[Avulsion fractures of the greater trochanter in children: two cases, review of the literature and proposition for a classification].

Avulsion fractures of the greater trochanter are very rare in children. We report two such cases which led to femoral head necrosis. Based on these two cases and an extensive review of the literature, we discuss the pathophysiology of this complication and propose a new classification system. Three types of lesions can be identified as a function of the mechanism causing fracture. Type 1 lesions are avulsion fractures of the greater trochanter secondary to acute contraction of the gluteus muscles. This contraction produces a vertical displacement of the greater trochanter. Femoral head necrosis has never been reported as a complication after this type of fracture mechanism. Type 2 avulsion fractures are associated with fracture of the femoral neck with a subsequent risk of femoral head necrosis. Type 3 associates hip dislocation with apophyseal avulsion with, according to the literature, an inevitable progression to head necrosis. The two cases reported look identical with those described by Linhart and Kawenblum illustrate type 3 avulsion fractures of the greater trochanter.