1. Eight cases of a relatively uncommon fracture of the lateral portion of the distal tibial epiphysis are described.
2. This fracture represents the adolescent counterpart of the fracture of Tillaux in adults and is caused by a lateral rotatory force with avulsion of the lateral portion of the distal tibial epiphysis by the inferior tibiofibular ligaments.
3. The middle and medial thirds of the distal tibial epiphyseal plate appear to close before the lateral. As a result for about eighteen months before closure becomes complete the middle portion of the epiphysis is united while the lateral portion is not. During this period the lateral portion of the epiphysis is vulnerable to fracture by lateral rotation stress.
4. When the fracture is recognized and the fragment is replaced a good anatomical and functional result may be expected.