The effect of loading on tibiotalar alignment in cadaver ankles

The tibiotalar movements which occur with axial loading, without applied moment forces were studied in cadaver ankles using a minimally constrained testing apparatus. Lateral translation of the talus measured up to 2 mm, which was associated with increased tibiotalar valgus angulation. Neither displacing the distal fibula laterally, nor sectioning the deltoid ligament, significantly influenced the talar shift. The tibiotalar motion which was observed after simple axial loading in a stable configuration (e.g., fibula and deltoid ligament intact) is of the same magnitude that is usually regarded as signifying an unstable ankle fracture. Consequently, this study suggests that the criteria for an unstable ankle fracture may need closer scrutiny.