The Effect of Humeral and Ulnar Bone Tunnel Placement on Achieving Ulnar Collateral Ligament Graft Isometry: A Cadaveric Study

Abstract

To assess simulated ulnar collateral ligament (UCL) graft length change, using surgically dissected anatomic landmarks, between multiple combinations of humeral and ulnar bone tunnels. Three equidistant humeral and ulnar tunnels were created at each UCL footprint of 10 cadaveric elbows. Suture was passed between 9 possible tunnel combinations for each elbow and affixed to an isometry gauge. Each elbow was moved through an arc of 0, 30, 60, 90, and 120° for each tunnel combination. Changes in isometry gauge spring displacement (and, in effect, tension) were recorded. There was an overall significant effect (P < .0001) of tunnel placement at all degrees of flexion. Pairwise comparisons revealed increases in displacement between the central and posterior tunnel positions of the medial epicondyle, with significant differences (P= .0009) occurring when paired with both the central and posterior aspect of the sublime tubercle. Significant differences (P < .0001) were noted between the anterior and posterior humeral tunnel positions. Simulated UCL graft isometry is dependent upon optimal bone tunnel placement. No significant differences were noted between ulnar tunnel locations when paired with any given humeral tunnel. Conversely, deviation anterior or posterior from the centroid of the UCL footprint on the medial epicondyle significantly affected isometry at all degrees of flexion recorded with the greatest amount of displacement occurring with pairi4ng of posterior tunnels on both the humeral and ulnar footprints. This anatomic study highlights the importance of medial elbow bone tunnel placement and its effect on simulated UCL graft isometry.