Acetabular development in developmental dysplasia of the hip complicated by lateral growth disturbance of the capital femoral epiphysis

Background: Lateral growth disturbance of the capital femoral epiphysis is the most common type of physeal arrest complicating the treatment of develo pmental hip dysplasia. Although this type of physeal damage has been assume d to result in poor acetabular development, the natural history of dysplast ic hips affected by this pattern of growth disturbance is still unclear. To investigate this issue, we evaluated acetabular development in a retrospec tive study of fifty-eight hips in forty-eight patients who had lateral phys eal arrest after management of developmental hip dysplasia. Methods: Of the fifty-eight hips, thirty-six were reduced closed and twenty -two were reduced open. The average age of the patients,vas twenty-two mont hs (range, three to ninety-seven months) at the time of the reduction and t wenty-one years (range, ten to fifty-five years) at the time of the latest follow-up evaluation. Hips rated as Severin class I (an excellent result) o r II (a good result) were defined as having a satisfactory result, and thos e rated as Severin class III (a fair result) or IV (a poor result) were con sidered to have an unsatisfactory result. Specific femoral head changes wer e sought in the complete radiographic files on all hips, Various radiograph ic parameters of hip integrity, including the degree of lateral tilt of the capital femoral epiphysis, were measured over time, and comparisons were m ade between hips classified as satisfactory and those classified as unsatis factory at four tine-points: before the reduction, at two years after the r eduction, at six to eight years of age, and at the time of the final follow -up. Results: Lateral growth disturbance of the capital femoral epiphysis was fi rst evident by an average of ten years of age (range, four to fourteen year s of age). There was no consistent early pattern of changes in the epiphysi s, physis, or metaphysis related to later development of valgus tilt of the epiphysis, Thirty-four hips (59 percent) were rated as satisfactory and tw enty-four were rated as unsatisfactory at the latest follow-up evaluation, Hips classified as unsatisfactory exhibited poor acetabular development by an average age of seven gears. The inclination of the epiphyseal plate beca me progressively more horizontal or even reversed over time; however, seria l measurements of inclination were not significant predictors of Severin cl assification. Conclusions: Lateral growth disturbance of the capital femoral epiphysis is not necessarily associated with poor acetabular development, as when dyspl asia does occur it is generally evident prior to the identification of the physeal arrest. It is important to monitor acetabular development after red uction rather than search for radiographic changes of physeal arrest, which are difficult to defect in young children.