Diagnosis by ultrasound of congenital dislocation of the hip joint.

Two hundred thirty-four hips of 117 babies from one day to 18 months of age were examined ultrasonographically for congenital dislocation of the hip joint. Ten hips in eight babies were dislocated or subluxated and there were 11 hip dysplasias in seven babies. In the normal hip, the adaptation between the acetabulum and the femoral head is well demonstrated, and there is no apparent interposition of the limbus between the acetabular roof and the cartilaginous head. In the dislocated hip, the protrusion of the acetabular rim is not so clear as that of the normal hip, and the limbus is seen to be interpositioned between the acetabular roof and the cartilaginous head. In severe cases, the acetabular rim is hidden under the shade of the femoral head. Ultrasonography is an effective method of determining the incidence of dislocation and of diagnosing hip subluxation as well as dysplasia and does not have the hazards of x-ray examination.