Median 10-year whole blood metal ion levels and clinical outcome of ReCap-M2a-Magnum metal-on-metal total hip arthroplasty

Abstract

Background and purpose: We have previously reported that the whole blood (WB) chromium (Cr) and cobalt (Co) ion levels decrease in the short term after ReCap-M2a-Magnum large-diameter head (LDH) metal-on-metal (MoM) total hip arthroplasty (THA). This study reports long-term metal ion levels and clinical outcomes after ReCap-Magnum THA.Patients and methods: ReCap-M2a-Magnum LDH THA was used in 1,450 patients in our hospital district from 2005 to 2012. Median follow-up time was 10 years. 991 patients had 2 or more metal ion measurements. The median measurement interval was 4 years. Individual metal ion change was assessed using logarithmic metal ion values in a random coefficient model. Kaplan–Meier survival estimates were calculated for revision surgery for any reason for revision, and separately for metal-related adverse events (metalions above safe upper limit [SUL], revision due to ARMD, or pseudotumor).Results: Geometric mean of Cr decreased from 1.8 ppb (geometric standard deviation [GSD] 1.8) to 1.0 ppb (GSD 2.8, p < 0.001). The Co levels decreased from 1.7 ppb (GSD 2.4) to 1.4 ppb (GSD 2.8, p < 0.001). The hip-specific survival was 85% for revision due to any reason at 14 years and the hip-specific survival for any metal-related adverse event was 69% at 14 years.Interpretation: WB Cr and Co levels continued to decrease in the long-term follow-up of ReCap-M2a-Magnum THA patients. The amount of metal-related adverse events was rather high, but revision surgery was seldom required. We suggest that after 10 years from the implantation a 5-year measurement interval may be sufficient for asymptomatic ReCap-M2a-Magnum patients.

No difference in implant survival between 28-mm M2a RingLoc metal-on-metal and metal-on-polyethylene total hip arthroplasty: results from the Finnish Arthroplasty Register

“…In LH ReCap-M2a MoM THA, patients’ blood metal ion level decreased in the long-term follow-up. Also patient satisfaction was excellent or good in 76% of patients in spite of marginally elevated blood-metal ions ( 20 ).…”

Concentrations of Cobalt, Chromium and Titanium and Immunological Changes after Primary Total Knee Arthroplasty—A Cohort Study with an 18-Year Follow-Up

“…Even a decade after metal-on-metal hip arthroplasty, Co concentrations seem to remain unchanged, whereas Cr concentrations may slightly decline [8]. In some metal-on-metal hip devices, however, Co also declines after ten years [9]. By definition, our cross-sectional study design provides no longitudinal data, but extrapolation from studies on metal ion concentrations after TKA measured at short-term follow-up [4,5] indicates that there is no gross accumulation of metal ions in the long term after TKA.…”