Progression of Cervical Spine Instabilities in Rheumatoid Arthritis

A Prospective Cohort Study of Outpatients Over 5 Years

Takashi Yurube, MD; Masatoshi Sumi, MD; Kotaro Nishida, MD; Masato Takabatake, MD; Kozo Kohyama, MD; Tsukasa Matsubar a, MD; Takuma Ozaki, MD; Koichi ro Maeno, MD; Kenichiro Kakutani, MD; Zhongying Zhang, MD; Minoru Doita, MD

Disclosures

Spine. 2011;36(8):647-653. 

In This Article

Abstract and Introduction

Abstract

Study Design. 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.
Summary of Background Data. 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).
Conclusion. 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.

Introduction

heumatoid arthritis (RA) is a common inflammatory disease, with an estimated prevalence of 1% to 2% of the adult population in the world.[1] Every joint in the whole body is possibly affected by RA erosive synovitis, and the cervical spine is known to be a popular focus of destruction.[2] Rheumatoid involvement of the cervical spine often develops some characteristic instabilities; atlantoaxial subluxation (AAS)[3–7] and vertical subluxation (VS)[8,9] of the axis in the upper cervical spine, and subaxial subluxation (SAS)[10] in the lower cervical spine. Since these cervical instabilities may result in neural impairment through their developments, it is much important to understand the natural history and predictive factors for the aggravation.

Several studies have been reported to investigate the natural progression of RA cervical involvement, however, few papers have fully described its predictive factors. Furthermore, many of them have been studied retrospectively except for only a few prospective studies,[5–7,11–16] with some problems left in the study designs. Several papers focused only the course of AAS,[5–7] the study material was limited to patients with cervical complaints[11] or included "possible" or "probable" RA patients,[12,13] the number of materials was limited to small sizes of population,[6,7,14,15] or the range of follow-up periods was considerably wide.[16] Therefore, we prospectively investigated the incidences of cervical spine instabilities and their aggravations in a multicenter cohort study with a larger population of "definite" or "classical" RA outpatients and with a rigidly fixed follow-up period. The objectives of this study were to clarify the natural course of cervical instabilities in RA patients and to determine radiological predictive factors for the prognosis of RA cervical spine.

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