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Chapter Summary
• Context: Diagnostic imaging modalities of the vertebral column address distinct clinical questions and must be selected based on the target anatomical tissue, functional weight-bearing status, and pre-test clinical hypothesis. Plain radiographs remain indispensable as the primary weight-bearing investigation to demonstrate overall spinal alignment, degenerative instability on dynamic flexion-extension views, and global spinopelvic parameters. Computed tomography (CT) provides superior multiplanar resolution of osseous architecture, cortical breaches, osteolysis, pars defects, facet arthrosis, vacuum phenomena (gas), and ossification of the posterior longitudinal ligament (OPLL) without anatomical overlap. Magnetic resonance imaging (MRI) is the gold standard for evaluating neural structures (spinal cord, conus medullaris, cauda equina, exiting nerve roots), intervertebral disc morphology, bone marrow edema, soft-tissue collections, spinal infections (spondylodiscitis), and epidural tumors. Ultrasonography finds focused application in neonatal spinal dysraphism screening and image-guided interventional procedures. Bone scintigraphy and SPECT/CT detect altered osteoblastic turnover in facet arthropathy, active spondylolysis, pseudarthrosis, and metastatic disease. A fundamental clinical challenge is avoiding both the inappropriate selection of imaging modalities and the over-interpretation of incidental findings: asymptomatic disc bulges, degenerative Modic endplate changes, facet arthrosis, and benign vertebral hemangiomas are highly prevalent in healthy populations. Imaging findings must always be correlated strictly with the patient’s clinical history and neurological examination.
• Chapter Objective: To present the principles, indications, diagnostic strengths, and limitations of major spine imaging modalities (radiography, CT, MRI, ultrasound, nuclear medicine) across degenerative disc disease, canal stenosis, diffuse idiopathic skeletal hyperostosis (DISH), ankylosing spondylitis, spinal infections, acute trauma, and incidental findings. The reader should be able to select the optimal imaging modality, recognize characteristic imaging patterns, determine when intravenous contrast or dynamic views are required, and correlate radiographic findings with clinical pathology.
• Modalities: Radiography, CT, MRI, and ScintigraphyPlain radiographs (AP, lateral, obliques, dynamic flexion-extension) evaluate alignment, disc height loss, osteophytes, and dynamic spondylolisthesis (>3–4 mm translation or >10° angular motion). Multi-detector CT provides sub-millimeter isotropic osseous detail, indispensable for complex fractures, surgical instrumentation planning, and pseudarthrosis assessment. MRI utilizes T1-weighted (anatomical detail, fatty marrow), T2-weighted (CSF, disc hydration, cord edema, stenosis), STIR/T2 fat-suppressed (bone marrow edema, acute fractures, active inflammation), and gadolinium-enhanced T1 sequences (differentiating recurrent disc herniation from epidural scar, vascular malformations, tumors, and epidural abscesses).
• Degenerative Cascade, Modic Changes, and StenosisMRI readily depicts the degenerative cascade (Pfirrmann grading of disc degeneration 1–5). Modic endplate classifications reflect vertebral marrow changes: Type 1 (inflammatory/vascular edema, hypointense on T1, hyperintense on T2/STIR, highly correlated with active axial pain); Type 2 (fatty conversion, hyperintense on T1 and T2); Type 3 (sclerosis, hypointense on T1 and T2). Spinal canal and neural foraminal stenosis are categorized qualitatively and quantitatively (Schizas classification for lumbar central stenosis, Lee classification for foraminal stenosis) based on CSF obliteration, root compression, and epidural fat loss.
• DISH and Axial Spondyloarthritis (Ankylosing Spondylitis)Diffuse Idiopathic Skeletal Hyperostosis (DISH / Forestier disease) is defined radiographically by flowing anterolateral ossification spanning at least four contiguous vertebral bodies, preservation of disc height, and absence of sacroiliitis. Ankylosing Spondylitis (AS) features early bilateral symmetric sacroiliitis, squaring of vertebral bodies, Romanus lesions (shiny corners), Andersson lesions (inflammatory discitis), and thin, delicate syndesmophytes producing a "bamboo spine." Both conditions create a rigid, long-lever arm spine highly susceptible to catastrophic, highly unstable extension-distraction fractures after trivial trauma.
• Spinal Infections: Spondylodiscitis vs. TuberculosisPyogenic spondylodiscitis characteristically demonstrates early T2/STIR hyperintensity and post-contrast enhancement of the intervertebral disc and adjacent subchondral vertebral endplates, with rapid disc space collapse and endplate erosion. In contrast, tuberculous spondylodiscitis (Pott disease) frequently spares the intervertebral disc initially, involves multiple contiguous or non-contiguous vertebral bodies, causes extensive anterior subligamentous spread, large calcified cold paraspinal/psoas abscesses, and profound angular kyphotic collapse (gibbus deformity).
• Trauma Evaluation and Incidental FindingsIn acute trauma, whole-spine CT is the primary modality to identify fracture lines, retropulsed fragments, and facet dislocations. MRI is mandatory to evaluate spinal cord compression, intramedullary contusion/hemorrhage (presaging poor neurological recovery), and posterior ligamentous complex (PLC) disruption, which determines surgical instability under AO Spine and TLICS classifications. Incidental benign findings—such as typical vertebral hemangiomas (corduroy cloth appearance on coronal CT, hyperintense on T1 and T2) and Tarlov cysts—must be recognized to prevent unnecessary biopsies or surgeries.
• Clinical Application: In clinical practice, imaging must always be guided by the clinical question. In suspected mechanical instability or spondylolisthesis, weight-bearing dynamic flexion-extension radiographs are essential because supine MRI can mask significant translational instability. In suspected cauda equina syndrome, cervical myelopathy, or epidural abscess, emergent MRI (with contrast for infection/tumor) is the modality of choice. In patients with previous spine surgery presenting with recurrent leg pain, gadolinium-enhanced MRI differentiates non-enhancing avascular recurrent disc herniation from diffusely enhancing vascularized epidural scar tissue. In rigid spine patients (ankylosing spondylitis or DISH) presenting with new back pain following minor falls, thin-cut CT of the entire spine is mandatory, as lethal transdiscal/transvertebral fractures are frequently missed on plain radiographs. Recognizing that Modic 1 changes represent active inflammatory remodeling helps guide targeted non-operative and interventional therapies.
