TY  - JOUR
T1  - The Seven-Year Wear of Highly Cross-Linked Polyethylene in Total Hip ArthroplastyA Double-Blind, Randomized Controlled Trial Using Radiostereometric Analysis
AU  - Thomas, Geraint E.R.
AU  - Simpson, David J.
AU  - Mehmood, Shahid
AU  - Taylor, Adrian
AU  - McLardy-Smith, Peter
AU  - Singh Gill, Harinderjit
AU  - Murray, David W.
AU  - Glyn-Jones, Siôn
Y1  - 2011/04/20
N1  - 10.2106/JBJS.J.00287
JO  - The Journal of Bone & Joint Surgery
SP  - 716
EP  - 722
VL  - 93
IS  - 8
N2  - Background: 
  The use of highly cross-linked polyethylene is now commonplace in total hip arthroplasty. Hip simulator studies and short-term in vivo measurements have suggested that the wear rate of highly cross-linked polyethylene is significantly less than that of conventional ultra-high molecular weight polyethylene. However, long-term data to support its use are limited. The aim of this study was to compare the intermediate-term steady-state wear of highly cross-linked polyethylene compared with that of conventional ultra-high molecular weight polyethylene acetabular liners in a prospective, double-blind, randomized controlled trial with use of radiostereometric analysis.Methods: 
  Fifty-four patients were randomized to receive hip replacements with either conventional ultra-high molecular weight polyethylene acetabular liners (Zimmer) or highly cross-linked polyethylene liners (Longevity; Zimmer). All patients received a cemented, collarless, polished, tapered femoral component (CPT; Zimmer) and an uncemented acetabular component (Trilogy; Zimmer). Clinical outcomes were assessed and the three-dimensional penetration of the head into the socket was determined for a minimum of seven years. Linear regression was used to calculate the steady-state wear rate following the creep-dominated penetration seen during the first year.Results: 
  At a minimum of seven years postoperatively, the mean total femoral head penetration was significantly lower in the highly cross-linked polyethylene group (0.33 mm; 95% confidence interval [CI], ±0.10 mm) than it was in the ultra-high molecular weight polyethylene group (0.55 mm; 95% CI, ±0.10 mm) (p = 0.005). The mean steady-state wear rate of highly cross-linked polyethylene was 0.005 mm/yr (95% CI, ±0.015 mm/yr), compared with 0.037 mm/yr (95% CI, ±0.019 mm/yr) for conventional ultra-high molecular weight polyethylene (p = 0.007). No patient in the highly cross-linked polyethylene group had a wear rate above the osteolysis threshold of 0.1 mm/yr, compared with 9% of patients in the ultra-high molecular weight polyethylene group.Conclusions: 
  This study demonstrates that highly cross-linked polyethylene has a significantly lower steady-state wear rate compared with that of conventional ultra-high molecular weight polyethylene. Longer-term follow-up is required to determine if this will translate into improved clinical performance and longevity of these implants.Level of Evidence: 
  Therapeutic Level I. See Instructions to Authors for a complete description of levels of evidence.
SN  - 0021-9355
M3  - doi: 10.2106/JBJS.J.00287
UR  - http://dx.doi.org/10.2106/JBJS.J.00287
ER  -