Primary charnley total hip arthroplasty - A comparison of American and Japanese cohorts followed for 10-20 years

Primary Charnley total hip arthroplasties (THAs) followed for 10 to 20 year s were compared between an American (183 sockets and 178 femoral prostheses ) and a Japanese (145 sockets and 148 femoral prostheses) series, each perf ormed by a single surgeon at a single hospital using similar techniques. Th e primary etiology was developmental dysplasia of the hip (70%) in the Japa nese series and primary osteoarthrosis (50%) in the American series. Radiog raphic socket survival was inferior in the Japanese series at 4- to 11-year follow-up, which was attributed mainly to the etiologic difference. The Am erican patients had higher levels of postoperative activity and developed m ore accelerated polyethylene wear which may lead to an increased loosening rate of sockets greater than or equal to 10 years after THA. The American s eries had higher rates of femoral revision at greater than or equal to 9 ye ars follow-up, which was attributed mainly to lower canal flare indices in that series.