Injuries of the talus and its joints.

To understand the mechanism of injury and classify fractures of the talus requires knowledge of the anatomy of the hindfoot, its function and the nature of the traumatic forces. The talus has an irregular shape with articular surfaces for tibia, fibula, calcaneus and navicular. It functions as a complex universal joint between the leg and foot created by the ankle, sub-talar and midtarsal joints. Injury may disturb function and create serious disability. As in the femoral head, osteonecrosis is a serious problem after injury to the talus. The reason for this lies in a peculiar distribution of the arterial circulation which exposes it to some injuries, but not to others. To understand the mechanism of injury is to be better prepared to properly treat these injuries and to more accurately predict their consequences. Injury occurs as motion caused by an extrinsic force is applied to the part, and when the motion is forceful enough to overcome resistance. For the talus and its joints the mechanisms of injury are: extension, flexion, inversion, eversion, and compression. Rotation, medial and lateral, may be important in the production of fractures of the talar trochlea. Combinations of these mechanisms cause complex injuries.