Prevalence and aggravation of cervical spine instabilities in rheumatoid arthritis during over 10 years: a prospective multicenter cohort study

We designed a prospective multicenter cohort study to clarify a long-term, > 10-year prevalence and aggravation of cervical spine instabilities in rheumatoid arthritis (RA). In 2001-2002, 634 outpatients were enrolled, and 233 (36.8%) were followed for > 10 years. Cervical spine instability was defined as atlantoaxial subluxation (AAS, > 3-mm atlantodental interval), vertical subluxation (VS, < 13-mm Ranawat value), and subaxial subluxation (SAS, ≥ 2-mm irreducible vertebral translation). The aggravation was determined as ≥ 2 mm decrease of the Ranawat value in VS, ≥ 2-mm increase of slippage in SAS, and these new developments. The prevalence of VS and SAS increased during both the initial and last > 5 years (all, p ≤ 0.049). While VS aggravation was associated with pre-existing AAS (p = 0.007) and VS (p = 0.002), SAS aggravation correlated with pre-existing VS (p = 0.002). Multivariable analysis found hand mutilating changes (odds ratio [OR] = 4.048, p = 0.008), RA duration ≥ 5 years (OR = 3.711, p = 0.013), C-reactive protein (CRP) level ≥ 3.8 mg/dL (OR = 2.187, p = 0.044), and previous joint surgery (OR = 2.147, p = 0.021) as predictors for VS aggravation. Pre-existing VS (OR = 2.252, p = 0.024) and CRP ≥ 1.0 mg/dL (OR = 2.139, p = 0.013) were disclosed as predictors for SAS aggravation. Low disease activity and clinical remission before the development of VS and advanced peripheral joint destruction are essential to prevent progressive cervical spine instability in RA.