Magnetic Resonance Imaging of anatomical variants of the subtalar joint

To evaluate MRI with thin slices to depict anatomical variations of the subtalar and talocalcaneonavicular joints. Ankle MRI was performed in 51 patients. The articular configurations were differentiated on sagittal T1-weighted and three-dimensional (3D) DESS images. Multiplanar reconstructions were performed. The variation in curvature of the posterior facet of the calcaneus and talus was analysed. 3D surface-rendered images of the calcaneus were obtained. All images were studied by an experienced physical therapist. Analysis revealed that 18 (36.7%) of the subjects had 3 distinct facets on the calcaneus. A missing anterior facet was revealed in five (10.2%) of subjects. Twenty-six (53.1%) subjects showed a fusion of the anterior and middle facets. In four cases, an articulation was found between the talus and the cuboid bone. At the posterior talocalcaneal articulation, variations were observed of the curvature of the medial side of the joint. The configuration of the facets of the talocalcaneal joints can be analysed on MR images. On 3D images, an articular connection was seen between the talus and the cuboid bone, as well as variations in the curvature of the posterior talocalcaneal joint. These anatomical variations may have implications for mobility and stability of the ankle.