What is the SINS Score?
The Spinal Instability Neoplastic Score (SINS) is an 18-point classification system that evaluates spinal stability in patients with metastatic spine disease, categorizing lesions as stable (0-6 points), potentially unstable (7-12 points), or unstable (13-18 points) to guide surgical consultation and treatment decisions. 1
Core Components of SINS
The SINS combines six clinical and radiographic parameters to generate a total score: 1
Location of the lesion: Junctional spine regions (occiput-C2, C7-T2, T11-L1, L5-S1) and mobile spine segments (C3-C6, L2-L4) carry higher risk scores due to increased mechanical stress 1
Character of pain: Mechanical or postural pain (pain with movement or weight-bearing) indicates higher instability risk and receives a higher score 1
Bone quality: Assessed on MRI T1-weighted and STIR sequences, with lytic lesions representing the highest risk 1
Spinal alignment: Subluxation or translation receives the highest score, while de novo deformity (kyphosis or scoliosis) receives a moderate score 1
Degree of vertebral body collapse: Greater collapse percentage correlates with higher instability 1
Posterolateral involvement: Involvement of posterior elements (pedicles, facets, costovertebral joints) increases instability risk 1
Clinical Interpretation and Application
The binary classification is most clinically useful: scores 0-6 indicate stability, while scores 7-18 indicate current or possible instability requiring surgical consultation. 2
Patients with SINS 13-18 are at significantly higher risk of fracture progression after radiation therapy (hazard ratio 4.37) compared to stable lesions 3
Patients with SINS 10-12 have higher odds ratios for requiring surgical management compared to those with scores 7-9 1
The score is used by spine oncology surgeons and radiation oncologists for treatment planning, including decisions about vertebral augmentation, percutaneous ablation, radiation therapy, or systemic chemotherapy 1
Reliability and Validation
The SINS demonstrates excellent reliability across multiple specialties: 4, 2, 5
Radiologists: Excellent validity (κ=0.88) and interobserver agreement (κ=0.76) using the binary scale 4
Radiation oncologists: Substantial interobserver reliability (κ=0.76) and excellent intraobserver reproducibility (κ=0.80) 2
Spine surgery trainees: Near perfect interobserver (ICC=0.990) and intraobserver (ICC=0.907) agreement for total scores 5
Critically, radiologists rated 98.7% of potentially unstable cases with scores ≥7, appropriately triggering surgical referral 4
Optimal Imaging Protocol
Non-contrast MRI with T1-weighted and STIR sequences provides optimal evaluation of bone quality and spinal alignment for SINS scoring. 1
STIR or fat-saturated T2-weighted sequences identify bone marrow edema and unhealed fractures 1
Contrast-enhanced MRI is helpful for evaluating epidural, foraminal, and paraspinal disease extension 1
Important Clinical Caveats
The Dutch National Guideline (2018) advises against using SINS as a predictor for progressive spinal instability due to lack of prospective validation and contradictory findings on reliability. 6
However, the guideline acknowledges SINS remains useful as a communication tool between physicians of different specialties and for facilitating decision-making during surgical consultations 6
Real-world implementation data shows that introducing SINS into routine practice decreased the average SINS score in both surgical (from 11.2 to 10.3) and radiotherapy cohorts (from 8.4 to 7.2), suggesting increased awareness leads to earlier referrals before severe instability develops 7
Physical Therapy Implications
Patients with SINS 0-6 are cleared for standard physical therapy, while those with SINS 7-12 require individualized assessment with modified activity restrictions and possible bracing, and patients with SINS ≥13 should not undergo physical therapy until surgical stabilization. 1