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

Abstract

Background: Lateral growth disturbance of the capital femoral epiphysis is the most common type of physeal arrest complicating the treatment of developmental hip dysplasia. Although this type of physeal damage has been assumed to result in poor acetabular development, the natural history of dysplastic hips affected by this pattern of growth disturbance is still unclear. To investigate this issue, we evaluated acetabular development in a retrospective study of fifty-eight hips in forty-eight patients who had lateral physeal 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 was twenty-two months (range, three to ninety-seven months) at the time of the reduction and twenty-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) or II (a good result) were defined as having a satisfactory result, and those rated as Severin class III (a fair result) or IV (a poor result) were considered to have an unsatisfactory result. Specific femoral head changes were sought in the complete radiographic files on all hips. Various radiographic parameters of hip integrity, including the degree of lateral tilt of the capital femoral epiphysis, were measured over time, and comparisons were made between hips classified as satisfactory and those classified as unsatisfactory at four time-points: before the reduction, at two years after the reduction, 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 first evident by an average of ten years of age (range, four to fourteen years of age). There was no consistent early pattern of changes in the epiphysis, physis, or metaphysis related to later development of valgus tilt of the epiphysis. Thirty-four hips (59 percent) were rated as satisfactory and twenty-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 years. The inclination of the epiphyseal plate became progressively more horizontal or even reversed over time; however, serial measurements of inclination were not significant predictors of Severin classification. Conclusions: Lateral growth disturbance of the capital femoral epiphysis is not necessarily associated with poor acetabular development, as when dysplasia does occur it is generally evident prior to the identification of the physeal arrest. It is important to monitor acetabular development after reduction rather than search for radiographic changes of physeal arrest, which are difficult to detect in young children.