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The creep and wear behaviour of highly cross-linked polyethylene and standard polyethylene liners were examined in a prospective, double-blind randomised, controlled trial using radiostereometric analysis. We randomised 54 patients to receive hip replacements with either highly cross-linked polyethylene or standard liners and determined the three-dimensional penetration of the liners over three years. After three years the mean total penetration was 0.35 mm (SD 0.14) for the highly cross-linked polyethylene group and 0.45 mm (SD 0.19) for the standard group. The difference was statistically significant (p = 0.0184). From the pattern of penetration it was possible to discriminate creep from wear. Most (95%) of the creep occurred within six months of implantation and nearly all within the first year. There was no difference in the mean degree of creep between the two types of polyethylene (highly cross-linked polyethylene 0.26 mm, SD 0.17; standard 0.27 mm, SD 0.2; p = 0.83). There was, however, a significant difference (p = 0.012) in the mean wear rate (highly cross-linked polyethylene 0.03 mm/yr, SD 0.06; standard 0.07 mm/yr, SD 0.05). Creep and wear occurred in significantly different directions (p = 0.01); creep was predominantly proximal whereas wear was anterior, proximal and medial. We conclude that penetration in the first six months is creep-dominated, but after one year virtually all penetration is due to wear. Highly cross-linked polyethylene has a 60% lower rate of wear than standard polyethylene and therefore will probably perform better in the long term.

Original publication

DOI

10.1302/0301-620X.90B5.20545

Type

Journal article

Journal

J Bone Joint Surg Br

Publication Date

05/2008

Volume

90

Pages

556 - 561

Keywords

Aged, Arthroplasty, Replacement, Hip, Coated Materials, Biocompatible, Double-Blind Method, Equipment Failure Analysis, Female, Hip Joint, Hip Prosthesis, Humans, Male, Materials Testing, Middle Aged, Osteoarthritis, Hip, Polyethylene, Polyethylenes, Prospective Studies, Prosthesis Design, Prosthesis Failure, Radiography, Statistics as Topic, Time Factors