Lateral ankle ligament injuries. Inversion and anterior stress radiography.

Known anatomic lesions of the ankle ligaments were correlated with stress radiographic measurements on both anteroposterior and lateral projections, and the effect of foot position during stress radiography was determined. In autopsy specimens ankle ligaments were surgically divided to produce various single and combined lesions. The resulting instability was then assessed by stress radiography in two planes. Talar tilt and anterior displacement of the talus were related to the lesions present. Talar tilt did not normally exceed 4 degrees, and significant tilt occurred only when more than one component of the lateral ligament had been divided. Anterior displacement of the talus did not normally exceed 6 mm when measurement was made from the posterior lip of the tibia to the nearest part of the talar dome. Up to 14 mm of displacement was observed when the anterior talofibular ligament was divided alone or in combination with other ligaments with the foot plantigrade. The anterior stress radiograph should be obtained with the foot in this position. Both inversion and anterior stress radiographs are of value in demonstrating ankle instability and may help in the diagnosis of specific lesions.