Treatment of developmental dysplasia of the hip with the Pavlik harness: factors for predicting unsuccessful reduction.

To evaluate the risk factors for unsuccessful reduction, we reviewed 100 hips with developmental dysplasia of the hip treated with the Pavlik harness. We divided them into a successful reduction group (reduced without avascular necrosis) and an unsuccessful reduction group (reduced followed by avascular necrosis or unreduced). We compared Yamamuro's distance A, the acetabular angle and age at initial application of the Pavlik harness between the two groups. Our data suggest that a Yamamuro's distance A of 7 mm or smaller, an acetabular angle of 36 degrees or greater, and an age at initial application of 4 months or older are risk factors.