Spinal Instability Neoplastic Score (SINS) Guidelines

Introduction to SINS

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

The SINS combines six clinical and radiographic parameters to generate a total score, including location of the lesion, character of pain, bone quality, spinal alignment, degree of vertebral body collapse, and posterolateral involvement 1
Location of the lesion, such as junctional spine regions and mobile spine segments, carries higher risk scores due to increased mechanical stress 1
Character of pain, such as mechanical or postural pain, 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, such as subluxation or translation, receives the highest score, while de novo deformity receives a moderate score 1
Degree of vertebral body collapse, with greater collapse percentage correlating with higher instability 1
Posterolateral involvement, such as involvement of posterior elements, increases instability risk 1

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

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

The Dutch National Guideline advises against using SINS as a predictor for progressive spinal instability due to lack of prospective validation and contradictory findings on reliability, but acknowledges SINS remains useful as a communication tool between physicians of different specialties and for facilitating decision-making during surgical consultations 2, 3

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