The value of selected factors in predicting hip joint development after overhead traction for developmental dyplasia

Background. Residual dysplasia occurs in some hip joints with DDH treated conservatively. This may lead to osteoarthrosis in relatively near future. Our study aimed to determine which radiographic parameters and clinical factors could reliably predict hip joint development after closed reduction. Material and methods. We examined 81 patients and 107 hip joints treated with over-head traction. The age of the patients ranged from 5 to 33 months (average 14,3 months). Several radiographic parameters and clinical fators were assessed before reduction and five months later, and these results were compared with long-term outcome. The average age at final follow-up was 19,9 years, minimum 14 years. Results. The best outcome was obtained in younger patients. Bilateral involvement was associates with less favorable functional outcome. The pretreatment radiographic parameters of degree of displacement defined by Tonnis and breaking of the Shenton line, lateral (c/b) and superior (h/b) centering ratios, and the presence and size of the ossific nucleus were not prognostic for outcome. Only persistence of superior displacement 5 months after reduction measured by breaking of the Shenton line and decreased superior centering ratio (h/b) are suggestive for residual dysplasia at maturity. Conclusion. The remodeling of a dysplastic hip joint depends on the age of the patients, and final fuctional outcome on bilaterality of involvement. Only parameters describing superior displacement of the femoral head, such as breaking of the Shenton line and superior centering ratio (h/b) have prognostic value for future hip development.