Anterior Dislocation of the Hip in Cerebral Palsy

Hip dislocations are common in children with cerebral palsy (CP) if there is no early surveillance and early treatment. Most of these dislocations are posterior superior which present with limited hip abduction, increased hip flexion and internal rotation. However, there is an uncommon group of children with CP who present with an anterior hip dislocation. The radiographs of these hips are often not clearly abnormal because the femoral head displacement is in the plane of the anterior posterior radiographic image. A CT scan is usually required to get a clear image of the problem. The physical examination is more clear with the femoral head coming anterior in the groin and can be palpated. Three types of anterior hip dislocations occur, type I has the hip and knee in full and fixed extension and the hip in adduction and external rotation. Type II hips are in hip extension, external rotation, and abduction, with the knee in severe flexion. Type II hips occur in hypotonic children with no contractures who often ambulate. The main problem of the type I and II hips is severe difficulty sitting, and the type III hips usually are losing ability to the walk. The treatment of all three requires repair of the anterior acetabular deficiency, femoral varus osteotomy, and correction of the associated contractures. The outcome of the treatment should be improved seating for types I and II and improved gait for type III.