Dr. Ebraheim’s educational animated video describes the extensor carpi ulnaris subluxation.
The ECU tendon dislocates with supination of the forearm and relocates with pronation.
Other causes of click in the wrist:
• Ligament inguries.
• Arthritis.
• Wrist instability.
• Radioulnar joint dislocation and subluxation.
Anatomy:
The ECU tendon has a common extensor origin on the lateral epicondyle of the humerus.
It is inserted into the posterior surface of the base of the 5th metacarpal.
The ECU tendon lies in the sixth dorsal extensor compartment of the wrist.
The ECU tendon has its own fibroosseous tunnel near the wrist.
The ECU tendon passes through a groove on the ulna which is covered by an annular ligament.
The ECU acts to extend and ulnar deviate the hand at the wrist (it helps the ECRL and the ECRB in extension of the wrist).
The ECU is innervated by the posterior interosseous nerve.
Subluxation of the tendon is secondary to rupture of the ECU sheath and it usually subluxes in a volar to ulnar direction.
Recurrent dislocation will have a painful snap over the ulna dorsal aspect of the wrist especially during forearm rotation.
With supination and ulnar deviation, the tendon leaves the sheath and the groove.
The patient will have pain with an audible “snap” and this will cause tendonitis.
With supination, the tendon dislocates.
With pronation, the tendon relocates.
The ECU is more palpable with the patient’s wrist extended and ulnarly deviated.
This condition can be confused with recurrent subluxation of the distal radioulnar.
MRI may shoe tendonitis, tear, or may show a Triangular Fibrocartilage complex (TFCC) tear.
The diagnosis is usually clinical.
Attention should be given to the possibility of a TFCC tear.
Treatment of ECU Subluxation Early:
Immobilization with the forearm in pronation and the wrist in radial deviation.
Surgery may be needed in some cases by reconstruction of the pulley by using the extensor reticulum.
Other forms of treatment are available.


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Background music provided as a free download from YouTube Audio Library.
Song Title: Every Step