Objective: To compare neck muscle strength and mobility of the cervical spine in rheumatoid arthritis (RA) patients with and without atlantoaxial (AA) disorders (anterior atlantoaxial subluxation [AAS], AA impaction).
Design: Clinical cross-sectional study.
Setting: Outpatient rheumatology and rehabilitation clinics in a Finnish hospital.
Participants: Patients with RA (N=124; mean age +/- standard deviation, 62+/-12y [corrected]) on a waiting list for orthopedic surgery. Thirty (24%) patients presented with AA disorders (16 with anterior AAS, 8 with AA impaction, 6 with a combination of anterior AAS and AA impaction).
Interventions: Not applicable.
Main outcome measures: Neck function was measured by isometric neck strength and mobility tests, neck pain by a visual analog scale, erosion of the hands and feet by radiography, and the patients' function by the Health Assessment Questionnaire (HAQ).
Results: Maximal neck muscle strength against flexion, extension, and rotation was lower in patients with AA disorders compared with the other patients in both women (P=.012) and men (P=.017). Mobility was lowest in the AA impaction group in all measured directions (P<.001). Peripheral erosive disease was more frequent in the group with AA disorders. They also had longer disease duration and were more disabled (HAQ) than the other patients.
Conclusions: Neck muscle strength is significantly decreased in patients with AA disorders. Mobility of the cervical spine is most limited in patients with AA impaction, but can be normal in cases with solitary anterior AAS.