Rheumatoid Arthritis of the Spine

Definition

• A chronic idiopathic systemic disorder characterized by an inflammatory arthritis (erosive

synovitis) of the peripheral joints. Other rheumatic disorders are diffuse idiopathic skeletal
hyperostosis, fibromyalgia, gout, and systemic lupus erythematosis.

Epidemiology

• Cervical spine involvement in 50-88% of rheumatoid arthritis (RA) patients.

• Abnormality depends upon the location.

C1/C2

Atlanto-axial subluxation (AAS) can anterior, posterior, or lateral.

Commonest manifestation of cervical disease in RA (30%).

Atlanto-axial impaction (AAI).

C3-C7 (Subaxial Spine)

Subaxial subluxation below higher fusion.

Anterior spondylodiscitis.

Intercanalicular rheumatoid granulation.

Hyperlordotic deformity.

Endplate erosions.

Pathology

• Characterized by an inflammatory synovitis, ligamentous distension and rupture, articular

cartilage destruction, and finally bony changes (osteoporosis, cyst formation, and erosion).

• Granulation tissue (pannus) which represents a low grade inflammatory change with mononuclear
cell infiltrates, giant cells, and fibrosis.
Clinical Features

• Pain is present in 40-88% of patients.

• In AAS and AAI compression, the second cervical nerve root gives pain which radiates to the
neck and occiput.

• Neurological dysfunction occurs in 7-34% of cases. Secondary to commpression of the cervico-

medullary junction, ischemia secondary to compression of the vertebral or anterior spinal arteries,
or by arteritis of small perforating vessels of the brain stem and spinal cord.

• At risk of premature death although the role of AAS plays is still uncertain.

• Autopsy series of 104 patients with RA, >10% had compression of the cervicomedullary junction,
of which 7/11 patients died suddenly.

Natural History

• Spinal disease begins early in the course of the disease and is progressive.

• Radiological involvement of the cervical spine (43% to 70% incidence) over a period of 5 years in
an RA cohort study. AAS (3-5 mm) watched over a period of 5 years and progressed to 5-8 mm in
45%, and >8mm in 10% of cases.

• Excellent correlation between the peripheral manifestations of RA and cervical spine involvement.

Factors Correlating with Severity of Cervical Disease in RA

Male sex

Seropositivity

Rheumatoid nodules

Erosive, mutilating articular disease

Corticosteroid therapy

Imaging

• Risk factors which predispose to symptomatic cord compression include the following.
 1. AAS >9 mm.

2. The presence of AAI.

3. Lateral AAS.

• CT has largely superseded tomography in defining axial and sagittal relationships.

• MRI is excellent for soft tissue resolution to visulize the relationship of the pannus to the cord.
Cervical medullary angle <135° correlates with neural compression. Dynamic images in flexion and
extension may provide further details.

Antlantoaxial Subluxation (AAS)

• The most common manifestation in the cervical spine (32%) and in surgical series of RA patients
who required cervical arthrodesis the incidence is 70%.

• Joint involvement includes atlatoaxial, atlato-odontoid, atlato-occipital joints as well as the bursa
between the dens and the tranverse ligament of C1. This can also lead to loosening of the insertion
of the transverse ligament of the atlas. Pannus of granulation formms around the odontoid and
contributes further to cord compression.

1. Anterior AAS is by far the most common.

• Atlantodental interval >3 mm for adults and >4 mm for children is

abnormal.

• Atlantodental interval >12 mm implies complete destruction of the

entire ligamentous complex.

2. Posterior AAS (6.7%).

• Results from one or a combination of the following.

i) Incompetence of the anterior arch of the atlas.

ii) Erosion or fractures of the odontoid.

iii) Posterosuperior migration of the atlas.

• Kyphotic kinking of the high cervical cord may lead to a

myelopathy.
 3. Lateral AAS (10% of RA).

• Greater than 2 mm subluxation of lateral mass of C1 on C2. Presents

with non-reducible head tilt.

Atlanto-Axial Impaction

• aka basilar impression, or cranial settling. Diagnosed by a number of rules listed below.

• Occurs in 8% of patients with RA. Results from erosive changes in the atlanto-axial and occipito-
atlantal joints.

Imaging Assessment of Atlanto-axial Region in RA

• Although the following are useful for compiling statistics on the degree of deformity, for decision
making purposes, obtaining an MRI is essential and has superseded most other imaging studies with
the exception of CT with reconstructions for defining the bony anatomy.

1. Chamberlain's line extends from posterior aspect of hard palate to posterior lip
of the foramen magnum (>6 mm of odontoid protrusion is abnormal).

2. McRae's line is from the anterior to posterior aspect of foramen magnum (any
protrusion of odontoid is abnormal).

3. McGregor line is from the posterior aspect of hard palate to inferior aspect of the
most caudal portion of occiput (>4.5 mm is abnormal).

4. Method of Ranawat. A line is drawn from the anterior to the most posterior
aspect of C1 (line 1), and a second vertical line (line 2) is drawn from the center of
the sclerotic ring on the C2 body (pedicle) upward along the mid-axis of C2 to
intersect at right angles with previous line (line 1). Abnormal if line 2 is <13 mm.
One advantage of this technique is that it isn't dependant on visualizing the hard
palate or the dens which may be eroded.

5. Wackenheim's clival canal line joins the dorsum sella to the tip of the clivus.
Odontoid shoud be tangential or below this line.

6. Fischgold and Metzger. Abnormal if diagastric line >1cm above dens.

7. Redlund-Johnell. Abnormal if <34 mm in men and <29 mm in women.

Treatment and Results

Conservative

• Firm collar can afford some protection towards minor trauma and give relief of neck pain.

Surgical Indications

1. Pain refractory to conservative measures.

2. Neurologic dysfunction.

3. Asymptomatic patients with >8 mm AAS (comonly cited). Papadopoulos et al,

1991, recommends treating asymptomatic patients (<65 years of age and good
functional class with >6 mm AAS). (Instability is a controvesial indication for
surgery.)

4. Cord changes evident on MRI (according to Fehlings).

Surgical Considerations

1. Reduce the subluxation with traction (start with 5 pounds and gradually over a
week, with approximately 20% of cases being non-reducible).

2. C1/C2 fusion for isolated AAS, or occiput to C2 fusion if one of the following
present.

i) An associated AAI.

ii) Extensive C1/C2 erosive changes.

iii) Associated subaxial subluxations. C1 laminectomy and foramen

magnum enlargement required as part of the treatment.

3. Transoral decompression should be reserved for patients with AAS who continue
to have cervicomedullary compression posterior fusion, as the amount of pannus has
been shown to significantly decrease in size simply with posterior immobilization.
Sonntag recommends doing the transoral first.

Surgical Approaches

C1/C2 Fusion
 1. Brooks fusion*.

2. Gallie fusion*.

3. Halifax interlaminar clamps.

4. Sonntag fusion*.

5. C1/C2 transpedicular screws.

* Problems are, i) increased risk of passing sub-laminar wires due to

anterior pannus, and ii) poor bone healing and consequently high risk of
pseudoarthrosis (25%).

Occiput to C2 Fusion

1. CD horseshoe with either sublaminar or interspinous wiring.

2. Luque rectangle.

3. Contoured steinman pin.

Sub-axial Abnormalities

• 10-20% of RA patients. Most frequent between C2/C3 and C3/C4.

• Secondary to synovitis of the neurocentral joints with secondary erosion of disc and bone.

• Often at multiple levels producing a step ladder appearance.

• Compromise the cord by bone and/or pannus, or by the development of a pachmeningitis or

arachnoiditis.

• Changes may be accelerated below a previous fusion.

• The primary indication for surgery with sub-axial abnormaities is the development of neurologic
symptoms. Most problems should be dealt with through an anterior approach.

Updated 25/05/98