Abstract
Aim: Polyethylene used for Total Hip Artrhroplasty components can be sterilized with different methods. Among them there is gamma rays. This method is currently used for conventional polyethylene and has been used also for Hylamer, a high cristallinity polyethylene manufactured by Depuy in early nineties. Recently Hylamer polyethylene components gamma sterilized in air were ‘recalled’ by Health Authorities, due to excessive wear. Aim of the present study was to evaluate radiographic and clinical performance of Hylamer acetabular liners gamma sterilized in air, and compare them to same devices gamma sterilized in nitrogen atmosphere.
Methods: Thirty-one patients “gamma in air” were matched to thirty controls with the same implanted socket but with the insert sterilized in a nitrogen atmosphere in a retrospective matched case-control. Moreover, a second control group was matched from twenty-three patients with a different prosthesis (ABG cup, Stryker-Howmedica) but with a similar insert made by conventional polyethylene gamma sterilized in absence of oxygen. Clinical evaluation was made according to the Harris Hip-scoring system. Radiographic wear measurements and osteolytic lesion was performed comparing the post-operative pelvic radiograph with the last follow-up study.
Results: Among 3 groups there was no significant difference in the clinical performance. At a mean of seven years, we found a significant difference between the mean rate of wear and osteolytic lesion of Hylamer sterilized in air and Hylamer sterilized in a nitrogen atmosphere.
Conclusion: We concluded that the manufacturing and sterilization processes influence the resistance to oxidation and wear of the various types of ultra-high molecular polyethylene that are currently available.
The abstracts were prepared by Ms Grazia Gliozzi. Correspondence should be addressed to her at the Italian Orthopaedic Research Society, Laboratory for Pathophysiology, Instituti Ortopedici Rizzoli, University of Bologna, Bologna, Italy.
