Kurtz S M, Bartel D L, Rimnac C M
Failure Analysis Associates, Menlo Park, CA, USA.
Clin Orthop Relat Res. 1998 May(350):209-20.
Ultrahigh molecular weight polyethylene components oxidatively degrade because of gamma radiation sterilization and subsequent shelf aging in air. The effects of shelf aging on the stresses and strains associated with surface damage in tibial and acetabular components were examined. A material model was developed to predict the stress and strain relationship of oxidatively degraded polyethylene as a function of density using samples of polyethylene that were gamma radiation sterilized and evaluated immediately after irradiation and after 42 months of shelf aging. The finite element method was used to determine the stresses and strains before and after shelf aging for two tibial components with different conformities between the articulating surfaces and for an acetabular component. The stresses increased by 10% to 14% in the conforming tibial model after 42 months of aging, whereas the stresses in the nonconforming tibial model and in the acetabular model increased by only 4% to 8%. Aging decreased the principal strains by 5% to 10% in both tibial models and by 15% to 17% in the acetabular model. Postirradiation aging during shelf storage of polyethylene joint components is likely to worsen long term wear, based on the increased stresses and decreased strains predicted to occur as a result of aging.
超高分子量聚乙烯部件会因伽马射线灭菌以及随后在空气中的货架期老化而发生氧化降解。研究了货架期老化对胫骨和髋臼部件表面损伤相关应力和应变的影响。利用经伽马射线灭菌并在辐照后及42个月货架期老化后立即进行评估的聚乙烯样品，建立了一个材料模型，以预测氧化降解聚乙烯的应力和应变关系与密度的函数关系。采用有限元方法确定了两种关节面贴合度不同的胫骨部件以及一个髋臼部件在货架期老化前后的应力和应变。老化42个月后，贴合型胫骨模型中的应力增加了10%至14%，而不贴合型胫骨模型和髋臼模型中的应力仅增加了4%至8%。老化使两个胫骨模型中的主应变降低了5%至10%，使髋臼模型中的主应变降低了15%至17%。基于老化预计会导致应力增加和应变降低，聚乙烯关节部件在货架储存期间的辐照后老化可能会加剧长期磨损。
