[Clinical study on coxa magna during the treatment in congenital dislocation in the hip (author's transl)].

Enlargement of the femoral head is frequently observed in roentgenographs during the treatment of congenital dislocation of the hip. Clinical study was performed to clarify the definition, etiology and clinical entity of coxa magna. Three hundreds and three hip joints in 247 patients were examined roentgenographically and follow up for an average of 3.1 years. By measuring the longitudinal and cross-sectional lengths of both the femoral heads and necks, we felt that "coxa magna" should be defined as the condition with enlargement of all of these parameters. The incidence of coxa magna was 47% after open reduction, but only 5% after closed reduction. In most cases, coxa magna was roentgenographically evident approximately 10 months after open reduction. On the other hand, it was noticeable 18 months after closed reduction. In the hips without coxa magna, the acetabular index improved remarkably for 6 months following open reduction, but in the hips with coxa magna, it hardly improved. Coxa magna frequently developed femoral head deformity, unless persistent acetabular dysplasia had improved. The incidence of coxa magna appeared to be closely related to surgical intervention performed on acetabular dysplasia.