Vitamin E infused highly cross-linked cemented cups in total hip arthroplasty show good wear pattern and stabilize satisfactorily: a randomized, controlled RSA trial with 5-year follow-up

Abstract

Background and purpose

Vitamin E infused highly cross-linked polyethylene (VEPE) was introduced in order to enhance oxidative resistance in highly cross-linked polyethylene cups in total hip arthroplasty (THA). We have, with a follow-up of 5 years, evaluated wear characteristics of 2 identically designed cemented cups with the only difference being the material, VEPE or ultra-high molecular weight polyethylene (UHMWPE). Furthermore, we report cup migration and clinical outcome.

Patients and methods

48 patients with primary osteoarthritis were randomized to either UHMWPE or VEPE cups. Patients were followed with radiostereometric analysis (RSA) from the first postoperative day, at 3 months, 1, 2, and 5 years as well as with hip-specific outcome questionnaires.

Results

At 3 months the mean proximal head penetration for UHMWPE was 0.07 mm (95% CI 0.03–0.11) and for VEPE 0.06 mm (–0.01 to 0.13). Thereafter, there was a continuous annual wear of 0.08 mm/year, up to 0.46 mm (0.36–0.57) at 5 years, for the UHMWPE cup. The VEPE cup showed low annual wear of 0.01 mm/year, up to 0.09 mm (0.02–0.16) at 5 years. In the first 3 months the UHMWPE cup migrated cranially 0.08 mm (0.03–0.13) whereas the VEPE cup migrated 0.17 mm (0.10–0.24), Thereafter, they showed similar migration patterns with stabilization between 2 and 5 years up to 0.21 mm (0.04–0.39) and 0.24 mm (0.13–0.36) respectively. The HOOS remained good up to 5 years, and no cup was revised.

Interpretation

Compared with otherwise identical UHMWPE cups the cemented VEPE cup shows statistically significant reduction of wear up to 5 years and both cup types stabilize well with good clinical outcome.