By: Terry R. Yochum, DC, DACBR, Fellow, ACCR, and Chad J. Maola, DC
These two young athletes had a severe inversion strain of their ankles playing soccer and could barely bear weight. (Figures 1 & 2) Note the oblique radiolucent fracture line through the distal fibula of both patients.
The routine radiographic evaluation of the ankle consists of three views: anteroposterior, lateral, and medial oblique. The medial oblique projection is taken with 35–45 % of internal rotation of the foot. Special projections (i.e., stress views) may be helpful in demonstrating subtle fractures or dislocations.
The stress views are valuable to confirm ligamentous injuries. They should also be obtained bilaterally whenever there is a question of an increase in width of either the medial or lateral clear space on the radiograph.1 The views should be obtained with adduction or abduction of the heel and inversion or eversion of the foot, depending upon which ligament is suspect.2
Fractures of the Ankle
Medial Malleolus Fracture. The medial malleolus is the most distal portion of the tibia. The fracture is usually transverse or oblique in its orientation. This is due to angular forces generated by movement of the talus against the medial malleoli. Fractures of the medial malleolus distal to the corner formed in the ankle mortise within the plafond are more stable than those that arise either within the plafond or at the medial corner of the plafond. The plafond is defined as the distal tibial joint surface and is a French term meaning “ceiling.” The medial malleolus fracture is best seen on the anteroposterior radiograph as a radiolucent line with adjacent soft tissue swelling.
Lateral Malleolus Fracture. The most distal portion of the fibula is the lateral malleolus. The most common fracture of the lateral malleolus is an oblique or spiral fracture extending from the inferior and anterior margin upward and backward to the posterior margin of the shaft of the distal fibula (Figures 1 & 2). This fracture occurs as a result of outward or external rotation of the foot and is best observed on the medial oblique projection as a radiolucent oblique line with adjacent soft tissue swelling. A variety of small avulsion fractures occur around the tips of either the medial or lateral malleolus. These occur as a result of pull mediated by the medial or lateral collateral ligaments.
Bimalleolar Fracture. Bimalleolar fracture represents a fracture through both the medial and lateral malleolus. The fracture on one side is transverse, because of tensile forces, and the opposite fracture is oblique or spiral.2 Diffuse soft tissue swelling over the malleoli is often present, alerting the observer to look close for fracture.
1. Yochum TR, Rowe LJ. Essentials of Skeletal Radiology, 3rd ed. Baltimore: Williams & Wilkins, 2005.
2. Kleiger B. Mechanisms of ankle injury. Orthop Clin North Am 1974; 5:127.