A1199. MID-TERM RESULTS OF HYBRID TOTAL HIP ARTHROPLASTY FOR TREATMENT OF OSTEOARTHRITIS SECONDARY TO DEVELOPMENTAL DYSPLASIA OF HIP-CHINESE EXPERIENCE

Objective: Considering the high incidence and misdiag-nostic rate of developmental dysplasia of hip (DDH) in China, some patients suffer from severe pain in the hip at early age, and a total hip arthroplasty would be necessary. To our knowledge, the intermediate-term(equal to or more than five years) results of total hip arthroplasty (THA) in patients with osteoarthritis secondary to developmental dysplasia of the hip has not been studied in China previously. This study evaluated more than five-year clinical and radiographic outcomes associated with total hip arthroplasty (THA) in a consecutive series of patients with osteoarthritis secondary to developmental dysplasia of the hip. Methods: From February 2000 to July 2002, 55 patients (69 hips) underwent THA in our hospital were involved in this study. Clinical outcomes were evaluated according to Harris evaluate score. Components migration, periprosthetic bone changes, the polyethylene wear rate were measured radiologically. Kaplan-Meier analysis was performed to evaluate the survival of the acetabular and femoral component. End point was obvious radiological loosening or revision either or both of the acetabular and femoral component for any reason. Results: Forty-five patients (57 hips) were followed up at least 5 years. The average preoperative Harris hip score was (46.19±18.01) points, which improved to (91.78±3.52) points at final follow-up. There were 48 excellent hips (84.21%), 7 good hips (12.28%), 2 fair hips (3.51%) and no poor hip. There is no significant difference of Harris score between the dysplasia group, the low dislocation group and the high dislocation group (P>0.05, ANOVA). The mean polyethylene liner wear rate was (0.27±0.14)mm/year. According to the statistical relevant analysis, the wear rate of the polyethylene liner had relationship with the age(r=−0.288, P=0.040), the abnormal abduction angle of the acetabular cup (r=0.317, P=0.023)and the osteolysis rate (r=0.573, P=0.026), while had no significant relationship with the thickness of the polyethylene liner (P=0.326), gender(P=0.097), DDH classification(P=0.958) and the Harris score(P=0.598). There are 5 pelvic osteolysis and 8 proximal femoral osteolysis. Using loosening or revision as the end point for failure, the survival rate of both components was 1.0 (95% confidence interval, 0.98–1.00). Conclusions: In conclusion, improved surgical technique and design in the components provided favorable mid-term results in Chinese patients with osteoarthritis secondary to developmental dysplasia of the hip. Bulk autogenous or allografting is not needed if more than 70% of the acetabular component is covered by host bone. Although the Asia life style includes more squatting and cross-legged, the results of this series in Chinese population are comparable to the satisfactory results of other reported DDH series whose patients are mainly western people. The mid-term results of THA are equivalent in the group of patients with dysplasia, low dislocation, and high dislocation types both in ace-tabular and femoral components. However, the authors continue to be anxious about the high rate of liner wear and osteolysis, which deserve the necessary long-term follow-up.