Gamma-irradiation Sterilization in an Inert Environment: A Partial Solution

Background In the mid to late 1990s, to sterilize UHMWPE bearings, manufacturers changed from gamma-irradiation-in-air (gamma-air) sterilization, which initiated oxidation leading to bearing fatigue, to gamma-irradiation sterilization in an inert environment (gamma-inert). The change to gamma-inert...

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Bibliographic Details
Published in:Clinical orthopaedics and related research 2012-07, Vol.470 (7), p.1805-1813
Main Authors: Berry, Daniel J., Currier, Barbara H., Mayor, Michael B., Collier, John P.
Format: Article
Language:English
Subjects:
Arthroplasty, Replacement, Knee - adverse effects
Arthroplasty, Replacement, Knee - instrumentation
Basic Research
Biomechanical Phenomena
Conservative Orthopedics
Device Removal
Equipment Failure Analysis
Gamma Rays
Humans
Knee Prosthesis
Medicine
Medicine & Public Health
Minnesota
Orthopedics
Oxidation-Reduction
Polyethylenes - adverse effects
Polyethylenes - chemistry
Polyethylenes - radiation effects
Product Packaging
Prosthesis Design
Prosthesis Failure
Reoperation
Spectroscopy, Fourier Transform Infrared
Sports Medicine
Sterilization - methods
Stress, Mechanical
Surgery
Surgical Orthopedics
Symposium: Retrieval Studies
Tensile Strength
Time Factors
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Summary:Background In the mid to late 1990s, to sterilize UHMWPE bearings, manufacturers changed from gamma-irradiation-in-air (gamma-air) sterilization, which initiated oxidation leading to bearing fatigue, to gamma-irradiation sterilization in an inert environment (gamma-inert). The change to gamma-inert sterilization reportedly prevented shelf oxidation before implantation but not in vivo oxidation. Questions/purposes We asked: (1) Has the change to gamma-inert sterilization prevented shelf oxidation that led to early in vivo fatigue damage in gamma-air-sterilized tibial inserts? And (2) has the change to gamma-inert sterilization prevented the occurrence of fatigue secondary to in vivo oxidation? Methods We rated 183 retrieved gamma-air- and 175 retrieved gamma-inert-sterilized tibial inserts for clinical fatigue damage and analyzed 132 gamma-air- and 174 gamma-inert-sterilized tibial inserts for oxidation by Fourier transform infrared spectroscopy. Results Oxidation led to decreased mechanical properties in shelf-aged gamma-air-sterilized tibial inserts. Barrier packaging prevented shelf oxidation in gamma-inert-sterilized tibial inserts. Gamma-air- and gamma-inert-sterilized inserts oxidized in vivo. Fatigue damage (delamination) occurred more frequently in inserts retrieved after longer time in vivo. Longer in vivo time correlated with higher oxidation and more accumulated cycles of use. Conclusions Published oxidation projections suggest gamma-inert-sterilized tibial inserts would reach the critical oxidation for the onset of fatigue after 11 to 14 years in vivo. These retrievals appear to follow the projected oxidation trends. Frequency of fatigue damage increased with increasing oxidation. Clinical Relevance Fatigue of tibial inserts becomes more likely, especially in active patients, after more than a decade of good clinical performance.
ISSN:0009-921X
1528-1132
DOI:10.1007/s11999-011-2150-1