Prognostic value of severity of dislocation in late-detected developmental dysplasia of the hip

PURPOSE: The aims of this study were to evaluate the reliability of three classifications of severity of dislocation in late-detected developmental dysplasia of the hip (DDH), especially to assess whether they are predictive of long-term outcomes. METHODS: Two groups of patients were analyzed. Group 1 (57 patients, 69 hips) underwent closed reduction between 1958 and 1962. Mean age at reduction was 20.3 months (4 to 65). Group 2 (50 patients, 54 hips) treated between 1996 and 2005, was used for analysis of the association between severity of dislocation and treatment (open or closed reduction). The primary radiographs were graded according to the Tönnis classification, the classification of the International Hip Dysplasia Institute and a new method based on the position of the most lateral point of the proximal femoral metaphysis (lateral metaphysis height classification, LMH). The outcome at a mean age of 51.2 years (55 to 60) was graded according to the occurrence of osteoarthritis (OA) and total hip arthroplasty (THA). RESULTS: There were significant associations between the classifications, and the intra- and interobserver agreements were high. More severe grades of DDH were significantly associated with age ≥ 18 months and with open reduction. None of the classifications were significantly associated with long-term OA. The LMH method was significantly associated with the need for THA, whereas the other classifications were not. CONCLUSION: All the classifications were reliable in grading severity of DDH. The LMH method seems preferable in clinical practice because the main landmarks were easy to define and because it had long-term prognostic value. LEVEL OF EVIDENCE: III