The seven-year wear of highly cross-linked polyethylene in total hip arthroplasty: a double-blind, randomized controlled trial using radiostereometric analysis

Reference:

Thomas, G. E., Simpson, D. J., Mehmood, S., Taylor, A., McLardy-Smith, P., Gill, H. S., Murray, D. W. and Glyn-Jones, S., 2011. The seven-year wear of highly cross-linked polyethylene in total hip arthroplasty: a double-blind, randomized controlled trial using radiostereometric analysis. Journal of Bone and Joint Surgery, American Volume, 93 (8), pp. 716-722.

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Official URL:

http://dx.doi.org/10.2106/JBJS.J.00287

Related URLs:

• http://www.ncbi.nlm.nih.gov/pubmed/21508278

Abstract

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.

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