全人工髋关节超高分子量聚乙烯髋臼杯组件取出物之磨耗分析

Analysis of UHMWPE insert wear in total hip replacement

目的针对全人工髋关节超高分子量聚乙烯髋臼杯组件取出物(以下简称PE内衬组件)之磨耗进行相关性的评估,以磨耗计分的方式量化PE内衬组件表面的磨耗情形。方法研究材料取自1993年至2003年间在马偕纪念医院接受全人工髋关节再置换手术病患之人工髋关节组件取出物,以DePuy公司AMLPlus系列、Mecron公司Mecring系列与Osteonics公司OmnifIt系列等三种人工髋关节为主,故本研究针对此三种人工髋关节的取出物进行磨耗分析。研究中定义磨耗评分=程度因子×表现数值,其中程度因子以磨耗型态来决定,而表现数值以磨耗面积决定。磨耗型态分成八种,依程度共分七级,包括磨、擦痕、变形、刮痕、坑洞、层状剥落、磨穿和破裂。磨耗面积依磨耗面积百分比表示共分三级。利用立体光学显微镜得知其磨耗型态及面积,求出磨耗评分。最后,分析磨耗分数与人工髋关节组件设计之间的差异。结果本研究PE内衬组件的主要磨耗型态为磨:33%、擦痕:100%、刮痕:36%、磨穿及破裂:40%。统计分析显示磨耗评分与病患之性别、患侧、体重、再置换年龄、植入时间之间的相关性不显著,但是,磨耗评分与倾斜角有显著相关性。结论临床变异因子对磨耗评分影响较小而不同人工髋关节的设计才是影响磨耗评分的主要因素之一。

Objective This study analyzed the UHMWPE insert wear in total hip replacement of different prosthesis designs and wear conditions. Methods Specimens of acetabular cups were selected among the total hip prosthesis revisions at Mackay Memorial Hospital, Taipei, during the years from 1993 to 2003. The specimens included products of DePuy-AML Plus series, Mecron-Mecring series and Osteonics-Omnifit series, which were of totally different designs. This study focused on differentiating the wear among these three types of products. In our study, the wear score was defined as the severity factor （determined by the wear pattern） × the amount present （determined by the worn area）. The number was multiplied by a severity factor assigned to each wear pattern on a scale of 0-7. A classification system was designed which identified the following eight pattern of damage on the surface： burnishing, abrasion, deformation, scratching, pitting, delamination, wear-through and component fracture. In each region the severity of each pattern was graded on a scale of 0-3, based on the percent area of the region affected, to give a total cumulative wear score for each UHMWPE insert. We inspected the UHMWPE insert with light stereomicroscopy to measure worn area and to classify the wear pattern. The wear scores thus calculated were analyzed to demonstrate the difference in wear related to designsof components in the types of hip prostheses. Results The most common types of wear observed, abrasion （100%）, wear-through, component fracture （40%）, scratching （36%） and burnishing （33%）. Multiple linear regression analysis was used to determine possible associations between wear score and the patient’s gender, age and weight at the time of the operation, the duration that the implant had been in situ. It was found no relationship between any clinical variable and the visually evaluated wear score. There was a significant positive correlation between the wear score and the angle of the inclination of the cup. Conclusion Clinical variables have little influence on polyethylene wear of well functioning hip replacements. Alternatively, it may be related to the variety of cup designs included in our study.