Clinical-Radiological Heterogeneity Within Intermediate Spinal Instability Neoplastic Scores (7-12): Factors Associated with Instrumented Stabilization in a Surgical Cohort.
OBJECTIVE To describe how the intermediate Spinal Instability Neoplastic Score (SINS 7-12) category was operationalized in a real-world surgical spine oncology practice and identify preoperative factors associated with instrumented stabilization. METHODS Adults surgically treated for histopathologically confirmed spinal metastases at a single center between 2020 and 2025 were retrospectively analyzed. Patients required complete clinical and imaging data for SINS and epidural spinal cord compression (ESCC) assessment. Intermediate SINS cases were compared according to instrumentation status. Total SINS discrimination was assessed using receiver operating characteristic analysis and exploratory multivariable models. RESULTS Of 105 surgical cases, 103 had complete SINS data: 11 were stable, 78 intermediate, and 14 unstable. Among intermediate SINS cases, 61/78 (78%) underwent instrumented stabilization and 17/78 (22%) decompression alone. Stabilized patients more often had symptom duration >14 days (93% vs 53%, p < 0.001), Frankel grade E (62% vs 18%, p = 0.002), and ECOG 0-II (79% vs 41%, p = 0.005). Total SINS did not differ between groups (median 10 vs 10; p = 0.79) and showed limited discrimination (AUC 0.52; 95% CI 0.36-0.67). In exploratory multivariable analyses, symptom duration >14 days and Frankel grade E were associated with stabilization, whereas ≥3 spinal metastases were associated with lower likelihood of instrumentation. High-grade ESCC was associated with stabilization in sensitivity analysis, although precision was limited. CONCLUSIONS Intermediate SINS represents a clinically heterogeneous gray zone. In our institutional practice, stabilization decisions were not based on total SINS alone but on integrated clinical-radiological assessment, supporting avoidance of rigid SINS cutoffs.