Biomechanical Strength of Thumb Metacarpophalangeal Joint Ulnar Collateral Ligament Reconstruction With Button Autograft and Suture Suspension (BASS) Technique in a Cadaveric Osteolysis Model.

Abstract

Polyetheretherketone anchors used for thumb metacarpophalangeal (MP) joint ulnar collateral ligament (UCL) repair/reconstruction may be associated with osteolysis and subsequent failure, which presents challenges to revision reconstruction. This study evaluated the biomechanical integrity of thumb UCL reconstruction in a cadaveric osteolysis model. Twelve thumb MP joints at 0° of flexion were loaded to failure by applying valgus force to produce UCL injury. Both clinical failure, defined as the force necessary to elicit 30° of angular displacement or 11.5 mm of vertical displacement across the MP joint, and structural failure, the maximum force applied to produce a decrease in resistance, were recorded. One specimen fractured during testing and was excluded. In the remaining 11 specimens, osseous tunnels (5 mm diameter × 10 mm depth) were drilled at the ligament proximal origin and distal insertion to simulate osteolysis. The UCL was reconstructed with button suspension of palmaris longus tendon autograft and nonabsorbable suture (button autograft and suture suspension, BASS), and the MP joints were again loaded to clinical and structural failure recording force, anatomic location, and mode of failure. The experimental group was compared to intrinsic native ligament controls using paired t tests. Eleven specimens had complete data for comparison of the reconstruction to native ligament. Native UCLs failed clinically at 112 ± 38 N and structurally at 169 ± 75 N, whereas BASS UCL reconstruction in the osteolysis model failed at significantly less force: clinically 27 ± 12 N and structurally at 68 ± 37N. All UCL reconstructions failed by fracture: 8/11 at the proximal phalanx and 3/11 at the metacarpal. BASS UCL reconstruction in the setting of osteolysis produced a weaker construct than the native UCL but provided biomechanical strength similar to established UCL reconstruction methods. This study detailed the biomechanical strength of this technique and informs postoperative rehabilitation considerations when osteolysis is present.