Primary posterior cruciate-retaining total knee arthroplasty: a comparison of American and Japanese cohorts.

Excessive polyethylene wear is recognized as one of the most important factors affecting the durability of total knee arthroplasty; however, bearing surface wear is a multifactorial problem. The purpose of this study was to identify factors for polyethylene wear and failure in primary posterior cruciate-retaining (PCR) total knee arthroplasty (TKA) in two disparate cohorts (American and Japanese). Seventy-three total knee arthroplasty operations were performed on 48 Japanese patients, and 76 on 63 American patients with noninflammatory arthritides. All patients were evaluated clinically and radiographically using a total joint arthroplasty database. Age, weight, diagnosis, Knee Society patient category, prosthesis size, insert thickness, alignment, polyethylene wear, osteolysis, Knee Society knee score, Knee Society pain score, and radiographic and clinical survivorship were evaluated. Seventy-three Japanese TKAs were followed for a mean of 6.6 years (range, 2.0-10.6). Three (4.1%) Japanese patients required revision. Seventy-six American TKAs were followed for a mean of 9 years (range, 2-10.2). Two (2.6%) American patients required revision. The American patients were significantly older, heavier, male predominant, and required larger size implants. The Japanese patients were significantly more female predominant and had a significantly less postoperative arc of motion. Knee Society knee and pain scores, survivorship, average total polyethylene wear, and annual wear rates were not different among the two cohorts. PCR TKA had similar survivorship in disparate cohorts of Japanese and American total knee arthroplasty patients despite smaller stature patients in the Japanese cohort. Cultural, gender-specific, and morphologic differences need to be considered for knee implant design. However, survivorship and polyethylene wear rates appear to be independent of these factors in disparate populations.