No difference in whole-blood metal ions between 32-mm and 36- to 44-mm femoral heads in metal-on-polyethylene total hip arthroplasty: a 2-year report from a randomised control trial

Abstract

Aim: To investigate the effect of femoral head size on blood metal-ion levels caused by taper corrosion in metal-on-polyethylene total hip arthroplasty, comparing 36- to 44-mm heads with 32-mm heads. Methods: In a randomised, controlled, single-blinded trial, 96 patients were allocated to receive either a 32-mm metal head or the largest possible metal head (36–44 mm) that could be accommodated in the thinnest available vitamin E, cross-linked polyethylene insert. Blood metal ion levels were collected at 1- and 2-year follow-ups. Results: At 1-year, metal-ion levels did not differ between the groups. The median (interquartile range) blood-ion levels for the 32-mm versus the 36- to 44-mm group were 0.11 µg/L (0.08–0.15) versus 0.12 µg/L (0.08–0.22), p = 0.546, for cobalt, 0.50 µg/L (0.50–0.59) versus 0.50 µg/L (0.50–1.20), p = 0.059, for chromium and 1.58 µg/L (1.38–2.05) versus 1.48 µg/L (1.14–1.87), p = 0.385, for titanium. At 2 years, there was no difference either and the corresponding values were 0.15 µg/L (0.12–0.24) versus 0.18 µg/L (0.12–0.28), p = 0.682 for cobalt, 0.50 µg/L (0.50–0.50) versus 0.50 µg/L (0.50–0.57), p = 0.554, for chromium and 1.54 µg/L (1.16–1.87) versus 1.42 µg/L (1.01–1.72), p = 0.207 for titanium. Conclusions: The use of the largest possible metal head (36–44 mm) compared to a 32-mm head in metal–on-polyethylene bearings does not appear to elevate blood metal-ion levels up to 2 years postoperatively. As taper corrosion is probably time-dependent, longer-term reports are needed to evaluate the association between large metal heads and blood metal ion levels. Trial registration: ClinicalTrials.gov (reg. ID NCT0231 6704)

Similarly low blood metal ion levels at 10‐years follow‐up of total hip arthroplasties with Oxinium, CoCrMo, and stainless steel femoral heads. Data from a randomized clinical trial

“…The median cobalt and chromium levels for the 28 mm head group were 0.66 μg/L and 0.68 μg/L, respectively. Similarly, no difference was found in cobalt and chromium blood levels in a randomized study comparing 32 mm, 36 mm and 40 mm modular CoCrMo heads at 1‐ and 2‐years follow‐up 33 …”

“…Similarly, no difference was found in cobalt and chromium blood levels in a randomized study comparing 32 mm, 36 mm and 40 mm modular CoCrMo heads at 1-and 2-years follow-up. 33 Neck taper flexural rigidity also affect trunnion corrosion and one study showed that lower stem flexural rigidity predicted stem fretting and corrosion damage in a ceramic head cohort, but not in the metal head cohort. 23 Care should therefore be taken to generalize the results to different stem designs and materials.…”

“…Similarly, no difference was found in cobalt and chromium blood levels in a randomized study comparing 32 mm, 36 mm and 40 mm modular CoCrMo heads at 1‐ and 2‐years follow‐up. 33 …”