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Cadaveric study of Radial and Ulnar based Extensor Retinaculum Reconstruction for Extensor Carpi Ulnaris Instability
Daniel Y Hong, MD
1; Taylor Paskey, MD
2; Varun Arvind, MD, PhD
2; Robert J Strauch, MD
11Columbia University Medical Center, New York, NY; 2Columbia University, New York, NY
INTRODUCTION: Extensor carpi ulnaris (ECU) instability can be treated with subsheath reconstruction after failure of nonoperative management. This cadaveric study sought to analyze two described techniques of radial (RBR) and ulnar based (UBR) extensor retinaculum sling reconstruction of the ECU subsheath with respect to the amount of retinaculum available to create the ECU sling.
MATERIALS and METHODS: The ECU subsheath and ER was exposed and studied on twelve fresh frozen upper extremities. 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 most distal aspect of the ER visible; this was typically the insertion of the retinaculum onto the flexor carpi ulnaris and the radial border of the second dorsal compartment respectively. Descriptive statistics are reported as averages with 95% confidence intervals. Comparison of reconstruction lengths were performed with Student's t-test; statistical significance was set at p< 0.05.
RESULTS: After harvesting the flaps for reconstruction, the mean transverse (26.1 mm) and oblique (36.0 mm) UBR were statistically longer than the mean transverse (18.3 mm) and oblique (21.6 mm) RBR (p< 0.05). We observed that given the base of both retinacular reconstructions insert on the radius, especially with forearm pronation, both repairs are non-anatomic. Even if the ECU tendon lies within its groove in neutral forearm position, with forearm pronation, this insertion of the retinaculum on the radius pulls the entire reconstruction radially. This result is even more dramatic with the radial based reconstructions given their shorter flap lengths. The radial ER insertion was also variable in the cadavers and was found to be primarily the pisiform and flexor carpi ulnaris (100%), followed by the distal ulna (41.7%) and triquetrum (33.3%).
CONCLUSIONS: In this cadaveric anatomic study, all reconstructions could further be lengthened by taking the retinaculum as an oblique strip as opposed to a transverse strip, however, ulnar based reconstructions were statistically significantly longer than radial based reconstructions. Given the base of both retinacular insertions is off of the radius, both reconstructions are pulled radially with forearm pronation making them non-anatomic.
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