A radiographic evaluation of the tibiofibular syndesmosis.

A radiographic evaluation of the normal as well as the progressively widened tibiofibular interval in the area of the syndesmosis was done using 12 fresh cadaver lower extremities. The width of the tibiofibular "clear space" and the amount of tibiofibular overlap was determined on accurately positioned anterior-posterior and mortise radiographs. Based on a 95% confidence interval, measurements obtained for the intact specimens would support the following criteria as consistent with a normal tibiofibular relationship: (1) a tibiofibular "clear space" on the anterior-posterior and mortise views of less than approximately 6 mm; (2) tibiofibular overlap on the anterior-posterior view of greater than approximately 6 mm or 42% of fibular width; (3) tibiofibular overlap on the mortise view of greater than approximately 1 mm. The width of the tibiofibular "clear space" on both anterior-posterior and mortise views appeared to be the most reliable parameter for detecting early syndesmotic widening.