TriPreM i-Kohza, Department of Mechanical Precision Engineering, Malaysia-Japan International Institute Technology (MJIIT), Universiti Teknologi Malaysia, 54100 Kuala Lumpur, Malaysia.
National Orthopaedic Centre of Excellence in Research and Learning (NOCERAL), Department of Orthopaedic Surgery, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia.
J Mech Behav Biomed Mater. 2018 Nov;87:1-9. doi: 10.1016/j.jmbbm.2018.07.017. Epub 2018 Jul 11.
A revision of a metal-on-ultra high molecular weight (UHMWPE) bearing couple for total hip replacement was performed due to aseptic loosening after 23 years in-vivo. It is a major long-term failure identified from wear generation. This study includes performing failure analysis of retrieved polyethylene acetabular cup from Zimmer Trilogy Acetabular system. The UHMWPE acetabular cup was retrieved from a 61 years old male patient with ability to walk but limited leg movement when he presented to hospital in early 2016 with complaint left thigh pain. It was 23 years after his primary total hip replacement procedure. Surface roughness and morphology condition were measured using 3D laser microscope and Scanning Electron Microscope (SEM) to evaluate and characterize the wear features on polyethylene acetabular cup surface. ATR-Fourier Transform Infra-Red (ATR-FTIR), differential scanning calorimetry (DSC) and gel permeation chromatography (GPC) were used to characterize the chemical composition of carbon-oxygen bonding, crystallinity percentage and molecular weight of the polymer liner that might changes the mechanical properties of polyethylene. Nano indentation is to measure hardness and elasticity modulus where the ratio of hardness to elastic modulus value can be reflected as the degradation of mechanical properties. A prominent difference of thickness between two regions resulted from acentric loading concentration was observed and wear rate were measured. The linear wear rate for thin side and thick side were 0.33 mm/year and 0.05 mm/year respectively. Molecular weight reduction of 57.5% and relatively low ratio of hardness to elastic modulus (3.59 × 10) were the indicator of major mechanical properties degradation happened on UHMWPE acetabular cup. This major degradation was contributed by oxidation and polishing wear feature accompanied with delamination, craters, ripple and cracks were the indication of extensive usage of UHMWPE from the suggested life span of acetabular cup application.
由于体内 23 年后无菌性松动，对全髋关节置换的金属-超高分子量聚乙烯（UHMWPE）轴承进行了修改。这是从磨损产生中确定的主要长期失效。本研究包括对 Zimmer Trilogy 髋臼系统中取出的聚乙烯髋臼杯进行失效分析。从一名 61 岁男性患者中取出 UHMWPE 髋臼杯，该患者能够行走，但在 2016 年初就诊时腿部活动受限，主诉左大腿疼痛。这是他初次全髋关节置换手术后的 23 年。使用 3D 激光显微镜和扫描电子显微镜（SEM）测量表面粗糙度和形貌条件，以评估和表征聚乙烯髋臼杯表面的磨损特征。ATR-FTIR、差示扫描量热法（DSC）和凝胶渗透色谱法（GPC）用于表征聚合物衬里的碳氧键合、结晶度百分比和分子量的化学成分，这些可能会改变聚乙烯的机械性能。纳米压痕用于测量硬度和弹性模量，其中硬度与弹性模量值的比值可以反映机械性能的降解。观察到由于偏心载荷集中导致两个区域之间的厚度存在明显差异，并测量了磨损率。薄侧和厚侧的线性磨损率分别为 0.33mm/年和 0.05mm/年。分子量降低了 57.5%，硬度与弹性模量的比值相对较低（3.59×10），这表明 UHMWPE 髋臼杯的主要机械性能发生了严重退化。这种主要退化是由氧化和抛光磨损特征以及分层、凹坑、波纹和裂缝引起的，这表明 UHMWPE 的广泛使用超出了髋臼杯应用的建议使用寿命。
