Biomechanical Comparison of Two Fixation Techniques for Lateral Ulnar Collateral Ligament Repair With Ligament Bracing.

PURPOSE

Ligament bracing is a technique of suture reinforcement that can be used to augment lateral ulnar collateral ligament repair in the treatment of posterolateral rotatory instability of the elbow, thereby improving early stability of the repair. However, multiple failures of the ulnar anchor during implantation have been documented. We hypothesized that the use of a cortical button for ulnar fixation of the ligament brace would be biomechanically comparable to a suture anchor construct.

METHODS

Sixteen elbows were tested with a materials testing machine. The intact, dissected, and repaired lateral collateral ligament complex was tested with a cyclic varus rotational torque of 0.5-3.5 Nm in 120°, 90°, 60°, and 30° elbow flexion. For the repair, the specimens were randomized into 2 groups: ulnar fixation of the ligament bracing using a suture anchor and ulnar fixation of the ligament bracing using a cortical button. The number of implant failures was documented. A load-to-failure protocol was conducted in 90° elbow flexion.

RESULTS

Load to failure was comparable and was found to be 20.7 Nm in the suture anchor group and 21.8 Nm in the cortical button group. Laxity after ligament bracing did not differ significantly between suture anchor and cortical button fixation. Compared with the native ligament, the laxity was significantly reduced after ligament bracing. The failure mode was slippage of the suture tape through the humeral anchor in all cases. Additionally, the capitellum was damaged in 9 of 16 cases.

CONCLUSIONS

A cortical button for ulnar fixation of the ligament bracing was comparable with a suture anchor fixation with regard to biomechanical properties such as laxity and load to failure.

CLINICAL RELEVANCE

A cortical button fixation is less prone to failure of insertion. This would improve the implantation technique, while clinical results are expected to be comparable.