Facet Abnormality, Non-Traumatic

Facet Abnormality, Non-Traumatic

Lubdha M. Shah, MD

DIFFERENTIAL DIAGNOSIS

Common

Normal Variant
- Facet Tropism
Facet Arthropathy
- Facet Synovial Cyst
Tumor Destruction
- Metastases, Lytic Osseous
- Lymphoma
- Multiple Myeloma

Less Common

Rheumatoid Arthritis, Adult
Congenital Fusion
Septic Facet Joint Arthritis

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Assess vertebral abnormalities, multiplicity (i.e., metastases), & soft tissue component (i.e., RA pannus, epidural abscess)

Helpful Clues for Common Diagnoses

Normal Variant
- Facet Tropism
  - Asymmetry in orientation of zygapophyseal joint surfaces up to 35%
  - L5-S1 > L4-5
  - Stress hypertrophy of pedicle on the more coronally oriented side
Facet Arthropathy
- Osseous facet overgrowth with encroachment upon neural foramina
- Cartilage erosion & joint space narrowing
- Facet Synovial Cyst
  - Extradural cystic mass extending from degenerative facet joint
  - Internal high T1/low T2 signal due to hemorrhage or proteinaceous content & low T2 rim 2° wall calcification
Tumor Destruction
- Lytic mets: Irregular preservation of trabeculae & buttressing, isolated fronts of cortical bone resorption coalescing to confluence
- Multiple myeloma: Sharply defined, spheroid lesions with smooth borders & effaced/erased trabeculae, absence of remodeling

Helpful Clues for Less Common Diagnoses

Rheumatoid Arthritis, Adult
- Inflammatory arthritis involve synovial joints (facet & uncovertebral) w/erosions
- Cervical spine involvement in 60%
  - C1-C2 instability in 33%; atlantoaxial subluxation in 5%
Congenital Fusion
- Segmentation failure of 2 or more cervical vertebra
- Vertebral body narrowing at fused rudimentary disc space
- ± Fusion of facets & spinous processes
Septic Facet Joint Arthritis
- T2 hyperintensity and enhancement extends into adjacent soft tissues
- ± Epidural abscess/phlegmon

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