Ch17: Spine Radiology（脊柱影像）

# Ch17: Spine Radiology（脊柱影像）

Preparatory Mindset

Spinal imaging: plain film has a role in spinal disorders, particularly trauma; CT is poor at the spinal cord and nerve roots; MRI is the gold standard for the cord and nerve roots; myelography needs contrast injection into the subarachnoid space; radionuclide bone scans are particularly useful for bony metastases. Master the radiographic signs of spinal abnormality (disc space narrowing, vertebral collapse, pedicle abnormalities, dense vertebrae) and the imaging of trauma, degeneration, infection and tumors.

Core Concepts

Normal vertebral anatomy

• Vertebral body, pedicles, laminae, spinous process, transverse process, facet joints (superior/inferior articular facets), disc space, central canal, exit foramen.
• Disc space height increases from L1 to L5 except L5/S1 which is normally narrower than the one above.
• Cervical spine: lateral view must include the C7/T1 junction.

Imaging techniques

• Plain film: trauma (screening).
• CT: bone detail; poor at cord/nerve roots.
• MRI: gold standard for disc, cord, nerve roots.
• Myelography: contrast into subarachnoid space.
• Radionuclide bone scan: bony metastases.

Radiographic signs of spinal abnormality

• Disc space narrowing — disc degeneration (osteophytes + sclerosis of adjoining vertebral surfaces).
• Collapse of vertebral bodies — metastasis, osteomyelitis, trauma, osteoporosis, eosinophilic granuloma (child: vertebra plana — collapsed to a thin disc).
• Pedicle abnormalities — destruction (metastasis), sclerosis (prostatic mets, lymphoma, Paget's, hemangioma, healing fracture); "winking owl" sign = absent pedicle (metastasis).
• Dense vertebrae — metastases (breast), lymphoma, Paget's (coarse trabeculae), hemangioma (vertical striations), healing fracture.

Spinal cord compression

• T2WI shows metastases in body/pedicle causing cord compression; extradural compression from posterior mass; fluid-fluid level = hemorrhage within metastasis.
• MRI is key when cord compression is suspected.

Trauma

• Alignment of vertebral bodies and facet joints; fractures of bodies/pedicles/laminae/spinous processes; indirect sign = prevertebral soft tissue swelling.
• C-spine evaluation: entire cervical spine + C7/T1 junction on lateral; SCIWORA (spinal cord injury without radiological abnormality) in children — best imaged with MRI; atlanto-dens distance: adults ≤3 mm, children ≤5 mm.
• Three columns of the spine: anterior (anterior longitudinal ligament + anterior 2/3 of body); middle (posterior 1/3 of body + posterior longitudinal ligament); posterior (pedicles, laminae, spinous processes).
• Mechanism: hyperflexion is the commonest C-spine injury (wedge fracture; flexion teardrop highly associated with cord injury); hyperextension → hangman's fracture (pars interarticularis of C2); axial compression → Jefferson's fracture (burst of C1 ring), burst fracture (all three columns, posterior fragment → cord compression).
• Atlanto-axial subluxation: widening of space between dens of C2 and anterior arch of C1 (rheumatoid arthritis).

Degenerative spinal disease

• Primarily from intervertebral disc degeneration + facet joint arthropathy → nerve root compression in exit foramina.
• Disc herniation: herniation of disc material beyond the normal margins of the intervertebral space; size varies (small to broad base); best identified on MRI (CT can show); described by location (central, paracentral, subarticular, foraminal, far lateral) and compressed structures.
• Spondylolisthesis: forward slip (e.g. L5 on S1); defect in the pars interarticularis = spondylolysis.

Infection

• Haematogenous route: early — disc space narrowing; later — bone destruction → vertebral collapse → sclerosis.
• Bacterial discitis: loss of intervertebral height, non-visualization of corticated endplate; T2 high-signal pus in disc; intense enhancement of adjacent vertebral bodies.
• TB of the spine: more insidious; may preserve the disc space; bone collapse → sharp angulation (focal kyphosis) = gibbus; large inflammatory mass into the spinal canal compressing the cauda equina; psoas abscess.

Inflammatory spondylarthropathy (seronegative)

• Ankylosing spondylitis, psoriatic arthropathy, Reiter's syndrome; share sacroiliitis and spine arthropathy.
• Ankylosing spondylitis: sacroiliac joints irregular/fuzzy; advanced: whole spine fused = "bamboo spine"; transverse fractures through fused disc spaces.

Congenital — spina bifida

• Incomplete formation of posterior elements; tethered cord (conus low at L5/S1); associated scoliosis/hemivertebra.

Cord and cauda equina compression by site

• Extradural: myeloma, lymphoma, metastases (commonest malignant), infection, degenerative disc protrusions.
• Intradural extramedullary: meningioma, nerve sheath tumors.
• Intradural intramedullary: primary spinal cord tumor.

High-Yield Points

• Key Point: MRI = gold standard for cord/disc/nerve roots; CT for bone; plain film for trauma screening; bone scan for mets.
• Key Point: Disc space height increases L1→L5 except L5/S1 (narrower).
• Key Point: Vertebral collapse DDx: metastasis, osteomyelitis, trauma, osteoporosis, eosinophilic granuloma (vertebra plana in child).
• Key Point: Dense vertebra: mets, lymphoma, Paget's, hemangioma, healing fracture.
• Key Point: Three columns: anterior/middle/posterior; burst fracture = all three.
• Key Point: Hangman's = pars interarticularis of C2 (hyperextension); Jefferson's = burst of C1 (axial loading); flexion teardrop = cord injury.
• Key Point: TB spine: disc preserved + gibbus; bacterial discitis: disc destroyed + endplate loss.
• Key Point: Bamboo spine = ankylosing spondylitis.
• Key Point: SCIWORA (children) → MRI.

Topic Summary

Spine radiology: MRI is the gold standard for cord/disc; plain film and CT for trauma; bone scan for metastases. Signs: disc space narrowing (degeneration), vertebral collapse (mets/osteomyelitis/trauma/osteoporosis/vertebra plana), pedicle destruction (mets — winking owl), dense vertebrae (mets/Paget's/hemangioma). Trauma uses the three-column model with characteristic fractures (flexion teardrop, hangman's, Jefferson's, burst). Degeneration: disc herniation (MRI, by location), spondylolisthesis. Infection: bacterial discitis (disc destroyed) vs TB (disc preserved + gibbus). Ankylosing spondylitis = bamboo spine; seronegative arthropathies share sacroiliitis.