- See:
-
Atlantoaxial Rotary Subluxation- Discussion:
-
Transverse Ligament Rupture:
- Discussion:
- subluxation can occur in up to 70% of patients with rheumatoid arthritis, but frank dislocation occurs in about 25%;
- approximately 11% of rheumatoid arthritis patients will develop cord compression from atlantoaxial subluxation;
- among patients that develop myelopathy, 5 years survival rate is 80% but the 10 year survival rate is 28%, (as noted by T. Mori MD et al 1998);
- C1-C2 articulation is synovial which accounts for its frequent involvement in RA;
- anterior instability is much more common than posterior instability and occurs more often in men;
-
etiology:
- results from pannus formation at synovial joints between dens,
C1, & transverse ligament, resulting in
destruction of transverse ligament, dens or both;
-
transverse ligament elongation and rupture:
- stretching and destruction of these structures allows
atlas vertebra to move forward relative to the
axis;
- w/ C-spine flexion, atlas moves forward relative to axis;
- spinal cord being compressed between posterior arch of the atlas and the odontoid peg;
- dens erosion:
- in some cases odontoid is totally eroded by inflammatory reaction;
-
risk factors:
- corticosteroid use;
- seropositivity;
- RA nodules;
- erosive and deforming disease;
- Exam:
- limitation of motion, upper motor neuron signs, & detection of clunk w/ neck flexion (Sharp & Purser signs - not recommended);
- rheumatoid compression of spinal cord or nerve roots results in long tract signs and root pain;
- root pain is caused by anterior subluxation of
Atlas on
Axis leading to suboccipital (
C2) root pain;
- can be severe & is usually episodic & provoked by sudden movement;
- Radiographic Work Up;
-
cross table lateral:
-
dynamic flexion & extension view :
-
anterior atlantodens interval (ADI) is evaluated;
- instability is present when a 3.5 mm ADI difference on flex/ext views,
- 7 mm difference may imply disruption of the alar ligaments;
- difference of
> 9 mm is associated with an increase in neurologic injury & will require posterior fusion and wiring;
- Non Operative Treatment:
- note that the most severe instability takes place in flexion, and therefore the main goal is to prevent flexion with an orthosis;
- ref: Headmaster collar restricts rheumatoid atlantoaxial subluxation.
M. Kauppi MD PhD et al.
Spine. Mar 1999. Vol 24 No 6. p526.
- Surgical Treatment:
-
indications for surgery:
- more than 9 mm of anterior atlantoaxial subluxation places pt at high risk for development of
cord compression;
- ADI of > 7 to 10 mm or posterior space (SAC) < 13 mm is contraindication surgery in other areas of body & C-spine should be stabilized first;
-
atlanto-axial fusion:
- most indicated for patients w/ C1/C2 subluxation which is reducible;
- results may be unacceptable if myelopathy is present;
- sublaminar wiring may be contra-indicated in these patients when the SAC is less than 12 mm;
- in RA, periodontoid pannus tissue is often present and can contribute to cord compression;
- after posterior cervical fusion, this pannus tissue will often resolve;
-
occipito-cervical fusion:
- if myelopathy is present, this may be the procedure of choice;
- if there is an associated irreducible atlanto-axial dislocation then consider additional decompressive laminectomy of the atlas;
- Complications:
- surgery is less successful in patients w/ servere Ranawat IIIb lesions (non ambulatory with objective weakness);
- complications include pseudoarthrosis & recurring
myelopathy;
- pseudoarthrosis rate can be decreased by extending fusion to occiput with wire fixation;
Cervical myelopathy and posterior atlanto-axial subluxation in patients with rheumatoid arthritis.
Atlantoaxial instability and neurologic indicators in rheumatoid arthritis.
Upper cervical instability in rheumatoid arthritis.
3 to 11 year follow up of occiptiocervical fusion for rheumatoid arthrtis. T. Mori MD et al. CORR No 351. p 169-179.
1998.
Results after 24 years of prophylactic surgery for rheumatoid atlantoaxial subluxation.
