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C1-C2 in Rheumatoid Arthritis

July 2012 - Donna Magid, M.D., M.Ed.

Up to 90% RA pts have CS involvement:

Increases proportional to:

  • Duration of disease
  • # joints involved

RA: inflammatory; articular cartilage, ligamentous destruction, bone erosion

  • 32% sublux “significantly” (>4mm) - usual atlanto-axial (C1-C2)     
  • Basilar invagination (atl-axial impaction) 2nd, occurs later
  • More distal CS: joints of Lushka, facets
  • “Trespassing” pannus into disc, anterior longitudinal ligament (ALL)
  • Less caudal cord space (~14 mm); therefore more symptoms

C1-C2: normal anterior ADI is 2.5-3 mm, (3-5, peds) w/o change during flex/ext.

  • Change >3.5 mm, fl/ext, implies ligamentous compromise
  • 7 mm change: implies alar ligament disruption
  • >9 mm change: increasing % neurologic insult, myelopathy

C1-C2 subluxation in RA very gradual, less neurologic damage than similar subluxations occurring during acute trauma BUT leave pt. more vulnerable to morbid subluxation with falls, MVC, even violent sneezes. Erosions and osteopenia of RA also magnify risks.

Thecal canal 14-17 mm AP diameter at C1-C2: widest part of cervical thecal canal BUT cord also widest here as comes off brainstem. Narrowing by subluxation odontoid therefore impinges cord and causes symptoms, sometimes initially noted only when pt. flexes (“When I bend over to tie my shoes I get electrical flashes down my arms” or “flashing from my neck to my head"). Ongoing progressive cord impingement may progressive spasticity, hyper-reflexia, clonus, potentially can lead to quadriplegia, and death.

C1-C2 subluxation in RA = ligamentous AND bone changes

  • Transverse ligament= #1 pathology: insertion on dens erodes, destabilizing C1-2    
  • Joint capsule destroyed-granulation tx between C1-2 lateral masses
  • Radiographic changes may precede symptoms

Posterior atlanto-axial interval (=s thecal canal at that level)

  • <14 mm diameter correlates w/ neurologic change more directly than anterior ADI. Diameter = bony stability/subluxation PLUS impinging pannus, granulation tissue.

JBJS 1993: 

  • >14mm space pre-op all near-complete recovery post op (>13mm if also impacted)
  • >10mm pre-op all showed some neurologic improvement
  • <10mm pre-op no post-op recovery of neurologic changes

Sx: radiculopathy-may be confused w/ peripheral flare of RA

  • Neck pain, Decreasing ROM, Crepitation
  • Occipital headache
  • Neurologic change is gradual: hyperreflexia, pain sensation, 2-point discrimination, suboccipital pain, parasthesias, clumsiness, LE spasticity, urinary changes, leg spasms

Treatment: control RA (anti-inflammatories), orthosis, surgery

Surgery: Untreated, mortality up to 50%

  • Symptomatic (pain), subluxation > 8 mm even if NO sx.
  • Pre-op traction (3-5 lb, spinal monitoring)
  • Extension of fusion to occiput helps fusion rate, decreases pseudarthrosis/failure

Even in normals, little bony volume to anchor screws; osteopenic RA pt. can be even more problematic, harder to stabilize mechanically and slower to heal.

 

July 2012 - Donna Magid, M.D., M.Ed.