Prevalence of C1/C2 involvement in Czech rheumatoid arthritis patients, correlation of pain intensity, and distance of ventral subluxation. 
The aim of this study was to determine the prevalence of C1/C2 involvement in rheumatoid arthritis (RA) in Czech patients and to identify typical pain symptoms and their relationship to radiologic findings at the C1/C2 level.  Four hundred patients with RA were selected randomly and examined by plain X-ray.  Cervical spine involvement was found in 45.8% of these patients.  Cervicocranial syndrome was the most common symptom of any spine involvement at the C1/C2 level and was present in 54.6%.  Cervicocranial syndrome was typical for ventral subluxation 3-6 mm and was found in 52.9%.  The distance of 8 mm or more was associated with mild pain.  The pain intensity at the C1/C2 level decreased with increasing distance of ventral atlantoaxial subluxation (P < 0.0001).