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

• intractable pain
• clear cut neurological deficit
• 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