Introduction: Neoplastic spinal instability is defined as movement-related pain, deformity, or neurologic compromise under physiologic loads with SINS developed to facilitate diagnosis. There is a paucity of evidence that mechanical instability correlates with pain and disability and that surgical stabilization significantly improves these patient-reported outcomes (PRO).
Methods: SINS and PRO (Brief Pain Inventory (BPI) and MD Anderson Symptom Inventory–Spine Tumor (MDASI-SP)) from patients who underwent instrumented surgical stabilization for spinal tumor treatment were prospectively collected. SINS was analyzed as a continuous and ordinal categorical variable (Stable 0-6, Low Indeterminate 7-9, High Indeterminate 10-12, Unstable 13-18). Association between SINS and pre-operative symptoms was analyzed using Spearman Rank Coefficient (rho) and an extension of the Cochran-Armitage trend test, with p-values <0.05 considered significant.
Results: 150 surgeries were performed with the average postoperative assessment at 35 days. There was a statistically significant positive correlation between increasing pre-operative SINS and the severity of pre-operative pain as measured by BPI worst pain (rho=0.18, p=0.02), BPI average pain (rho=0.23, p=0.005), and MDASI pain (rho=0.2, p=0.01) items. Increasing pre-operative SINS also correlated with increasing severity of pre-operative disability measured by BPI walking (rho=0.23, p=0.006), MDASI activity (rho=0.28, p=0.0006), and MDASI walking (rho=0.22, p=0.009) items. Similar associations were noted when SINS was analyzed as an ordinal categorical variable. The magnitude of symptom relief after surgery positively correlated with pre-operative SINS, as patients with higher pre-operative SINS experiencing greater symptom relief with BPI worst pain (p=0.03), BPI average pain (p=0.02), BPI activity (p=0.04), and MDASI pain (p=0.04) (Figure 1).
Conclusions: The association between increasing SINS and symptom burden provide PRO-based validation of SINS as a diagnostic instrument for spinal instability. The larger decrease in the severity of pain and activity interference in patients with neoplastic spinal instability supports the role of surgical stabilization in the setting of mechanically unstable spines.
Patient Care: Neurologic deterioration is the most frequent indication for surgery in patients with metastatic and primary spine tumors. However, mechanical pain due to instability is increasingly being recognized as a major contributor to poor quality of life in this population. The Spinal Instability Neoplastic Score (SINS) was developed by the Spinal Oncology Study Group in 2010 in order to standardize the evaluation of instability in cancer patients. Though often used in clinical practice, there are few validated studies comparing SINS with pain and functional status measures as well as response to stabilization surgery. Our study demonstrates that instrumented surgical stabilization benefits patients with higher SINS, and underscores the importance of this diagnostic measure.
Learning Objectives: By the conclusion of this session, participants should be able to 1) Discuss, in small groups, the components and significance of the Spinal Instability Neoplastic Score (SINS), 2) Recognize the patient related outcome (PRO) measures used in spine oncology patients, and 3) Describe the association between increasing SINS and PRO in the setting of instrumented surgical stabilization.