Extreme variations in racial rates of total hip arthroplasty for primary coxarthrosis: a population-based study in San Francisco.

OBJECTIVES To compare the incidence of all total hip arthroplasty, and total hip arthroplasty for primary coxarthrosis, among the Asian, black, Hispanic, and white populations living in one locale. METHODS We identified all San Francisco residents who underwent total hip replacements (THR) in the 17 hospitals for adults within or near San Francisco County during a five year period. Preoperative pelvic radiographs were read without prior knowledge of the gender or race of the subject, to diagnose the specific hip diseases. Age standardised THR incidence by race and gender was determined, as was the comparative THR incidence for specific diagnosis (primary and secondary osteoarthritis). RESULTS The greatest annual rate of total hip replacement occurred in white women (97 per 100,000 population), followed by white men, black women, black men, Hispanic women, and Hispanic men. The smallest numbers were found in Asians, whose THR rate was 10% that of whites. A primary coxarthrosis diagnosis was greatest among white subjects (66%), followed by black subjects (54%), Hispanics (53%), and Asians (28%). Age standardised THR rates for primary coxarthrosis per 100,000 population were likewise greatest among whites (43.0) and least among Asians (1.3 for Chinese). Mean age of patients undergoing THR for primary coxarthrosis was 70 years for white subjects and almost a decade younger in all other groups. CONCLUSIONS THR rates are much lower for Asians, Hispanics, and black subjects than for the white population living in San Francisco. The low rates of total hip arthroplasty in the non-white groups was related to the much lower incidence of THR for primary coxarthrosis among non-whites than among whites. The racial distribution of primary coxarthrosis among patients who underwent THR is consistent with distribution patterns reported internationally.