Plating of pilon fractures based on the orientation of the fibular shaft component: A biomechanical study evaluating plate stiffness in a cadaveric fracture model.

OBJECTIVES: To evaluate mechanically superior method of pilon fracture fixation by comparing axial stiffness between anterolateral and medial tibial locking plates in a cadaveric fracture model.

METHODS: Eight matched pairs of fresh frozen cadaver specimens (lower limb after through-knee disarticulation) were used to eliminate confounder of bone quality. Simulated pilon fractures were created so that each pair represented either varus or valgus fracture pattern (AO 43-A2) with associated fibular fractures (transverse or comminuted). Specimens were plated with DePuy anterolateral or medial locking plate and axial load applied, measuring displacement at the fracture site. Each lower extremity was tested with a fracture wedge in place and removed to mimic comminution. Average force at which failure occurred was compared between the two fixation methods, for varus and valgus fracture pattern respectively, with the use of a Mann-Whitney U test.

RESULTS: On average, medial plate fixation of varus fractures resulted in 2.27 times (range of 1.6-3.9) greater load prior to failure as compared to anterolateral plate. Similarly, valgus simulated fractures tolerated 1.6 times (range 1.12-2.34) higher force prior to failure if anterolateral plate was applied versus medial plate. Analysis utilizing the Mann-Whitney U test for fracture patterns vs plate configuration approached statistical significance (p = 0.081 varus failure and p = 0.386 valgus failure).

CONCLUSIONS: Lateral plate fixation is biomechanically superior for pilon fractures resulting from valgus force as evident by comminuted fibular fracture. Similarly, medial plate location resulted in improved stiffness in compression for varus type fractures, evident by transverse fibular fracture. We approached statistical significance, however our lack of power regarding adequate sample size is an issue that is consistent with other biomechanical studies in this area.