Influence of various displacement modes of lateral malleolus associated with ankle fracture on tibiotalar joint contact: a finite element analysis

Abstract

Objective To investigate the impacts of various displacement modes of lateral malleolus on the tibiotalar joint contact in ankle fractures. Methods The computed tomography scans of a normal adult volunteer were used for three-dimensional reconstruction of the whole ankle joint, including its cartilage and adjacent ligaments. Axial compressive loads during mid-stance and boundary conditions were set to sim-ulate the lateral displacement, shortening, internal rotation and external rotation of the fibula following ankle fracture. Magnitude and distribution of the peak contact stress on the tibiotalar joint were compared among various displacement modes of the lateral malleolus. Results The magnitude and distribution of the peak contact stress on the tibiotalar joint varied among the 4 fibular displacement modes. Compared to the reference model, the deviations of peak contact stress for the modes of shortening, lateral displacement, internal rotation and external rotation were 10.23%, 45.22%, 17.68%, and 17.68%, respectively. Regarding the distri-bution of contact stress on the tibiotalar joint, the fibular shortening significantly increased the contact area on the anterior facet and the lateral displacement of the fibula widened the ankle joint and pulled the talus out-wards. This made the articular contact migrate medially, resulting in a decreased contact area. When either internal or external rotation occurred to a certain extent, the contact area was transferred from the medial malleolus to the anterior tibiotalar facet. Conclusions In ankle fractures, various displacement modes of the lateral malleolus may affect the tibiotalar contact condition, especially the lateral displacement, internal rotation and external rotation of the lateral malleolus. This study may provide a theoretical basis for diagnosis and reconstruction of malreduction, maluion, secondary joint pain and arthritis following an ankle fracture. Key words: Ankle joint; Fractures, bone; Biomechanics; Finite element analysis