A biomechanical evaluation of ulnar collateral ligament reconstruction using a novel technique for ulnar-sided fixation

Abstract

Background: Techniques for ulnar collateral ligament (UCL) reconstruction have evolved since its original description.

Hypothesis: Ulnar collateral ligament reconstruction using the ZipLoop for ulnar-sided fixation, as combined with the humeral docking technique supplemented with an interference screw, will restore valgus stability similar to that of the Jobe technique and the native ligament.

Study design: Controlled laboratory study.

Methods: Kinematic testing was performed on 8 matched pairs of cadaver elbows with an electromagnetic tracking system through an arc of motion for the intact, disrupted, and reconstructed states of the UCL in an unloaded and loaded condition. From each pair, the docking technique using the ZipLoop for ulnar fixation and humeral docking technique supplemented with an interference screw and the traditional Jobe technique were performed with matched gracilis allograft tendons. After kinematic testing, both reconstruction groups were tested to failure at 70 degrees of flexion.

Results: Kinematic results for the unloaded condition showed that both reconstruction techniques significantly overcorrected (less valgus angulation) the specimens between 40 degrees and 120 degrees of flexion when compared with the intact ligament (all P values < .027). Under loaded conditions, the ulnar trajectories for both reconstruction techniques exhibited significantly greater valgus angulation (undercorrection) at 20 degrees of flexion (Jobe, P = .0084; ZipLoop, P = .0289) when compared with the intact ligament but were not significantly different over the remaining arc of motion. Failure testing resulted in no significant statistical difference between the 2 reconstruction groups. Failure testing demonstrated that humeral tunnel egress, midsubstance elongation, and ulnar tunnel egress of the ligament were similar between the reconstruction techniques.

Conclusion: The docking technique using the ZipLoop for ulnar-sided fixation is biomechanically equivalent to the Jobe technique for UCL reconstruction. Both reconstruction techniques restore valgus stability similar to that of the native UCL ligament.

Clinical relevance: This modification in the docking technique restores elbow kinematics while eliminating the risk of ulnar bone bridge fracture, and it allows for retensioning of the graft after cortical fixation.