Lower deep-to-superficial extensor muscle ratio (DSR) as an independent risk factor for early titanium implant subsidence following single-level anterior cervical corpectomy and fusion.

To investigate the impact of cervical paraspinal muscle characteristics on early implant subsidence following single-level anterior cervical corpectomy and fusion (ACCF). A retrospective analysis was conducted on 110 patients who underwent single-level ACCF with titanium implants. The cross-sectional area (CSA) of paraspinal muscles was measured on preoperative magnetic resonance imaging (MRI), and the deep-to-superficial extensor muscle ratio (DSR) was calculated. Sagittal alignment parameters-including C2-7 sagittal vertical axis (SVA), C2-7 Cobb angle, and C7 Slope (C7S) were also assessed. Patients were stratified into two groups based on implant subsidence (≥ 3 mm segmental height loss [SH loss]). Univariate, multivariate linear and logistic regression analyses were performed to identify risk factors. Implant subsidence occurred in 19 patients (17.3%). No significant differences were found in demographic characteristics between groups. The subsidence group demonstrated significantly lower DSR at the C6 level (C6 DSR, p = 0.001) and higher C7S (p = 0.003) compared to the non-subsidence group. After adjusting for confounding variables, both C6 DSR (p = 0.006) and C7S (p = 0.014) remained significantly associated with SH loss in the multivariate linear regression model. Further multivariate logistic regression identified C6 DSR (p = 0.002) and C7S (p = 0.004) as independent predictors of subsidence. The area under the receiver operating characteristic (ROC) curve (AUC) for the model was 0.810. Reduced C6 DSR and increased C7S are significant independent risk factors for early titanium implant subsidence following ACCF. These findings underscore the importance of cervical extensor muscle balance and sagittal alignment in maintaining implant stability.