title: Accelerated development of cervical spine instabilities in rheumatoid arthritis: a prospective minimum 5-year cohort study.
abstract: OBJECTIVE
  To clarify the incidence and predictive risk factors of cervical spine instabilities which may induce compression myelopathy in patients with rheumatoid arthritis (RA).
  
  
  METHODS
  Three 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.
  
  
  RESULTS
  Patients 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).
  
  
  CONCLUSIONS
  This 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.
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Chuo-ku, Kobe, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Yurube
authors.affiliation: Department of Orthopaedic Surgery, Kobe Rosai Hospital, Chuo-ku, Kobe, Japan.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Sumi
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Chuo-ku, Kobe, Japan.
authors.forename: Kotaro
authors.initials: K
authors.lastname: Nishida
authors.affiliation: Department of Orthopaedic Surgery, Kobe Medical Center, Suma-ku, Kobe, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Miyamoto
authors.affiliation: Department of Orthopaedic Surgery, Kohnan Kakogawa Hospital, Kanno-cho, Kakogawa, Japan.
authors.forename: Kozo
authors.initials: K
authors.lastname: Kohyama
authors.affiliation: Department of Orthopaedic Surgery, Matsubara Mayflower Hospital, Fujita, Kato, Japan.
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Matsubara
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Chuo-ku, Kobe, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Miura
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Chuo-ku, Kobe, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Hirata
authors.affiliation: Department of Evidence-Based Laboratory Medicine, Kobe University Graduate School of Medicine, Chuo-ku, Kobe, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Sugiyama
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Chuo-ku, Kobe, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Doita
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000150:complications*; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D007593:Joint Instability / Q000145:classification / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000209:etiology*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011859:Radiography