Adult Rheumatoid Arthritis

Rheumatoid arthritis (RA)

Location

• Cervical spine: Approximately 50-60% of RA patients

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    C1-odontoid articulations, occipital condyles

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    Facet and uncovertebral joints

• Severity of craniovertebral junction (CVJ) involvement is factor of disease duration and severity

• Rarely involves sacroiliac joints or lumbar spine

• Hands &/or feet involved if spine involved

Radiography

• Erosions of dens, uncovertebral joints, and facet joints

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    Dens may be completely eroded

• Neutral, flexion, and extension lateral radiographs to evaluate for instability

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    Voluntary movement of neck to maximum range of motion possible for patient without technologist assistance

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    Subluxation(s) assessed in flexion; reducibility assessed in extension

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    Subluxation(s) primarily seen in flexion

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    Extension views useful to assess reducibility of subluxation

• Craniocervical instability

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    Due to erosions of occiput-C1 facets

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    Transverse ligament synovium-lined bursa susceptible to pannus formation

• C1-C2 instability

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    Normal: < 2 mm between inner margin anterior ring of C1 and dens (anterior atlantodental interval [AADI])

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      Neurologic symptoms usually present if distance ≥ 9 mm

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    Spinal canal < 14 mm at C2 (posterior atlantodental interval [PADI]) also correlates with neurologic symptoms

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    Instability seen in 5% of patients with cervical RA

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    Atlantoaxial instability (AAI) in 20-86% of patients with RA

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    Extension view is useful to determine if pannus precludes full reduction

• Acquired basilar invagination (BI): Decreased distance occiput to C2

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    Used synonymously with cranial settling

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    Bony erosions of occipital condyles and C1 lateral masses where cranium moves downward (settles) relative to dens

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      Dens may protrude through foramen magnum

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      C1 maintains normal relationship with clivus

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      Alar and apical ligaments involved

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      Occurs in 5-8% of RA patients

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    Due to facet joint erosions

• Acquired basilar impression (BI)

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    Used synonymously with cranial settling

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    High vertebral column indents skull base

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    C1 maintains normal relationship with C2

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    Measurements

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      McRae: Positive if tip of dens extends beyond line drawn from basion to opisthion

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      McGregor line: Positive if dens > 4.5 mm above line from posterior hard palate to inferior point of occipital curve

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      Redlund-Johnell: Line from mid caudal surface of C2 body to McGregor line

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      Positive if < 34 mm in males or < 29 mm in females

• Instability may also be present at lower levels of cervical spine

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    Often multilevel (“stepladder”) subluxations

• Ankylosis of spine not seen in adult RA

• Osteopenia: Difficult to reliably detect on radiographs

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    Not radiographically evident unless severe

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    Can be masked by or mistaken for senile osteoporosis

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    Can be absent (“robust RA”)

• Sacroiliitis

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    Erosions 1st seen on iliac side of joint

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    May be unilateral or bilateral

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    Rarely progress to fusion

• Disc and adjacent vertebral body destruction (extremely rare)

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    Synovitis extends from apophyseal joint

Bone CT

• Increased conspicuity of odontoid erosions compared to radiographs

• Pannus around dens may be seen; never calcifies

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    Pannus is mass-like, surrounds and erodes dens, facet joints, uncovertebral joints

• Erosions of uncovertebral and facet joints

• Preoperative planning and postoperative follow-up

CT of craniocervical junction (CCJ) can also be performed in flexion/extension

Pannus

• Low signal intensity (SI) on T1WI

• Heterogeneous SI on fluid-sensitive sequences

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    May be predominantly low SI

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    Usually predominantly intermediate SI

• Contrast-enhanced T1WI MR may be able to discriminate between joint effusion and various forms of pannus

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    Hypervascular pannus is distinguished from hypovascular and fibrous pannus on T2WI MR

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    Joint effusion and pannus are detected in patients with negative radiographic findings

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    No concordance between MR findings and clinical symptoms

• Enhances avidly with gadolinium

Subluxations may lead to spinal stenosis

• Myelopathic changes are common