title: Progression of cervical spine instabilities in rheumatoid arthritis: a prospective cohort study of outpatients over 5 years.
abstract: METHODS
  A 5-year prospective cohort study of cervical spine instabilities in rheumatoid arthritis (RA). OBJECTIVE.: To clarify the natural course of cervical instabilities in RA patients and to determine predictors for the prognosis of RA cervical spine.
  
  
  BACKGROUND
  Although several previous studies investigating the natural history of RA cervical spine have been reported, few of them have described radiological predictive factors for the aggravation of these instabilities.
  
  
  METHODS
  Two hundred sixty-seven outpatients with "definite" or "classical" RA initially assigned were prospectively followed for over 5 years. Radiographic cervical findings were classified into three representative instabilities: atlantoaxial subluxation (AAS), vertical subluxation (VS), and subaxial subluxation (SAS). The aggravations of these instabilities were identified in the cases with a decrease of at least 2 mm in the Ranawat value of VS, an increase of at least 1 mm in translation of SAS, or a new development of respective instabilities. RA stages and mutilating changes were assessed in the hand radiograms.
  
  
  RESULTS
  Fifty-two point four percent of 267 patients, without any cervical instability at the beginning of follow-up, decreased to 29.6% at the end (P < 0.01), whereas VS and SAS increased significantly (P < 0.01). The aggravation of VS was observed at statistically higher rates in patients with pre-existing instabilities as follows; 25.7% of AAS (P = 0.01), 49.1% of VS (P < 0.01), and 41.2% of SAS (P = 0.06). The aggravation of SAS was also detected in 47.2% of VS and 64.7% of SAS (P < 0.01). Patients with pre-existing mutilating changes exhibited the aggravations of VS and SAS in significantly higher incidences (P < 0.01). Furthermore, the cases with development into mutilating changes during the follow-up showed significantly higher tendencies for the aggravations of these instabilities (P < 0.01).
  
  
  CONCLUSIONS
  The incidences of VS and SAS significantly increased during the minimum 5-year follow-up. Prognostic factors of these instabilities were revealed to be the initial radiological findings of VS, SAS, and mutilating changes.
authors.affiliation: Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Yurube
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Sumi
authors.forename: Kotaro
authors.initials: K
authors.lastname: Nishida
authors.forename: Masato
authors.initials: M
authors.lastname: Takabatake
authors.forename: Kozo
authors.initials: K
authors.lastname: Kohyama
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Matsubara
authors.forename: Takuma
authors.initials: T
authors.lastname: Ozaki
authors.forename: Koichiro
authors.initials: K
authors.lastname: Maeno
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Kakutani
authors.forename: Zhongying
authors.initials: Z
authors.lastname: Zhang
authors.forename: Minoru
authors.initials: M
authors.lastname: Doita
mesh_terms: D001172:Arthritis, Rheumatoid / Q000150:complications / Q000503:physiopathology*; D001268:Atlanto-Axial Joint / Q000503:physiopathology* / Q000528:radiation effects; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000503:physiopathology*; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007593:Joint Instability / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011859:Radiography