Twelve hips in eleven infants with developmental dysplasia of the hip (DDH) treated by open reduction were reviewed. According to Graf's classification ultrasonographically there was one type D hip, seven type III hips and four type IV hips. Magnetic resonance imaging showed that all 12 limbuses were interposed between the acetabulum and femoral head. The shape of limbuses on magnetic resonance imaging represent the complexities of developmental dysplasia of the hips more clearly than ultrasonographic classifications. Two types of DDH resulted in open reduction. The first type had iatrogenic complexities and the second type teratologic. The former type of DDH was derived from missed diagnosis at the time of examination of newborn hips or inadequate usage of the Pavlik harness in the course of treatment. Conservative treatment is effective for this type of hip by addressing the given problems; however, open reduction may be more effective for the latter type of DDH because of complexities.
