Risk factors for cage subsidence in patients undergoing cervical fusion: a systematic review and meta-analysis

We conducted a systematic search of the literature in PubMed, EMBASE and the Cochrane Library until February 27, 2024. We also performed a manual search, including screening reference lists of previous systematic reviews and meta-analyses, to retrieve additional relevant articles for analysis. A random effects model was used to estimate pooled effects. On the basis of sample size, the P value of the Egger test, and interstudy heterogeneity, observational study evidence was classified as high quality (class I), medium quality (class II or III), or low quality (class IV). Sensitivity analyses also assessed the susceptibility of the findings of this meta-analysis. Of the 2,200 articles screened, 38 unique cohort studies comprising 3,736 patients were included in the data synthesis. Studies with high-quality evidence showed that male patients (OR, 1.30; 95% CI, 1.00 ~ 1.70) were at greater risk for cage subsidence. Studies with moderate-quality evidence suggested that patients with TMC without end-caps (OR 2.77; 95% CI, 1.25 ~ 6.16) were at greater risk for cage subsidence. Studies with low-quality evidence revealed that two-level surgery (OR, 1.72; 95% CI, 1.05 ~ 2.82), three-level surgery (OR, 1.96; 95% CI, 1.01 ~ 3.79), and multiple-level surgery (OR, 1.83; 95% CI, 1.17 ~ 2.85) were high risk factors for cage subsidence after cervical fusion. The meta-analysis revealed no associations between tobacco use, diabetes, cage type, or specific segment of surgery and cage subsidence. Our meta-analysis revealed significant risk factors for cage subsidence, including 1 patient-related risk factor (male) and 4 surgery-related risk factors (including TMC without end-caps and two-level, three-level, and multi-level surgeries). However, these findings must be interpreted with caution, as most risk factors in the study population were rare. Nevertheless, the findings may help clinicians identify high-risk patients to improve outcomes.