Department of Orthopaedic Surgery, Mie University, Graduate School of Medicine, 2-174 Edobashi, Tsu 514-8507, Mie, Japan.
Department of Orthopaedic Surgery, Mie University, Graduate School of Medicine, 2-174 Edobashi, Tsu 514-8507, Mie, Japan.
Acta Biomater. 2018 Jan 15;66:157-165. doi: 10.1016/j.actbio.2017.11.012. Epub 2017 Nov 7.
Highly cross-linked polyethylene (HXLPE) hip liners grafted with 2-methacryloyloxyethyl phosphorylcholine (MPC) on their bearing surfaces have recently been commercialized as components of a new generation of artificial hip joints, while improvements in wear resistance and biocompatibility were reported based on in vitro studies. The present study aimed at evaluating the surface modification and oxidative degradation in short-term retrieved MPC-grafted liners by X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR) with attenuated total reflection (ATR) equipment and Raman spectroscopy. In none of 3 samples of retrieved MPC-grafted liners, detectable MPC graft remained on the bearing surfaces although 2 samples yet contained remains of MPC polymer in their rim zone. These results revealed that the MPC polymer might have quickly disappeared from the bearing surface under in vivo loading, which is more severe than the in vitro one. Furthermore, a detectable oxidation index (OI) value (>0.1) was not only observed in any zone of any sample investigated, but also in the rim zones of Samples 1 and 2, which surprisingly experienced the most remarkable increase in OI value detected in this study. We thus confirmed that: (i) annealing of HXLPE cannot completely remove free radicals; (ii) the MPC graft has no beneficial effect in protecting HXLPE against oxidation and wear; and, (iii) lipid absorption occurred even in the rim zone where the MPC layer remained. Based on these evidences we consider that the declaimed advanced MPC technology is not a suitable one to elongate the in vivo lifetime of hip joints.
Several studies reported that highly crosslinked polyethylene (HXLPE) have resulted in reduced wear in total hip arthroplasty. Beyond those studies, HXLPE hip liners grafted with 2-methacryloyloxyethyl phosphorylcholine (MPC) on their bearing surface were extensively studied in vitro and then commercialized as a new generation of artificial hip joints. The present study reports for the first time results about the evaluation of surface modification and oxidative degradation in retrieved the MPC grafted liners. The findings of this investigation clearly show that the MPC layer has been peeled off on the bearing surface of the liner main wear zone although the MPC layer remained on the surface of the rim zones. Furthermore, we assessed the microstructural modifications and the oxidation drifts that occurred in vivo in the hip joints despite the presence of the MPC layer.
最近，高交联聚乙烯（HXLPE）髋关节衬垫的承载表面接枝了 2-（甲基丙烯酰氧基）乙基磷酸胆碱（MPC），作为新一代人工髋关节的组件已商业化，而体外研究报道了耐磨性和生物相容性的提高。本研究旨在通过 X 射线光电子能谱（XPS）、傅里叶变换衰减全反射红外光谱（FT-IR-ATR）和拉曼光谱评估短期回收 MPC 接枝衬垫的表面修饰和氧化降解。在 3 个回收 MPC 接枝衬垫的样本中，虽然 2 个样本在边缘区域仍残留有 MPC 聚合物，但在承载表面上都没有检测到可检测的 MPC 接枝。这些结果表明，MPC 聚合物可能在体内负荷下迅速从承载表面消失，这比体外负荷更严重。此外，在研究的任何样本的任何区域都观察到了可检测的氧化指数（OI）值（>0.1），并且在样本 1 和 2 的边缘区域也观察到了，这令人惊讶地是在本研究中检测到的 OI 值增加最显著的区域。因此，我们确认：（i）HXLPE 的退火并不能完全消除自由基；（ii）MPC 接枝对保护 HXLPE 免受氧化和磨损没有有益的作用；（iii）即使在保留 MPC 层的边缘区域也发生了脂质吸收。基于这些证据，我们认为宣称的先进 MPC 技术不适合延长髋关节的体内寿命。
几项研究报告称，高交联聚乙烯（HXLPE）已导致全髋关节置换术中的磨损减少。除了这些研究，在体外广泛研究了在承载表面接枝 2-（甲基丙烯酰氧基）乙基磷酸胆碱（MPC）的 HXLPE 髋关节衬垫，然后将其商业化作为新一代人工髋关节。本研究首次报告了关于回收 MPC 接枝衬垫的表面修饰和氧化降解评估的结果。该研究的结果清楚地表明，尽管 MPC 层仍留在边缘区域的表面上，但在衬垫的主要磨损区域的承载表面上，MPC 层已经剥落。此外，我们评估了髋关节内发生的微观结构变化和氧化漂移，尽管存在 MPC 层。
