Biomechanical comparison of graft fixation at 30° and 90° of elbow flexion for ulnar collateral ligament reconstruction by the docking technique

Abstract

Ulnar collateral ligament (UCL) injuries have been successfully treated by the docking reconstruction. Although fixation of the graft has been suggested at 30° of elbow flexion, no quantitative biomechanical data exist to provide guidelines for the optimal elbow flexion angle for graft fixation. Testing was conducted on 10 matched pairs of cadaver elbows with use of a loading system and optoelectric tracking device. After biomechanical data on the native UCL were obtained, reconstruction by the docking technique was performed with use of palmaris longus autograft with one elbow fixated at 30° and the contralateral elbow at 90° of elbow flexion. Biomechanical testing was undertaken on these specimens. The load to failure of the native UCL (mean, 20.1 N-m) was significantly higher (P = .004) than that of the reconstructed UCL (mean, 4.6 N-m). There was no statistically significant difference in load to failure of the UCL reconstructions fixated at 30° of elbow flexion (average, 4.86 N-m) compared with those at 90° (average, 4.35 N-m). Elbows reconstructed at 30° and 90° of elbow flexion produced similar kinematic coupling and valgus laxity characteristics compared with each other and with the intact UCL. Although not statistically significant, the reconstructions fixated at 30° more closely resembled the biomechanical characteristics of the intact elbow than did reconstructions fixated at 90°. No statistically significant difference was found in comparing the docking technique of UCL reconstruction with graft fixation at 30° vs. 90° of elbow flexion.