Summary Rheumatoid Cervical Spondylitis comprises of 3 specific patterns of cervical spine instability seen in rheumatoid arthritis that consist of atlantoaxial subluxation, basilar invagination, and subaxial subluxation. Diagnosis is made radiographically with cervical spine flexion-extension radiographs and supplemented with MRI studies to measure the degree of spinal cord compression. Treatment may be observation versus decompression with instrumentation depending on patient neurological status, degree of mechanical instability, and severity of spinal cord compression. EPIDEMIOLOGY Present in 90% of patients with RA diagnosis often missed ETIOLOGY Cervical rheumatoid spondylitis includes three main patterns of instability atlantoaxial subluxation most common form of instability basilar invagination subaxial subluxation Classification Ranawat Classification Class I Pain, no neurologic deficit Class II Subjective weakness, hyperreflexia, dysesthesias Class IIIA Objective weakness, long tract UMN signs, ambulatory Class IIIB Objective weakness, long tractUMNsigns, non-ambulatory. Do NOT operate Presentation Symptoms symptoms and physical exam findings similar to cervical myelopathy neck pain neck stiffness occipital headaches due to lesser occipital nerve, which is branch of the C2 nerve root gradual onset of weakness and loss of sensation Physical exam hyperreflexia upper and lower extremity weakness ataxia (gait instability and loss of hand dexterity) Imaging Radiographs flexion-extension xrays always obtain before elective surgery see subtopic for radiographic lines and measurements CT scan useful to better delineate bony anatomy and for surgical planning MRI study of choice to evaluate degree of spinal cord compression and identify myelomalacia General Treatment Nonoperative pharmacologic therapy pharmacologic treatment for RA has seen significant recent advances has led to a decrease in surgical intervention Operative spinal decompression and stabilization indications goal is to prevent further neurologic progression and surgery may not reverse existing deficits Atlantoaxial Subluxation Introduction present in 50-80% of patients with RA most common to have anterior subluxation of C1 on C2 (can have lateral and posterior) Mechanism caused by pannus formation between dens and ring of C1 that leads to the destruction of transverse ligament and dens Radiographs controlled flexion-extension views to determine AADI and SAC/PADI AADI (anterior atlanto-dens interval) instability defined as > 3.5 mm of motion between flexion and extension views instability alone is not an indication for surgery > 7 mm of motion may indicate disruption of alar ligament > 10 mm motion is indication for surgery because of increased risk of neurologic injury PADI / SAC (posterior atlanto-dens interval and space available for cord describe same thing) <14 mm is an indication for surgery because of increased risk of neurologic injury >13mm is the most important radiographic finding that may predict complete neural recovery after decompressive surgery Treatment nonoperative indicated in stable atlantoaxial subluxation operative posterior C1-C2 fusion general indications for surgery AADI > 10 mm (even if no neuro deficits) SAC / PADI < 14 mm (even if no neuro deficits) progressive myelopathy indications for posterior C1-2 fusion able to reduce C1 to C2 so no need to remove posterior arch of C1 technique adding transarticular screws eliminated need for halo immobilization (obtain preoperative CT to identify location of vertebral arteries) occiput-C2 fusion ± resection of posterior C1 arch indications when atlantoaxial subluxation is combined with basilar invagination resection of C1 posterior arch for complete decompression leads to indirect decompression of anterior cord compression by pannus may be required if atlantoaxial subluxation is not reducible odontoidectomy indications rarely indicated used as a secondary procedure when there is residual anterior cord compression due to pannus formation that fails to resolve with time following a posterior spinal fusion pannus often resolves following posterior fusion alone due to decrease in instability Basilar Invagination Introduction also known as superior migration of odontoid (SMO) tip of dens migrates above foramen magnum present in 40% of RA patients often seen in combination with fixed atlantoaxial subluxation Mechanism cranial migration of dens from erosion and bone loss between occiput and C1&C2 Imaging radiographic lines Ranawat C1-C2 index center of C2 pedicle to a line connecting the anterior and posterior C1 arches normal measurement in men is 17 mm, whereas in women it is 15 mm distance of < 13 mm is consistent with impaction most reproducible measurement McGregor's line line drawn from the posterior edge of the hard palate to the caudal posterior occiput curve cranial settling is present when the tip of dens is more than 4.5 mm above this line can be difficult when there is dens erosion Chamberlain's line line from dorsal margin of hard palate->posterior edge of the foramen magnum abnormal if tip of dens > 5 mm proximal Chamberlain's line normal distance from tip of dens to basion of occiput is 4-5 mm this line is often hard to visualize on standard radiographs McRae's line defines the opening of the foramen magnum the tip of the dens may protrude slightly above this line, but if the dens is below this line then impaction is not present MRI cervicomedullary angle < 135° suggest impending neurologic impairment Treatment operative C2 to occiput fusion indications progressive cranial migration (> 5 mm) neurologic compromise cervicomedullary angle <135° on MRI transoral or anterior retropharyngeal odontoid resection indications brain stem compromise Subaxial Subluxation Introduction present in 20% with RA often occurs at multiple levels often combined with upper c-spine instability lower spine involvement more common with steroid use males seropositive RA nodules present severe RA Pathophysiology pannus formation and soft tissue instability of facet joints and Luschka joints Radiographs subaxial subluxation (of vertebral body) of >4mm or >20% indicates cord compression cervical height index (body height/width) < 2.0 is almost 100% sensitive and specific for predicting neurologic compromise Treatment operative posterior fusion and wiring indications > 4mm / >20% subaxial subluxation + intractable pain and neurologic symptoms Operative Complications Failure to improve symptoms outcome less reliable in Ranawat Grade IIIB (objectively weak with UMN signs and nonambulatory) Pseudoarthrosis 10-20% pseudoarthrosis rate decreased by extension to occiput Adjacent level degeneration