Outcomes of open reduction for developmental dysplasia of the hip: does bilateral dysplasia have a poorer outcome?

BACKGROUND: The purpose of this study was to compare the outcomes of surgical treatment in children of walking age with unilateral and bilateral developmental dysplasia of the hip (DDH).

METHODS: We examined the records of fifty-six children of walking age with bilateral dysplasia and 156 children of walking age with unilateral dysplasia treated with open reduction and pelvic osteotomy with or without femoral osteotomy from 1990 to 2000. The minimum duration of follow-up was five years. The mean age at surgery was thirty-four months in the bilateral group and twenty-five months in the unilateral group. Preoperative radiographs were evaluated to determine the Tönnis grade of the dislocation and the acetabular index, and the latest radiographs were evaluated to determine the Severin classification. The Kalamchi and MacEwen classification was used to assess osteonecrosis, and the McKay classification was used to assess the clinical outcome at the time of the latest follow-up. For the statistical analyses, we selected the worse side in patients in the bilateral group as the index hip if the outcome was asymmetrical and the left hip if the outcome was symmetrical. The Fisher exact and Student t tests were used for comparisons of outcomes between the groups. Multiple logistic regression models were used to analyze factors associated with osteonecrosis and with the McKay classification.

RESULTS: Age at surgery and preoperative Tönnis grade differed significantly between the groups. Forty-five (80.3%) of the patients in the bilateral group and 135 (86.5%) of the patients in the unilateral group had a satisfactory Severin classification (Ia, Ib, or II); the difference between the groups was not significant. According to the McKay classification, twenty-six (46%) of the patients in the bilateral group had an satisfactory outcome compared with 111 (71%) of the patients in the unilateral group (p = 0.006). Osteonecrosis was significantly greater in the bilateral group as well (p = 0.01). Patient age at surgery and Tönnis grade were risk factors for osteonecrosis. Older age and bilaterality were associated with a poorer McKay classification. The logistic regression analysis was repeated after removing the nineteen patients (34%) in the bilateral group who had an asymmetrical outcome, and this analysis confirmed that asymmetrical outcome was a risk factor for a poorer McKay classification.

CONCLUSIONS: Our data confirmed that the clinical outcome of bilateral developmental dysplasia of the hip was worse primarily because of asymmetrical outcomes. Age and Tönnis grade played an important role in the risk of occurrence of osteonecrosis. The radiographic outcome according to the Severin classification did not differ significantly between the groups.