The Evaluation of a Flexor Digitorum Profundus-to-Volar Plate Zone I Repair Versus Button Repair: An In vitro Biomechanics Study

Purpose: The purpose of the study was to evaluate joint kinematics and tendon work of flexion (WOF) following a flexor digitorum profundus (FDP)-to-volar plate (VP) repair technique relative to a pullout button for zone I flexor tendon injuries.

Methods: Fourteen digits were tested using an in vitro active finger motion simulator under 3 repaired conditions following a simulated zone I avulsion: button, FDP-VP, and "no slack" FDP-VP (corrected for additional VP length). Outcome metrics included active joint range of motion (ROM), fingertip strength, FDP and flexor digitorum superficialis tensile loads, and WOF.

Results: The button and FDP-VP techniques restored WOF to the intact condition for FDP and flexor digitorum superficialis. All repairs restored distal interphalangeal joint ROM and kinematics to the intact condition. Similarly, all repairs restored WOF; however, the "no slack" FDP-VP significantly increased WOF by 10% to 12% over the simple FDP-VP repair. The button technique had similar fingertip strength to the intact condition, whereas the FDP-VP repairs significantly reduced peak fingertip strength from intact, albeit only 1-2 N compared with the button repair.

Conclusion: In this in vitro cadaveric model, the button and FDP-VP techniques restored WOF and ROM to within intact levels, with no difference between these repairs in all measured outcome metrics.

Clinical relevance: Based on its initial strength and its equal biomechanical performance compared with the button repair, the FDP-VP technique may be a viable option for treating FDP avulsions.