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.

Incidence and risk factors of distal adjacent disc degeneration in adolescent idiopathic scoliosis patients undergoing fusion surgery: a systematic review and meta-analysis.

PURPOSE: The objective of this meta-analysis was to determine the incidence of disc degeneration in patients with surgically treated adolescent idiopathic scoliosis (AIS) and identify the associated risk factors. METHODS: PubMed, EMBASE, Scopus, and Cochrane Collaboration Library databases were searched. The outcomes of interest were the incidence of disc degeneration, SRS-22, and radiological risk factors. The lower instrumented vertebra (LIV) was also evaluated. Fixed effects were used if there was no evidence of heterogeneity. Statistical analysis was performed using Review Manager. RESULTS: A meta-analysis was conducted including nine studies with a total of 565 patients. The analysis revealed that the global incidence of intervertebral disc degeneration in patients with surgically treated AIS patients was 24.78% (95% CI 16.59-32.98%) 10 years after surgery, which significantly increased to 32.32% (95% CI 21.16-43.47% at an average of 13.8 years after surgery. Among patients with significant degenerative disc changes, the SRS-22 functional, self-image, and satisfaction domains showed significantly worse results (MD - 0.25, 95% CI - 0.44 to - 0.05; MD - 0.50, 95% CI - 0.75 to - 0.25; and MD - 0.34, 95% CI - 0.66 to - 0.03, respectively). Furthermore, instrumentation at or above the L3 level was associated with a lower incidence of intervertebral disc degeneration compared to instrumentation below the L3 level (OR 0.25, 95% CI 0.10-0.64). It was also found that the preoperative and final follow-up lumbar curve magnitudes (MD 8.11, 95% CI 3.82-12.41) as well as preoperative and final follow-up lumbar lordosis (MD 0.42, 95% CI - 3.81 to 4.65) were associated with adjacent disc degeneration. CONCLUSIONS: This meta-analysis demonstrated that the incidence of intervertebral disc degeneration significantly increased with long-term follow-up using fusion techniques, reaching up to 32% when patients were 28 years of age. Incomplete correction of deformity and fusion of levels below L3, were identified as negative prognostic factors. Furthermore, patients with disc degeneration showed worse functional outcomes.

Retinal Nerve Fiber Layer Analysis in Children With Migraine With and Without Aura Using Optical Coherence Tomography: A Case-Control Study.

PURPOSE: To evaluate retinal nerve fiber layer (RNFL) thickness in children with migraine, with and without aura, compared to healthy controls using optical coherence tomography (OCT). METHODS: In this cross-sectional case-control study, patients with a diagnosis of migraine with aura (MwA) or without aura (MwoA) were considered and healthy children were included as controls. Age, sex, duration of migraine, number of episodes per month, duration of episodes, and use of prophylactic treatment with magnesium were recorded. All patients underwent complete ophthalmologic, neurologic, and pediatric examination. Optic nerve OCT images were obtained using Heidelberg Spectralis OCT (Heidelberg Engineering) and mean global RNFL thickness and the average thickness for each sector were noted. RESULTS: Thirty-seven children were included: 17 with migraine (9 MwoA and 8 MwA) and 20 controls, the mean age being 13.8 ± 2.9 (range: 8 to 16) and 13.4 ± 2.5 (range: 7 to 16) years, respectively. No significant differences in RNFL thickness were found when comparing all patients who had migraine with healthy controls. However, children with MwA showed statistically significant reductions in RNFL thickness in the temporal (mean difference: 7.83; 95% CI: 0.52 to 15.14, P = .027) and inferior-temporal (mean difference: 16.06; 95% CI: 1.95 to 30.16, P = .027) sectors compared to patients with MwoA. None of the other sectors showed statistically significant differences between groups (all P > .05). In the migraine group, negative correlations were detected between the number of episodes per month and RNFL thickness in the nasal-superior quadrant (r = -.420; P = .021). CONCLUSIONS: Children with MwA may present a decrease in RNFL thickness, which is associated with the number of episodes per month. [J Pediatr Ophthalmol Strabismus. 2023;60(3):196-202.].