It is unknown how possible preoperative factors influence the postoperative outcome of eccentric rotational acetabular osteotomy (ERAO). We aimed to determine these factors and to develop a scoring system for predicting the prognosis after ERAO in patients with symptomatic hip dysplasia.
We included 700 patients (54 men, 646 women) who underwent ERAO during September 1989 to March 2013. The patients' clinical background, preoperative clinical findings, and preoperative imaging findings were examined retrospectively. Univariate and multivariate Cox regression were performed using the time from the day of surgery to a Harris hip score (HHS) <80 as an endpoint. A failure score was defined to predict the prognosis for an HHS <80, and its predictive capacity was assessed.
Ninety patients had an HHS <80. Forty-two patients underwent conversion to total hip arthroplasty (THA) after their HHS decreased to <80. Five factors were identified in relation to an HHS <80: a history of congenital dislocation of the hip, joint congruity, body mass index, the preoperative minimum joint space width, and the preoperative abduction range of motion. We estimated the weight of each factor using the results of multivariate Cox regression, and the outcome prediction scoring was obtained (0-17 points). For three groups of patients (total points of each factors: 0-5, 6-9, and ≥10 points), the Kaplan-Meier event-free survival rates at 15 years postoperatively for an HHS <80 were 97%, 81%, and 55%, respectively; the survival rates for THA conversion using this prediction scoring were 99%, 96%, and 85%, respectively.
Five preoperative factors can easily and clearly predict the prognosis following ERAO. The prognosis score may be a useful tool when making a decision regarding operative treatments in adult patients with acetabular dysplasia.