Isometric Placement of Lateral Ulnar Collateral Ligament Reconstructions A Biomechanical Study

Background: Lateral ulnar collateral ligament (LUCL) reconstruction using a tendon graft is a well-accepted procedure used in the treatment of posterolateral rotatory instability. However, unlike most other ligament reconstructions, anatomical guidelines for the isometric points for tunnel placement of LUCL reconstruction have not been defined. Purpose: To determine if isometric points exist for tunnel placement for LUCL reconstruction and, if so, to determine their anatomical guidelines. Study Design: Controlled laboratory study. Methods: A series of 1.8-mm drill holes was placed in potential ligament reconstruction origin and insertion sites in 13 normal cadaveric elbows along the supinator crest of the ulna and in the lateral epicondyle of the humerus. The prepared specimens were mounted in a plastic test frame with electromagnetic sensors inserted into the drill holes. The distance between each potential pair of insertion sites was measured throughout the arc of elbow motion to determine the most isometric combinations of humeral and ulnar insertion sites. Results: We could not locate truly isometric points for tunnel placement for LUCL reconstruction. For LUCL reconstruction, the position of most isometric tunnel placement was on the supinator crest 16 to 20 mm distal to the proximal margin of the radial head for the proximal wall of the ulnar tunnel, and between the 3:00 and 4:30 o'clock positions on the lateral epicondyle for the posterior/distal wall of the humeral tunnel. Conclusion: Similar to the native LUCL, there is no truly isometric location for LUCL tendon graft reconstruction tunnels. Also similar to the native LUCL, the distance between the optimal tunnel position decreases in elbow extension and often increases in elbow flexion. Clinical Relevance: The most isometric position for LUCL reconstruction tunnel placement was defined using anatomical references.