1. Spine Manifestations in Rheumatoid Arthritis
Nav Chaudhary, VA Spine Fellow
February 9, 2015

2. Incidence RA incidence is 1% of population
Cervical spine involvement in 50 – 85% of RA patients

3. Types of Cervical Spine Involvement
Upper cervical involvement in 44-88% of RA
Anterior atlanto-axial subluxation- most common (up to 25%)
Basilar impression – upward translocation of the odontoid process (8%)
Pannus– forms around the odontoid
Sub-axial cervical spine – most common at C2-3 and C3-4
Less common involvement in the cervical spine in RA
Posterior atlanto-axial subluxation – associated fracture or erosion of odontoid
VBI secondary to changes in cranio-cervical junction

4. Clinical Pain (40 - 88%) Neurological deficit (7 - 34%)
Headache and neck pain
C1 or C2 nerve root can cause pain that radiates to the neck and occiput
Neurological deficit (7 - 34%)
Compression of CMJ or spinal cord
Ischemia secondary to compression of VA, ASA  transient blackouts in 55% with BI
Arteritis of small perforating vessels of brain stem and spinal cord
Premature death
Autopsy series of 104 patients with RA, > 10 % had compression of the CMJ, of which 7/11 patients died suddenly

5. Ranawat Classification of Myelopathy
Description I
No neural deficit II
Subjective weakness + hyper-reflexia + dysesthesia
III
Objective weakness + long tract signs
III A- ambulatory
III B- quadriplegic & non-ambulatory

6. Other CNS Involvement Peripheral neuropathy Vasculitis Pachymeningitis
Carpal Tunnel Syndrome
Vasculitis
Pachymeningitis
Effects of steroids and DMARDS
Spine infections d/t immunosuppression
Fractures d/t osteoporosis

7. 1. Atlanto-Axial Subluxation

8. Atlanto-Axial Subluxation
Inflammatory involvement of the atlanto-axial synovial joints causes erosive changes in the odontoid (anteriorly at the synovial joint with the C1 arch, and posteriorly at the synovial joint with the transverse ligament) and loosening of the TL insertion on the atlas
These changes can lead to instability causing anterior subluxation of C1 on C2
AAS occurs in 25% of patients with RA
Mean time between the onset of RA symptoms to the diagnosis of AAS in 15 patients was 14 years

9. Atlanto-Axial Subluxation Clinical
AAS is usually slowly progressive
Mean age at onset of AAS symptoms is 57 years old
Pain is experienced locally (upper cervical and suboccipital regions, often from compression of C2 nerve root)
Hyperreflexia
Spasticity
Paresis
Sensory disturbance
VBI may occur from VA involvement

10. Atlanto-Axial Subluxation Radiographic Evaluation
Anterior atlantodental interval (ADI)
Normal ADI in adults is <3-4 mm
Widening of ADI suggests possible incompetence of the TL
ADI does not correlate with the risk of neurological injury and is not predictive of progression from asymptomatic to symptomatic AAS
Posterior atlantodental interval (PADI)
The amount of room available for the spinal cord can vary for any given ADI depending on the AP diameter of the spinal canal and the thickness of any pannus
PADI correlates with the presence and severity of symptoms, and can predict neurological recovery following surgery
Patients with paralysis from AAS showed no recovery if the pre-op PADI was <10mm
PADI <14mm has been proposed as an indication for surgical stabilization

11. Lateral radiograph - ADI (black arrows) and PADI (white arrows)

12. Atlanto-Axial Subluxation MRI
The optimal test to evaluate the source and magnitude of upper cord or medulla compression
Demonstrates location of odontoid process and extent of pannus

13. Atlanto-Axial Subluxation Natural History
Natural history: AAS in most patients progresses, with a small percentage either stabilizing or fusing spontaneously. In one series with 4.5 years mean follow-up:
45% of patients with a 3.5-5mm subluxation progressed to 5-8mm, and 10% of these progressed to >8mm
The worse the myelopathy, the higher the risk of sudden death
Correlation between the peripheral manifestations of RA and cervical spine involvement
Life expectancy of patients with RA is 10 years less than the general population

14. Atlanto-Axial Subluxation When to Treat?
Symptomatic patients:
Most require surgical stabilization +- decompression
Asymptomatic patients:
ADI > 8mm
PADI <14mm
Patients are often placed in a rigid collar

15. Atlanto-Axial Subluxation Surgical Management
Goals: either reduce the subluxation +- decompress the upper cord before doing a fusion (C1-C2 or O-C2)
Traction:
Start with 5lbs, and gradually increase over a period of a week
Most cases reduce within 2-3 days
If not reduced after 7 days, then its probably not reducible
20% of cases are not reducible (most of these have odontoid >15mm above the foraman magnum)

16. Postoperative lateral xray: transarticular screw fixation and interspinous wire fixation in RA atlantoaxial instability (left) Lateral and AP X-ray: C1 lateral mass and C2 screw technique (middle, right)

17. Atlanto-Axial Subluxation Surgical Management
Posterior fusion alone does not provide adequate relief if the subluxation is irreducible, or if pannus causes significant compression (however, there may be decrease of pannus after reduction)
In these cases, transoral odontoidectomy may be indicated

18. Atlanto-Axial Subluxation Surgical Morbidity & Mortality
Because of the frequency of simultaneous involvement of other systems in RA, operative mortality ranges from 5-15%
The non-fusion rate for C1-2 wiring and fusion has been reported as high as 50% (18% of patients in one series developing a fibrous union)
The most common site of failure of osseous fusion in the interface between the bone graft and the posterior arch of C1

19. Atlanto-Axial Subluxation Postoperative Care
Impaired healing in RA dictates that the Halo be worn until fusion is well established, as seen on xray (usually 8-12 weeks)
Evaluate with flexion-extension films

20. 2. Basilar Impression

21. Basilar Impression
Erosive changes in the lateral masses of C1 telescoping of the atlas onto the body of C2:
Upward displacement of the dens
Posterior arch of C1 often protrudes superiorly through the foraman magnum
Pannus also contributes to compressive symptoms
VA and/or ASA compression may also cause neurologic dysfunction

22. Basilar Impression Clinical
Pain may occur as a result of compression of C1 and C2 nerve roots
Cranial nerve dysfunction
INO
Vertigo
Diplopia
Downbeat nystagmus
Sleep apnea
Progressive difficulty ambulating, spastic quadriparesis
Hyperreflexia and Babinski
Sensory changes

23. Basilar Impression Radiographic Evaluation
Erosion of the tip of the odontoid, commonly seen in RA, obviates use any measurements that is based on the location of the odontoid tip
Other measures have been developed, including Redlund-Johnwell (<33 mm for men and <27 mm for women), and Ranawat criteria (<13 mm)
Even these methods miss up to 6% of cases of BI in RA

24. Lateral illustration of the upper cervical spine and lower occiput depicting radiographic measurement criteria to determine cranial settling
McRae’s - basion to the posterior aspect of the foramen magnum. Projection of the odontoid above this line is abnormal. Chamberlain’s - posterior hard palate to the posterior lip of the foramen magnum. Projection of the odontoid more than 3 mm past this line is abnormal.
McGregor’s - posterior hard palate to the most caudal aspect of the occiput
Ranawat’s line- A line drawn between the posterior and anterior arch of C1. - distance between this line and the middle point of C2. As cranial settling increases, this distance becomes shorter. <13 mm is abnormal.
Redlund-Johnell’s - distance from the McGregor’s line to the sagittal midpoint at the base of the axis. Abnormality < 33 mm for men and <27 mm for women.

25. Basilar Impression Imaging
MRI
Optimal for demonstrating brainstem impingement
Cervicomedullary angle – angle between a line drawn through the long axis of the medulla on a sagittal MRI and a line drawn though the cervical spinal cord
Normal CMA is deg
CMA < 135 deg correlates with signs of cervicomedullary compression, myelopathy or C2 radiculopathy
CT- primarily done to assess bony anatomy (erosion, fractures)
CTA- helpful when surgery is contemplated, to show VA anatomy

26. Cranial settling: superior migration of the odontoid into the foramen magnum

27. Cervicomedullary angle: MRI of a myelopathic RA patient with a CMA measuring 130 degrees (dotted white line).
Notice the effect of progressive cranial settling combined with an increasing retrodental pannus on the craniocervical junction.

28. Basilar Impression Treatment
Cervical traction
Begin with 7 lbs
Slowly increase to 15 lbs
Some may require several weeks of traction to reduce

29. Basilar Impression Surgery
Reducible cases
posterior occipitocervical fusion +- C1 decompressive laminectomy
Irreducible cases
Requires transoral resection of odontoid

30. 3. Sub-axial abnormalities

31. Sub-axial abnormalities
 10-20% of RA patients
Often at multiple levels producing a stepladder appearance
Compromise of the cord by:
Bone
Pannus
Arachnoiditis
Changes may be accelerated adjacent a previous fusion

32. Sub-axial abnormalities Imaging
Multiple subluxations
Hyperlordotic deformity
Narrow disk space, esp. C2-3, C3-4
Erosions of vertebral endplates
Facet joint erosion

33. Lateral radiograph demonstrating subaxial subluxation of the cervical spine at multiple levels, resulting in the classic “stepladder” deformity.

34. Sub-axial abnormalities Treatment
Primary indication for surgery with sub-axial abnormalities is the development of neurologic symptoms
If multiple subluxations or lordotic deformity:
Attempt halo reduction
Follow with multilevel posterior fusion

35. Overall RA Management Considerations
Optimize medically pre-op
Assess cardiac, respiratory and nutritional status
r/o +- treat osteoporosis
Rheumatologist to hold immunosuppression/steroids if possible
Firm collar can afford some protection towards minor trauma and give relief of neck pain
Anesthesia: awake, fiberoptic intubation
Neuromonitoring

36. Overall RA Management Considerations
Surgery: 3 major indications, relative indications
Intractable pain
Neurologic dysfunction
Radiculopathy secondary to subaxial subluxation
Asymptomatic patients:
> 8 mm AAS
ADI > 8mm
PADI < 13-14mm

37. Overall RA Management Considerations
Attempt preoperative reduction
Approximately 20% of cases are non-reducible
if reducible  posterior fusion
if irreducible  transoral decompression
ecompression AND posterior fusion