The influence of ankle positioning on the radiography of the distal tibial tubercles.

Three embalmed human lower legs, with the anterior and posterior tubercles of the distal tibia marked with needles, were radiographed in four positions of rotation to describe the projection and the configuration of the distal tibial tubercles and the tibiofibular syndesmosis, since the distal tibial tubercles are often described incorrectly in the literature. The anterior and posterior tubercles have distinct features that can be recognized in different positions of rotation. The anterior tubercle has an angular shape with its maximum dimension approximately 1 cm above the joint line. The posterior tubercle is a rounded structure in continuity with the posterior lip of the tibia, projecting caudally from the anterior tubercle superimposed on the talus. It was shown that the tibiofibular clear space (TFCS) and the tibiofibular overlap (TFO) differ considerably with rotation and that neither the TFCS nor the TFO depicts a constant syndesmotic interval. Both change considerably with varying rotational projections. To achieve uniformity it is recommended that the TFCS be measured as the distance between the medial border of the fibula and the floor of the incisura, and the TFO as the distance between medial border of the fibula and the anterior tubercle, both on the anteroposterior radiograph.