Glen Richardson MD MSc FRCSC, and Michael J. Dunbar MD PhD FRCSC Division of Orthopaedic Surgery, Department of Surgery, Dalhousie University, Halifax, NS, Canada The purpose of HCLPE is to improve the longevity of THA by decreasing the wear rate of the bearing used during THA. The use of THA in younger and presumably more active patients has led surgeons to be concerned about the wear rate of polyethylene and to seek out expensive alternate bearings such as HCLPE, ceramic on ceramic, or metal on metal. Clearly any change made to polyethylene has the potential for decreasing wear rates but also increasing adverse events. The clinical importance of decreasing polyethylene wear rates is significant to THA recipients. The main theory of late failure of THA is that the wear of the bearing generates particulate debris that leads to loosening, mechanical failure, and/or instability of the THA. Ten high‐quality randomized controlled trials (RCTs), level I, are available to answer this question. A considerable amount of research on the topic of THA wear rates has been published. Many of the studies are RCTs to demonstrate the improvement in wear rates with HCLPE as compared to regular polyethylene. What complicates the interpretation of the literature is that various different types of HCLPE, which use different techniques to achieve crosslinking and eliminating free radicals, have been used in the clinical studies. In order to interpret the substantial amount of reported data on HCLPE, a basic knowledge of the different methods to measure in vivo wear of polyethylene is necessary. There are manual techniques that rely on manual edge detection to calculate the migration of the femoral head.1 To improve accuracy and reproducibility, computer‐aided techniques have been developed.2,3 The most accurate method of measuring wear is radiostereometric analysis (RSA).4,5 Studies looking at wear rates require follow up of at least two years, in order to get a true estimate of steady state wear rate because of the effect of plastic deformation, otherwise known as bedding in or creep.6–8 There have been eight papers that have performed RCTs using cobalt chrome femoral heads on HCLPE and have used some form of computer‐assisted technique to measure the polyethylene wear.9–16 Many of the major manufactures of HCLPE are represented in these articles. Marathon (5 Gy), Durasul (9.5 Gy), Longevity (10 Gy), and Crossfire (7.5 Gy) have all demonstrated significant reductions in steady state wear rates compared to UHMWPE. The reduction in wear varies from 55 to 95% and this often is a function of the wear properties of the control group. Importantly, the follow‐up was 2 to 10 years confirming the improved wear of HCLPE. There have been 12 RSA studies, eight of which are level I studies, reported in the literature.617–25 Arcom, E1 Vitamin E poly, Reflection, Durasul, Longevity, and Crossfire HCLPE have all been demonstrated to have significantly decreased wear rates compared to UHMWPE. The length of follow‐up varied from 2 to 13 years. There has been concern that the smaller wear particles of THA will lead to an increased risk of osteolysis compared to UHMWPE.26,27 One of the major reasons for revision of THA is the presence of progressive osteolysis (Figure 22.1).28 Thus, it is important to understand if HCLPE results in reduced osteolysis. Figure 22.1 AP and lateral views of bilateral hip replacements with UHMWPE demonstrating advanced polyethylene wear and associated osteolysis six years postoperatively in a modestly active female. Source: Glen Richardson, Michael J. Dunbar. There are six level I RCTs and three level III systematic reviews of case‐controlled and retrospective studies that aim to answer this question. There have been a number of studies that have looked at wear and reported on the incidence of osteolysis as part of an RCT.9,16
22 Highly Crosslinked Polyethylene in Total Hip Arthroplasty
Clinical scenario
Top three questions
Question 1: In patients receiving a THA, does highly crosslinked polyethylene (HCLPE) result in a reduction in the wear rate compared to standard UHMWPE?
Rationale
Clinical comment
Available literature and quality of the evidence
Findings
Resolution of clinical scenario
Question 2: In patients receiving a THA, does HCLPE result in a reduction in osteolysis compared to UHMWPE?
Rationale
Clinical comment
Available literature and quality of the evidence
Findings
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