Extract
To The Editor:We read with great interest the article "Magnetic Resonance Imaging
of the Cervical Spine. Current Techniques and Spectrum of Disease"
(2002;84[Suppl 2]:S70-S80), by Khanna et al. As unstable anterior atlantoaxial
subluxation is often detected in patients with rheumatoid arthritis and is
usually evaluated with magnetic resonance imaging before operative treatment,
we would like to raise an important point concerning that matter. In our study
of twenty-three patients with rheumatoid arthritis, functional magnetic
resonance imaging often failed to detect the extent of even severely unstable
anterior atlantoaxial subluxation (>9 mm) noted on functional
radiography1. The main reason for this is probably the patient's
supine position during the magnetic resonance imaging procedure, which may
make it difficult to attain an adequate degree of neck flexion to elicit the
full extent of the damage. With radiography, neck flexion is more easily
attained because the patient is sitting during the examination and gravity
pulls the head and atlas apart from the axis (i.e., creates anterior
atlantoaxial subluxation) if the ligaments are injured. One should thus not
rely on magnetic resonance imaging alone; functional radiographs should also
be made to evaluate the magnitude of unstable anterior atlantoaxial
subluxation in patients with rheumatoid arthritis.