FASCIA
AND SUPERFICIAL ANATOMY OF THE HAND
The fascia of the
palm of the hand is continuous with the antebrachial fascia of the flexor
aspect of the forearm and with the palmar carpal ligament. At the borders of
the hand, it is continuous with the fascia of the dorsum at attachments to the
first and fifth metacarpals. The hypothenar fascia invests the muscles
of the little finger and bounds the hypothenar compartment of the hand
by means of a palmar attachment to the radial side of the fifth metacarpal. In
a similar manner, the fascia over the thumb muscles dips deeply to attach to
the palmar aspect of the first metacarpal and bounds, with the metacarpal, a thenar
compartment in the hand. The central compartment of the palm is
covered by the intervening part of the fascia of the palm, but this portion is reinforced
superficially by the palmar aponeurosis, an expansion of the tendon of
the palmaris longus muscle. Recognizable in the palmar aponeurosis are a superficial
stratum of longitudinally running fibers (which is continuous with the tendon
of the palmaris longus muscle) and a deeper layer of transverse fibers. The
transverse fibers are continuous with the thenar and hypothenar fasciae;
proximally, they are continuous with the flexor retinaculum and the transverse
carpal ligament. The palmar aponeurosis broadens distally in the palm and
divides into four digital slips, some of its fibers meanwhile attaching to the
overlying skin at the skin creases of the palm. The central parts of these
slips pass into the digits, attaching superficially to the skin of the crease
at the base of each digit; deeply, they attach to the fibrous sheath of the digit.
The marginal fibers sink deeply between the heads of the metacarpals and attach
to the metacarpophalangeal joint capsules, the deep transverse metacarpal
ligaments, and the proximal phalanges of the digits. There is usually no
digital slip for the thumb, but longitudinal fibers of the aponeurosis usually
curve over onto the thenar fascia.
The deep attachments
of the margins of the digital slips of the palmar aponeurosis define the
entrance to the fibrous sheath of each digit, but they are also continued
proximally into the palm for varying distances. They attach to the palmar
interosseous fascia and to the shafts of the metacarpals, thus providing
communicating subcompartments for each pair of flexor tendons and the
associated lumbrical muscles (see Plate 4-15). The septum reaching the third
metacarpal is stronger and more constant; it separates a surgical thenar
space under the aponeurosis to its radial side and a midpalmar space to
its ulnar side.
Accumulations of the deeper
transverse fibers of the aponeurosis appear between the diverging digital
slips. Located at the level of the heads of the
metacarpals, these fibers are designated as the superficial transverse metacarpal
ligament. Distally, the webs of the fingers are reinforced by another
accumulation of transverse fibers designated as transverse fasciculi.
The fascia of the
dorsum of the hand is continuous with the antebrachial fascia of the
extensor surface of the forearm and with the extensor retinaculum. It encloses the tendons of the extensor muscles as they pass to the digits and
continues into the extensor expansions on the dorsum of the digits; deep to it
is a subaponeurotic space. This interfascial cleft separates the fascia
of the dorsum from the deeper dorsal interosseous fascia covering the
dorsal interosseous muscles and the descending branches of the dorsal carpal arterial arch (see Plate
4-16).
The superficial
lymphatic vessels of the upper limb begin in the hand and pervade the skin and
subcutaneous tissues (see Plates 4-16 and 4-17). The
dense digital lymphatic plexuses are drained by channels accompanying the
digital arteries. At the interdigital clefts (and also more distally),
collecting vessels of the palmar surfaces of the fingers pass to join dorsal
collecting vessels and empty into the plexus of the dorsum of the hand.
Drainage of the thumb,
index finger, and radial portion of the third finger is by
collecting vessels that ascend along the radial side of the forearm; channels
draining the ulnar fingers ascend along the ulnar side. Vessels from the lymphatic
plexus of the palm radiate to the sides of the hand and also upward through
the wrist, coalescing into two or three collecting vessels that ascend in the
middle of the anterior surface of the forearm. The radial and ulnar channels
turn onto the anterior surface of the forearm, lying parallel to the middle
group, and all continue subcutaneously through the forearm and arm to reach the
axillary nodes.
Some of the ulnar
lymphatic channels are efferent to the cubital lymph nodes. This
superficial group of one or two nodes is located 3 to 4 cm above the medial epicondyle
of the humerus and below the aperture in the brachial fascia for the basilic
vein. The afferent vessels of these nodes include channels originating in the
ulnar three fingers and the ulnar portion of the forearm. The efferent vessels
accompany the basilic vein under the brachial fascia and reach the lateral and
central groups of axillary lymph nodes.
Several lymphatic
channels collecting from the dorsal surface of the arm follow the upper course
of the cephalic vein to the deltopectoral triangle, perforate the costocoracoid
membrane with the vein, and terminate in an apical node of the axillary group.
In about 10% of cases, this channel is interrupted in the deltopectoral
triangle by one or two small deltopectoral nodes.
AXILLARY LYMPH NODES
The axillary lymph
nodes, usually large and numerous, are arranged in five subgroups, some related
to the axillary walls and others to vessels.
A lateral group of
three to five nodes lies medial and posterior to the distal segment of the
axillary vein. These nodes are in the direct line of lymph drainage from the
upper limb, except for the drainage lymphatics along the cephalic vein.
Efferent vessels from these nodes drain to the central and apical nodes.
A pectoral group is
located along the lateral thoracic artery adjacent to the axillary border of
the pectoralis minor muscle. These three to five nodes
receive the lymphatic drainage of the anterolateral part of the thoracic wall,
including most of the lateral drainage from the mammary gland, and of the skin
and muscles of the supraumbilical part of the abdominal wall. Efferent
lymphatic vessels reach the central and apical groups.
A subscapular group
of five or six nodes is stretched along the subscapular blood vessels, from
their origin in the axillary vessels to their contact with the chest wall. These nodes drain the skin and muscles of the posterior thoracic
wall and shoulder region and also the lower part of the back of the neck. Their
efferent lymph channels pass to the central axillary nodes.
A central group of
four or five nodes lies under the axillary fascia, embedded in its fat. Among
the largest of the axillary nodes, these nodes receive some lymphatic vessels
directly from the arm and mammary regions; but primarily, they receive lymph
from the lateral, pectoral, and subscapular groups. Their efferent channels pass
to the apical nodes.
The apical group, consisting
of 6 to 12 nodes, lies along the axillary vein at the apex of the axilla and
adjacent to the superior border of the pectoralis minor muscle. The apical
nodes receive efferent vessels of all other axillary groups, lymphatic vessels
that accompany the cephalic vein, and lymphatic vessels from the mammary gland.
From lymph vessels interconnecting the apical nodes arises a larger common
channel, the subclavian lymphatic trunk.
Deep Lymphatics
These vessels serve
the upper limb, draining joint capsules, periosteum, tendons, nerves, and, to a
lesser extent, muscles. Collecting vessels accompany the major arteries, along
whose paths lie small intercalated lymph nodes. The deep lymphatics are
afferent to the central and lateral axillary nodes.
SUPERFICIAL VEINS
The subcutaneous veins
of the limb are interconnected with the deep veins of the limb via perforating
veins. Certain prominent veins, unaccompanied by arteries, are found in the
subcutaneous tissues of the limbs. The cephalic and basilic veins, the
principal superficial veins of the upper limb, originate in venous radicals in
the hand and digits.
Anastomosing
longitudinal palmar digital veins empty at the webs of the fingers into
longitudinally oriented dorsal digital veins. The dorsal veins of
adjacent digits then unite to form relatively short dorsal metacarpal veins,
which end in the dorsal venous arch. The radial continuation of the
dorsal venous arch is the cephalic vein, which receives the dorsal veins
of the thumb and then ascends at the radial border of the wrist. In the
forearm, it tends to ascend at the anterior border of the brachioradialis
muscle, with tributaries from the dorsum of the forearm. In the cubital space,
the obliquely ascending median cubital vein connects the cephalic and
basilic veins. Above the cubital fossa, the cephalic vein runs in the lateral
bicipital groove and then in the interval between the deltoid and pectoralis
major muscles, where it is accompanied by the small deltoid branch of the
thoracoacromial artery. At the deltopectoral triangle, the cephalic vein
perforates the costocoracoid membrane and empties into the axillary vein. An
accessory cephalic vein passes from the dorsum of the forearm spirally laterally
to join the cephalic vein at the elbow.
The basilic vein continues
the ulnar end of the venous arch of the dorsum of
the hand (see Plate 4-17). It ascends along the ulnar
border of the forearm and enters the cubital fossa anterior to the medial epicondyle of the humerus. After receiving the median cubital vein, the
basilic vein continues upward in the medial bicipital groove, pierces the
brachial fascia a little below the middle of the arm, and enters the neurovascular
compartment of the medial intermuscular septum, where it lies superficial to
the brachial artery. In the distal axilla, it joins the brachial veins to form the
axillary vein.
The median
antebrachial vein is a frequent collecting vessel of the middle of the
anterior surface of the forearm. It terminates in the cubital fossa in the
median cubital vein or in the basilic vein. It sometimes divides into a median
basilic vein and a median cephalic vein, which borders the biceps
brachii laterally and joins the cephalic vein. The median antebrachial vein may
be large or absent.
