Biomechanical Evaluation of Opponensplasty for Low Median Palsy: A Cadaver Study

PURPOSE: Impaired thumb opposition associated with advanced carpal tunnel syndrome may be treated by opponensplasty at the time of open carpal tunnel release. However, it is unclear which opponensplasty technique achieves the greatest functional improvement. This study aimed to compare the biomechanics of thumb opposition after Camitz, modified Camitz, and Burkhalter opponensplasties. METHODS: We used 6 fresh-frozen cadaveric arms. Each procedure was reproduced on each arm: Camitz opponensplasty, modified Camitz opponensplasty involving palmaris longus transfer routed around the flexor carpi ulnaris pulley, and Burkhalter opponensplasty. Arms were fixed with the wrist in 0° flexion and the forearm in neutral pronosupination, and sensors were placed on the thumbnail, radial styloid, and dorsal aspect of the second metacarpal head. The donor tendon was pulled using a mechanical testing machine with a maximum force of 25 N, and the locations of the sensors in thumb opposition were recorded. The first web space and thumb pronation angles were measured for each procedure and compared. RESULTS: The mean first web space and pronation angles produced using 25 N were 55° and 20°, 57° and 26°, and 53° and 29° for the Camitz, modified Camitz, and Burkhalter opponensplasties, respectively. The first web space angle was significantly larger after modified Camitz opponensplasty compared with Burkhalter opponensplasty with 25 N loading. Camitz opponensplasty resulted in a significantly smaller pronation angle compared with modified Camitz and Burkhalter opponensplasties with 25 N loading. CONCLUSIONS: The modified Camitz opponensplasty produces a relatively balanced biomechanical outcome in terms of the first web space and pronation angles. Conversely, Burkhalter opponensplasty has been shown to be a favorable technique for improving pronation. CLINICAL RELEVANCE: Modified Camitz opponensplasty with a pulley offers effective restoration of thumb opposition, including pronation. On the other hand, Burkhalter opponensplasty represents a suitable option not only for patients with high median palsy and injury to the palmar aponeurosis but also for those who require improved pronation.