Vertical subluxation of the axis in rheumatoid arthritis.

Involvement of the upper cervical spine in rheumatoid arthritis is now well documented and recognized as a common feature of the disease. Forward subluxation of the atlas on the axis on flexion of the neck is one of the most frequent and characteristic findings, occurring in 25 per cent. of a series of patients reported by Conlon, Isdale, and Rose (1966) and confirmed by Mathews (1969) in a tomographic study. Backward displacement of the atlas on the axis has been described in two cases of severe rheumatoid arthritis by Isdale and Corrigan (1970) and in one patient by Crellin, Maccabe, and Hamilton (1970). Minor degrees of vertical subluxation of the axis have been found in radiological studies by several authors including, Sharp and Purser (1961), Bland, Davis, London, Van Buskirk, Duarte, and Burlington (1963), and Martel (1961). Mathews (1969) found that the odontoid peg protruded above the level of the foramen magnum in 5 per cent. of his 76 cases. The particular danger of this lesion was emphasized by Ball and Sharp (1971) and compression of the brainstem and cord by a vertically subluxed odontoid peg was considered to be the main cause of death in the cases reported by David and Markley (1951), Storey (1958), and Martel and Abell (1963), although in the case reported by Webb, Hickman, and Brew (1968) death was due to massive thrombosis of the distorted vertebral arteries. Rana and Taylor (1971) described a case of vertical migration of the odontoid process associated with acute cord compression, which was relieved by skull traction and posterior occipito-atlanto-axial fusion. Another non-fatal case reported by Newman and Sweetman (1969) showed subjective improvement after occipito-cervical fusion. In general, the outlook for these patients, asjudged by these case reports, is poor. Two patients are therefore reported below who, despite alarming radiological signs, have survived with conservative care. A third patient who has improved after occipital decompression is also described.