Biomechanical analysis of new cross locking plates for metacarpal neck fracture

Purpose In this study, the fixation strength of the new cross locking plate for metacarpal neck fracture was compared with Kirschner-wire (K-wire) or traditional dorsal locking plate. Methods Transverse metacarpal neck fracture models were created on 24 artificial metacarpal bone specimens using saw blade. The specimens were then divided into three groups of different fixation methods: (1) Two K wires (KW group); (2) Traditional dorsal locking plate (TP group); and (3) New cross locking plate (NP group). All specimens were examined with cantilever bending test on a material testing system, and the maximum fracture force and stiffness were used as indicators to evaluate the facture fixation strength. The results were compared using a one-way analysis of variance and Tukey test for post hoc analysis. Results For the maximum fracture force, the fixation capacities of the three metacarpal neck fracture groups were ranked as follows: TP group (355.8±42.5 N, mean±standard deviation)≅NP group (353.9±49.3 N) > KW group (193.3±32.8 N). For stiffness, the fixation capacities of the three groups were ranked as follows: TP group (69.0±4.8 N/mm)≅NP group (64.2±6.3 N) > KW group (27.0±5.8 N). Conclusion The fixation strength of the new cross locking plate was similar to that of the traditional dorsal locking plate and was substantially higher than that achieved when only two K-wires were used. In addition, the new cross locking plate may reduce the occurrence of tendon adhesion, joint stiffness, and the screws being pulled out from the metacarpal head, which can be caused by traditional dorsal locking plates.