Distal Junctional Disease after Occipitothoracic Fusion for Rheumatoid Cervical Disorders: Correlation with Cervical Spine Sagittal Alignment.

Study Design Retrospective radiographic study. Objective We have performed occipitothoracic (OT) fusion for severe rheumatoid cervical disorders since 1991. In our previous study, we reported that the distal junctional disease occurred in patients with fusion of O-T4 or longer due to increased mechanical stress. The present study further evaluated the association between the distal junctional disease and the cervical spine sagittal alignment. Methods Among 60 consecutive OT fusion cases between 1991 and 2010, 24 patients who underwent O-T5 fusion were enrolled in this study. The patients were grouped based on whether they developed postoperative distal junctional disease (group F) or not (group N). We measured pre- and postoperative O-C2, C2-C7, and O-C7 angles and evaluated the association between these values and the occurrence of distal junctional disease. Results Seven (29%) of 24 patients developed adjacent-level vertebral fractures as distal junctional disease. In group F, the mean pre- and postoperative O-C2, C2-C7, and O-C7 angles were 12.1 and 16.8, 7.2 and 11.2, and 19.4 and 27.9 degrees, respectively. In group N, the mean pre- and postoperative O-C2, C2-C7, and O-C7 angles were 15.9 and 15.0, 4.9 and 5.8, and 21.0 and 20.9 degrees, respectively. There were no significant differences between the two groups. The difference in the O-C7 angle (postoperative angle - preoperative angle) in group F was significantly larger than that in group N (p = 0.04). Conclusion Excessive correction of the O-C7 angle (hyperlordotic alignment) is likely to cause postoperative distal junctional disease following the OT fusion.