Elevated cobalt levels in metal-on-polyethylene knee megaprostheses: a prospective 1-year cohort study of 56 patients with hip and knee megaprostheses

Background and purpose - Concerns have emerged regarding elevated levels of cobalt and chromium in patients with metal -on -metal megaprostheses. This prospective study aims to identify systemic cobalt and chromium levels in metal -on -polyethylene knee and hip megaprostheses and their associations with other factors. Methods - 56 patients underwent knee or hip megaprosthesis surgery at 2 sarcoma centers. Serum cobalt and chromium levels were measured preoperatively and thrice within the first year using inductively coupled plasma mass spectrometry. Results - A statistically significant difference in serum cobalt levels (1.4 ppb; 95% confidence interval [CI] 0.0-3.3) was observed 1 year after knee megaprosthesis surgery compared with preoperative levels. In contrast no difference in chromium levels was observed after 1 year compared with preoperative levels (0.05 ppb; CI 0.0-0.8). An association between younger age, higher eGFR, and increased cobalt levels was observed. No significant correlations were found between ion levels and resection length or the number of modular connections. Conclusion - We found elevated serum ion levels in metal -on -polyethylene knee megaprostheses in contrast to metal -on -polyethylene hip megaprostheses. Furthermore, a positive correlation between cobalt and chromium levels, and between cobalt and eGFR was identified, along with a negative correlation between cobalt and age. This study highlights the importance of monitoring systemic cobalt and chromium levels in patients with megaprostheses.