Abstract
Background and purpose — The long-term survival of arthroplasty components may be limited by polyethylene wear-related problems such as periprosthetic osteolysis and aseptic loosening. Highly cross-linked polyethylene (HXLPE) blended with vitamin E was introduced to improve oxidative stability and to avoid long-term embrittlement. This study clinically compares the tribological behavior and clinical outcome of vitamin E blended HXLPE with ultra-high molecular weight polyethylene (UHMWPE) in an isoelastic monoblock cup for uncemented total hip arthroplasty.Patients and methods — In this randomized controlled trial (RCT), 199 patients were included: 102 patients received the vitamin E blended HXLPE cup, 97 patients the UHMWPE cup. Clinical and radiographic parameters were obtained preoperatively, directly postoperative and at 3, 12, and 24 months. Wear rates were compared using the mean linear femoral head penetration (FHP) rate.Results — 188 patients (94%) completed the 2-year follow-up. Mean patient satisfaction was higher in the vitamin E blended HXLPE group (8.9 [1]) than in in the control group (8.5 [2], p = 0.03). The Harris Hip Score (HHS) was higher in the vitamin E blended HXLPE group (95 [8]) than in the control group (92 [11], p = 0.3). The FHP rate was lower in the vitamin E blended HXLPE group: 0.046 mm/year compared with 0.056 mm/year in the control group (p = 0.05). No adverse reactions associated with the clinical application of vitamin E blended HXLPE were observed during follow-up, with an excellent 2-year survival to revision rate of 98% for both cups.Interpretation — This study shows the superior performance of the HXLPE blended with vitamin E acetabular cup with lower linear femoral head penetration rates and better clinical results compared with the UHMWPE acetabular cup after 2 years.
Highlights
Joost H J VAN ERP 1,2, Julie R A MASSIER 1,2, Jelle J HALMA 1, Thom E SNIJDERS 1, and Arthur DE GAST 1,2
The femoral head penetration (FHP) rate was lower in the vitamin E blended HXLPE group: 0.046 mm/year compared with 0.056 mm/year in the control group (p = 0.05)
The vitamin E blended HXLPE showed a lower (p = 0.05) FHP rate of 0.046 mm/year compared with the conventional HXLPE cup (0.056 mm/year)
Summary
This single-blinded RCT was carried out at the Diakonessenhuis Hospital, a medium-size general hospital in Utrecht/ Zeist, the Netherlands. Baseline characteristics, Harris Hip Score (HHS), numeric rating scale (NRS) score for rest and load pain, and patient satisfaction were documented. An RCT by Dorr et al (2005) found a lower mean wear rate at 2 years in the group treated with the HXLPE cup (0.150 mm [SD 0.09]) than in the group with an UHMWPE cup (0.191 mm [SD 0.09]). The sample size was determined on the basis of an overall a-error of 0.05 and a statistical power of 80% (ß = 0.20). This resulted in a sample size of 80 patients per group, which was increased to 100 patients per group to account for possible withdrawal and loss-to-follow-up. The investigators were able to withdraw a subject from the study for urgent medical reasons.
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