Comparison of the Biomechanical Profile of the Intact Ulnar Collateral Ligament with the Modified Jobe and the Docking Reconstructed Elbow

Abstract

Background The modified Jobe and Docking techniques are commonly used to reconstruct the elbow's ulnar collateral ligament. Hypothesis Valgus laxity and kinematic coupling after these reconstructive procedures are similar to those of the native ulnar collateral ligament. Study Design Controlled laboratory study. Methods Testing was conducted on 10 pairs of cadaver elbows using a 4 degrees of freedom loading system. Subfailure valgus loads were applied to the native elbows at different flexion angles; motion and ligament elongation were measured. The elbows were then loaded to failure in valgus at 90° of flexion. The reconstructive techniques were then applied and testing was repeated. Results Only the resting length of the anterior portion of the ulnar collateral ligament anterior bundle remained isometric throughout range of motion. Valgus laxity was nearly equal for the native and reconstructed ligaments at flexion angles of 90° or higher. However, both reconstructions provided less valgus stability than the native ulnar collateral ligament at low flexion angles. Kinematic coupling decreased with increased flexion for both native and reconstructed ligaments. Conclusion The modified Jobe and Docking techniques reconstruct restraint of the native ulnar collateral ligament to valgus laxity and kinematic coupling at 90° of flexion and higher angles where peak valgus torque is experienced in the throwing elbow. Clinical Relevance Both reconstructions provide valgus stability comparable to that of the native ulnar collateral ligament at 90° and higher, helping to explain their success in treating throwing athletes. Both reconstructions provide less valgus stability than the native ulnar collateral ligament at low flexion angles, suggesting that patients undergoing ulnar collateral ligament reconstruction should be cautioned against activities that provide valgus stress at low elbow flexion angles, such as side-arm throwing. This study suggests caution against overtightening the reconstructions at the common 30° of flexion.