Neonatal hip: from anatomy to cost-effective sonography.

Therapeutic success in treating congenital dysplasia of the hip is associated with early diagnosis, but the specific neonatal anatomy makes screening difficult. The purpose of this study was to determine whether this specific neonatal anatomy is taken into account by current ultrasound (US) techniques. Anatomic studies were performed on 22 hips, US examinations on 7750 neonatal hips; 2370 untreated hips were reexamined at 1 month by US and at 3 months by X-ray. The transformation of the neonatal cartilaginous acetabulum into an osseous cavity is dependent on harmonious metaphyseal growth and a properly seated femoral head. Defects in the acetabular roof, together with displacement of the femoral head, cause an abnormal anatomical relationship which leads to further deformities. The described sonographic techniques give only partial information on these specific abnormalities. The sonographic monoplanar methods as used in Graf's technique, which relies largely on acetabular development, lead to difficulties in assessing posterior coverage of the femoral head and difficulties in assessing alignment of the metaphyseal weight-bearing surface with the femoral head. Combining Graf's morphological analysis with Novick's dynamic technique enables one to more accurately define the relationship of the femoral head and the acetabulum and increases the reliability and predictive value of the examination, while reducing the number of doubtful cases. This makes screening cost effective.