Spinal Instability Neoplastic Scale (SINS)

Six domains (Fisher et al., Spine 2010). Total 0–18: stable 0–6, indeterminate 7–12, unstable 13–18.

Disclaimer: Educational support only. Imaging must be interpreted in clinical context; inter-rater variation and evolving disease can change scores. Decisions about surgery, radiation, or systemic therapy require qualified specialists.

SINS — criteria and interpretation

Overview

The Spinal Instability Neoplastic Score (SINS) stratifies neoplastic spinal lesions by six clinical and radiographic domains. Total score ranges from 0 to 18. Primary reference: Fisher CG et al., Spine (Phila Pa 1976) 2010;35(22):E1221–E1229. Educational summaries align with published component weights (e.g. Sci Rep 2021, Table 1). Tools such as MDCalc implement the same framework for bedside use.

Published component scores

Domain	Finding	Points
Location	Junctional (occiput–C2, C7–T2, T11–L1, L5–S1)	3
	Mobile (C3–C6, L2–L4)	2
	Semirigid (T3–T10)	1
	Rigid (e.g. sacrum, iliac, acetabulum, fused segments)	0
Pain	Mechanical (worse with movement/loading, better with rest)	3
	Occasional, not mechanical	1
	Pain-free lesion	0
Bone lesion	Lytic	2
	Mixed (lytic/blastic)	1
	Blastic	0
Spinal alignment	Subluxation or translation	4
	De novo deformity (kyphosis/scoliosis)	2
	Normal alignment	0
Vertebral body	>50% collapse	3
	<50% collapse	2
	No collapse with >50% of vertebral body involved	1
	None of the above	0
Posterolateral elements	Bilateral involvement (e.g. facets, pedicles, costovertebral)	3
	Unilateral	1
	None	0

Interpretation

0–6: stable by SINS
7–12: indeterminate / potentially unstable
13–18: unstable
Many pathways dichotomize 0–6 versus 7–18 for early surgical or interventional referral alongside radiation oncology planning.

Practice notes

Assign one option per domain from contemporaneous imaging and clinical assessment. MRI, CT, and plain films may each contribute different facets (e.g. epidural disease, marrow signal). SINS does not replace neurologic examination, oncologic staging, or multidisciplinary tumor board decisions.

What is the Spinal Instability Neoplastic Score?

The Spinal Instability Neoplastic Score (SINS) is a structured way to estimate how unstable a spinal segment may be when malignancy involves the vertebrae or adjacent elements. It was developed for adults with neoplastic disease of the spine so that oncologists, radiation oncologists, neurosurgeons, orthopedic spine surgeons, and other clinicians share a common language about mechanical risk, not to replace judgment about systemic treatment, prognosis, or neurologic emergencies.

Instability in this context refers to progressive deformity, pathologic fracture, or neurologic compromise under physiologic loads. The score combines where the lesion sits in the spinal column, how the patient experiences pain, how the lesion destroys or replaces bone, whether imaging shows malalignment, how much the vertebral body has collapsed or been replaced by tumor, and whether posterolateral elements are involved. Each domain is assigned one level; points are summed to a total from 0 to 18.

Why spine oncologists use SINS

Patients with skeletal metastases frequently have spine involvement. Many lesions can be managed with systemic therapy, bone-targeted agents, and radiation alone, but some patterns of bony destruction and alignment raise concern for mechanical failure or cord risk that may benefit from prophylactic or urgent stabilization, or from closer coordination between specialties. Before SINS, decisions often relied on implicit expert opinion; the score makes explicit which imaging and symptom features were associated with surgeon-perceived instability in consensus work.

SINS is widely used to flag cases for discussion with spine surgery or to document rationale when observation is chosen. It does not diagnose cancer, stage systemic disease, or by itself mandate an operation. Severe or progressive myelopathy, cauda equina symptoms, or high-grade epidural compression may require urgent action regardless of a numeric total.

How the total score is built

You assign exactly one option per domain, using contemporaneous imaging (often MRI and CT, with plain films when helpful) and the clinical history. If several findings could fit, choose the single best match for that domain as you would in a tumor board, rather than double-counting.

The six domains and their roles are:

Location — captures how much physiologic motion and transition stress apply at that segment.
Pain — emphasizes mechanical pain (worse with loading or movement, improved with recumbency), which parallels structural instability more than incidental tumor-related discomfort.
Bone lesion appearance — distinguishes lytic, mixed, and blastic patterns as surrogates for structural integrity.
Radiographic alignment — rewards detection of translation/subluxation and de novo deformity (new kyphosis or scoliosis attributable to the lesion).
Vertebral body collapse / involvement — separates severe height loss, moderate collapse, extensive tumor in the body without classic collapse, and neither.
Posterolateral element involvement — reflects extension into facets, pedicles, laminae, transverse processes, costovertebral junctions, or similar structures, unilaterally or bilaterally.

Domain 1: Location in the spinal column

Spinal segments differ in how much they move and how they transfer load from the skull and thorax to the pelvis. Junctional zones (occiput–C2, C7–T2, T11–L1, L5–S1) receive the highest weight because they sit at transitions between regions with different mobility. The mobile cervical and lumbar subregions (typically C3–C6 and L2–L4 in the published scheme) receive intermediate weight. The thoracic curve from roughly T3–T10 is relatively semirigid because of the rib cage. The rigid category includes the sacrum, iliac structures, acetabulum, and fused spinal segments, where global motion at the index level is limited.

When a tumor spans more than one category, teams usually assign the location of the dominant structural lesion or the segment that would be addressed first surgically. Consistency matters more than minor disagreements at zone boundaries.

Domain 2: Pain character

This domain separates mechanical pain from other pain types. Mechanical pain in SINS is typically worse with upright posture, movement, or axial loading and relieved or improved with lying down or rest. That pattern suggests that motion across the affected segment is symptomatically relevant. Occasional pain that is not mechanical receives a small number of points. A painless lesion receives none in this category even though it may still be structurally concerning on imaging.

Clinicians should integrate analgesics, neuropathic pain, prior radiation, and confounding musculoskeletal conditions. The goal is to characterize the dominant pain pattern related to the lesion, not to capture every symptom a patient reports.

Domain 3: Bone lesion appearance (lytic, mixed, blastic)

On CT or MRI, the lesion is classified by its dominant appearance. Purely or predominantly lytic disease implies more cortical and trabecular loss and scores highest in this domain. Mixed lytic and blastic change is intermediate. Predominantly blastic disease scores lowest here. Multifocal blastic disease can still be symptomatic or compress neural elements; the score only reflects the mechanical implication of the bone matrix pattern as defined in the original system.

Domain 4: Radiographic spinal alignment

Subluxation or translation across the affected level receives the most points in this domain, reflecting gross disruption of the normal load path. De novo deformity—new kyphosis or scoliosis attributed to tumor rather than long-standing degenerative change—occupies the middle tier. Normal alignment receives no points here. Teams often compare prior imaging when available to decide whether deformity is truly new.

Domain 5: Vertebral body collapse and tumor involvement

This domain uses up to four mutually exclusive tiers. The highest tier applies when there is greater than fifty percent loss of vertebral body height from the neoplastic process. The next tier is collapse present but fifty percent or less height loss. A separate tier captures no collapse by those definitions but with more than half of the vertebral body involved by tumor—substantial replacement of bone without the same degree of height loss. The final tier is none of the above. MRI signal abnormality without meaningful volume loss may fall into the lower tiers; exact application benefits from side-by-side review with a radiologist when feasible.

Domain 6: Posterolateral spinal element involvement

Tumor extension into posterolateral structures—such as pedicles, facets, laminae, transverse processes, or costovertebral joints—reduces the integrity of the ring that resists torsion and translation. Bilateral involvement scores highest; unilateral involvement is intermediate; no posterolateral involvement by these definitions scores zero. Epidural disease without clear osseous destruction of those named elements may still be clinically critical but is not always captured in this specific item.

Interpreting the numeric bands

After summing all six domains, the total is interpreted in three bands that describe relative mechanical instability risk in the neoplastic setting:

0–6 is labeled stable within the SINS framework.
7–12 is indeterminate or potentially unstable—many pathways treat this band as meriting specialist input even when no emergency exists.
13–18 is labeled unstable and is generally taken as a strong prompt for multidisciplinary evaluation of stabilization options alongside oncologic therapy.

A common binary simplification contrasts 0–6 with 7–18 to separate lesions that are usually observed with standard oncologic follow-up from those where spine surgery consultation is routinely considered. That dichotomy is operational, not a substitute for neurologic examination, systemic fitness, life expectancy, or patient goals.

Practical integration in multidisciplinary care

Radiation planning, systemic therapy changes, and procedural timing often depend on neurologic status, epidural disease grade, histology, and expected disease trajectory. SINS adds a reproducible snapshot of mechanical risk. Re-staging imaging after treatment may shift the score; lytic lesions that sclerose after therapy sometimes move to lower tiers in the bone-appearance domain, while alignment may improve or worsen with vertebral collapse.

Interobserver variation exists, especially for borderline collapse percentages, subtle translation, and whether pain is truly mechanical. When the score is near a cutoff, documenting the imaging series and clinical reasoning is as valuable as the number itself.

Limitations and appropriate use

SINS was designed for neoplastic spinal disease, not for degenerative stenosis, trauma without tumor, or infection. It does not quantify epidural spinal cord compression severity, motor strength, or bowel and bladder function. A “stable” SINS total does not guarantee that a patient will remain asymptomatic if tumor progresses quickly. Conversely, high scores require thoughtful triage because not every patient is a surgical candidate.

This calculator is an educational aid. It should be verified against primary literature and institutional pathways and should not override bedside assessment or specialist recommendations.

CalcMD.

Spinal Instability Neoplastic Scale (SINS) Score

Use the Spinal Instability Neoplastic Score (SINS) for spine metastases: six domains (location, pain, bone lesion, alignment, vertebral collapse, posterolateral involvement), total 0–18, with stable, indeterminate, and unstable bands.