Joyce T J
School of Mechanical and Systems Engineering, University of Newcastle upon Tyne, Newcastle upon Tyne - UK.
J Appl Biomater Biomech. 2005 Sep-Dec;3(3):141-6.
The potential for all-polymer prostheses has not been widely investigated. It might be expected that the wear of such biomaterial combinations would be excessive, but an in vivo study of all polymer knee prostheses reported that there were no failures due to wear, even after ten years of clinical use. This design of knee prosthesis used polyacetal and ultra high molecular weight polyethylene (UHMWPE) as the biopolymers. Similarly, an earlier in vitro study of polyacetal and UHMWPE hip prostheses indicated lower wear than for a cobalt chrome and UHMWPE combination. Therefore this study set out to test the poly-acetal and UHMWPE combination in a wear screening rig which had previously been validated against clinical data for artificial hip joints. Two different motion conditions were applied to the test samples and each biopolymer was tested as both pin and plate. Interestingly it was found that, whatever the contribution from pin or plate, the total mean wear factors were 1.5 10 -6 mm 3/Nm under reciprocation-only, and 4.1 10 -6 mm 3 /Nm under multi-directional motion. These wear factors were greater than those found when a conventional metal-on-UHMWPE couple was tested under the same loading, motion and lu-bricant conditions. A comparison was also undertaken with the wear of other orthopaedic biopolymer combinations, namely cross-linked polyethylene (XLPE) against itself, and UHMWPE against itself. The XLPE pairing showed somewhat lower wear than the polyacetal and UHMWPE couple, while the UHMWPE pairing showed the highest wear of all, approximately an or-der of magnitude greater than the polyacetal and UHMWPE combination.
全聚合物假体的潜力尚未得到广泛研究。人们可能认为，这种生物材料组合的磨损会很严重，但一项关于全聚合物膝关节假体的体内研究报告称，即使经过十年的临床使用，也没有因磨损而出现故障。这种膝关节假体设计使用聚缩醛和超高分子量聚乙烯（UHMWPE）作为生物聚合物。同样，一项早期关于聚缩醛和UHMWPE髋关节假体的体外研究表明，其磨损低于钴铬合金和UHMWPE组合。因此，本研究着手在一个先前已根据人工髋关节临床数据进行验证的磨损筛选试验台上测试聚缩醛和UHMWPE组合。对测试样品施加了两种不同的运动条件，每种生物聚合物都作为销和板进行了测试。有趣的是，发现无论销或板的作用如何，在仅往复运动下，总平均磨损系数为1.5×10⁻⁶立方毫米/牛米，在多向运动下为4.1×10⁻⁶立方毫米/牛米。这些磨损系数大于在相同载荷、运动和润滑条件下测试传统金属对UHMWPE配对时发现的磨损系数。还对其他骨科生物聚合物组合的磨损进行了比较，即交联聚乙烯（XLPE）自身配对，以及UHMWPE自身配对。XLPE配对的磨损略低于聚缩醛和UHMWPE配对，而UHMWPE配对的磨损在所有配对中最高，大约比聚缩醛和UHMWPE组合大一个数量级。
