Biomechanical Comparison of Fifth Carpometacarpal Fusion Methods: Kirschner Wires Versus Plate and Screws

BACKGROUND: Fractures and dislocations of the base of the fifth metacarpal can lead to arthritis of the fifth carpometacarpal (CMC) joint. For patients who are symptomatic and fail conservative management, arthrodesis of the fifth CMC joint can be offered. The fusion can be performed using Kirschner wires (K-wires), but can lead to complications such as pin tract infection and pin migration. A low-profile locking plate may represent an attractive alternative. The purpose of this study was to compare the biomechanical stability of these 2 fusion techniques. METHODS: Twelve fresh frozen cadaver hands were divided into 2 groups. The first group underwent fixation of the fifth CMC joint using 2 1.6 mm (0.062 inches) diameter K-wires in a cross-pin configuration. The second group underwent fixation using a 2.0 mm locking plate with 2 locking screws in the hamate and 3 nonlocking screws in the fifth metacarpal shaft. The specimens were then loaded in extension until failure. RESULTS: The stiffness was 15.0±7.2 N/mm for the K-wire group and 14.7±6.0 N/mm (mean±SD) for the plate group (P=0.9366). The peak loads were 62.5±40.0 N and 64.6±24.8 N for K-wire and plate groups, respectively (P=0.9181). The energy to peak load was 294±281 N mm for the K-wire group and 418±190 N mm for the plate group (P=0.3904). CONCLUSIONS: Fifth CMC fusion using either K-wires or plate and screws showed no significant difference in stiffness, peak load, and energy to peak load. These results suggest the 2 methods provide similar biomechanical stability.