Bone patellar tendon bone graft for ulnar collateral ligament reconstruction: a biomechanical study.

Background: Ulnar collateral ligament (UCL) tears are a common injury among overhead athletes, leading to a lengthy recovery period after surgical reconstruction. To explore alternatives to decrease recovery time, we compared the biomechanical properties of the standard palmaris reconstruction with a novel bone-patellar tendon-bone (BTB) reconstruction with interference screw fixation. Methods: Sixteen fresh frozen cadaver upper extremities and 8 cadaver knees were obtained (elbows 77 ± 9 years, male:female 1:3 ratio; knees 59 ± 7 years, male:female 3:1 ratio). Eight upper extremities were randomized to the BTB group and 8 to the palmaris longus group. The elbow was placed in neutral rotation at 90° of flexion and affixed to a custom test frame. A motion capture system was used to track displacement of the humeral construct insertion relative to the ulnar construct insertion. Loading was applied to the forearm to first induce a 0.5 Hz cyclic torque at the joint between 0.5 and 5 Nm for 500 cycles. Load to failure was then performed until either ligament failure or maximum displacement of the actuator was reached. This loading protocol was first performed for the native UCL, then the ligament was reconstructed with either BTB or palmaris longus, then the protocol was repeated. Results: The native UCL of the cadavers did not differ between the groups in initial ligament length, elongation during cycling, stiffness, or opening angle at failure. The palmaris reconstruction did not differ from the native UCL for any metric. The palmaris reconstruction demonstrated a higher torque at failure when compared to the BTB reconstruction (13.7 ± 4.9 Nm vs. 5.9 ± 1.0 Nm; Conclusion: The UCL reconstruction using a BTB fixated with interference screws demonstrated a high failure rate, with the graft largely failing at the bone-tendon junction on the humeral side. Standard practice UCL reconstruction with palmaris longus did not differ from the native UCL, and thus should remain the preferred graft choice among these 2 options.