Wear performance/rates UHMWPE

Xue et al. (16) observed that the wear rate of the UHMWPE/HDPE blend can be significantly reduced by adding CNTs, which can be correlated with an increase of the Young s modulus. The addition of 0.5 wt% CNTs to the UHMWPE/HDPE blend caused about 50% reduction of the wear rate, which is shown in Table 5.7. Besides, the composites reinforced with untreated CNTs had a better wear performance than the composites with pre-treated CNTs and the graphical... 

Chamley and coworkers first developed radiographic techniques for evaluating the wear rate of UHMWPE acetabular components in patients. In 1973, Chamley and Cupic reported on the long-term wear performance in the first cohort of patients to receive a UHMWPE component between November 1962 and December 1963. During this time period, 170 patients received a cemented LFA with an UHMWPE component a total of 185 acetabular cups were implanted. Because of the elderly population originally implanted with the components, many had died or were too infirm to travel to the clinic for followup examination (more than two-thirds of the patients were older than 60 years of age at the time of implantation). Thus, only 106 out of the original 185 UHMWPE cups could still be evaluated after 9 or 10 years of implantation. The complications for this series included a 4-6% rate of infection, 1-2% rate of mechanical loosening, and a 2% incidence of late dislocation. 

Although knee arthroplasty enjoys a remarkable clinical track record, problems with wear and fatigue damage of UHMWPE continue to limit the longevity of both unicondylar and bicondylar knee replacement components. Unlike in the hip, where radiographic techniques have been developed to quantify in vivo wear rates, there currently exist no standard and widely accepted techniques for tracking the clinical performance of UHMWPE in patients with knee replacement. Thus, today the most effective way to evaluate the in vivo performance of UHMWPE continues to be the analysis of retrieved components from revision surgery or from autopsy donations. 

Artificial disc replacemenfs have also been developed that do not incorporate UHMWPE components. These have a MOM bearing system, which presumably is to reduce the amoimt of wear produced. This once again shows the trend of borrowing concepfs from fhe TJR world and applying them to TDRs. In addition, for TDR designs, fhe wear performance of CoCr has been evaluated and was shown to have less wear rate in comparison with titanium alloy designs (Hellier, Hedman, and Kostuik 1992). 

A wear study by McKellop et al. indicated that Poly n exhibited a 10 times greater wear rate than UHMWPE against a variety of common counterfaces, such as 316 stainless steel and CoCr alloy [19]. Because the major mechanism of wear in carbon fiber-reinforced polyethylene is abrasive wear that induces the drawing out of fibers from bearing surfaces [20], the interface strength is of critical importance in the overall performance of Poly II and similar composites. 

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