The ossific nucleus in Developmental Dysplasia of the Hip. A study of relative ossific nuceus size in hips treated in the Pavlik harness and its predictive value in treatment outcome. Purpose To assess the value of measuring relative ossific nucleus (ON) size difference in Developmental Dysplasia of the hip (DDH) as a potential predictor of outcome of hips treated in the Pavlik Harness. Study Design Prospective study of all unilateral cases (n=68) of DDH identified in Southampton by dynamic ultrasound and treated in a Pavlik harness studying changes in relative ON size and acetabular indices over a mean follow up period of 3.6 years. Results All cases responding to the Pavlik harness showed a progressive correction of ON size difference. Initial ON size difference was not associated with any difference in acetabular index at the date of last follow-up. Ultrasound grading of dysplasia did not affect the rate of normalisation of ON size difference. Conclusion and clinical relevance In patients responding to treatment of DDH in a Pavlik harness, ON size difference was not found to be a useful prognostic indicator of outcome.
