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
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
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
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
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
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
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
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
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
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
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
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 (
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
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.
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
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
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
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
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.
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.
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
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
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
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
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
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
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
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
3.
Richard M. Stilman,M.D.,E.A.C.S.
General Surgery /Review And Assessment/
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.
7.
Philip Thorek. Anatomy In Surgery
/J.B.Lippincott Company/,1996.-935p.