The GraftLink ulnar collateral ligament reconstruction: biomechanical comparison with the docking technique in both kinematics and failure tests.

BACKGROUND

Ulnar collateral ligament (UCL) reconstruction aims to restore valgus stability, and numerous techniques have been described in the literature. HYPOTHESIS/ PURPOSE: To biomechanically compare the GraftLink (GL) technique with traditional bone tunnels used in the docking (DO) technique. It is hypothesized that the GL method will offer a stiffer, less lax construct compared with the DO.

STUDY DESIGN

Controlled laboratory study.

METHODS

Native and reconstructed states were tested in 7 matched pairs of cadaveric arms. To test kinematics, a 1.5-N·m valgus torque was applied and the resultant displacement at 15° to 90° of flexion was measured. Dissipated energy and the torque at the peak of the 10th cycle of preconditioning were analyzed during kinematic tests. Failure testing was performed by internal rotation of the humerus at 4.5 deg/s in 70° of flexion. Ulnotrochlear joint (UTJ) gapping was quantified during failure tests by use of video tracking.

RESULTS

Kinematics testing revealed no differences between the native state and the reconstructed state in either the DO or the GL group at any flexion angle. Stiffness was lower in the reconstructed specimens in both the DO (39.92 N·m/rad) and GL (50.74 N·m/rad) groups compared with their matched native states (DO Native, 71.41 N·m/rad, P = .005; GL Native, 86.36 N·m/rad, P = .002). There was no difference in stiffness between DO and GL. Reconstructed specimens in the GL group had lower torque at failure compared with native specimens (17.404 N·m vs 24.63 N·m, P = .038), but there was no difference in the DO group at failure. There was no difference in torque at failure between DO and GL. The DO exhibited higher angular displacement at failure compared with the native state (34.21° vs 21.79°, P = .010) and compared with the GL when normalized (1.58-fold vs 1.19-fold, P = .039). Compared with their native states, both DO and GL had significantly higher UTJ gapping at 3 N·m and at failure. The DO had significantly higher normalized UTJ gapping than the GL at 3 N·m (P = .037) and at failure (P = .043).

CONCLUSION

The DO and GL both restored joint kinematics under low loading conditions. Although less stiff, the GL exhibited lower joint gapping and laxity than did the DO.

CLINICAL RELEVANCE

Understanding the biomechanics of UCL reconstruction has significant implications for postoperative management as it relates to early rehabilitation. Biomechanically inferior constructs could risk graft failure or early loosening during rehabilitation, and comparing the biomechanics of new techniques to established, widely used procedures such as the docking technique can provide important information about the immediate postoperative performance.