Claw Hand(Archived)

Excerpt

Ulnar nerve palsy can result in loss of sensory and motor function. This can occur after injury to any portion of the ulnar nerve. The ulnar nerve is the terminal branch of the medial cord (C8, T1). The ulnar nerve innervates the flexor carpi ulnaris and the flexor digitorum profundus after it passes through the cubital tunnel.

The nerve provides sensation over the medial half of the 4th finger and the entire 5th finger, and the ulnar portion of the dorsal aspect of the hand.

Muscles innervated by the ulnar nerve include:

1. Abductor digiti minimi

2. Flexor digitorum profundus

3. Flexor digiti minimi

4. Opponens digiti minimi

5. Ring finger lumbricals

6. Small finger lumbricals

7. Dorsal and palmar interosseous muscles

8. Adductor pollicis

9. Deep head of flexor pollicis brevis

When the ulnar nerve is injured, the muscles innervated by the nerve begin to weaken. This leads to an imbalance between the strong extrinsic muscles (i.e., extensor digitorum communis) and the weakened intrinsic muscles (i.e., interossei and lumbricals). This imbalance is characterized clinically by metacarpophalangeal (MCP) hyperextension and proximal interphalangeal (PIP), and distal interphalangeal (DIP) flexion. After carpal tunnel syndrome, entrapment of the ulnar nerve is the second most common neuropathy of the upper extremity.

The ulnar nerve can be entrapped at several sites. The cubital tunnel is the most common. The other sites are the medial intermuscular septum, the ulnar groove in the epicondylar region, and the deep flexor pronator aponeurosis. Entrapment in Guyon's canal results in ulnar tunnel syndrome.