No association between blood count levels and whole-blood cobalt and chromium levels in 1,900 patients with metal-on-metal hip arthroplasty

Abstract

Background and purpose — The accelerated wear of poorly functioning metal-on-metal (MoM) hip implants may cause elevated whole-blood cobalt (Co) and chromium (Cr) levels. Hematological and endocrinological changes have been described as the most sensitive adverse effects due to Co exposure. We studied whether there is an association between whole-blood Co/Cr levels and leukocyte, hemoglobin, or platelet levels.

Patients and methods — We analyzed whole-blood Co and Cr values and complete blood counts (including leukocytes, hemoglobin, platelets) from 1,900 patients with MoM hips. The mean age at the time of whole-blood metal ion measurements was 67 years (SD 10). The mean time from primary surgery to whole-blood metal ion measurement was 8.2 years (SD 3.0). The mean interval between postoperative blood counts and metal ion measurements was 0.2 months (SD 2.7).

Results — The median Co value was 1.9 µg/L (0.2–225), Cr 1.6 µg/L (0.2–125), mean leukocyte count 6.7 × 10⁹/L (SD 1.9), hemoglobin value 143 g/L (SD 13), and platelet count 277 × 10⁹/L (SD 70). We did not observe clinically significant correlations between whole-blood Co/Cr and leukocyte, hemoglobin, or platelet counts.

Interpretation — Elevated whole-blood Co and Cr values are unlikely to explain abnormal blood counts in patients with MoM hips and the reason for possible abnormal blood counts should be sought elsewhere.

Supplementary data

Figures 1 and 2 are available as supplementary data in the online version of this article, http://dx.doi.org/10.1080/17453674. 2020.1827191

The authors would like to thank Ella Lehto RN, and Heli Kupari RN, Coxa Hospital for Joint Replacement, Tampere, Finland, for maintaining the study database. They thank Reija Autio Dr. Tech., University of Tampere, Faculty of Medicine and Life Sciences, Tampere, Finland, for statistical assistance.

NH: literature search, data collection and analysis, interpretation of data, statistics, writing and revision of the manuscript, and final approval. O. Lainiala: study design, literature search, data collection and analysis, interpretation of data, statistics, writing and revision of the manuscript, and final approval. O. Laine, AR, AE: study design, interpretation of data and statistics, writing and revision of the manuscript, and final approval.

Acta thanks Alister Hart, Raed Itayem and José M H Smolders for help with peer review of this study.