Atlantoaxial instability in a patient with neck pain and rheumatoid arthritis.

The purpose of this report is to describe the clinical decision-making process for a patient with rheumatoid arthritis with neck pain with underlying atlantoaxial instability. The patient was evaluated for worsening upper neck pain that began insidiously 1 year prior. The patient denied numbness or tingling in her upper or lower extremities, dizziness or lightheadedness, difficulty maintaining balance with walking, or muscle weakness. Cervical spine range of motion was limited in all planes due to pain and apprehension. The patient's neurological examination was unremarkable. Prior flexion and extension radiographs of the cervical spine were interpreted as unremarkable with alignment preserved in flexion and extension. However, upon further inspection, the cervical spine flexion radiograph was concerning for inadequate cervical motion, which may have limited the diagnostic utility of these radiographs. Additionally, a Sharp-Purser test was performed, which was positive for excessive motion. Flexion and extension radiographs of the cervical spine were then repeated ensuring the patient adequately flexed and extended during the imaging. Severe anterior subluxation of C1 relative to C2 with cervical flexion was noted, as C1 moved as much as 8-9 mm anterior to C2 with cervical flexion. Given the degree of atlantoaxial instability, the patient subsequently underwent successful posterior fusion from the occiput to C2. This case report demonstrates the importance of properly screening for upper cervical spine instability in patients with rheumatoid arthritis and neck pain and understanding the importance of obtaining adequate and appropriate diagnostic imaging.