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This chapter discusses soft tissue injuries distal to the volar wrist crease and fractures distal to the carpal bones.

The hand consists of 27 bones: 14 phalangeal bones, 5 metacarpal bones, and 8 carpal bones arranged in five rays of metacarpals and phalanges having its base at the carpometacarpal (CMC) articulation (Figure 265-1).

The carpal bones are made up of two rows, each with four bones. The bones are concave volar and are bridged by the flexor retinaculum. This forms the carpal tunnel through which the median nerve and the nine long flexor tendons of the fingers pass. The bases of the second and third CMC articulation are fixed, whereas the thumb, ring, and little finger have mobility at the CMC joint, allowing motion that enables grasp and adaptive movement of the hand. Multiple soft tissue structures support these bones and joints: capsular ligamentous structures provide stability, whereas the intrinsic muscles of the hand and their associated tendinous structures generate mobility. The collateral ligaments of the metacarpophalangeal joints are tightest in flexion (Figure 265-2). The interphalangeal collaterals are tight throughout the entire range of motion. The intrinsic muscles of the hand are those that have both their origins and insertions within the hand. They consist of the muscle of the thenar and hypothenar eminences, adductor pollicis, the interossei, and the lumbricals (Figure 265-3A).

Figure 265-2.

Ligament attachments of the metacarpophalangeal and interphalangeal joints.

Figure 265-3.

A. Palmar (volar) view of the hand showing relationship of muscles and tendon sheaths, and flexor zones of the hand. B. Dorsal view of the hand showing tendons and extensor zones of the hand. Extensor tendons of the hand and extensor retinaculum. The extrinsic extensor tendons include the following: extensor carpi radialis longus, extensor carpi radialis brevis, extensor carpi ulnaris, extensor digitorum communis, extensor digiti minimi, extensor indicis proprius, abductor pollicis longus, extensor pollicis brevis, and extensor pollicis longus.

The thenar muscles (abductor pollicis brevis, opponens pollicis, and flexor pollicis brevis) originate in the flexor retinaculum and carpal bones and insert at the base of the first metacarpal and first proximal phalanx, thus covering the thumb metacarpal. The median nerve innervates all three muscles. The adductor pollicis is innervated by the ulnar nerve and originates from the second and third metacarpals and inserts in the first proximal phalanx. The hypothenar muscles include the opponens digiti minimi, the flexor digiti minimi, and the abductor digiti minimi. These muscles, innervated by the ulnar nerve, originate in the flexor retinaculum and carpal bones and ...

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