Anatomy
6th compartment
- fibro-osseous tunnel overlying 1.5 cm to 2.0 cm of distal ulna
- held tight by the extensor carpi ulnaris tendon sheath
- the extensor retinaculum passes around the ulna to insert on the palmar aspect of the carpus
- extensor retinaculum is a separate structure from the ECU tendon sheath
Mechanism
Forced supination, palmar flexion, and ulnar deviation
- ECU tendon can rupture or attenuate the extensor carpi ulnaris tendon sheath
- dislocate in a palmar and ulnar direction
- the tendon relocates on forearm pronation
Most common in tennis players
Symptoms
Clicking or snapping of ECU with rotation
- may cause pain
Tends to dislocated dorsally with supination
Management
Acute cases
Immobilization in a long-arm plaster splint in pronation
Chronic cases
Operative reconstruction of the extensor carpi ulnaris tendon sheath
- using extensor retinaculum