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British Medical Books Health Issues Computerized Tomography

Rheumatoid Arthritis of the Cervical Spine

  • cervical instability - most serious & potentially lethal manifestation of RA
  • neck pain - 40-88% incidence of RA
  • cervical subluxations - 43 - 86%
  • neurological deficit - 7 to 34%
  • 10% incidence of sudden death

3 basic types of cervical instability

  • atlanto-axial subluxation
    • most common - 65% incidence
    • most have anterior subluxation
    • 20% lateral subluxation & 10% posterior subluxation
  • basilar invagination (cranial settling)
    • 20%
  • sub-axial subluxation
    • 15% incidence

Clinical evaluation

Pain

    • typically in the neck, occipital headache
    • stiffness & crepitus

Neurological deficit

  • range from parasthesias to L’Hermitte’s phenomenon

Ranawat classification of neural deficits

class 1 - pain, no neuro deficit
class 2 - subjective weakness, hyper-reflexia, dysthesia
class 3 - objective weakness, long tract signs

    • 3a - ambulatory
    • 3b - nonambulatory

Poor prognostic factors

  • Ranawat’s classification correlates well with recovery following surgery
  • location of the lesion - basilar invagination has a poorer outcome
  • pseudo-arthrosis following fusion
  • pre-op SAC < 10mm - poor recovery of motor function
  • sub-axial canal of < 14mm
  • vertebrobasilar insufficiency - tinnitis, vertigo
  • sudden death

X ray evaluation

Lateral flexion-extension films

A-A instability

  • ADI
    • unreliable (normal for adult is 3mm)
    • poor correlation with neurological deficit
  • SAC
    • best indicator
    • < 14mm reliable indicator for neurology
  • MRI
    • allows visualization of SC compression from bone & ST pannus
    • 2/3 of patients with A-A instability have 3mm diameter of pannus
    • pannus decreases after solid fusion
  • cervico-medullary angle
    • normal is 135 to 175°
    • if < 135° high correlation with a cervical myelopathy & paralysis

Basilar invagination

  • high frequency of severe neurology
  • parameters on plain films
    • McGregors line (N = 8mm for females, 9mm males), Chamberlains line
    • Ranawat method
  • tomo’s - very useful for this

Sub-axial subluxations

Posterior canal diameter (SAC)

  • most NB - < 13mm is dangerous
  • SAC is not = true space - unknown thickness of pannus

Panjabi & Whites criteria for instability

  • anterior subluxation of 3.5mm & angulation > 110

Treatment

Goals

  • avoid neurological impairment, sudden death & unnecessary surgery

Indications for surgery

  1. intractable pain
  2. clear cut neurological deficit
  3. more controversial group = radiographic instability but NO significant neurology
  • A-A subluxation
    • SAC < 13mm, especially in the presence of hypermobility
    • posterior fusion
  • A-A subluxation + basilar invagination
    • MRI in flexion:
    • if any evidence of SC compression - traction
    • if it reduces then Occ-cervical fusion
    • if no reduction, then Occ-cervical fusion + anterior peg removal or C1 laminectomy
  • isolated asymptomatic fixed basilar invagination: observe
  • basilar invagination with cervico-medullary angle < 135°
    • excessive protrusion above Chamberlains line
  • subaxial subluxation
    • no neurology - observe
    • if SAC > 14mm observe
    • if SAC < 13mm or there is significant hypermobility - posterior cervical spine fusion
    • if there is significant neurology & lesion is not reducible - ACF