Effect of various reduction degrees of posterior malleolus fracture on tibiotalar joint contact / 中华创伤杂志

ABSTRACT

Objective To evaluate the effect of various reduction degrees of large posterior malleolus fracture on contact condition of the tibiotalar joint using biomechanical and finite element methods.Methods Six fresh adult cadaveric calf-foot were tested with different loadings in neutral position,10 degree of dorsiflexion,and 15 degree of plantar flexion.Models included the intact ankle and posterior malleolus fracture (not fixed,fixed with 1 mm step-off,fixed with 2 mm step-off,fixed with 1 mm gap,or fixed with 2 mm gap).Tibiotalar joint contact area,contact pressure,and peak pressure were measured using the Tek-Scan pressure sensor.In addition,a three-dimensional finite element model of the ankle joint was established and tested under the simulated biomechanical conditions.Results Mter a 500 N axial loading in the intact ankle,contact area of the tibiotalar joint was (4.94 ± 0.67) cm2 and loading strength of the tibiotalar joint was (83.4 ± 2.7) ％ of total loading strength.Contact area of the tibiotalar joint in the fracture model fixed with 1 mm gap demonstrated no significant difference in all loading conditions compared with the intact model.In 15 degree of plantar flexion,contact area of the tibiotalar joint differed between the fracture model fixed with 1 mm step-off and the intact model (P ＜ 0.05).In multiple loading conditions,contact area of the tibiotalar joint differed between the fracture models fixed with 2 mm step-off or 2 mm gap and the intact model (P ＜ 0.05).Results of finite element analysis were conformed to the related biomechanical study.Conclusions Anatomic reduction should be pursued for large posterior malleolus fracture.If difficulty exists,fracture displacement should be within 1 mm step-off and 2 mm gap so as to restore the inter-joint congruity.