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 years were compared between an American (183 sockets and 178 femoral prostheses) and a Japanese (145 sockets and 148 femoral prostheses) series, each performed by a single surgeon at a single hospital using similar techniques. The primary etiology was developmental dysplasia of the hip (70%) in the Japanese series and primary osteoarthrosis (50%) in the American series. Radiographic socket survival was inferior in the Japanese series at 4- to 11-year follow-up, which was attributed mainly to the etiologic difference. The American patients had higher levels of postoperative activity and developed more accelerated polyethylene wear, which may lead to an increased loosening rate of sockets > or = 10 years after THA. The American series had higher rates of femoral revision at > or = 9 years follow-up, which was attributed mainly to lower canal flare indices in that series.