RESUMO
PURPOSE: We purpose to analyze the factors related to the polyethylene failure through the 7 exchanged polyethylene. MATERIALS AND METHODS: We experienced 7 cases of polyethylene failure from Apr. 1988 to Jan. 2000. The average duration of reoperation is 5 year 2 months(1 year 8 months-8 year 11 months), age at primary operation is 62 years old(55-64 years old), weight is 65kg(56-78kg) and height is 155cm(150-162cm). The used prostheses were AGC(Biomet, Warsaw, U.S.A) in 2 patients, AMK(Depuy, Warsaw, U.S.A) in 1 patient, ,MG II(Zimmer, Warsaw, U.S.A) in 1 patient, PFC(Johnson and Johnson, Warsaw U.S.A) in 2 patients and Series 7000(Osteonics, New Jersey, U.S.A.) in 1 patient. RESULTS: The thickness of polyethylene is Smm in 6 patients and 9mm in 1 patient. All of prostheses are cruciate retaining type with relatively flat surface geometry and low-height intercondylar eminence, and the minimal thickness of each system. CONCLUSION: We consider that the thicker polyethylene should be used when feasible in order to avoid reoperation which is caused by accelerated wear of polyethylene, and early detection of polyethylene wear is important. This can be got through knee standing AP, fluroscopic evaluation with varus and valgus stress.