Stability of the upper neck during isometric neck exercises in rheumatoid arthritis patients with atlantoaxial disorders

Objective: To study the effect of isometric neck strength exercises on upper cervical stability in patients with rheumatoid arthritis (RA). Methods: Twenty patients with a mean (SD) age of 58 (9) years and duration of RA of 27 (10) years volunteered for the study. Lateral radiographs of the cervical spine were taken to measure the current atlantoaxial distance (AAD) in flexion and extension. Maximal isometric neck flexion and extension strength values were measured by a dynamometer. Thereafter, AADs were measured from radiographs taken at 80-90% resistance of maximal strength. Results: According to the full flexion radiographs at baseline, the patients were classified into three groups: eight patients without anterior atlantoaxial subluxation (aAAS) [AAD=2.1 (2-3) mm], seven with unstable aAAS [AAD=6.6 (5-8) mm], and five with stable aAAS [AAD=5.5 (5-7) mm]. During resisted flexion the AAD decreased by 5 (3-7) mm (p < 0.001) in the unstable aAAS group, while in the other two groups the changes were minor. During resisted extension the AAD increased by 3 (2-6) mm (p < 0.001) in the cases with unstable aAAS only. Conclusion: Isometric exercising towards flexion decreases the AAD in cases with unstable aAAS. Submaximal loading of the neck extensors by pushing the back of the head against the resistance even in the neutral position of the cervical spine leads to a decrease in the width of the cervical spine canal and is not recommended in unstable aAAS.