Diastasis with low distal fibula fractures: an anatomic rationale.

Tibiofibular diastasis occurs infrequently in displaced ankle fractures that include a low fibula fracture. This is because the interosseous ligament, the major ligament resisting diastasis, lies above the level of the fracture. The anatomic study of the syndesmotic complex of the ankle reported here showed that the interosseous ligament has a variable attachment on the fibula, differing between specimens in its distance above the synovial reflection or joint line. Although most specimens had attachments approximately 1 cm or greater above the joint line, one of 18 specimens attached just above the synovial reflection. In such a case, a low fibula fracture would disrupt the interosseous ligament, which explains the anatomic basis for the infrequent diastasis in these ankle fractures.