Similar Biomechanics Between the Double–Cortical Button and Docking Techniques for Ulnar Collateral Ligament Reconstruction: A Cadaveric Evaluation

Abstract

Background: The docking technique is widely used to perform ulnar collateral ligament (UCL) reconstructions because of its high failure torque and reliable clinical outcomes. A double–cortical button technique was recently described, with advantages including the ability to tension the graft at the ulnar and humeral attachments and the creation of single bone tunnels. Purpose/Hypothesis: To compare the biomechanics between the docking and double-button UCL reconstruction techniques using cadaveric specimens. We hypothesized that there would be no difference in postoperative stiffness or maximum strength between the techniques. Study Design: Controlled laboratory study. Methods: Eight matched pairs of cadaveric elbow joints underwent controlled humeral valgus torsion cycles in a test frame. Toe region stiffness, elastic region stiffness, and maximum torque were measured during a 4-step protocol: intact, injured, reconstructed (10 and 1000 cycles), and ramp to failure. Graft strains were calculated using 3-dimensional motion capture. Results: After 10 cycles, intact ligaments from the docking and double-button groups exhibited mean ± SD elastic torsional stiffness of 1.60 ± 0.49 and 1.64 ± 0.35 N·m/deg ( P = .827), while docking (1.10 ± 0.39 N·m/deg) and double-button (1.05 ± 0.29 N·m/deg) reconstructions were lower ( P = .754). There were no significant differences in maximum torque between the docking (3.45 ± 1.35 N·m) and double-button (3.25 ± 1.31 N·m) groups ( P = .777). Similarly, differences in maximum graft strains were not significant between the docking (8.1% ± 7.2%) and double-button (5.5% ± 3.1%) groups ( P = .645). The groups demonstrated similar decreases in these measures after cyclic loading. Ramp-to-failure testing showed no significant differences in ultimate torque between the docking (8.93 ± 3.9 N·m) and double-button (9.56 ± 3.5 N·m) groups ( P = .739). Conclusion: The biomechanical behavior of the double-button technique was not significantly different from that of the docking technique. Both reconstruction techniques restored joint stability, but neither fully recapitulated preinjury joint stiffness. Clinical Relevance: With its procedural advantages, results preliminarily support the use of the double-button reconstruction technique for UCL reconstruction as a reliable single-tunnel technique for primary or revision cases.