Upper limb

Extensor Carpi Ulnaris, Ulnar Head

Musculus extensor carpi ulnaris, caput ulnare

Origin

Posterior border of the ulna

Insertion

Base of the fifth metacarpal bone

Function

Extension and ulnar deviation of the wrist

Innervation

Deep branch of the radial nerve (posterior interosseous nerve, C7–C8)

Movement & chain

Together with the humeral head forms extensor carpi ulnaris; works synergistically with flexor carpi ulnaris during pure ulnar deviation of the wrist.

Palpation

Palpable on the ulnar side of the dorsal forearm/wrist, distal to the olecranon toward the ulnar styloid process.

Clinical

Instability or subluxation of the common ECU tendon in the sixth extensor compartment can occur after wrist trauma involving pronation-flexion-ulnar deviation, with pain and clicking on the ulnar side of the wrist.

Segmental innervation

C7–C8.

In clinical practice

Focus on hand function and edema prevention; ensure IV cannulas and splints maintain functional hand position to prevent joint contractures.

Region in the model

Upper limb