Preoperative Spino Cranial Angle Predicts Adjacent Segment Degeneration After Single-Level Anterior Cervical Discectomy and Fusion.

BACKGROUND

Adjacent segment degeneration (ASD) is a common complication after anterior cervical decompression and fusion (ACDF). The spino cranial angle (SCA), a novel sagittal parameter reflecting head-to-cervical alignment, may be associated with ASD, yet its predictive value remains unclear.

METHODS

A total of 98 patients who underwent single-level ACDF with at least 24 months of follow-up were retrospectively analyzed. Radiographic evaluations were conducted preoperatively and at 3, 6, 12, and 24 months postoperatively. Patients were classified into ASD and non-ASD groups based on established radiographic criteria. Pre- and postoperative cervical sagittal parameters, including SCA, T1 slope (T1s), sagittal segmental alignment (SSA), sagittal alignment of the cervical spine (SACS), and C2-C7 sagittal vertical axis (cSVA) were measured. Clinical outcomes were assessed using the Japanese Orthopedic Association (JOA) score, Neck Disability Index (NDI), and Visual Analog Scale (VAS) scores. Multivariate logistic regression and Receiver operating characteristic (ROC) curve analysis were performed to identify independent predictors of ASD.

RESULTS

ASD occurred in 36 patients (36.7%). Preoperative SCA was significantly larger in the ASD group compared to the non-ASD group (86.7° ± 7.4° vs 80.5° ± 6.9°, p < 0.001), while T1s and SSA were significantly smaller (p = 0.015 and p = 0.001, respectively). Multivariate analysis identified preoperative SCA as the only independent risk factor for ASD (OR = 1.279, 95% CI: 1.010-1.619, p = 0.041). Patients with SCA > 84.2° showed a significantly higher incidence of ASD (55.8% vs 21.4%, p < 0.001). ROC analysis demonstrated that SCA had good predictive value for ASD development. No significant differences were observed in JOA, NDI, or VAS scores between the two groups at final follow-up.

CONCLUSION

Preoperative SCA is a significant predictor of ASD, and may be considered in preoperative risk assessment.