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Body Surface

The primary surface landmarks of the posterior forearm and dorsal hand are associated with the humerus (medial and lateral epicondyle), ulna (olecranon), radius (styloid process and dorsal tubercle), ulna (head) and the triceps brachii, abductor pollicis longus, extensor pollicis longus and extensor digitorum tendons. The skin overlying the posterior forearm and dorsal hand is innervated by the lateral, posterior and medial cutaneous nerves of the forearm, superficial branch of the radial nerve, and the dorsal and digital branches of the ulnar and median nerves.

Skeleton and Joints

The bones and joints associated with the posterior forearm and dorsal hand are the humerus, radius and ulna articulating at the elbow joint, the radius, ulna (articular disc) and proximal carpals articulating at the wrist joint, the carpals and metacarpals at the metacarpal-phalangeal joints and the proximal, intermediate and distal phalanges at the interphalangeal joints. The elbow joint moves in flexion and extension and contributes to pronation and supination of the forearm. The wrist joint moves in flexion and extension, and abduction and adduction. The carpal-metacarpal joints move in flexion and extension, abduction and adduction, and opposition (1st only). The interphalangeal joints move in flexion and extension.

Fascial Organization

The antebrachial (deep) fascia, its two intermuscular septa and the interosseous membrane divide the forearm into two compartments and a third region, the mobile wad. The intermuscular septa attach to the radius and separate the mobile wad (brachioradialis, and extensor carpi radialis longus and brevis) from the anterior (flexor) and posterior (extensor) compartments. The muscles of the mobile wad are typically grouped with the posterior compartment. The extensor retinaculum is a thickening of the antebrachial fascia extending from the pisiform and triquetral to the lateral aspect of the distal radius. It prevents bowstringing of the posterior compartment tendons during extension of the wrist. The tendons surrounded by synovial sheaths are positioned in six tunnels passing deep to the extensor retinaculum.

Muscles

The muscles of the mobile wad are active in flexion ( brachioradialis) of the forearm, and extension and abduction of the wrist ( extensor carpi radialis longus and brevis). The remaining muscles of the posterior compartment are active in extension of the elbow ( anconeus), supination of the forearm ( supinator), extension ( extensor carpi ulnaris and extensor digitorum) and adduction (extensor carpi ulnaris) of the wrist, abduction and extension of the 1st carpal – metacarpal joint ( abductor pollicis longus), extension of the 1st phalanges ( extensor pollicis brevis and longus) and extension of the 2nd – 5th phalanges ( extensor indicis, extensor digitorum and extensor digiti minimi).

Innervation

Branches of the radial nerve innervate all the muscles of the posterior compartment of the forearm including the mobile wad.

Blood Supply

Branches of the radial, posterior interosseous and anterior interosseous arteries supply the posterior compartment of the forearm.