Relation between atlantoaxial (C1/2) and cervical alignment (C2-C7) angles with Magerl and Brooks techniques for atlantoaxial subluxation in rheumatoid arthritis

Abstract

Background: A few studies have reported the relation between the atlantoaxial (C1/2) angle and cervical alignment (C2-C7) angle after a Magerl and Brooks (M&B) surgical procedure to treat atlantoaxial subluxation (AAS) in patients with rheumatoid arthritis (RA). However, no study has examined an optimum preoperative C1/2 angle reduction. We aimed to assess the relation between the C1/2 angle reduction and the C2-C7 angle change in patients with progressive RA who underwent the M&B procedure.

Methods: We retrospectively analyzed the relation between the preoperative C1/2 angle and C2-C7 angle in 28 consecutive RA patients using their clinical and radiological data. Differences in the preoperative and postoperative C1/2 and C2-C7 angles were detected. Correlations of these angles and the reduced degree of angles were examined. The Ranawat grading scale and Japanese Orthopaedic Association (JOA) scores were used to determine myelopathy. Pain was categorized into five categories according to severity. Clinical and X-ray evaluations were collected before surgery, at 3 and/or 6 months after surgery, and at final follow-up.

Results: Clinical symptoms, Ranawat grade, and JOA scores improved postoperatively, and patients achieved bony union within 3 months. We observed a strong and significant correlation between the reduced C1/2 angle and the change in the C2-C7 angle. Patients with a preoperative C1/2 angle of <20 degrees had markedly reduced cervical lordotic angle but this condition was not seen in patients with a preoperative C1/2 angle of >or=20 degrees . The optimum C1/2 angle was estimated as [20 degrees - (preoperative C1/2 angle)] in patients with a C1/2 angle <20 degrees or as an in situ angle in patients with a C1/2 angle of >or=20 degrees .

Conclusions: Surgeons performing the M&B procedure need to select patients carefully and avoid complete or overreduction of the C1/2 angle to prevent serious postoperative SAS and myelopathy.