203. OXINIUM VERUS METAL ON POLYETHYLENE: PROSPECTIVE RANDOMISED STUDY WITH MINIMUM TWO YEARS FOLLOW-UP USING THE MARTELL METHOD

Abstract

Purpose of the study: The purpose of this prospective randomised study was to evaluate the wear of cemented polyethylene cups as a function of the material of the femoral head: oxinium versus metal.

Material and methods: This series included 50 primary arthroplasties implanted from January 2006 to May 2006 in 50 patients (27 women and 23 men), mean age 60.6±11.4 years (21–75). The same femoral piece made of highly polished M30NW stainless steel with a quadrangular section was used for all implants. Similarly, all patients had a polyethylene cup sterilised with ethylene oxide (CMK21, Smith and Nephew). The femoral head was made of stainless steel for 25 hips and oxinium for 25 hips. The major outcome was penetration of femoral head into the cup (associated with true wear and creep) measured at minimum two years follow-up using the Martell method modified according to the recommendations of the author for an all-polyethylene cup. Patient-related and technique-related factors were studied. Non-parametric tests were used for the statistical analysis.

Results: There was no significant difference between the two groups regarding preoperative data. Two patients died, one was lost to follow-up; for three patients, the radiographs were excluded by the software. The analysis thus included 44 hips with a median follow-up of 2.01 years (1.9–2.3), 22 in the Oxinium™ group and 22 in the metal group. The median penetration rate was 0.16 mm/year in the Oxinium^® group versus 0.19 mm/year in the metal group (Mann-Whitney, p=0.46). Annual volumetric penetration in the Oxinium™ group was comparable with that of the metal group (Mann-Whitney, p=0.76). conversely, using the radiograph taken at one year as the reference value (true wear), wear was 0.066 mm/y in the Oxinium™ group versus 0.19mm/y in the metal group (Mann-Whitney, p=0.38).

Discussion and Conclusion: The results of this series indicate that using an oxinium femoral head reduces polyethylene wear. Mid-term results appear to be necessary to confirm these findings.