Repeated cobalt and chromium ion measurements in patients with bilateral large-diameter head metal-on-metal ReCap-M2A-Magnum total hip replacement

摘要

Background and purpose — Whole-blood (WB) chro-mium (Cr) and cobalt (Co) measurements are vital in the fol-low-up of metal-on-metal total hip replacement (MoM THR)patients. We examined whether there is a substantial changein repeated WB, Co, and Cr levels in patients with bilateralReCap-M2A-Magnum THR. We also specified the numberof patients exceeding the safe upper limit (SUL) of WB Coand Cr in the repeated measurement.Patients and methods — We identified 141 patientswith bilateral ReCap-M2A-Magnum THR operated in ourinstitution. 61 patients had repeated WB metal ion measure-ments with bilateral MoM implants still in situ in the secondmeasurement. The mean time elapsing from the first mea-surement (initial measurement) to the second (control mea-surement) was 1.9 years (SD = 0.6, range 0.2–3.5). We usedearlier established SUL levels for bilateral implants by VanDer Straeten et al. (2013).Results — The median (range) Co and Cr valuesdecreased in the repeated measurement from 2.7 (0.6–25) to2.1 (0.5–21) and 2.6 (0.8–14) to 2.1 (0.5–18) respectively. In13% of the patients Co levels exceeded the SUL in the initialmeasurement and the proportion remained constant, at 13%,in the repeated measurement. In 5% of the patients, Cr levelswere above SUL in the initial measurement and an equal 5%in the control measurement.Interpretation — Repeated WB metal ion levels did notincrease in patients with bilateral ReCap-M2A-MagnumTHR with a mean 1.9-year measurement interval. Long-termdevelopment of WB metal ion levels is still unclear in thesepatients.