Four-Strand Versus 2-Strand Suture-Button Constructs in First Carpometacarpal Arthroplasty: A Biomechanical Study.

BACKGROUND: Suture-button fixation is an alternative to no fixation, first metacarpal distraction techniques, or Kirschner wire fixation after trapeziectomy in treatment of first carpometacarpal (CMC) arthritis. A 4-strand suture-button construct requires a 2.7-mm tunnel, whereas a 2-strand construct requires a 1.1-mm tunnel, potentially decreasing the risk of metacarpal fracture. We compared stability and failure criteria of 4-strand versus 2-strand construct in a biomechanical model of first CMC joint arthroplasty.

METHODS: Ten fresh-frozen matched pairs of human cadaveric hands were randomized to receive a 4-strand or 2-strand suture-button device. Trapeziectomy and fluoroscopic measurement of the fixed posttrapeziectomy space was performed before and after cycling 1000 times at 0.2 Hz in a custom loading device. The constructs were loaded to failure and failure mechanism was noted.

RESULTS: There was no significant difference between the groups in unfixed posttrapeziectomy, fixed precyclic loading, or postcyclic loading height. No difference in pinch pressure was found in any group. No difference in load to failure was observed. The 4-strand device failed through the first ray in 8 of 11 specimens, and the suture of the 2-strand device failed in 5 of 9 specimens.

CONCLUSIONS: The 4-strand and 2-strand suture-button constructs provide comparable biomechanical stability for first CMC arthroplasty. If construct stability is similar between these procedures, the smaller tunnel used with the 2-strand construct may offer an advantage.