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Updated: Jun 25 2021

Rheumatoid Cervical Spondylitis

Images xray atlantoaxial subluxation small_moved.jpg lines xray_moved.jpg invagination 2_moved.jpg subluxation large_moved.jpg
  • Summary
    • Rheumatoid Cervical Spondylitis comprises of 3 specific patterns of cervical spine instability seen in rheumatoid arthritis that consist of atlantoaxial subluxation, basilar invagination, and subaxial subluxation.
    • Diagnosis is made radiographically with cervical spine flexion-extension radiographs and supplemented with MRI studies to measure the degree of spinal cord compression. 
    • Treatment may be observation versus decompression with instrumentation depending on patient  neurological status, degree of mechanical instability, and severity of spinal cord compression. 
    • Present in 90% of patients with RA
      • diagnosis often missed
    • Cervical rheumatoid spondylitis includes three main patterns of instability
      • atlantoaxial subluxation
        • most common form of instability
      • basilar invagination
      • subaxial subluxation
  • Classification
      • Ranawat Classification
      • Class I 
      • Pain, no neurologic deficit
      • Class II
      • Subjective weakness, hyperreflexia, dysesthesias
      • Class IIIA
      • Objective weakness, long tract UMN signs, ambulatory
      • Class IIIB
      • Objective weakness, long tractUMNsigns, non-ambulatory. Do NOT operate
  • Presentation
    • Symptoms
      • symptoms and physical exam findings similar to cervical myelopathy
      • neck pain
      • neck stiffness
      • occipital headaches
        • due to lesser occipital nerve, which is branch of the C2 nerve root
      • gradual onset of weakness and loss of sensation
    • Physical exam
      • hyperreflexia
      • upper and lower extremity weakness
      • ataxia (gait instability and loss of hand dexterity)
  • Imaging
    • Radiographs
      • flexion-extension xrays
        • always obtain before elective surgery
        • see subtopic for radiographic lines and measurements
    • CT scan
      • useful to better delineate bony anatomy and for surgical planning
    • MRI
      • study of choice to evaluate degree of spinal cord compression and identify myelomalacia
  • General Treatment
    • Nonoperative
      • pharmacologic therapy
        • pharmacologic treatment for RA has seen significant recent advances
          • has led to a decrease in surgical intervention
    • Operative
      • spinal decompression and stabilization
        • indications
          • goal is to prevent further neurologic progression and surgery may not reverse existing deficits
  • Atlantoaxial Subluxation
    • Introduction
      • present in 50-80% of patients with RA
      • most common to have anterior subluxation of C1 on C2 (can have lateral and posterior)
    • Mechanism
      • caused by pannus formation between dens and ring of C1 that leads to the destruction of transverse ligament and dens
    • Radiographs
      • controlled flexion-extension views to determine AADI and SAC/PADI
        • AADI (anterior atlanto-dens interval)
          • instability defined as > 3.5 mm of motion between flexion and extension views
            • instability alone is not an indication for surgery
          • > 7 mm of motion may indicate disruption of alar ligament
          • > 10 mm motion is indication for surgery
            • because of increased risk of neurologic injury
        • PADI / SAC (posterior atlanto-dens interval and space available for cord describe same thing)
          • <14 mm is an indication for surgery
            • because of increased risk of neurologic injury
          • >13mm is the most important radiographic finding that may predict complete neural recovery after decompressive surgery
    • Treatment
      • nonoperative
        • indicated in stable atlantoaxial subluxation
      • operative
        • posterior C1-C2 fusion
          • general indications for surgery
            • AADI > 10 mm (even if no neuro deficits)
            • SAC / PADI < 14 mm (even if no neuro deficits)
            • progressive myelopathy
          • indications for posterior C1-2 fusion
            • able to reduce C1 to C2 so no need to remove posterior arch of C1
          • technique
            • adding transarticular screws eliminated need for halo immobilization (obtain preoperative CT to identify location of vertebral arteries)
        • occiput-C2 fusion ± resection of posterior C1 arch
          • indications
            • when atlantoaxial subluxation is combined with basilar invagination
            • resection of C1 posterior arch for complete decompression
              • leads to indirect decompression of anterior cord compression by pannus
              • may be required if atlantoaxial subluxation is not reducible
        • odontoidectomy
          • indications
            • rarely indicated
            • used as a secondary procedure when there is residual anterior cord compression due to pannus formation that fails to resolve with time following a posterior spinal fusion
              • pannus often resolves following posterior fusion alone due to decrease in instability
  • Basilar Invagination 
    • Introduction
      • also known as superior migration of odontoid (SMO)
        • tip of dens migrates above foramen magnum
      • present in 40% of RA patients
      • often seen in combination with fixed atlantoaxial subluxation
    • Mechanism
      • cranial migration of dens from erosion and bone loss between occiput and C1&C2
    • Imaging
      • radiographic lines
        • Ranawat C1-C2 index
          • center of C2 pedicle to a line connecting the anterior and posterior C1 arches
          • normal measurement in men is 17 mm, whereas in women it is 15 mm
          • distance of < 13 mm is consistent with impaction
          • most reproducible measurement
        • McGregor's line
          • line drawn from the posterior edge of the hard palate to the caudal posterior occiput curve
          • cranial settling is present when the tip of dens is more than 4.5 mm above this line
          • can be difficult when there is dens erosion
        • Chamberlain's line
          • line from dorsal margin of hard palate->posterior edge of the foramen magnum
          • abnormal if tip of dens > 5 mm proximal Chamberlain's line
          • normal distance from tip of dens to basion of occiput is 4-5 mm
          • this line is often hard to visualize on standard radiographs
        • McRae's line
          • defines the opening of the foramen magnum
          • the tip of the dens may protrude slightly above this line, but if the dens is below this line then impaction is not present
      • MRI
        • cervicomedullary angle < 135° suggest impending neurologic impairment
    • Treatment
      • operative
        • C2 to occiput fusion
          • indications
            • progressive cranial migration (> 5 mm)
            • neurologic compromise
            • cervicomedullary angle <135° on MRI
        • transoral or anterior retropharyngeal odontoid resection
          • indications
            • brain stem compromise
  • Subaxial Subluxation
    • Introduction
      • present in 20% with RA
      • often occurs at multiple levels
      • often combined with upper c-spine instability
      • lower spine involvement more common with
        • steroid use
        • males
        • seropositive RA
        • nodules present
        • severe RA
    • Pathophysiology
      • pannus formation and soft tissue instability of facet joints and Luschka joints
    • Radiographs
      • subaxial subluxation (of vertebral body) of >4mm or >20% indicates cord compression
      • cervical height index (body height/width) < 2.0 is almost 100% sensitive and specific for predicting neurologic compromise
    • Treatment
      • operative
        • posterior fusion and wiring
          • indications
            • > 4mm / >20% subaxial subluxation + intractable pain and neurologic symptoms
  • Operative Complications
    • Failure to improve symptoms
      • outcome less reliable in Ranawat Grade IIIB (objectively weak with UMN signs and nonambulatory)
    • Pseudoarthrosis
      • 10-20% pseudoarthrosis rate
      • decreased by extension to occiput
    • Adjacent level degeneration
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