Cranioventral Subluxation of the Odontoid Process With Accompanying Neo(pseudo)arthrosis in Rheumatoid Arthritis

Cervical spine involvement is a common feature in the course of long existing rheumatoid arthritis (RA).We describe a rare type of vertical subluxation with pronounced cranioventral disposition of the odontoid process and neo(pseudo)arthrosis between the skull and the tip of the odontoid processus. This 74-year-old women with RA for 40 years had progressive neck symptoms over the previous 5 years. She no longer had signs of active synovitis. Plain roentgenographs performed in a neutral position and full flexion and extension gave information about neither the osseous integrity nor the subluxation of the dens axis. Computed tomography and MR imaging techniques established the nature of the atlantoaxial and atlantooccipital joint involvement. During 2 years, this rare cranio-ventral subluxation with neo(pseudo)arthrosis seems to be rather solid, and follow up CT-images demonstrate no signs of progressive migration or suggestion of immediate fracture risk. Pronounced reduction of cervical spine mobility by long standing destructive cases of RA should always raise suspicions for cervical subluxation at the atlantoaxial level, irrespective of serological and clinical signs of rheumatoid arthritis. Vertical subluxation as seen in this patient may be missed on routine x-rays.