Extensor carpi ulnaris (ECU) instability can be treated with subsheath reconstruction using the extensor retinaculum (ER). This cadaveric study studied two described techniques of radial- (RBR) and ulnar-based (UBR) extensor retinaculum reconstruction of the ECU subsheath.

The ECU subsheath and ER were exposed on 12 fresh frozen arms. Transverse and oblique RBR and UBR based on the ulnar aspect of the fifth dorsal compartment were created and measured. The transverse RBR and UBR were elevated from the ulnar aspect of the ulnar styloid and Lister's tubercle, respectively. The oblique RBR and UBR were elevated from the insertion of the retinaculum onto the flexor carpi ulnaris and the radial border of the second dorsal compartment, respectively.

The mean styloid to styloid width for the ER was 50.3 ± 1.8 mm. Mean proximal to distal retinacular height was found to be 30.6 ± 2.0 mm. The mean transverse UBR (26.1 mm) was longer than the mean transverse RBR (18.3 mm), and the mean oblique UBR (36.0 mm) was longer than the mean oblique RBR (21.6 mm). All reconstructions were long enough to wrap around the ECU tendon and prevent the tendon from subluxating palmarly with wrist supination, ulnar deviation, and flexion.

In this cadaveric model, UBR and RBR of the ECU subsheath were sufficient to stabilize the ECU tendon, but UBR were significantly longer than RBR. Both reconstructions pull the ECU radially in pronation.

Received: 17 October 2024

Accepted: 26 May 2025

Article published online:
23 June 2025

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