[Femoroacetabular impingement related to Legg-Calvé-Perthes disease].

Femoroacetabular impingement is an undesirable contact between acetabular rim and femoral neck and presents abnormality of proximal femoral part and acetabulum, as well. Two forms may appear: cam impingement and pincer impingement. Femoroacetabular impingement related to Legg-Calvé-Perthes disease may be caused by various reasons, as the consequence of the disease itself, and as the consequence of its treatment. Coxa magna deformity (large femoral head and neck) and coxa brevis deformity (shortened femoral neck) may produce cam femoroacetabular impingement during hip flexion. After the disease, the flattened femoral head (coxa plana) may persist. Chiari pelvic osteotomy is the only treatment option for such femoral head deformity. Acetabular labrum squeezed continuously between the femoral head and the non-articular part of the cut iliac bone lead to cam femoroacetabular impingement, as well. If Salter or triple pelvic osteotomy is used that may cause a very large iatrogenic acetabular retroversion, we can also refer to radial type pincer femoroacetabular impingement. Treatment of Legg-Calvé-Perthes disease should be conducted according to the natural course of the disease and prognosis. Treatment should start on time, well before a crushed femoral head develops, because it is the easiest way to establish hip spherical congruency at the end of treatment. This is the best option to prevent secondary hip arthrosis caused by femoroacetabular impingement or by insufficient head coverage at the end of remodelling. In each case of delayed hip pain, followed by a limited range of movements, femoroacetabular impingement should be taken into consideration, confirmed, and treated by some of the available therapeutic methods.