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

Abstract

Background and purpose — Whole blood (WB) cobalt (Co) and chromium (Cr) ion levels have a major role in the follow-up of metal-on-metal total hip replacement (MoM THR). We investigated, first, if there was a change in WB Co or Cr levels over repeated measurements in patients with ReCap-M2A-Magnum THR, and, second, determined how many patients had WB Co or Cr levels that exceeded the safe upper limits (SUL) in the repeated whole blood metal ion assessment. Patients and methods — A Recap-M2A-Magnum THR was used in 1,329 operations (1,188 patients) at our institution between 2005 and 2012. We identified all patients (n = 319) with unilateral ReCap-M2A-Magnum implants who had undergone at least 2 repeated metal ion measurements with the first blood sample taken mean 5.5 years (1.8–9.3) after surgery and the second taken mean 2 years (0.5–3) after the first. Results — The median WB Co and Cr ion levels decreased in repeated measurements from 1.40 (0.40–63) ppb to 1.10 (0.20–68) ppb and from 1.60 (0.60–13.0) ppb to 1.10 (0.30–19.0) ppb, respectively. 7% of the Co ion values exceeded SUL at the initial measurement, and 7% at the control measurement. The proportion of Cr ion values exceeding the safe upper limit (SUL) decreased during the measurement interval from 5% to 4%. Interpretation — Repeated metal ion measurements in unilateral ReCap-M2A-Magnum patients in a mean 2-year time interval did not show any increase. Long-term ion levels are, however, not yet known.

15-year follow-up of MoM 36-mm THA: clinical, laboratory, and radiological (CT and MRI) prospective assessment

“…To simplify statistical analysis, patients were stratified according to Cr or Co levels into low; (<2 μg/L), medium; (⩾2 and <7 μg/L) and high-risk; (⩾7 μg/L) for ALTR. 5,15,25 At 15-year follow-up the study protocol was implemented and every patient (both symptomatic and nonsymptomatic, irrespectively of ion levels) underwent a hip sonography, an MRI and a CT ( Figure 1). Sonographic results were classified according to Nishii et al, 26 developed as a qualitative screening of the soft tissue findings in MoM THA.…”

“…At 5, 10 and 15 years follow-up, patients were evaluated clinically, including common outcome scores (Harris Hip Score [HHS], Oxford Hip Score [OHS], University of California at Los Angeles [UCLA] activity scale, 19–21 standard radiographs, 22,23 and measurement of Cr-Co blood levels. 5,24 Cr-Co level evaluations were conducted in the same Industrial Hygiene and Toxicology Laboratories. Results are expressed in μg/L; normal ranges are 0.05–1.0 μg/L for Co and 0.1–0.5 μg/L for Cr.…”

“…To simplify statistical analysis, patients were stratified according to Cr or Co levels into low; (<2 μg/L), medium; (⩾2 and <7 μg/L) and high-risk; (⩾7 μg/L) for ALTR. 5,15,25…”

“…[1][2][3][4] The Pinnacle acetabular shell (DePuy Inc., Warsaw, IN, USA) has been widely used with good shortand medium-term survival rates; it allows a modular 15-year follow-up of MoM 36-mm THA: clinical, laboratory, and radiological (CT and MRI) prospective assessment 36 mm MoM liner to be inserted. 5,6 Both European and US guidelines suggest a scheduled follow-up for MoM THA, including clinical evaluation, imaging and measurement of blood metal ion levels. 7,8 Due to limited knowledge of the long-term results (>10 years) of MoM THA, particularly concerning clinical outcomes, adverse local tissue reaction (ALTR), Cr-Co ions level and revision rate, [9][10][11] long-term data could help in defining the course and best management for these patients.…”

“…1–4 The Pinnacle acetabular shell (DePuy Inc., Warsaw, IN, USA) has been widely used with good short- and medium-term survival rates; it allows a modular 36 mm MoM liner to be inserted. 5,6 Both European and US guidelines suggest a scheduled follow-up for MoM THA, including clinical evaluation, imaging and measurement of blood metal ion levels. 7,8…”