Abstract
The purpose of this study was to elucidate the factors influencing bony fusion rate in atlantoaxial- or occipito-cervical fixations using wires and/or rods in patients with rheumatoid arthritis (RA). Thirty-two RA patients who underwent modified Gallie fixation (n=8) or occipito-cervical fixations using Ransford loop with sublaminal wiring (n=24) were evaluated. Follow-up average duration was 3.8 years. Classes and duration of RA, Ranawat’s score, type of cervical lesion, bony fusion, and X-ray measurements including atlas-dens interval (ADI) and space available for spinal cord (SAC) were retrospectively investigated. Bony fusion was confirmed in 23 cases (72%, fused group) and absent in 9 (28%, non-fused group). When the preoperative measurements between the groups were compared, preoperative ADI in neck flexion was significantly smaller in fused than non-fused group (7.2±3.6, 11.4±2.2mm), respectively. Cut-off value of preoperative ADI in neck flexion for estimated bony fusion was calculated as 9mm. However, even in fused group preoperative SAC in neck extension was larger than postoperative SAC (17.3±3.9, 15.4±3.8), respectively; suggesting that bony fusion had occurred during mild progression of atlantoaxial subluxation. Atlantoaxial- or occipito-cervical fixations without screw reinforcement in patients with rheumatoid arthritis yield satisfactory results when 1) preoperative ADI in neck flexion is equal or less than 9mm, 2) preoperative SAC in neck extension is affordable for another 2mm subluxation, and 3) a postoperative halo-vest fixation is used.
