The John Charnley Award: Highly crosslinked polyethylene in total hip arthroplasty decreases long-term wear: a double-blind randomized trial

Abstract

Background: The use of highly crosslinked polyethylene (HXLPE) is now commonplace for total hip arthroplasty. Hip simulator studies and short-term in vivo measurements suggest that the wear rate of some types of HXLPE is significantly less than conventional ultrahigh-molecular-weight polyethylene (UHMWPE). However, there are few long-term data to support its use.

Questions/purposes: The aim of this study was to measure the long-term steady-state wear of HXLPE compared with UHMWPE liners in a prospective, double-blind, randomized controlled trial using radiostereometric analysis.

Methods: Fifty-four patients were randomized to receive hip arthroplasties with either UHMWPE liners or HXLPE liners. Complete followup was available on 39 of these patients (72%). All patients received the same cemented stem and an uncemented acetabular component. Three-dimensional penetration of the head into the socket was determined at 10 years using a radiostereometric analysis system, which has an in vivo accuracy of <0.1 mm. Oxford Hip Scores were compared between the groups.

Results: At 10 years there was significantly less wear of HXLPE (0.003 mm/year; 95% confidence interval [CI], ±0.010; SD 0.023; range, -0.057 to 0.074) compared with UHMWPE (0.030 mm/year; 95% CI, ±0.012; p<0.001; SD 0.0.27; range, -0.001 to 0.164). The volumetric penetration from 1 to 10 years for the UHMWPE group was 98 mm3 (95% CI, ±46 mm3; SD 102 mm3; range, -4 to 430 mm3) compared with 14 mm3 (95% CI, ±40 mm3; SD 91 mm3; range, -189 to 242 mm3) for the HXLPE group (p=0.01).

Conclusions: This study demonstrates that HXLPE has little detectable steady-state in vivo wear. This may result in fewer reoperations from loosening; however, careful clinical followup into the second decade still needs to be performed.

Level of evidence: Level I, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Fig. 1

CONSORT 2010 flow diagram depicts the passage of patients through the randomized controlled trial with details on enrollment, intervention allocation, followup, and analysis.

Fig. 2

Line graph shows the mean total linear penetration (with vertical bars representing the 95% CIs) over 10 years for both HXLPE and UHMWPE.

Fig. 3

Linear regression between 1 and 10 years shows steady-state wear rate (with 95% CIs) for both HXLPE and UHMWPE.

Fig. 4

Graph shows individual patient-level wear rates from 1 to 10 years in both the HXLPE and UHMWPE groups. The osteolysis threshold of 0.1 mm/year is shown.