Pascal‐André Vendittoli MD MSc1, William Blakeney MBBS MSc MS FRACS2, Ebru Oral3,4, and Orhun Muratoglu3,4 1 Surgery Department, Université de Montréal, Hôpital Maisonneuve Rosemont, Montréal, QC, Canada 2 Albany Health Campus, Department of Surgery, Albany, Australia 3 Harris Orthopaedic Laboratory, Massachusetts General Hospital, Boston, MA, USA 4 Department of Orthopaedic Surgery, Harvard Medical School, Boston, MA, USA The main purported benefit of XLPE is increased resistance to wear. Loosening and lysis related to wear are the most common reasons for TKA revision. Table 49.1 Clinical trials of TKAs using XLPE. § Four patients had osteolysis in the conventional polyethylene group and four had aseptic loosening (p = ns). * No patients in the conventional polyethylene group had osteolysis or aseptic loosening either. ‡ There were zero patients in the conventional polyethylene with osteolysis and three patients with aseptic loosening (p = ns). † Two patients in the conventional polyethylene group had osteolysis and none had aseptic loosening (p = ns). CCT: controlled clinical trial; RCT: randomized controlled trial; PCT: placebo controlled trial. Knee simulator studies on the wear behavior of tibial knee inserts have looked at the effects of long‐term testing, artificial aging, presence of third body particles, implant design, and malpositioning of implants. The studies uniformly showed improved adhesive/abrasive wear with XLPE compared to non‐XLPE in both cruciate retaining and posterior stabilized designs.1–8 Two case‐control trials reported an increase in radiolucent lines in patients with non‐XLPE compared with XLPE. However, there was no evidence of loosening or osteolysis and no failures in either group.9,10 Three randomized controlled trials (RCTs) and a prospective cohort study demonstrated no differences in radiographic outcomes between TKAs with XLPE and non‐XLPE.11–13 A meta‐analysis that included all the above trials found no difference in incidence of radiolucent lines, osteolysis or prosthesis loosening between XLPE and non‐XLPE.14 Analysis of synovial fluid aspirates of patients at one‐year post TKA have shown significantly fewer polyethylene wear particles in knees with XLPE versus non‐XLPE.15–17 The particles produced from the XLPE are also smaller than those produced by non‐XLPE.15–17 The biological implications of these smaller particles, however, remain unknown. For XLPE to be considered superior to non‐XLPE, it needs to demonstrate a lower revision rate and/or provide better clinical outcomes. The key factors of importance to a patient undergoing TKA are clinical outcomes and prosthesis survivorship.
49 Highly Cross‐Linked Polyethylene in Total Knee Arthroplasty
Top three questions
Question 1: For patients with total knee arthroplasty (TKA), is highly cross‐linked polyethylene (XLPE) more resistant to wear than conventional polyethylene (non‐XLPE)?
Rationale
Clinical comment
Available literature and quality of the evidence
Author
Year
Trial design
Knees (n)
Follow‐up (yr)
Implant and polyethylene
Radiolucency (%)
Osteolysis (%)
Aseptic loosening (%)
Hodrick et al.10
2008
CCT
100
6.3 (5.8–6.8)
Natural Knee II, CR (Zimmer); Durasul
2 (2.4)
0§
0§
Minoda et al.9
2009
CCT
89
2
NexGen, CR (Zimmer); Prolong
5 (5.6)
0*
0*
Kim and Park11
2014
RCT
308
5.9 (5–6.8)
NexGen LPS‐Flex, PS (Zimmer); Prolong
—
0*
0*
Kindsfater et al.13
2015
RCT
179
5
PFC Sigma, CR/PS (DePuy); XLK
13 (7.3)
2 (1.1)‡
1 (0.6)‡
Meneghini et al.18
2016
PCT
114
5 (4.3–7.4)
Triathlon PS (Stryker); X3
8 (8.1)
0*
0*
Lachiewicz and Soileau12
2016
RCT
94
4.5 (2–8)
NexGen LPS‐Flex, PS (Zimmer); Prolong
15 (16)
0†
0
Findings
Resolution of clinical scenario
Question 2: For patients with TKA, does XLPE provide better clinical outcomes and a lower revision rate than conventional polyethylene (non‐XLPE)?
Rationale
Clinical comment
Available literature and quality of the evidence
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