INTERFERENCE KNOT FIXATION IN THE RECONSTRUCTION OF THE ULNAR COLLATERAL LIGAMENT OF THE ELBOW

Abstract

We describe a new a technique for reconstructiing the ulnar collateral ligament (UCL) of the elbow, and test this new technique biomechanically comparing it with an established technique. The UCL is commonly injured in the throwing athlete. We describe a reconstruction using semi-tendinosis allograft with humeral fixation by interference knot. 30 fresh frozen cadaveric arms were harvested and amputated at the mid-humerus. Soft tissue was stripped to the level of the elbow sparing the UCL. The native ligament was ruptured in a materials testing machine (Bionix 858, MTS) by placing a rotational torque on the humerus, with the elbow was fixed at a right angle. Load to failure and stiffness were noted. These arms were randomly assigned to be reconstructed with one of three techniques: 1. Palmaris longus allograft with docking technique humeral fixation 2. Palmaris longus allograft with interference knot humeral fixation 3. Semitendinosis allograft with interference knot humeral fixation The techniques were then tested in the materials testing machine, load to failure and stiffness were noted. Group 1: load to failure 13.31 N/m (+/− 4.2) and stiffness 19.4 N/mm. Group 2: load to failure 13.86 N/m (+/− 5.5) and stiffness 19.1 N/mm. Group 3: load to failure 20.57 (+/− 7.4) and stiffness 20.4 N/mm. The semitendinosis interference technique had a significantly higher strength (p< 0.005) but was not significantly stiffer. None of the techniques approached the strength or stiffness of the native ligament: load to failure 34.2 N/mm and stiffness 45.3N/mm. A new technique to reconstruct the UCL of the elbow uses interference knot fixation in the humeral tunnel. When a palmaris longus allograft is used this technique has a similar biomechanical profile to the established docking technique. When semi-tendinosis is used this technique is significantly stronger and may result in earlier rehabilitation in the clinical setting.