Odontoid erosions in rheumatoid arthritis: utility of the open mouth view.

To determine if odontoid erosions are a marker for more severe cervical spine disease in rheumatoid arthritis (RA), 25 patients with RA were enrolled and had radiographs of the cervical spine including lateral and open mouth odontoid (OMO) views. The presence of odontoid erosions and of anterior atlantoaxial subluxation (AAS) was noted. Lateral cervical spine views were available for 19 patients, 11 of whom demonstrated odontoid erosions. Seven of 22 patients who had OMO views available demonstrated odontoid erosions. In only 3 of the 15 patients could odontoid erosions be seen on both views. Anterior AAS was present in 6 of 25 patients, 5 of whom had odontoid erosions. Anterior AAS was seen more commonly in patients with odontoid erosions. We propose that if erosions are present, patients should be more closely monitored for AAS and neurologic signs. OMO views are not as sensitive but are complementary to lateral cervical spine views in the detection of odontoid erosions.