Biomechanical comparative study of the JuggerKnot™ soft anchor technique with other common mallet finger fracture fixation techniques

Abstract

BACKGROUND: Bony mallet finger involves an avulsion fracture of the terminal extensor tendon insertion. Most do well with conservative treatment using splinting. Surgical fixation is indicated in open injuries, avulsion fracture involving at least one third of the articular surface and failed splinting treatment. Both treatment methods have limitations. Usual splinting protocol requires 6 weeks of full-time use and another 6 weeks for weaning. They are cumbersome, have compliance issues and most result in extension lag. Currently, there is no biomechanical sound repair that can allow mobilization after fixation and thus most result in loss of flexion range. This study was designed to compare the peak load resistance of the JuggerKnot™ (Biomet) soft anchor fixation to other fixation methods (Kirschner wire, pull-out wire, tension-band wiring) and to assess whether the suture anchor technique can allow early mobilization without protection. MATERIALS AND METHODS: Four different fixation techniques were assigned among twenty-four specimens (all fingers, no thumbs) from six cadaveric human hands in a randomized block fashion. Only one technique was performed on each finger. A downward load was applied to flex the distal phalanx and the maximum loading force was recorded. The load was tested at 30 degrees, 45 degrees and 60 degrees of flexion of the distal interphalangeal joint. Two separate data sets were performed for each finger before and after the osteotomy and fixation. The data underwent Shapiro-Wilk normality testing before analysis. The values of the mean peak load of the four groups were compared using the one-way analysis of variance test. RESULTS: All data points passed the Shapiro-Wilk test for normality. The mean peak load of the tension-band wiring group was 67.8N at 60 degrees of flexion which was significantly higher than the other three groups (p=0.008). The JuggerKnot™ fixation had mean peak loads of 13.35N (30°), 22.51N (45°) and 32.96N (60°) which were all above the required load for mobilization. No complications of implant failure or fragmentation of the dorsal fragment was noted. CONCLUSION: Tension-band wiring was the strongest fixation method but most technically demanding. The JuggerKnot™ soft anchor fixation was the most user-friendly, does not require trans-articular Kirschner wire fixation for protection and allows for safe immediate mobilization of the joint after fixation. Future studies are required to assess the fatigue strength of the fixation and the applicability in the clinical setting.