Low-friction arthroplasty in patients younger than 40 years old: 20- to 25-year results.

A total of 67 low-friction arthroplasties were performed from 1971 through 1978 in patients <40 years old and followed an average of 21.7 years. There have been 33 cup loosenings and 17 stem loosenings. The average rate of wear of the cup was 0.12 mm/y for the entire series and 0.16 mm/y for the revised cups. Although the preoperative diagnosis leading to low-friction arthroplasty commonly reflected some deficiency in bone structure, particularly in the acetabulum, there were no primary osteoarthrosis cases. The femoral stem proved to be durable, but acetabular cups gave poorer results in younger patients than in older patients. The 2 major factors limiting the longevity of the cemented cup were acetabular bone quality and wear.