Does the use of the largest possible metal head increase the wear of vitamin E-doped cross-linked polyethylene? Two-year results from a randomized controlled trial

Abstract

Aims We aimed to investigate if the use of the largest possible cobalt-chromium head articulating with polyethylene acetabular inserts would increase the in vivo wear rate in total hip arthroplasty. Methods In a single-blinded randomized controlled trial, 96 patients (43 females), at a median age of 63 years (interquartile range (IQR) 57 to 69), were allocated to receive either the largest possible modular femoral head (36 mm to 44 mm) in the thinnest possible insert or a standard 32 mm head. All patients received a vitamin E-doped cross-linked polyethylene insert and a cobalt-chromium head. The primary outcome was proximal head penetration measured with radiostereometric analysis (RSA) at two years. Secondary outcomes were volumetric wear, periacetabular radiolucencies, and patient-reported outcomes. Results At two years, 44 patients in each group were available for RSA assessment. The median total two-year proximal head penetration was -0.02 mm (IQR -0.09 to 0.07; p = 0.548) for the largest possible head and -0.01 mm (IQR -0.07 to 0.10; p = 0.525) for 32 mm heads. Their difference was not statistically significant (p = 0.323). Neither group demonstrated a bedding-in period. The median steady-state volumetric wear rates were 6.1 mm3/year (IQR -59 to 57) and 3.5 mm3/year (-21 to 34) respectively, and did not differ between the groups (p = 0.848). There were no statistically significant differences in periacetabular radiolucencies or patient-reported outcomes. Conclusion The use of the largest possible metal head did not increase vitamin E-doped cross-linked polyethylene wear compared with 32 mm heads at two years. Linear wear was negligible and volumetric wear rates were very low in both head size groups. There was a tendency towards higher values of volumetric wear in large heads that warrants longer-term evaluation before any definite conclusions about the association between head size and wear can be drawn. Cite this article: Bone Joint J 2021;103-B(7):1206–1214.

Thin highly cross-linked polyethylene liners combined with large femoral heads in primary total hip arthroplasty show excellent survival and low wear rates at a mean follow-up of 12.8 years

“…HXLPE liners with vitamin E do not show statistically significant lower wear rates, even when combined with the largest possible head. 30,31 Together, all studies reporting excellent wear rates with thin liners contradict an earlier in vitro report by Johnson et al, 10 which found higher wear rates in thinner HXLPE liners compared to thicker HXLPE liners.…”

To what extent could the acetabular liner thickness be reduced yet remaining tribologically acceptable in metal‐on‐vitamin E‐diffused crosslinked polyethylene hip arthroplasty?

“…They reported that the mid‐term wear, cup migration, and clinical outcomes did not differ between the different head size groups, and their annual linear wear rates ranging from 0.023 to 0.028 mm/year were well below 0.1 mm/year of the wear threshold to increase the frequency of osteolysis 38 . In another study, Tsikandylakis et al 39 reported on 88 hips treated either with the largest possible (36–44 mm) metal head in the thinnest possible (4.3–5.3 mm) Vit‐E diffused XLPE liner or a standard diameter metal head (32 mm) in 6.7–11.3 mm‐thick Vit‐E diffused XLPE liner. They showed that the use of the largest possible heads did not significantly increase wear compared with 32 mm heads at 2 years although there was a tendency toward higher values of volumetric wear in the largest possible heads.…”

Vitamin E-diffused liners show less head penetration than cross-linked polyethylene liners in total hip arthroplasty: a ten-year multi-arm randomized trial

“…This finding aligns with previous studies that demonstrated that total head penetration and wear rates are independent from femoral head size. [27][28][29] No patients experienced aseptic loosening, and only one underwent revision due to dislocation two days after surgery. Given that the THA lifespan is usually 20 years, 2,14 the sample size was small, and the wear rate was low, other revisions would have been unlikely.…”