Definition
- Cervical instability from rheumatoid synovitis destroying ligaments, bone and synovial joints
- Three patterns are atlantoaxial subluxation, basilar invagination (cranial settling) and subaxial subluxation
- Upper cervical spine most often involved
Aetiology
- Autoimmune inflammatory synovitis of the synovial joints of the cervical spine
- Risk factors include severe erosive peripheral disease and long disease duration
- RF and anti-CCP positivity associated with cervical involvement
- Long term corticosteroid use associated
- Disease modifying and biologic agents have reduced incidence
Epidemiology
- cervical spine is severely affected in 30% of rheumatoid patients
Anatomy
- Transverse ligament is the primary stabiliser of the atlantoaxial joint
- Alar and apical ligaments are secondary stabilisers
- Normal adult ADI under 3 mm
- Steel rule of thirds at C1 with dens, cord and free space each one third
- Synovial joints include atlanto-dens, atlanto-occipital, lateral mass and subaxial facet joints
Pathology
Three types of lesion (instability) are common;
- Erosion of the atlanto-axial joints & the transverse ligament with resulting instability
- Erosion of the atlanto-occipital articulations allowing the odontoid to ride up into the foramen magnum
- Erosion of the facet joints in the mid cervical region which may result in ankylosis but usually instability & subluxation
Classification
Ranawat neurological classification
| Class | Description |
|---|---|
| 1 | Pain, no neurological deficit |
| 2 | Subjective weakness, dysaesthesia and hyperreflexia |
| 3A | Objective weakness and long tract signs, ambulatory |
| 3B | Objective weakness and long tract signs, non-ambulatory |
Original publication Ranawat CS, O’Leary P, Pellicci P, Tsairis P, Marchisello P, Dorr L. Cervical spine fusion in rheumatoid arthritis. J Bone Joint Surg Am. 1979;61(7):1003-10.
History
- Usually a women with advanced rheumatoid disease
- Has neck pain & may support her head in her hands & have marked restriction of movement
- Symptoms & signs of root or cord compression may appear in the upper & lower limbs (cervical myelopathy)
Examination
- Restricted neck movement, especially rotation
- Long tract signs with hyperreflexia, Hoffmann sign, clonus and upgoing plantars
- Lhermitte sign on neck flexion
- Gait and hand dexterity assessment for myelopathy
- Signs may be masked by peripheral joint deformity and pain
- Cranial nerve and brainstem signs with basilar invagination
Investigations
X-rays
- Atlanto-axial instability is evident in the lateral view when taken in flexion & extension
- (greater than 5mm gap = instability)
- Flexion views show subluxation in the mid cervical region
Differential Diagnosis
- Degenerative cervical myelopathy
- Peripheral neuropathy and carpal tunnel syndrome
- Rheumatoid tendon ruptures mimicking weakness
- Ankylosing spondylitis and psoriatic spondyloarthropathy
- Atlantoaxial instability from os odontoideum, Down syndrome or trauma
- Infection or tumour of the cervical spine
Treatment
- Despite the X-Ray appearance serious neurological complications are rare
- Symptomatic relief can usually be achieved by wearing a collar & with anti-rheumatic medication
- Spinal fusion may be indicated if the disability is severe or there is progressive neurological involvement (occipito-cervical, Gallie or mid cervical fusion may be indicated)
Complications
- Sudden death from brainstem compression
- Progressive myelopathy and quadriparesis
- Vertebral artery insufficiency
- Pseudarthrosis and infection after fusion, more frequent with poor bone and steroid use
- Subaxial subluxation below an occipitocervical or C1 to C2 fusion
- Difficult airway at intubation
Prognosis
- Untreated myelopathy carries high mortality
- Ranawat 3B patients have high surgical mortality and limited neurological recovery
- Earlier surgery before severe deficit gives better neurological recovery
- Preoperative PADI of 10 mm or more predicts neurological recovery after surgery (Boden)
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.