| Abstract: | The factors which determine the rate and amount of acetabular growth in congenital dislocation of the hip are ill-understood. A prospective radiological study has been devised in order to assess the influence of the age of congruity, femoral anteversion and neck/shaft angles on acetabular growth. To be included, the children must have reached at least 8 years of age. Those with associated congenital abnormalities and subluxation were excluded, as were those who had operations for acetabular reconstruction. Seventy-four hips were suitable for analysis, and the age range at follow-up was from 8 to 17 years. The acetabular angle was used as an index of acetabular growth. Measurement of this angle, and the anteversion and neck/shaft angles were made before, and each year after reduction of the hip. Congruity was assessed from a radiograph with the legs in the functional position. A satisfactory acetabulum was obtained in 44 hips and the mean age of congruity was 33 months; the acetabulum was unsatisfactory in 30 hips, with a mean age of congruity of 48 months. Four years is the critical age, for if congruity is obtained later, the risk of producing a moderate or severely dysplastic acetabulum is more than doubled. If congruity is obtained under four years of age, growth of the acetabulum with continue in most patients up to 8 and in some to 11 YEARS OF age; the resulting acetabulum was normal or mildly dysplastic. Fifty-nine per cent of the satisfactory hips at follow-up had a normal anteversion angle, and 6 per cent a normal neck/shaft angle. Correction of these angles by themselves, seems not to be a major importance for promoting acetabular growth. |
