Kurtz S M, Rimnac C M, Bartel D L
Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York, USA.
J Orthop Res. 1997 Jan;15(1):57-61. doi: 10.1002/jor.1100150109.
Ultra-high molecular weight polyethylene components for total joint replacement chemically degrade before and after implantation, and the degradation is associated with an increase in density. The goal of this study was to determine the average rate of density change in these components following sterilization by gamma radiation in air as a function of shelf age and implantation time. Using the density gradient column method, density profiles were obtained through the thickness from loaded and unloaded regions of 10 retrieved Insall-Burstein/Posterior-Stabilized II tibial components and one operating-room inventory component for which the initial density profile and patient history (if applicable) were known. The average density of the components increased at a constant rate of 0.000186 g/cc/month during the first 50 months after sterilization (r2 = 0.54) but was not significantly affected by loading (p > 0.05). The quantitative degradation rates may be useful to help verify kinetic models to predict bulk degradative changes on the basis of micro-structural and chemical processes. This research also suggests the hypothesis that degradation of ultra-high molecular weight polyethylene can be modeled in terms of changes in bulk or average properties.
用于全关节置换的超高分子量聚乙烯部件在植入前后会发生化学降解，且这种降解与密度增加有关。本研究的目的是确定这些部件在空气中经伽马射线灭菌后，密度变化的平均速率与储存时间和植入时间的关系。使用密度梯度柱法，从10个回收的Insall-Burstein/后稳定型II胫骨部件的加载区和未加载区以及一个已知初始密度分布和患者病史（如适用）的手术室库存部件的厚度方向上获得密度分布。部件的平均密度在灭菌后的前50个月以0.000186 g/cc/月的恒定速率增加（r2 = 0.54），但加载对其没有显著影响（p > 0.05）。定量降解速率可能有助于验证动力学模型，以便根据微观结构和化学过程预测整体降解变化。本研究还提出了一个假设，即超高分子量聚乙烯的降解可以根据整体或平均性能的变化来建模。
