Fisher John, McEwen Hannah M J, Tipper Joanne L, Galvin Alison L, Ingram Jo, Kamali Amir, Stone Martin H, Ingham Eileen
Institute for Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, Leeds, UK.
Clin Orthop Relat Res. 2004 Nov(428):114-9. doi: 10.1097/01.blo.0000148783.20469.4c.
Cross-linked polyethylene currently is being introduced in knee prostheses. The wear rates, wear debris, and biologic reactivity of non cross-linked, moderately cross-linked, and highly cross-linked polyethylene have been compared in multidirectional wear tests and knee simulators. Multidirectional pin-on-plate wear studies of noncross-linked, moderately cross-linked (5 Mrad), and highly cross-linked (10 Mrad) polyethylene showed a 75% reduction in wear with the highly cross-linked material under kinematics found in the hip, but only a 33% reduction under wear in kinematics representative of the knee. In knee simulator studies, with the fixed-bearing press-fit, condylar Sigma cruciate-retaining knee under high kinematic input conditions, the wear of 5 Mrad moderately cross-linked polyethylene was 13 +/- 4 mm per 1 million cycles, which was lower (p < 0.05) than the wear of clinically used, gamma vacuum foil GUR 1020 polyethylene (23 +/- 6 mm/1 million cycles). For the low-contact stress mobile-bearing knee, the wear of moderately cross-linked polyethylene was 2 +/- 1 mm per 1 million cycles, which was lower (p < 0.05) than GVF GUR 1020 polyethylene (5 +/- 2 mm/1 million cycles). The wear debris isolated from the fixed-bearing knees showed the moderately cross-linked material had a larger percentage volume of particles smaller than 1 mum in size, compared with GVF GUR 1020 polyethylene. Direct cell culture studies of wear debris generated in sterile wear simulators using multidirectional motion showed a increase (p < 0.05) in tumor necrosis factor-alpha levels and reactivity for GUR 1050 cross-linked polyethylene debris compared with an equivalent volume of noncross-linked GUR 1050 polyethylene. The use of cross-linked polyethylene in the knee reduces the volumetric wear rate. However, the clinical significance of reduced fracture toughness, elevated wear in abrasive conditions, and the elevated tumor necrosis factor-alpha release from smaller more reactive particles warrant further investigation.
交联聚乙烯目前正被引入膝关节假体。在多向磨损试验和膝关节模拟器中，已对非交联、适度交联和高度交联聚乙烯的磨损率、磨损碎屑及生物反应性进行了比较。非交联、适度交联（5兆拉德）和高度交联（10兆拉德）聚乙烯的多向销盘磨损研究表明，在髋关节运动学条件下，高度交联材料的磨损减少了75%，但在代表膝关节的运动学磨损条件下仅减少了33%。在膝关节模拟器研究中，对于高运动学输入条件下的固定承重压配式、髁型Sigma十字韧带保留型膝关节，5兆拉德适度交联聚乙烯的磨损为每100万次循环13±4毫米，低于临床使用的伽马真空箔GUR 1020聚乙烯的磨损（23±6毫米/100万次循环，p<0.05）。对于低接触应力活动承重膝关节，适度交联聚乙烯的磨损为每100万次循环2±1毫米，低于GVF GUR 1020聚乙烯（5±2毫米/100万次循环，p<0.05）。从固定承重膝关节分离出的磨损碎屑显示，与GVF GUR 1020聚乙烯相比，适度交联材料中尺寸小于1微米的颗粒体积百分比更大。使用无菌磨损模拟器通过多向运动产生的磨损碎屑进行的直接细胞培养研究表明，与等量的非交联GUR 1050聚乙烯相比；GUR 1050交联聚乙烯碎屑的肿瘤坏死因子-α水平和反应性有所增加（p<0.05）。在膝关节中使用交联聚乙烯可降低体积磨损率。然而，交联聚乙烯断裂韧性降低、在磨蚀条件下磨损增加以及较小的更具反应性的颗粒释放肿瘤坏死因子-α增加的临床意义，仍需进一步研究。
