Anterior versus Posterior Surgery for Single-Level Metastatic Cervical Spinal Tumors : Comparative Analysis of Sagittal Alignment and Kyphotic Progression.
Objective To compare clinical and radiological outcomes of anterior (ACSS) and posterior cervical spine surgery (PCSS) in patients with single-level metastatic cervical spinal tumor (MCST). Methods We retrospectively reviewed 27 patients with single-level MCST treated at a single institution between January 2001 and February 2024, categorized into ACSS (n = 16) and PCSS (n = 11) groups. Clinical outcomes were assessed using the Eastern Cooperative Oncology Group (ECOG) performance status, Nurick scale, and visual analog scale (VAS) for neck pain. Radiological parameters-C2-C7 cervical lordosis, sagittal vertical axis, T1 slope, neck tilt, and segmental Cobb angle (SCA)-were evaluated preoperatively, at 1 month postoperatively, and at final follow-up. Baseline bone quality (adjacent vertebral Hounsfield units), bone-modifying agent use, and adjuvant radiotherapy/systemic therapy were also assessed. Index vertebral collapse was defined as a decrease in SCA exceeding 10° from 1 month postoperatively to final follow-up. Time to kyphotic progression was compared using Kaplan-Meier and Cox proportional hazards analyses. Results Short-term clinical outcomes did not differ between groups, and both groups achieved comparable kyphosis correction at 1 month postoperatively. However, from 1 month to final follow-up, SCA loss was significantly greater in ACSS (-15.6° ± 7.8° vs -5.5° ± 4.5°; p < 0.001), and index vertebral collapse occurred more frequently in ACSS (81.3% vs 18.1%; p = 0.003). Compensatory changes in T1 slope and neck tilt were significantly greater in ACSS, suggesting greater cranio-cervical adaptation. The median time to SCA decrease exceeding 10° was shorter in ACSS (0.4 vs 2.0 years; log-rank p = 0.0018), and multivariate Cox analysis confirmed a significantly lower hazard of kyphotic progression in PCSS. Operative time was shorter in PCSS (199.1 ± 17.6 vs 245.8 ± 22.5 minutes; p < 0.001). Adjacent vertebral bone density and adjuvant therapy were balanced between groups, although all PCSS cases were performed in the recent era. Conclusion While short-term clinical outcomes were comparable, PCSS was associated with slower kyphotic progression and a lower rate of index vertebral collapse, suggesting more durable radiographic stability that warrants confirmation in larger prospective studies.