压缩成型超高分子量聚乙烯的纳米压痕特性

Ho S P, Riester L, Drews M, Boland T, LaBerge M

Department of Preventative and Restorative Dental Sciences, University of California San Francisco, San Francisco, USA.

Proc Inst Mech Eng H. 2003;217(5):357-66. doi: 10.1243/095441103770802522.

This paper investigates the elastic modulus and hardness of untreated and treated compression-moulded ultra-high molecular weight polyethylene (UHMWPE) tibial inserts of a total knee replacement (TKR) prosthesis. Investigations were carried out at a nanoscale using a Nanoindenter at penetration depths of 100,250 and 500 nm. The nanomechanical properties of surface and subsurface layers of the compression-moulded tibial inserts were studied using the untreated UHMWPE. The nanomechanical properties of intermediate and core layers of the compression-moulded tibial insert were studied using the cryoultrasectioned and etched UHMWPE treated samples. The cryoultrasectioning temperature (-150 degrees C) of the samples was below the glass transition temperature, Tg (-122 +/- 2 degrees C ), of UHMWPE. The measurement of the mechanical response of crystalline regions within the nanostructure of UHMWPE was accomplished by removing the amorphous regions using a time-varying permanganic-etching technique. The percentage crystallinity of UHMWPE was measured using differential scanning calorimetry (DSC) and the Tg of UHMWPE was determined by dynamic mechanical analysis (DMA). Atomic force microscopy (AFM) was used to assess the effect of surface preparation on the samples average surface roughness, Ra. In this study, it was demonstrated that the untreated UHMWPE samples had a significantly lower (p < 0.0001) elastic modulus and hardness relative to treated UHMWPE cryoultrasectioned and etched samples at all penetration depths. No significant difference (p > 0.05) in elastic modulus and hardness between the cryoultrasectioned and etched samples was observed. These results suggest that the surface nanomechanical response of an UHMWPE insert in a total joint replacement (TJR) prosthesis is significantly lower compared with the bulk of the material. Additionally, it was concluded that the nanomechanical response of material with higher percentage crystallinity (67 per cent) was predominantly determined by the crystalline regions within the semi-crystalline UHMWPE nanostructure.

本文研究了全膝关节置换（TKR）假体未处理和经处理的压缩成型超高分子量聚乙烯（UHMWPE）胫骨衬垫的弹性模量和硬度。使用纳米压痕仪在100、250和500纳米的穿透深度下进行纳米级研究。使用未处理的UHMWPE研究压缩成型胫骨衬垫表面和亚表面层的纳米力学性能。使用冷冻超薄切片和蚀刻的UHMWPE处理样品研究压缩成型胫骨衬垫中间层和芯层的纳米力学性能。样品的冷冻超薄切片温度（-150℃）低于UHMWPE的玻璃化转变温度Tg（-122±2℃）。通过使用随时间变化的高锰酸盐蚀刻技术去除非晶区，完成了UHMWPE纳米结构内结晶区力学响应的测量。使用差示扫描量热法（DSC）测量UHMWPE的结晶度百分比，并通过动态力学分析（DMA）确定UHMWPE的Tg。使用原子力显微镜（AFM）评估表面处理对样品平均表面粗糙度Ra的影响。在本研究中，结果表明，在所有穿透深度下，未处理的UHMWPE样品相对于经冷冻超薄切片和蚀刻的处理UHMWPE样品，其弹性模量和硬度显著更低（p<0.0001）。在冷冻超薄切片和蚀刻样品之间未观察到弹性模量和硬度的显著差异（p>0.05）。这些结果表明，与材料本体相比，全关节置换（TJR）假体中UHMWPE衬垫的表面纳米力学响应显著更低。此外，得出的结论是，结晶度百分比更高（67%）的材料的纳米力学响应主要由半结晶UHMWPE纳米结构内的结晶区决定。