Elevated blood metal ion levels in patients undergoing instrumented spinal surgery: a systematic review and meta-analysis

BACKGROUND CONTEXT: Elevated blood metal levels have been reported in patients after spinal surgery using metallic implants. Although some studies have suggested an association between heightened blood metal concentrations and potential adverse effects, estimates of the incidence of abnormal metal levels after spinal surgery have been inconsistent. PURPOSE: The aims of this systematic review and meta-analysis were to assess: (1) mean differences in blood metal ion levels between patients undergoing spinal fusion surgery and healthy controls, (2) odds of elevated blood metal ion levels after surgery compared to presurgery levels, and (3) pooled incidence of elevated blood metal ions overall and by metal type. STUDY DESIGN: Systematic review and meta-analysis. PATIENTS SAMPLE: The patient sample included 613 patients from 11 studies who underwent spinal surgery instrumentation. OUTCOME MEASURES: Blood metal ion concentrations and the incidence of patients with elevated metal levels compared with in those the control group. METHODS: A comprehensive search was conducted in PubMed, EMBASE, Scopus, and Cochrane Library to identify studies reporting blood metal ion levels after spinal fusion surgery. Mean differences (MD), odds ratios (OR), and incidence rates were pooled using random effects models. Heterogeneity was assessed using I2 statistics, and fixed-effects models were used if no heterogeneity was detected. Detailed statistical analysis was performed using the Review Manager version 5.4 software. RESULTS: The analysis included 11 studies, with a total of 613 patients. Mean blood metal ion levels were significantly higher after spinal fusion surgery (MD 0.56, 95% CI 0.17 - 0.96; I2=86%). Specifically, titanium levels were significantly elevated (MD 0.81, 95% CI 0.32 - 1.30; I2=47%). The odds of elevated blood metal ions were higher after surgery (OR 8.17, 95% CI 3.38 - 19.72; I2=41%), primarily driven by chromium (OR 23.50, 95% CI 5.56 - 99.31; I2=30%). The incidence of elevated chromium levels was found to be 66.98% (95% CI 42.31 - 91.65). CONCLUSION: In conclusion, blood metal ion levels, particularly titanium and chromium, were significantly increased after spinal fusion surgery compared to presurgery levels and healthy controls. Approximately 70% of the patients exhibited elevated blood levels of chromium and titanium. (c) 2024 Elsevier Inc. All rights reserved.