Study design: A prospective minimum 5-year follow-up study of the cervical spine in patients with rheumatoid arthritis (RA) initially without cervical involvement.
Objective: To clarify the incidence and aggravation of cervical spine instabilities and their predictive risk factors in patients with RA.
Summary of background data: Many reports have shown the progression of cervical spine involvement in RA. However, few articles have described comprehensive evaluation of its prognostic factors.
Methods: A total of 140 patients with "definite" or "classical" RA initially without cervical involvement were prospectively followed for more than 5 years. Radiographical cervical findings were classified into 3 instabilities: atlantoaxial subluxation (AAS: atlantodental interval >3 mm), vertical subluxation (VS: Ranawat value <13 mm), and subaxial subluxation (SAS: irreducible translation ≥ 2 mm). "Severe" extents were defined as AAS with atlantodental interval 10 mm or more, VS with Ranawat value 10 mm or less, and SAS with translation 4 mm or more or at multiple levels. Incidence of these developments and predictors for "severe" instabilities were investigated.
Results: During 6.0 ± 0.5 years, 43.6% of 140 patients developed cervical instabilities: AAS in 32.1%, VS in 11.4%, and SAS in 16.4% with some combinations. "Severe" instabilities were exhibited in 12.9% of patients: AAS in 3.6%, VS in 6.4%, and SAS in 5.0%. Furthermore, 4.3% presented canal stenosis, with 13 mm or less space available for the spinal cord (SAC) due to "severe" AAS or "severe" VS in 2.9% and 12 mm or less SAC due to "severe" SAS in 2.1%. Multivariable logistic regression analysis identified corticosteroid administration, mutilating changes at baseline, and the development of nonmutilating into mutilating changes during the follow-up period correlated with "severe" instabilities (P < 0.05).
Conclusion: A minimum 5-year follow-up reveals the occurrence of cervical instabilities in 43.6%, "severe" aggravation in 12.9%, and decreased SAC in 4.3% of patients with RA. Characteristics of severe disease activity-established mutilating changes, progressive development into mutilating changes, and potentially concomitant corticosteroid treatment-are indicators for poor prognosis of the cervical spine in RA.