Biomechanical Comparison of 3 Thumb Ulnar Collateral Ligament Repair Methods.

PURPOSE

Differences in range of motion, pinch strength, biomechanical strength, or joint angulation have previously been investigated for various means of treatment of ulnar collateral ligament (UCL) tears. We sought to address a gap in the literature by comparing thumb metacarpophalangeal (MCP) joint angle measurements and biomechanical strength before complete, acute UCL tear and after repair with suture anchors (SA), suture tape (ST) anchor augmentation, or reconstruction with palmaris longus graft (PL).

METHODS

Thumbs and, if present, the PL tendon were harvested from 15 fresh-frozen cadavers. Each thumb specimen was secured into a servohydraulic biomechanical testing frame to evaluate native radiographic MCP joint angles at 0° flexion when loaded with 0, 5, and 13 N of radial force. Subsequently, a single hand surgeon (S.M.K.) performed complete transection and UCL repair via 1 of 3 methods: SA (n = 5), ST (n = 5), or reconstruction with PL (n = 5). Following repair, MCP joint angles were radiographically evaluated. Specimens that did not fail during joint angle testing were transferred to a separate testing frame for load-to-failure testing. Angle measurements and mean load-to-failure were compared between the groups, and angulation was also compared with each group's native control.

RESULTS

Both ST and SA groups demonstrated comparable stiffness to their native controls, whereas the PL group was significantly more lax. The ST repair was significantly stiffer than the other constructs. ST also required higher forces to reach failure compared to both SA and PL. No difference was found between SA and PL groups.

CONCLUSIONS

Although both ST and SA constructs recapitulate native joint stiffness, repair with ST demonstrated the greatest biomechanical strength in stiffness and load-to-failure.

CLINICAL RELEVANCE

For complete, acute tears of the thumb UCL, ST may be superior for maintaining MCP joint stability and strength over SA and PL.