Enlarged Vertebral Body/Posterior Element

Lubdha M. Shah, MD

DIFFERENTIAL DIAGNOSIS

Common

Facet Arthropathy
- Facet Arthropathy, Cervical
- Facet Arthropathy, Lumbar
- Baastrup Sign
Paget Disease
Aggressive Hemangioma
Compensatory Enlargement
- Scoliosis
- Spondylolysis
Congenital Fusion

Less Common

Metastases, Lytic Osseous
Aneurysmal Bone Cyst
Osteoblastoma
Chordoma

Rare but Important

Fibrous Dysplasia
Chondrosarcoma
Osteochondroma

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Osteoblastoma should always be considered in the differential diagnosis of painful scoliosis
Center of the lesion in the vertebral body vs. posterior element may help with the differential diagnosis

Helpful Clues for Common Diagnoses

Facet Arthropathy, Cervical
- Capsular laxity and joint space narrowing may lead to degenerative spondylolisthesis
- Osteoarthritis of synovial-lined zygapophyseal joints
- Hypertrophic changes with osteophytes, normal bone mineralization, & joint space narrowing
Facet Arthropathy, Lumbar
- Osseous hypertrophy with articular joint space narrowing and encroachment upon neural foramen
- Irritation of synovium produces synovial hyperplasia with paradoxical joint space widening
- Facet arthrosis syndrome with low back, hip, and buttock pain aggravated by rest
Baastrup Sign
- Close approx. & contact of adjacent spinous process with reactive sclerosis, enlargement & flattening of apposing interspinous surfaces
- “Kissing” spinous processes
- Cystic degeneration of interspinous ligaments and posterocentral epidural cyst
Paget Disease
- Enlarged vertebra and neural arch with diffusely coarsened & haphazard bony trabecular pattern
  - Most commonly L3 & L4
  - Cortex is thickened
  - Anterior concavity of the vertebral body is lost
- Can cause spinal stenosis & neural foraminal narrowing
- No epidural soft tissue component unless sarcomatous degeneration
Aggressive Hemangioma
- Expanded & indistinct cortex, irregular honeycombing pattern, & soft tissue mass
  - Trabecular condensation thinner in comparison to Paget disease
- Lesions commonly involve entire vertebral body with extension into neural arch
- Typically occur between T3 & T9
- Epidural extension may cause cord compression
- Can become symptomatic with growth, which often occurs during pregnancy
Compensatory Enlargement
- Scoliosis
  - Minimal structural vertebral deformities & advanced degenerative changes
  - Facet osseous overgrowth, asymmetric disc space, & discogenic sclerosis at the concave aspect of the scoliosis
  - Unilateral radicular symptoms on the side of the concavity of the deformity
- Spondylolysis
  - Defects in pars interarticularis (PI) may be due to repetitive stress injury
  - Spinal canal is elongated at the level of the pars defect on axial imaging
  - Most common at L5
  - Sclerosis of PI, volume averaging of superior facet spur, partial facetectomy, blastic metastases may mimic spondylolysis
Congenital Fusion
- Vertebral bodies smaller than normal with tapered contour at fused disc space
- Rudimentary disc space with reduced height & diameter, “wasp waist”
- Degenerative changes at adjacent levels
- ± Fusion of posterior elements

Helpful Clues for Less Common Diagnoses

Metastases, Lytic Osseous
- 50-70% bone destruction required for detection on radiography
- Lesion involves posterior cortex & pedicle
- Diffuse involvement of marrow gives the appearance of brighter disc than bone on T1WI
- Fat suppression on enhanced T1WI helpful to unmask lesions
Aneurysmal Bone Cyst
- Arise in the neural arch with the majority (75-90%) extending into the vertebral body
- Expansile remodeling of bone with cortical thinning
- Fluid-fluid levels with hemorrhage
- No tumor matrix
Osteoblastoma
- Originate in the neural arch, often extend into the vertebral body
- > 1.5 cm (osteoid osteoma < 1.5 cm)
- Narrow zone of transition with sclerotic rim
- Bone matrix on CT or radiograph
- May be associated with an aneurysmal bone cyst (10-15%)
- Painful scoliosis (50-60%)
Chordoma
- Rare involvement of the vertebral body
- Purely lytic
- T2 hyperintense with multiple septations
- Variable enhancement
- Amorphous intratumoral Ca++ in 30% of vertebral lesions

Helpful Clues for Rare Diagnoses

Fibrous Dysplasia
- Neural arch involvement > vertebral body
- Spine involvement in polyostotic disease
- Mildly expansile lesion with characteristic ground-glass matrix
- Heterogeneous T1 & T2 signal and enhancement
Chondrosarcoma
- Lytic, destructive lesion with cortical destruction and extension into the soft tissues
- ± Chondroid matrix (50%) of “rings & arcs”
Osteochondroma
- Sessile or pedunculated osseous lesion contiguous with the parent vertebra
- Cartilaginous cap > 1.5 cm in adults concerning for malignant transformation