Abstract
Introduction
Although hip arthroplasty has been very successful in relieving pain and optimising function, problems have arisen with wear and osteolysis. Highly cross linked polyethylene has been developed to address this problem. The aim of this study was to compare the in vivo wear of standard versus highly cross linked polyethylene (HXLP) in primary total hip arthroplasty at 5-year follow up.
Methods
Approval was obtained through the Regional Ethics Committee before commencement of the study. 122 patients were enrolled in a prospective, double blinded, randomised trial and followed annually to assess their progress. Annual radiographs were analysed using previously validated edge detection software to assess for 2 dimensional, 3 dimensional and volumetric wear. To reduce the disproportionate effects of bedding in and creep, the initial x-ray used was that taken at 6 months following surgery.
Results
The average age of the patients undergoing surgery was 61yrs (range 46-75). No statistically significant difference was found between groups with respect to age, sex, operative side, surgeon, cup size or cup positioning (anteversion or abduction angle). The 2D wear measurements for HXLP showed 0.05mm/year compared to 0.26mm/year in the conventional group. This is statistically significant (95% CI=0.03-0.07 p< 0.0001). A similar picture is seen with 3D and volumetric wear. For each type of wear, this became significant by the year two follow-up (p< 0.0001).
Conclusion
Highly cross linked polyethylene undergoes significantly less wear than conventional polyethylene. The effect of hip arthroplasty longevity will need to be assessed with longer term studies, but this may lead to a decreased need for revision due to less wear and osteolysis.
