Abstract
ObjectiveTo clarify the incidence and predictive risk factors of cervical spine instabilities which may induce compression myelopathy in patients with rheumatoid arthritis (RA).MethodsThree types of cervical spine instability were radiographically categorized into “moderate” and “severe” based on atlantoaxial subluxation (AAS: atlantodental interval >3 mm versus ≥10 mm), vertical subluxation (VS: Ranawat value <13 mm versus ≤10 mm), and subaxial subluxation (SAS: irreducible translation ≥2 mm versus ≥4 mm or at multiple). 228 “definite” or “classical” RA patients (140 without instability and 88 with “moderate” instability) were prospectively followed for >5 years. The endpoint incidence of “severe” instabilities and predictors for “severe” instability were determined.ResultsPatients with baseline “moderate” instability, including all sub-groups (AAS+ [VS− SAS−], VS+ [SAS− AAS±], and SAS+ [AAS± VS±]), developed “severe” instabilities more frequently (33.3% with AAS+, 75.0% with VS+, and 42.9% with SAS+) than those initially without instability (12.9%; p<0.003, p<0.003, and p = 0.061, respectively). The incidence of cervical canal stenosis and/or basilar invagination was also higher in patients with initial instability (17.5% with AAS+, 37.5% with VS+, and 14.3% with SAS+) than in those without instability (7.1%; p = 0.028, p<0.003, and p = 0.427, respectively). Multivariable logistic regression analysis identified corticosteroid administration, Steinbrocker stage III or IV at baseline, mutilating changes at baseline, and the development of mutilans during the follow-up period correlated with the progression to “severe” instability (p<0.05).ConclusionsThis prospective cohort study demonstrates accelerated development of cervical spine involvement in RA patients with pre-existing instability—especially VS. Advanced peripheral erosiveness and concomitant corticosteroid treatment are indicators for poor prognosis of the cervical spine in RA.
Highlights
Rheumatoid arthritis (RA) is a chronic inflammatory disease, which affects 0.5–1% of the adult population [1]
Baseline radiographic analysis of the cervical spine identified that 228 patients consisted of 140 without any instability, 57 with atlantoaxial subluxation (AAS)+, 24 with vertical subluxation (VS)+, and 7 with subaxial subluxation (SAS)+
The current analysis further demonstrates that patients with pre-existing VS are highly likely to develop myelopathy and/or brainstem symptoms, which is similar to other studies [8,9,10,17,22,27,28,29,30]
Summary
Rheumatoid arthritis (RA) is a chronic inflammatory disease, which affects 0.5–1% of the adult population [1]. Rheumatoid arthritis often causes three characteristic instabilities in the cervical spine: atlantoaxial subluxation (AAS) [3,4,5,6,7,8,9,10,11], vertical subluxation (VS) of the axis [12,13,14], and subaxial subluxation (SAS) [15]. These subluxations should be noted as one of the most serious pathologies in patients with RA since they can introduce irreversible neural impairment, non-ambulation, respiratory dysfunction, or sudden death [16]. While many studies have investigated the progression of instabilities retrospectively, limited prospective studies have been published [7,8,10,17,18,19,20,21,22]
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