Ceramic-on-polyethylene bearing surfaces in total hip arthroplasty - Seventeen to twenty-one-year results

Background: Polyethylene wear debris, and the resulting inflammatory respon se leading to osteolysis and loosening, is the primary mode of failure limi ting the longevity of total hip replacements. Alternative bearing surfaces, including ceramic-on-polyethylene, have been investigated in an effort to decrease the amount of polyethylene wear debris. The purpose of this study was to evaluate the seventeen to twenty-one-year results of the use of cera micon-polyethylene total hip prostheses. Methods: Sixty-four total hip prostheses were implanted with cement, by one surgeon, in fifty-six patients from 1978 to 1981. The average age at the i ndex arthroplasty was sixty-nine years (range, fifty-one to eighty-four yea rs). The components consisted of a cemented Charnley-Muller stem with a 32- mm modular alumina femoral head and a cemented all-polyethylene acetabular component. All patients who retained the index prosthesis were assessed cli nically with use of Harris hip scores and were evaluated radiographically a t the time of the latest follow-up. Results: At the time of this latest follow-up, of the original sixty-four i mplants, eighteen (28%) were still in place and five (8%) had been revised. The remaining forty-one implants were in patients who had died and were fu nctioning well until the patient's death. No patient was lost to follow-up. Of the eighteen hips with an intact prosthesis in the surviving patients, seven had an excellent clinical result; nine, a good result; and two, a fai r result. One asymptomatic hip had definite radiographic evidence of femora l loosening. No hip had definite signs of acetabular loosening or evidence of osteolysis. Survivorship analysis revealed that the probability of survi val of the prostheses without revision was 95% at five years, 95% at ten ye ars, 89% at fifteen years, and 79% at twenty years. The mean linear and vol umetric polyethylene wear rates were 0.034 mm/yr and 28 mm(3)/yr, respectiv ely. There were no fractures of the ceramic heads. Conclusions: Outstanding long-term clinical and radiographic results were a ttained despite the use of what are now considered substandard techniques ( an inferior stem design, a 32-mm head, and first-generation cementing techn iques). The wear rates in this study are lower than previously reported met al-on-polyethylene wear rates and are consistent with the lowest reported i n vivo ceramic-on-polyethylene wear rates. These findings support the consi deration of ceramic-on-polyethylene bearing surfaces in total hip arthropla sty.