Biomechanical Assessment of Docking Ulnar Collateral Ligament Reconstruction after Failed Ulnar Collateral Ligament Repair with Suture Augmentation.

Abstract Background Ulnar collateral ligament (UCL) repair with single-strand suture augmentation has been introduced as a viable surgical option for throwers with acute UCL tears. For the original single-strand suture augmentation construct, revision UCL reconstructions can be challenging due to the bone loss at the site of anchor insertion in the center of the sublime tubercle. This biomechanical study assessed a small diameter (1.5mm) ulnar bone tunnel technique for double-strand suture-augmented UCL repair that may be more easily converted to salvage UCL reconstruction if necessary, and a salvage UCL reconstruction with a docking technique after a failed primary suture-augmented UCL repair. Methods 7 fresh-frozen cadaveric upper-extremities (mean age: 66.3 years) were used with a custom shoulder testing system to simulate the late cocking phase of throwing. Elbow valgus opening angle was evaluated using a Miscroscribe 3DLX for progressively increasing valgus torque (0.75 - 7.5 Nm; 0.75 Nm increments) at 90o of flexion. Valgus angular stiffness (Nm/degree) was defined as the correlation of progressively increasing valgus torque with valgus opening angle through simple linear regression (slopes of the valgus torque - valgus opening angle curve). Four conditions were tested: an intact elbow, distal UCL avulsion, primary UCL repair with double-strand suture augmentation using small diameter bone tunnels, and subsequent docking UCL reconstruction in the same specimen. Load-to-failure tests were performed for primary UCL repair with double-strand suture augmentation and subsequent docking UCL reconstruction. Results With increasing elbow valgus torque, the valgus opening angle increased linearly in each condition (R2≥0.98, P Conclusion Primary UCL repair with double-strand suture augmentation using small diameter bone tunnels was able to restore valgus stability. Upon failure, this technique retains enough cortical bone to permit subsequent docking UCL reconstructions. Level of evidence Basic Science Study; Biomechanics