[A radiological study of the hip in cerebral palsy in relation to pathogenesis of dislocations]

In recent years it has been reported that dislocation of the hip in cerebral palsy (CP) occurs most frequently in the non-ambulatory patient. This study compares the radiographic anatomy of the hip in CP with normal values and suggests the cause of dislocation. The cases of CP were divided into three groups according to ambulation and dislocation: group 1 consisted of 111 hips in a total of 64 ambulatory children, group 2, 116 hips in 72 non-ambulatory children, and group 3, 37 hips including 13 dislocated hips and 24 subluxated hips in 32 children. Of these 37 hips, patients with a dislocated hip and 3 subluxated hips were ambulatory but the beginning of their independent walking was as late as 5 years of age or even later. The following results were obtained. Femoral antetorsion was markedly increased in CP, and the difference was statistically very significant for all groups 1, 2 and 3 (p less than 0.001, and p less than 0.01 between groups 1 and 2). In CP groups there was no regression with age. Significant increases in femoral inclination were found in CP groups (p less than 0.001). There was, however, no significant differences among groups 1, 2 and 3, and so the degree to which these were the cause for dislocation was less than that of femoral antetorsion. Significant shortness of the femoral neck was noted between groups 1 and 3 (p less than 0.01), with significant regression with age in all CP groups. The mean value of the acetabular index in group 3 was 34.5 +/- 5.9, which was significantly higher than in group 1, and group 2 (p less than 0.001). In groups 2 and 3 there was no regression with age. Thus dislocation and subluxation of the hip in CP can be caused by the increase of antetorsion of the femur and acetabular dysplasia and depend on the ability of walking.