Page 216 - Clinical Anatomy

ECA3 7/18/06 6:45 PM Page 201

The spaces of the hand 201

Fig. 145◊The distal pulp space of the finger—note the distribution of the arterial
supply to the distal phalanx.

artery in the middle segment of the finger and therefore survives. At each of
the skin creases of the fingers, the skin is bound down to the underlying
flexor sheath so that the pulp over each phalanx is in a separate compart-
ment cut off from its neighbours. Infection may, however, track from one
space to another along the neurovascular digital bundles.
Over the palm of the hand there is very little subcutaneous tissue, the
skin adhering to the underlying palmar aponeurosis; in contrast, the skin of
the dorsum of the fingers and hand is loose and fluid can, therefore, readily
collect beneath it. Unless this is remembered, the marked dorsal oedema
which may accompany sepsis of the palmar aspect of the fingers or hand
may result in the primary site of the infection being overlooked.

The ulnar and radial bursae and the synovial
tendon sheaths of the fingers (Fig. 146)

The flexor tendons traverse a fibro-osseous tunnel in each digit. This tunnel
is made up posteriorly by the metacarpal head, the phalanges and the
fronts of the intervening joints. The anterior fibrous part consists of con-
densed deep fascia attached to the sharp anterolateral margin of each
phalanx and termed the fibrous flexor sheath. This is particularly tough over
the phalanges but loose over the front of each joint; it therefore holds the
flexor tendons in place without ‘bow-stringing’ during flexion of the
fingers, but does not impede movement of the joints.
Distally, the fibrous sheath ends at the insertion of the profundus
tendon (or flexor pollicis longus tendon in the case of the thumb) at the base
of the distal phalanx.
These fibrous sheaths are lined by synovial membrane which is
reflected around each tendon. The tendons of the 2nd, 3rd and 4th fingers
have synovial sheaths which are closed off proximally at the metacarpal
head, but the synovial sheaths of the thumb and little finger extend proxi-
mally into the palm.
That of the long flexor tendon of the thumb extends through the palm,
deep to the flexor retinaculum, to about 1 | in (2.5 | cm) proximal to the wrist
and is termed the radial bursa. The synovial sheath of the 5th finger contin-
ues as the ulnar bursa, an expanded synovial sheath which encloses all the