Odontoid Deformity
Julia Crim, MD
DIFFERENTIAL DIAGNOSIS
Common
Trauma
Odontoid C2 Fracture
Os Odontoideum
Arthritis
Rheumatoid Arthritis, Adult
CPPD
Seronegative Spondyloarthropathy
Juvenile Idiopathic Arthritis
Tumor
Metastases, Lytic Osseous
Multiple Myeloma
Craniovertebral Junction Variants
Less Common
Congenital
Spondyloepiphyseal Dysplasia
Hypoplastic Odontoid Process
Klippel-Feil Spectrum
Down Syndrome
Mucopolysaccharidoses
Tumor
Osteochondroma
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
Erosion vs. hypoplasia vs. trauma
Erosion of odontoid: Odontoid may have pencil tip or erosion at base
Soft tissue mass around odontoid
Infection
Rheumatoid arthritis
CPPD
Rarely, gout
Hypoplasia: Odontoid short and body of C2 dysmorphic
Helpful Clues for Common Diagnoses
Acute Trauma: Odontoid may be displaced or angled posteriorly on lateral view
Often difficult to see fracture on odontoid view, especially in osteopenic patients
Chronic Post-Traumatic Deformity
Os Odontoideum: Rounded ossicle
Angular Deformity: Tip of odontoid points posteriorly
Bone Tumor: Marrow abnormality visible on CT or MR; lytic lesions difficult to see on radiographs due to overlying structures
Rheumatoid Arthritis (RA): Pannus never calcifies; arthritis always present in hands or feet if seen in neck
Seronegative Spondyloarthropathy
Syndesmophytes fuse multiple vertebrae; erosions of odontoid may look same as RA
CPPD: Soft tissue mass contains calcification
Infection: Usually unifocal; often epidural extensionRelated posts:
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