and the flexor pollicis brevis, which are superficial, and the opponens pollicis, which lies deeper. They all are supplied by the recurrent branch of the median nerve. These muscles lie to the radial side of the flexor pollicis longus tendon and make up the thenar eminence. They are supplied by the recurrent branch of the median nerve, which turns back after appearing from under the distal margin of the transverse carpal ligament. Since the deep fascia is very thin over this area, this important nerve is almost subcutaneous and is unprotected. A guide to it is the superficial palmar branch of the radial artery, which lies medial to it. The 3 thumb muscles arise together from the transverse carpal ligament and the lateral carpal bones (navicular and greater multangular). The abductor pollicis brevis muscle forms the upper or lateral part of the ball of the thumb. It is inserted into the lateral side of the base of the proximal phalanx of the thumb. Its action pulls the thumb directly forward so that it comes to lie at right angles to the plane of the palm. The flexor pollicis brevis muscle is medial to the abductor and inserts with it. Its action produces flexion at the metacarpophalangeal joint of the thumb. The opponens pollicis muscle is visible only after the other two have been divided. Its fibers spread out and insert into the lateral half of the palmar surface of the first metacarpal bone. At times it is separable into superficial and deep laminae. Its action brings the metacarpal bone of the thumb across the palm of the hand, and also rotates it medially so that the pad of the tip of the thumb faces and comes into contact with the pads of the tips of the other fingers. This action should not be confused with adduction. The nerve to these muscles is seen after the superficial muscles are reflected. It is a short branch which, having given off superficial twigs to the flexor brevis and the abductor, passes between these two to enter the opponens. The three muscles are segregated from the central space of the palm by a fascial sheet which passes dorsally (under the muscles) from the radial edge of the palmar aponeurosis and attaches to the first metacarpal bone. Therefore, pus formed among these muscles shows no tendency to spread to the palm. Incisions into this space should be placed laterally to avoid the median nerve. The 3 muscles of the hypothenar eminence correspond to those of the thenar group and are the abductor digiti quinti, the flexor digiti quinti and the opponens digiti quinti. They are supplied by the deep branch of the ulnar nerve. These 3 muscles originate from the transverse carpal ligament and from the medial 2 carpal bones (pisiform and hamate). The abductor digiti quinti muscle inserts into the medial side of the base of the proximal phalanx of the little finger. By its action it abducts the little finger from the axial line of the middle finger. The flexor digiti quinti muscle is inserted with the abductor. It is partly fused with the abductor and sometimes it is partly incorporated in the opponens. By its action it flexes the metacarpophalangeal joint of the little finger. The opponens digiti quinti muscle lies on a deeper plane and is inserted into the whole length of the medial part of the front of the 5th metacarpal bone. The deep branch of the ulnar nerve enters from the lateral side of the hypothenar eminence; hence, incisions into this space are made along the medial side. The space is separated from the central space of the palm by a septum similar to that described under the thenar eminence. This septum attaches to the 5th metacarpal bone.

DORSAL REGION OF THE HAND The surface anatomy of this region reveals the extensor tendons as being both visible and palpable over the dorsum of the hand. The metacarpal bones can be felt easily. In contrast with the palmar surface of the hand, the dorsal surface is covered with skin of finer texture which has numerous sebaceous glands and short hairs. The cutaneous nerve supply is derived from the dorsal rami of the ulnar, the radial and the dorsal antibrachial cutaneous nerves. The dorsal subcutaneous space is a rather extensive area of loose areolar tissue within definite boundaries. If infected, pus can spread quite readily over the entire dorsum of the hand. The dorsal subaponeurotic space should not be confused with the dorsal subcutaneous space. Over the dorsum of the hand the extensor tendons are united by oblique bands, thus forming an aponeurotic sheet; this is attached on each side to the 2nd and the 5th metacarpal bones. The dorsal subaponeurotic space lies between this sheet and the interosseous muscles; it is filled with loose connective tissue.

FIG. The dorsal subcutaneous and the subaponeurotic spaces.

 

FIG. The cutaneous nerve supply of the dorsum of the hand.

 

Pus in this space is limited distally at the metacarpophalangeal joints and proximally at the bases of the metacarpal bones. The extensor digitorum communis is enclosed with the extensor indicis in a synovial sheath which is in a compartment of the extensor retinaculum. It divides into tendons which diverge to the fingers. On the dorsal surface of the proximal phalanx each tendon expands to form the dorsal extensor expansion, which is inserted into the bases of the middle and the distal phalanges. It is supplied by the posterior interosseous nerve and, as its name suggests, it extends the phalanges and the hand. The extensor carpi radialis longus tendon is crossed by the extensors of the thumb; it is enclosed in a synovial sheath, with the

FIG. Diagrammatic presentation of the anatomy of a finger: (A) cross sectional study; (B) the superficial and the deep flexor tendons.

 

FIG. The tendons of the dorsum of the wrist and the hand.

 

extensor carpi radialis brevis, under the extensor retinaculum. The extensor digiti minimi tendon is ensheathed in the compartment of the extensor retinaculum that lies between the radius and the ulna. It is inserted with the tendon from the extensor digitorum to the little finger. The extensor carpi ulnaris tendon also is enclosed in a synovial sheath and is inserted into the base of the 5th metacarpal bone.

PHALANGES (FINGERS) The hand has a thumb and 4 fingers. Some authorities prefer to refer to the thumb as the first of 5 digits, but this is a matter of convenience rather than one of argument. The construction of all 5 fingers is essentially the same, except that the thumb has 2 phalanges and the other fingers have 3. The thumb also has a short thick metacarpal associated with it which adds to its strength and mobility. Skin. The skin of the flexor surface of the digits is thick, contains some subcutaneous fat, is only slightly mobile and is devoid of hair follicles. That over the dorsum is thinner, more mobile and has very little subcutaneous fat. The transverse flexor creases do not indicate the exact positions of the underlying joints. The proximal digital crease is distal to the metacarpophalangeal joint. The middle crease is a good guide to the joint, since it lies directly opposite it; the distal crease is somewhat proximal to the distal interphalangeal joint. Therefore, the only digital transverse crease that can be used as an exact landmark of the joint is the middle one. These creases are bound closely to the underlying flexor tendon sheaths by fibrous tissue strands. The amount of fat is minimal or even entirely absent beneath them; hence, a penetrating wound at the crease is likely to penetrate the underlying synovial sheath. The subcutaneous tissue over the flexor surface is made up of fibrous tissue enclosing small amounts of fat. These septa connect the skin to the fibrous layers of the tendon

FIG. The terminal phalanx and the distal closed space: (A) cross section; (B) longitudinal section.

 

sheath below and to the periosteum in the terminal phalanges. The last-named relationship is important in the treatment of a felon. The digital vessels and nerves run in this subcutaneous tissue layer. Distal Closed Space. The important distal closed space can be understood if the arrangement of the subcutaneous tissue is visualized properly. In the distal phalanx the subcutaneous tissue is arranged in such a way that it consists of a number of strong fibrous septa which radiate from the periosteum to the skin. In the compartments thus formed between these septa, fatty tissue is found. Therefore, the distal four fifths of the phalanx is converted into a closed space and, together with the diaphysis, receives its blood supply from the 2 palmar digital arteries which are found anterolateral to the bone. If a transverse section of the distal closed space is studied, it will be seen that dense connective tissue separates the subungual space or nail bed from the anterior closed space. The epiphysis receives its blood supply from the digital arteries before those vessels enter the closed space. If inflammatory exudates and edema occur within this space, the tension rises, shuts off the blood supply, and a necrosis of the diaphysis occurs. Even after the age of 20 and after union of the epiphysis and the diaphysis, necrosis usually is limited to the diaphyseal region alone, and new bone may grow from the epiphyseal end. The phalanges are the bones of the fingers. There are 14 in all, 3 (proximal, middle and distal) for each finger and 2 for the thumb. They are built on the same general plan as the metacarpals but are shorter, the distal phalanx being the shortest of all and having a rough distal end which underlies the tips of the fingers. The distal ends of the terminal phalanges are neither weight-bearing nor force-transmitting. The surface under the fingernail is smooth; the surface under the finger pad is rough, owing to the attachment of the fibrous bands which bind the skin to it. The dorsal aspect of the proximal and the middle phalanges is smooth, rounded and covered by the extensor expansions.

FIG. Suppurating callosity and web space infections: (A) path of extension of a suppurating callosity to a web (lumbrical) space; (B) incision into the abscess.

 

The palmar surfaces take part in the floor of the osseofibrous tunnel in which the flexor tendons run. The borders of the middle phalanx are more prominent because they receive the attachment of the slips for the insertion of the flexor digitorum sublimis tendon. The bases of the proximal phalanges articulate with the rounded knuckles and, therefore, are concave. The common volar digital arteries arise from the convexity of the superficial volar arch and give off digital branches which supply contiguous sides of the thumb and the fingers as well as the distal part of their dorsal surfaces. The proximal part of the dorsum of the fingers receives its arterial supply via the dorsal digital arteries, which arise from the dorsal metacarpal arteries from the dorsal carpal arch. On the fingers, the digital arteries and nerves run side by side in contact with the fibrous flexor sheath, not with the phalanges. Each of these vessels gives off a branch to the epiphysis of the terminal phalanx before entering the anterior closed space. The branches ramify across the anterior aspect of the phalanx, sending nutrient vessels to the bone. The digital nerve lies anterior or anteromedial to its fellow artery. The distribution of these nerves has been discussed elsewhere.

 

FIG. Infection of the ulnar bursa. (A) This bursa is usually infected as a result of extension from an infected tendon sheath of the 5th finger. The arrows indicate the possible paths of extension from the infected ulnar bursa to surrounding structures. (B) Combined digital and palmar incision. Accessory incisions are shown to drain Parona's retroflexor space.

 

 

SURGICAL CONSIDERATIONS

WEB SPACE INFECTIONS AND SUPPURATING CALLOSITY Web space infections may start as a suppurating callosity which spreads down toward the commissural or web space. The pus tends to spread backward or laterally. It can spread from one web to another and thus may involve 3 web spaces without going deeply. Since there are deficiencies in the palmar aponeurosis between its digital prolongations, the infection can burrow backward so that a "collar button" abscess is formed. Adequate drainage can be instituted by making an incision through the web between the fingers and continuing into the palmar aspect of the hand. TENOSYNOVITIS Tenosynovitis, or infection, in the tendon sheath of the little finger and the thumb is discussed under ulnar and radial bursae infections. Tenosynovitis of the middle, the ring and the index fingers has a tendency to remain localized, since the sheath ends in the region of the heads of the metacarpal bones. The incision which drains a digital tenosynovitis should be made at the side of the sheath and at the site of the known infection. The incision is carried along the shaft of the proximal and the middle phalanges but usually leaves that part which is over the joint untouched to prevent herniation of the tendon. INFECTION OF THE ULNAR BURSA Infection of the ulnar bursa usually results from an extension of an infection in the flexor tendon sheath of the little finger. Perforating wounds, an infected midpalmar space and infections of the tendon sheath of the middle or the ring fingers may also spread to this bursa. In the last case, the pus breaks through the proximal end of the synovial sheath, passes along the lumbrical muscle into the midpalmar space and from there secondarily involves the ulnar bursa. An infection of the ulnar bursa may spread to the underlying bone or joint, to the lumbrical canal, to the middle palmar space, to the radial bursa or into the wrist. Since this condition usually results from extension of a tenosynovitis of the little finger, the treatment of the latter should becarried out first. The incision is placed either on the lateral or the medial side of the finger and is carried down into the palm and into the hypothenar eminence.

FIG. Infection of the radial bursa. (A) This bursa is usually infected as a result of extension from an infected tendon sheath of the thumb. The arrows indicate the possible paths of spread from the infected radial bursa to surrounding structures. (B) The incisions used in the treatment of an infected radial bursa and flexor poUicis longus tendon.

 

FIG. The infected thenar space. (A) The arrows indicate the possible paths of extension into the thenar space. (B) Drainage of the infected thenar space.

 

The tendon sheath may be absent between the little finger tendon sheath and the ulnar bursa. This should be kept in mind in order to avoid contaminating a healthy bursa. The combined palmar and digital incision makes it possible to drain both the tendon sheath of the 5th finger and the ulnar bursa at the same time. It extends to the flexor retinaculum. If the infection has extended into the forearm, an incision is placed

FIG. The infected midpalmar space. (A) The arrows indicate the possible paths of extension into the midpalmar space. (B) Drainage of the infected midpalmar space.

 

along the ulna. Accessory incisions on the radial side may be necessary sometimes for through-and-through drainage of Parona's retroflexor space. INFECTIONS OF THE RADIAL BURSA Infections of the radial bursa usually arise from an infected tendon sheath of the flexor pollicis longus, an infected ulnar bursa or an infected thenar space. The infection may spread from the flexor pollicis longus to the interphalangeal joint, the bone, the ulnar bursa, the thenar space or under the anterior annular ligament and into the wrist. The incision for an infected radial bursa and flexor pollicis longus tendon starts as an anteromedial incision at the distal volar skin crease and extends through the thenar eminence down to within 1 ½ inches of the anterior annular ligament, but no farther. This precaution is taken because the motor branch of the median nerve to the thenar muscles is in this region (the dime area). The bursa itself should be drained in the forearm via the approach described under ulnar bursitis; this permits drainage of both bursae and, unlike the approach from the radial side, involves no risk to the radial artery. INFECTIONS OF THE THENAR SPACE Infections of the thenar space occur as a result of a perforating wound directly into the space or following a tenosynovitis of the index or the middle finger, abrasions of the thumb, radial bursitis and midpalmar space abscesses. Abscesses of this space occasionally have been reported following osteomyelitis of the 1st, the 2nd or even the 3rd metacarpal bones. When it follows a tenosynovitis of the index finger, as it usually does, the cellulitis of the tendon sheath extends downward and bursts through the proximal end of the sheath; it then comes to lie in the loose areolar tissue around the lumbrical muscle which guides it into the thenar space. The pus lies anterior to the adductor muscle of the thumb, and ballooning of the web between the thumb and the index finger becomes visible. The treatment is immediate incision and drainage, the incision being placed along the anterior border of the lateral side of the 2nd metacarpal bone or along the web between the thumb and the index finger. A hemostat is placed into the space between the flexor tendons and the adductor pollicis. Pus may accumulate behind the adductor muscle, and an incision placed as described above can drain both anterior and posterior adductor partitions of the thenar space. The hemostat which is placed into the thenar space should not be thrust past the middle metacarpal bone because the fascial septum may be perforated and the midpalmar space contaminated.

FIG. Felon. (A) and (B) "Fishmouth" type of incision. (C) Closed space arrangement of the distal phalanx. (D) and (E) "Hockey-stick" type of incision.

 

INFECTIONS IN THE MIDPALMAR SPACE Infections in the midpalmar space occur from a tenosynovitis involving one or any of the 3 medial digits, from an infected ulnar bursa or from osteomyelitis of the underlying metacarpals. The condition also may be caused by extension from an infected thenar space, direct penetrating wounds or from infections of one of the medial 3 web spaces traveling along a lumbrical muscle. When the midpalmar space is involved, the concavity of the palm is lost. Since direct attack on the space would endanger too many structures, effective drainage can be obtained via a lumbrical space by opening a web between the ring and the middle finger or the ring and the little finger. In this way a hemostat can be placed beneath the flexor tendons and into the midpalmar space. It should not be thrust past the middle metacarpal bone, since this in turn may involve the thenar space. FELON (WHITLOW) Felon (whitlow) is an infection of the anterior closed space of the finger; it is extremely painful, common and dangerous. The connective tissue arrangement accounts for the fact that if pus develops here, it has no means of escape and produces marked pressure. This shuts off the blood supply and causes early necrosis. Since the epiphysis (base of the bone) receives its blood supply from vessels which do not pass through this space, it does not become necrotic, as does the rest of the bone, and new bone can grow from it, especially in the young. A "hockey stick" incision or "fish mouth" type of incision may be used to establish adequate drainage and open these spaces. Incisions of this type place the scar away from the very sensitive tactile surface of the finger. A midline incision is an error, since the drainage produced would be inadequate, the tactile sense interfered with and the flexor tendon sheath possibly could be involved. PARONYCHIA Paronychia is an acute infection involving the subepithelial tissue at the side of the nail. If incised and drained early, no ill effects result, but, if neglected, the infection may spread along the side and the base of the nail, forming a so-called "run around." The pus may lodge beneath the overlying epithelium (eponychium) and then travel underthe nail itself, forming a subungual abscess. In the treatment of paronychia, a lateral incision should be made over the point of maximum tenderness; bilateral incisions should be used if

 

 

FIG. Treatment of uncomplicated and complicated paronychia.

 

the infection has run around the nail. If a subungual abscess results, an eponychial flap is raised, and the nail bed is removed, for the nail acts as a foreign body in the subungual abscess cavity. The distal portion of the nail is not removed, as it protects the underlying sensitive tissue. FRACTURES OF THE METACARPAL BONES The metacarpal bones frequently are fractured when the fist is clenched and a blow is struck. McNealy and Lichtenstein have emphasized the important points regarding the mechanism and the treatment of hand fractures. In metacarpal bone fractures exclusive of the thumb, a typical deformity results, which is characterized by shortening of the bone due to bowing of the fragments. This results in a dorsal projection at the fracture site and volar displacement of the metacarpal head because of the action of the interosseus muscle which flexes the proximal phalanx. The distal fragment of the metacarpal bone is attached to the proximal phalanx through the metacarpophalangeal joint and is drawn into a flexed position. An inverted-V deformity is typical for fractures of the metacarpal bones and requires immobilization on a straight dorsal splint. This removes the deformity and restores the normal horizontal contour to the dorsum of the hand. The 3rd and the 4th metacarpal bones are splinted laterally by their adjacent metacarpals, but the 2nd and the 5th, lacking such support, require lateral splinting in addition to the dorsal. The usual deformity in fractures of the first metacarpal (thumb) is adduction of the distal fragment and abduction of the proximal. The treatment for such fractures is abduction, which overcomes the contraction of the abductor muscles and maintains the web of the thumb. In a Bennett's fracture (fracture of the base of the first metacarpal), abduction may fail to restore the alignment of the bones and, in addition to abduction, traction may be necessary. DISLOCATION OF THE METACARPOPHALANGEAL JOINTS Dislocation of the metacarpophalangeal joints occurs frequently because of their ballandsocket arrangement. Dislocation of the thumb occurs usually after a fall which produces forceful dorsiflexion on the hyperextended hand. This results in a tear in the glenoid (volar accessory) ligament and permits the phalanx to pass backward. The resultant deformity is typical, as the proximal phalanx comes to rest on the dorsal aspect of the thumb metacarpal. The head of the metacarpal is caught between the tendons of the flexor pollicis brevis and the flexor pollicis longus. Because of this, reduction cannot be accomplished with traction alone, but the joint must be hyperextended almost to a right angle, followed by pressure at the proximal end of the phalanx to force it over the head of the metacarpal. Should this fail, it becomes necessary to make an incision and enlarge the opening in the capsule so that reduction may be accomplished. Dislocations of the middle and the distal phalanges occur quite frequently and usuallyare produced by a blow struck at the tip of the finger. They may be accompanied by a fracture and, since the extensor tendon usually is ruptured at its insertion into the base of the terminal phalanx, a "dropped finger" or "loose ball finger" results. The extensor tendon does not retract because of its attachment along its lateral expansion. FRACTURES OF THE PHALANGES Distal Phalanx. In fractures of the distal phalanx, the distal part of the bone is not subject to pull of either intrinsic or extrinsic muscles; therefore, displacement is minimal, even

 

FIG. Fractures of the proximal and the middle phalanges.

 

if crushing is marked. The fingernail may be used as a suitable splint, and the fragments can be molded into place. Fractures involving the proximal portion of the terminal phalanx are affected by the pull of the flexor digitorum profundus and the extensor digitorum communis. This is the same injury described under "dropped finger." Hyperextension usually aligns the fragments and can be maintained by some such splint as described by Lewin. Middle Phalanx. The deformity and the treatment of fractures of the middle phalanx depend on whether the fracture is proximal or distal to the insertion of the flexor digitorum sublimis. If it is distal, then flexion of the proximal fragment and dorsal displacement of the distal fragment result. When the fracture is proximal to the tendon insertion, flexion of the distal fragment, with the proximal fragment in an extended position, results. Therefore, a fracture distal to the tendon insertion produces a V-shaped deformity, but a fracture proximal to the tendon insertion produces an inverted V-shaped deformity. A straight splint will correct the deformity in a fracture proximal to the tendon insertion, and a curved volar splint will correct the deformity found in a fracture distal to the tendon insertion. Proximal Phalanx. In fractures of the proximal phalanx, flexion of the proximal fragment is produced by the pull of the interosseous and the lumbrical muscles, and dorsal displacement is brought about by the action of the lumbrical muscles. This results in a V-shaped deformity which can be corrected by a curved splint, which approximates the broken ends of the bone.

 

 

RECOMMENDED LITERATURE:

1.     Mark W. Wolcott. Ambulatory Surgery End The Basic Of Emergency Surgical Care.-Philadelphia:J.B.Lippincott Company,2001.-752p.

2.     Michael F. Mulroy.Regional Anesthesia /The Virginia Mason Medical Center/ Little, Brown and Company,1998.-327p.

3.     Richard M. Stilman,M.D.,E.A.C.S. General Surgery /Review And Assessment/ Appleton Century Crofts, 1999.-328p.

4.     Kent M. Van De Graff, Stuart Ira Fox, Karen M. Lafleur. Synopsis of Human Anatomy and Physiology /WCB McGraw-Hill/, 2004.-675p.

5.     John J. Jacobs. Shearer’s Manual Of Human Dissection /McGraw-Hill Information Services Company, 1998.-300p.

6.     Branislav Vidic,S.D. Manual Of Dissection /The C.V.Mosby Company/ St.Louis Toronto Princeton, .1997.-120p.

7.     Philip Thorek. Anatomy In Surgery /J.B.Lippincott Company/,1996.-935p.