Diagnosis and relevance of suspected dysplasia of the hip joint, radiologic investigation starting with the age of 3 months.

Abstract

The acetabular angle (Hilgenreiner 1940) was determined on 2194 hip joints of 1097 unselected infants without history or suspicion of dysplasia at the admittance to the hospital. The mean values and standard deviations were compared to the values published by Tonnis and Brunken (1968) in Berlin and Kristen et al. (1976) in Vienna. The data of Tonnis and Brunken show considerably higher values than our investigations, probably due to some selection, as infants with a history of suspicious signs of dysplasia and repeated investigations at different ages in the same patients are included. The differences to the tables, given by Kristen et al. are of minor degrees and explainable with the small number of determinations. The serial X-ray investigations of apparently normal hip joints seemed to be justified as we used a standardized X-ray technique with gonad protection by a fenestrated lead shield in the shape of a butterfly (Krepler 1976) and ultra-high speed screen-film combinations. The radiation dose in the girls, measured in the rectum, was reduced to 0.12 mrad and in boys behind the testes less than 0.1 mrad. In the line of this investigation we found in 11.1% of the hip joints some radiologic suspicion of dysplasia, in 2.2% on account of an acetabular angle outside of the limit of +2 SD, 2.2% between 1 and 2 SD and in 6.4% because of only insufficient development of the acetabulum, especially the edge of the roof. In 9 infants (0.82%) the X-ray showed clear dislocation of the femoral head with urgent need for reposition treatment. The importance of early diagnosis of signs of dysplasia of the acetabulum by radiological investigations in infants beyond the age of 3 months is discussed in respect of prophylactic treatment, with the aim to prevent early arthrosis of the hip caused by incongruences of the femoral head and acetabulum. The mechanisms of a possible change for the worse of dysplasia in older infants must be different to accepted theories of the causation of congenital luxation in the newborn as laxity of the capsule and ligaments of the hip joints caused by maternal hormones. Instead of the laxity of the capsule, signs of contracture develop and the failure in the formation of the acetabular roof—if not corrected spontaneously or by early treatment—is an important secondary cause of later damage to the hip joint.