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ORGANIZATION OF THE FASCIA OF THE HAND

BIG PICTURE

The fascia of the hand is continuous with the fascia of the forearm (antebrachium). In the hand, the fascia varies in thickness and divides the hand into five separate compartments that correspond with the five digits and have similar blood supply, innervation, and actions.

FASCIAL LAYERS OF THE PALMAR SIDE OF THE HAND (FIGURE 33-1A)

  • Palmar aponeurosis. A triangular shaped portion of the deep fascia (located over the palm of the hand) that is continuous with the palmaris longus tendon.

    • Forms four longitudinal digital bands that radiate distally and become continuous with the fibrous digital sheaths.

  • Fibrous digital sheaths. Tunnels composed of dense collagenous connective tissue that encloses the flexor tendons of digits 2 to 5 and the tendon of the flexor pollicis longus muscle (digit 1) and their associated synovial sheaths.

  • Flexor retinaculum (transverse carpal ligament). A band of dense collagenous connective tissue that forms a roof over the concavity of the carpal bones thus forming the carpal tunnel; anchors to the pisiform and the hook of the hamate (medially) and the scaphoid and trapezium (laterally). The carpal tunnel has the following contents:

    • Four flexor digitorum superficialis tendons (and associated synovial sheaths).

    • Four flexor digitorum profundus tendons (and associated synovial sheaths).

    • One flexor pollicis longus tendon (and associated synovial sheath).

    • One median nerve.

Figure 33-1:

A. Fascia of the palm of the hand and carpal tunnel. B. Fascia of the posterior hand and extensor compartments. C. Actions of digits 2–4. D. Actions of digit 1 (thumb). E. Bones of the hand (anterior view).

FASCIAL COMPARTMENTS OF THE PALMAR SIDE OF THE HAND

The fascial layers divide the palmar side of the hand into the following compartments (Figure 33-1A):

  • Thenar compartment. Contains three muscles that act on digit 1 (thumb).

  • Hypothenar compartment. Contains three muscles that act on digit 5.

  • Central compartment. Located between the thenar and hypothenar compartments and contains the flexor tendons and the lumbrical muscles.

  • Adductor compartment. Contains the adductor pollicis muscle.

  • Interosseous compartment. Located between the metacarpals and contains the dorsal and palmar interossei muscles.

FASCIAL LAYERS OF THE DORSAL SIDE OF THE HAND

  • Extensor retinaculum. Continuous with the fascia of the forearm; retains the tendons that are near the bone while allowing proximal and distal gliding of the tendons (Figure 33-1B).

  • Dorsal digital expansions. An aponeurosis covering the dorsum of the digits and attaches distal to the distal phalanx.

    • Proximally and centrally, the extensor digitorum, extensor digiti minimi, extensor indicis, and extensor pollicis brevis muscles attach to the dorsal digital expansion.

    • The small intrinsic muscles that attach laterally (lumbricals and interossei) are responsible for delicate finger movements ...

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