Rheumatoid arthritis (RA) is a chronic disease that affects approximately 1% of the U.S. population. RA is an autoimmune disease that results in the inflammation and destruction of the synovial tissue (special cells and tissue that form the lining) of the joints in the body. RA can and often does affect almost every joint in the body, especially as people get older. Although RA affects the joints of the hands and legs which can severely decrease function and mobility, people with significant disease in the spine are at risk for neurologic damage such as paraplegia, in addition to problems with pain, mobility, and function. Rheumatoid disease of the spine is most common in three regions and causes distinct clinical problems. The first is basilar invagination (also called cranial settling or superior migration of the odontoid), a condition in which arthritic destruction at the base of the skull causes the skull to “settle” into spinal column, causing a pinching of the spinal cord between the skull and the 1st cervical vertebrae. The second condition, and the most common, is atlanto-axial instability. A synovitis and erosion of the joint and ligaments connecting the 1st (atlas) and 2nd (axis) cervical vertebrae causes instability of the joint, which may lead to a dislocation and spinal cord compression. In addition, a pannus (localized mass/swelling of rheumatoid synovial tissue) can also form at this location, causing even more spinal cord compression. The third clinical scenario is called subaxial subluxation, and involves bony and ligamentous destruction of the lower cervical vertebrae (C3-C7) causing instability and/or spinal stenosis.
The precise cause of rheumatoid arthritis is unknown. It is a disease that affects the body’s immune system, and is considered to be an autoimmune disorder. In rheumatoid arthritis, a patient’s own immune system (white blood cells and antibodies) attacks the body’s normal synovial cells and tissues of the joints. The initial stage of rheumatoid disease produces pain, swelling, warmth, and stiffness in the affected joints. The second stage of disease causes an overgrowth or thickening of the synovium (called pannus). The third stage of disease involves enzymatic destruction of the bone and cartilage of the joints, which usually results in significant joint pain, malalignment, stiffness, and instability.
Rheumatoid arthritis can affect any joint, but usually begins in the small joints of the hand and fingers. Over time, more and more joints are affected, including the spine. Following the initial diagnosis, there is no specific pattern as to how fast the disease will progress, which joints will be affected, or how severely these joints will be affected. Patients with cervical spine involvement may have mild or severe neck pain, as well neurologic abnormalities such as weakness, numbness, or bowel/bladder dysfunction. Severe rheumatoid disease of the cervical spine may cause difficulty or inability to walk and decreased function and coordination of the arms and hands. In addition to neurologic symptoms and joint pain/dysfunction, patients will often have constitutional symptoms such as low-grade fever, fatigue, malaise, stiffness, weakness, and/or loss of appetite, among others.
Swelling and deformity of the small joints of the hands and fingers are the most common physical findings in patients with rheumatoid arthritis, especially when the condition is advanced. Signs of cervical spine involvement include neck tenderness and decreased range-of-motion. The neurologic examination will generally be normal until the cervical disease is advanced. Hyperreflexia will be noted as patients develop spinal cord compression. Positive special tests such as the test for clonus, rapid alternating hand movements, and Hoffman’s sign indicate myelopathy.
Plain x-rays of the cervical spine are essential to adequately evaluate patients with rheumatoid arthritis. X-rays will show the overall alignment of the spine, and whether there is obvious cranial settling or instability. It is often difficult to visualize the detailed bony anatomy at the base of the skull, therefore a computed tomography (CT) scan with contrast (injection of dye within the thecal sac) is ordered. A magnetic resonance imaging (MRI) test is useful to evaluate the severity of nerve compression or spinal cord injury, and allows visualization of all structures, including the nerves, muscles, and soft tissues. Flexion/extension x-rays of the cervical spine are often obtained to evaluate for evidence of ligamentous instability, particularly at C1-C2 level. This imaging test involves a plain lateral x-ray (looking at the neck and head from the side view) being taken with the patient flexing forward and another lateral x-ray being taken with the patient extending the neck backwards. The two x-rays are then compared to see if the spine bones move excessively and demonstrate instability.
Laboratory tests (blood tests) are routinely used to help confirm the diagnosis of rheumatoid arthritis. Tests for rheumatoid factor (RF) and anti-nuclear antigen (ANA) are the most commonly ordered tests. Other laboratory tests can also be ordered to rule out infection or other medical/rheumatologic conditions.
The diagnosis of rheumatoid arthritis can generally be made with a thorough history and detailed physical examination. The diagnosis is confirmed with specific laboratory tests as described above. Cervical x-rays and additional imaging tests (MRI, CT scans) are generally necessary to determine if the disease is affecting the cervical spine, as well as to evaluate the severity.
The general treatment for rheumatoid arthritis is typically managed by a rheumatologist or primary care physician. Patients with disease affecting the cervical spine are generally managed by spine surgeons with advanced training in cervical surgery and rheumatologic disease. Patients with cervical disease who do not have instability or stenosis can usually be managed with medical (non-operative) treatments, yet should continue to be followed regularly by a spine surgeon. The common medical treatments for rheumatoid arthritis are listed below.
- Nonsteroidal anti-inflammatory drugs – ibuprofen, etc.
- Analgesic drugs – acetoaminophen, hydrocodone, etc.
- Glucocorticoids (steroids) – prednisone, etc.
- Disease modifying antirheumatic drugs (DMARDs) – methotrexate, sulfasalizine, gold, etc.
- Biologic response modifiers – etanercepts, infliximab, etc.
- Protein-A immunoadsorption therapy – removal of antibodies from the blood
When a patient with rheumatoid arthritis develops cervical instability and/or spinal stenosis with myelopathy, surgical intervention is considered. The goal of surgery is to stabilize the spine and remove the compression from the spinal cord, to improve a patient’s pain and level of function, as well as prevent further deterioration of function and worsening pain. A patient with isolated cranial settling and/or atlanto-axial instability without cord compression can be treated with posterior (back of the neck) occipital-cervical fusion with instrumentation. However, patients with severe anterior (front of the neck) cord compression from a pannus at the C1-C2 joint will be indicated for a transoral decompression surgery combined with a posterior occipital-cervical fusion with instrumentation. Patients with subaxial subluxation may have instability or stenosis, or both. Treatment options vary depending on each patient’s clinical and radiopgraphic presentation. Patients with subaxial instability may only require a spinal fusion. Patients with stenosis and myelopathy require surgical decompression, and often fusion as well. If the majority of pressure is coming from osteophytes in the front (anterior) of the spine, then an anterior corpectomy with strut graft and fusion may be considered. If the majority of the compression is occurring due to ligamentum flavum hypertrophy in the back part of the spinal cord, then a laminectomy or laminaplasty may be performed. Occasionally, patients with severe, multiple level stenosis and instability will require both front (anterior) and back (posterior) of the neck surgery to adequately decompress and stabilize the spine. Generally, a cervical spinal fusion will always be required and recommended in addition to the decompression component. Spinal instrumentation will typically be utilized to impart immediate stability and increase the fusion (bone healing and mending together) rate. There is a higher rate of improvement for rheumatoid patients with cervical instability and/or neurologic dysfunction treated surgically than those treated nonsurgically. However, careful preoperative evaluation and delicate perioperative and postoperative management is particularly important to ensure success and avoid complications.
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