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A randomized prospective double-blind trial comparing highly cross-linked with conventional polyethylene in total hip
Peter A Devane1, James G Horne1, Agnes Chu1
1Wellington Hospital, Wellington, New Zealand.
Aims:
Highly cross-linked polyethylene (XLPE) was developed in an attempt to address the problems of wear and osteolysis causing failure in patients who undergo total hip arthroplasty (THA). The aim of this study was to compare the rates of PE wear and revision, and the clinical outcomes of conventional polyethylene (CPE) and XLPE, in a prospective double-blind randomized controlled trial (RCT) with a minimum follow-up of 20 years.
Methods:
A total of 122 patients were randomized to be treated with either a CPE (Enduron) or an XLPE liner (Marathon; both DePuy Synthes, USA). Other than the liners, identical components were used: a Duraloc 300 metal shell, a 28 mm diameter cobalt-chromium femoral head, and a cemented Charnley Elite femoral component. All patients were followed with anteroposterior (AP) and lateral radiographs at two days, six weeks, three and six months, and one, two, three, four, five, ten, and 20 years. PE wear was measured using PolyMig, which has a phantom validated accuracy of approximately 0.09 mm. The outcomes at ten years' follow-up in these patients have previously been reported.
Results:
At a minimum follow-up of 20 years, 47 patients had died, five of whom had undergone a revision. Another 32 patients had undergone a revision and were alive, leaving 43 patients who had not undergone a revision and were alive (15 in the Enduron group and 28 in the Marathon group). No patients were lost to follow-up, but radiographs could not be obtained at final follow-up in two due to dementia, leaving 41 patients (15 in the Enduron group and 26 in the Marathon group) available for the measurement of PE wear. After the bedding-in period, the rate of wear was 0.181 mm/yr (95% CI 0.175 to 0.188) in the Enduron group and 0.034 mm/yr (95% CI 0.028 to 0.039) in the Marathon group. At 20-year follow-up, 37 patients had required revision. Those with CPE liners had a revision rate three times higher (28/37) than those with XLPE liners (9/37).
Conclusion:
This is the longest-term RCT showing substantially improved clinical and radiological results when XLPE is used as the bearing surface in patients who undergo primary THA.
