Low friction arthroplasty at 10 to 20 years. Consequences of plastic wear

One hundred eighty-seven patients, in whom 224 low friction arthroplasties were done by 1 surgeon from 1972 to 1983, were observed for 10 to 20 years. An attempt was made to reassess each patient annually. Pain, walking, and passive range of motion were graded on a 6-point scale (d'Aubigné and Postel assessment). Active movements, straight leg raising, and abduction against gravity were recorded in degrees. The average scores, based on 224 assessments done preoperatively, 1914 assessments done during the first 10 years, and 590 assessments done during the second 10 years, were as follows: pain--3.28, 5.71, and 5.59 points; walking--3.34, 5.16, and 4.87 points; passive range of motion--3.42, 4.61, and 4.54 points; straight leg raising--40.5 degrees, 60.8 degrees, and 54.9 degrees points; and abduction against gravity--8.8 degrees, 24.3 degrees, and 19.0 degrees points. The percentage of cases with no cement-bone interface demarcation based on > 2000 radiologic observations was as follows: cup Zone I--9.9%, Zone II--26.4%, and Zone III--26.3%; and femoral Zone 1--72.5%, Zone 2--96.7%, Zone 3--94.2%, Zone 4--89.6%, Zone 5--96.7%, Zone 6--96.3%, and Zone 7-72.6%. A relationship was seen between wear of the socket, and cup migration and revision, development of femoral endosteal erosions (significant at 95% confidence level), and femoral prosthesis migration and revision. Ultra high molecular weight polyethylene particles that migrate to the cement-bone interface are believed to be an important cause of loosening and failure in total hip arthroplasty.