Kyomoto Masayuki, Moro Toru, Takatori Yoshio, Tanaka Sakae, Ishihara Kazuhiko
Department of Materials Engineering, The University of Tokyo, Tokyo, Japan,
Clin Orthop Relat Res. 2015 Mar;473(3):942-51. doi: 10.1007/s11999-014-3995-x.
Modifying the surface and substrate of a crosslinked polyethylene (CLPE) liner may be beneficial for high wear resistance as well as high oxidative stability and excellent mechanical properties, which would be useful in contributing to the long-term performance of orthopaedic bearings. A grafted poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) layer on a vitamin E-blended crosslinked PE (HD-CLPE[VE]) surface may provide hydrophilicity and lubricity without compromising the oxidative stability or mechanical properties.
QUESTIONS/PURPOSES: (1) Will the modifications (PMPC grafting and vitamin E blending) affect the lubrication characteristics of the CLPE surface? (2) Will the modifications affect wear resistance? (3) Will the modifications affect fatigue resistance?
We investigated the effects of surface and substrate modifications (PMPC grafting and vitamin E blending) on the wear and fatigue fracture of thin CLPE samples. For each of the untreated and PMPC-grafted CLPE surfaces with and without vitamin E blended (four groups), wettability and lubricity surface analyses were conducted as well as multidirectional wear and impact-to-wear tests using a pin-on-disk testing machine.
The water wettability and lubricity (CLPE [mean ± 95% confidence interval]: 23.2° ± 1.8°, 0.005 ± 0.001; HD-CLPE[VE]: 26.0° ± 2.3°, 0.009 ± 0.003) of the PMPC-grafted surfaces were greater (p < 0.001) than that (CLPE: 90.3° ± 1.2°, 0.067 ± 0.015; HD-CLPE[VE]: 90.8° ± 2.0°, 0.063 ± 0.008) of the untreated surface regardless of vitamin E additives. It was observed that the PMPC grafting (CLPE: 0.23 ± 0.06 mg; HD-CLPE[VE]: 0.05 ± 0.10 mg) was associated with reduced gravimetric wear (CLPE: 0.53 ± 0.08 mg, p = 0.004 HD-CLPE[VE]: 0.23 ± 0.07 mg, p = 0.038) in the multidirectional wear test. The PMPC-grafted surface characteristics did not appear to affect the impact fatigue resistance regardless of vitamin E blending.
PMPC grafting improved the surface hydrophilicity and lubricity, and it reduced the gravimetric wear in terms of multidirectional sliding. It did not result in differences in terms of the impact-to-unidirectional sliding regardless of vitamin E blending. Further research is needed to evaluate the wear resistance of PMPC-grafted HD-CLPE(VE) in long-term hip simulator tests under normal and severe conditions, which may offer useful clues to the possible performance of these materials in vivo.
Our preliminary in vitro findings suggest that some improvement in the wear performance of crosslinked polyethylene acetabular liners in total hip arthroplasty could be obtained using PMPC grafting. Further research is needed to evaluate the wear resistance of PMPC-grafted HD-CLPE(VE) in long-term hip simulator tests under normal and severe conditions, which may offer useful clues to the possible performance of these materials in vivo.
对交联聚乙烯（CLPE）衬垫的表面和基底进行改性，可能有利于提高耐磨性、氧化稳定性及机械性能，这有助于提升骨科植入物的长期性能。在含维生素E的交联聚乙烯（HD-CLPE[VE]）表面接枝聚（2-甲基丙烯酰氧乙基磷酰胆碱）（PMPC）层，可在不影响氧化稳定性和机械性能的前提下提供亲水性和润滑性。
问题/目的：（1）这些改性（PMPC接枝和维生素E混合）会影响CLPE表面的润滑特性吗？（2）这些改性会影响耐磨性吗？（3）这些改性会影响抗疲劳性吗？
我们研究了表面和基底改性（PMPC接枝和维生素E混合）对CLPE薄样品磨损和疲劳断裂的影响。对于未处理的、接枝PMPC的CLPE表面，以及添加和未添加维生素E的情况（四组），进行了表面润湿性和润滑性分析，并使用销盘试验机进行了多向磨损和冲击磨损试验。
无论是否添加维生素E，接枝PMPC的表面的水润湿性和润滑性（CLPE[均值±95%置信区间]：23.2°±1.8°，0.005±0.001；HD-CLPE[VE]：26.0°±2.3°，0.009±0.003）均高于未处理表面（CLPE：90.3°±1.2°，0.067±0.015；HD-CLPE[VE]：90.8°±2.0°，0.063±0.008）（p<0.001）。在多向磨损试验中，观察到PMPC接枝（CLPE：0.23±0.06mg；HD-CLPE[VE]：0.05±0.10mg）与重量磨损降低相关（CLPE：0.53±0.08mg，p=0.004；HD-CLPE[VE]：0.23±0.07mg，p=0.038）。无论是否添加维生素E，接枝PMPC的表面特性似乎均不影响抗冲击疲劳性。
PMPC接枝改善了表面亲水性和润滑性，并降低了多向滑动时的重量磨损。无论是否添加维生素E，在冲击与单向滑动方面均未产生差异。需要进一步研究以评估接枝PMPC的HD-CLPE(VE)在正常和严苛条件下的长期髋关节模拟器试验中的耐磨性，这可能为这些材料在体内的可能性能提供有用线索。
我们初步的体外研究结果表明，采用PMPC接枝可使全髋关节置换术中交联聚乙烯髋臼衬垫的磨损性能得到一定改善。需要进一步研究以评估接枝PMPC的HD-CLPE(VE)在正常和严苛条件下的长期髋关节模拟器试验中的耐磨性，这可能为这些材料在体内的可能性能提供有用线索。
