Abstract
The purpose of the present study is to report the failure rate after total knee replacements performed with poly-ethylene inserts that had been sterilized with gamma irradiation in air and implanted after a prolonged shelf life. 395 PFC total knees were performed using polyethylene that had been sterilized by gamma irradiation in air. Shelf life of all polyethylene inserts was determined from manufacturer data. A Chi-square test revealed that the proportion of implants that required a revision for polyethylene failure was related to the number of years that the implant had been stored on the shelf.
Report failure rate of PFC total knee replacements performed with polyethylene sterilized by gamma irradiation in air and implanted after a prolonged shelf life.
There was an increased revision rate in total knees with polyethylene sterilized by gamma irradiation in air and implanted after a shelf life greater than two years.
Polyethylene sterilized by gamma irradiation in air should not be implanted after a shelf life of greater than two years.
Ten of twelve revisions had polyethylene inserts with a shelf life greater than two years. A Chi-square test revealed that the proportion of implants that required a revision was related to the number of years that the implant had been on the shelf, particularly if greater than two years χ2 (1)=7.427, p=.006
395 PFC total knees were performed using polyethylene sterilized by gamma irradiation in air. Shelf life of all polyethylene inserts was determined from manufacturer data. A retrospective review was undertaken to determine which patients underwent revision surgery as a result of aseptic loosening secondary to polyethylene failure. The data was then used to determine the relationship between shelf life and revision status.
The mechanical toughness of polyethylene that has been sterilized by gamma irradiation in air decreases with a prolonged shelf life. This results in an unacceptably high revision rate. We therefore recommend against the use of polyethylene that has been gamma irradiated in air and stored for greater than two years on the shelf.
Funding: This study has been sponsored in part by Johnson& Johnson/Depuy Orthopedics.
Correspondence should be addressed to Cynthia Vezina, Communications Manager, COA, 4150-360 Ste. Catherine St. West, Westmount, QC H3Z 2Y5, Canada
