Given the number of synovial joints present within the axial skeleton, it is easy to understand why systemic inflammatory arthritis can inflict devastating problems upon the spine, with cervical and lumbar spine being most affected. The two major types of inflammatory arthritis affecting the spine are rheumatoid arthritis and ankylosing spondylitis. Rheumatoid arthritis seems to affect the cervical spine more often with ankylosing spondylitis affecting the entire axial skeleton.

Rheumatoid arthritis affects the joints of the axial skeleton in a manner similar to the effect on the larger synovial joints of the body. It is characterized usually by insidious onset producing symptoms as a result of the synovial destruction of the joints, ligaments, and bones. As in other areas of the skeleton, when joint destruction occurs, subluxation can result. The major area of involvement is the atlantoaxial segment. Destruction of this joint often will develop within the first few years of onset of the disease. Patients describe pain and in up to 80 per cent of the cases, there is destruction of the transverse ligament, allowing subluxation of the atlas upon the axis. Subluxation can result in neurological disturbance in up to 34 per cent of the patients if displacement of greater than 3.5 mm is present. Symptoms include myelopathy and radiculopathy but there can also be compression of the vertebral artery. Radiographic evaluation may reveal three types of subluxation. Displacement may occur in an anterior or posterior direction or in a vertical direction with a shift of the skull downward in relation to the atlas. In this type of subluxation, the odontoid is noted to protrude into the foramen magnum.

Patients who are asymptomatic but who are noted to have a C1 - 2 subluxation on radiography require observation with follow-up radiographs every 6 months. These patients also need an explanation as to the possible progressive nature of the disease.

Indications for surgical treatment in patients with rheumatoid arthritis of the upper cervical spine include pain, neurological abnormalities, or impending neurological deficit. If the subluxation is greater than 8 mm or spinal cord or root compression is revealed by radiography, serious consideration should be given for surgical stabilization. Patients are usually placed in preoperative halo traction. The most common procedure is a Brooks fusion, stabilizing the atlas to C2. If neurological compromise involves the brain-stem, decompression of the foramen magnum may be required and extension of the fusion from the occiput to the second cervical vertebra may be necessary. Wire is usually recommended for initial stabilization. Occiput to C2 fusion may require contoured rod or plate and possible reinforcement with methyl methacrylate. In all cases, however, arthrodesis should be attempted using autogenous bone graft. If the majority of the compression appears anteriorly, as a result of spur formation about the odontoid and if reduction is not possible, a transoral decompression of the odontoid may be necessary followed by a posterior stabilization. Complications of surgical treatment for rheumatoid arthritis are high and include death, infection, non-union, and instability below the fusion.

The area of the cervical spine below C2 may also be involved in rheumatoid arthritis and the neurocentral joints of Luschka in addition to the posterior facets may also be affected. Up to 60 per cent of the patients with rheumatoid arthritis have persistent neck pain and radiographic studies will show subaxial involvement. Clinical manifestations include pain and stiffness in addition to possible compression of nerve roots and compression of the spinal cord as a result of subluxation. Treatment of subaxial subluxation depends upon the symptoms and the degree of subluxation. Most patients can be treated with observation and anti-inflammatory medication; surgical stabilization should be considered if subluxation is greater than 4 mm or if pain and/or neurological compromise becomes disabling. Treatment is with interspinous process wiring and posterior fusion with decompression of cord and nerve roots as indicated.

Ankylosing spondylitis is a chronic inflammatory disease characterized by involvement of joints of the spine, sacroiliac joint, and less frequently synovial joints of the appendicular skeleton. Incidence is 1 in 3000 subjects with young men showing the greatest risk. Ninety-five per cent of patients have the HLA-B27 antigen. Onset of symptoms is usually in the third decade. Patients often present with pain localized to several areas of low back or hip. Onset of pain is usually insidious, often with pain or stiffness being most severe on rising and then clearing but developing once again in the late afternoon or evening. Physical examination shows restriction of spinal mobility and there is also a limitation of chest expansion of less than 5 cm due to involvement of the costovertebral joints. Radiography shows a squaring of the vertebral bodies, as a result of the inflammatory reaction, with loss of the usual concavity. As gradual calcification of the prevertebral space occurs bridging of the disc space ensues, leading to the radiographic appearance of a bamboo spine.

Treatment of ankylosing spondylitis usually involves the use of non-steroidal anti-inflammatory medication in addition to a well integrated programme of rest and exercise in an attempt to maintain mobility and prevent deformity. Patients may often become ankylosed in the flexed position with a typical chin-on-chest position or have severe kyphosis with a secondary loss of lumbar lordosis. Such a deformity will not only produce pain but will also prevent patients from being able to see directly to the front. The deformity may become so disabling that it may be necessary to consider osteotomy of the spine. In the majority of deformities in the thoracic or lumbar spine, osteotomy is usually carried out at L2 - 3 level using a posterior approach and closing wedge osteotomy. Reduction is then held with wire instrumentation and a hyperextension cast is applied. If the major deformity is in the cervical spine with a chin-on-chest deformity, osteotomy posteriorly through the C7 T1 level can be carried out. This procedure may be carried out under local anaesthetic in an attempt to monitor the patient's neurological function. By using spinal cord monitoring, it is now possible to perform this procedure under general anaesthesia. Patients are immobilized in a halo vest.

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