This investigation examined the validity of the hypothesis that the acetabulum in congenital dislocation of the hip will develop satisfactorily provided accurate congruous and concentric reduction is obtained as early as possible, and is maintained throughout growth.

Seventy-two patients with eighty-five hips were studied. The children were more than one year old on admission and over ten years at the time of review. Acetabular development was assessed radiologically by measurement of the acetabular angle. Angles of less than 21 degrees were regarded as normal, and more than 21 degrees as indicating some failure of development. Satisfactory acetabular development occurred in 80 per cent (angles 24 degrees or below), and was unsatisfactory in 20 per cent (angles above 24 degrees).

If three errors in management, namely failure to obtain congruity, failure to maintain congruity and ischaemic necrosis secondary to manipulative reductions, are excluded from the analysis, it is found that 95 per cent of acetabula develop satisfactorily. The outcome is largely independent of the age on admission up to four years old, and of bilateral involvement. It is concluded that acetabuloplasty should not be necessary if the patient is admitted under the age of four or congruity is obtained in the functional position under four and a half years.