Radiographic Assessment of Cervical Fusion

Radiographs, including the anteroposterior, lateral plain, and flexion-extension radiographs, were collected before surgery, on the first day after surgery, and at each follow-up. The measured parameters included C2-C7 lordosis, segmental angle, and subsidence. The C2-C7 lordosis, also called cervical lordosis, was measured by using the Cobb angle between the lower endplates of C2 and C7. The segmental angle was only limited to fusion levels. Therefore, the measurement approach for this parameter was to use the Cobb angle between the upper endplate of the cephalad and the lower endplate of the caudal vertebrae (2 (link)). The subsidence was defined as a change of operative segmental height at the latest follow-up compared with the immediate postoperative height (11 (link)). The segmental height was defined as the distance between the midpoint of the superior border of the cephalad-affected vertebral body and the midpoint of the inferior border of the caudal-affected vertebral body. The angle of motion (ROM) ≤4° and translation ≤1.25 mm in the affected levels on flexion-extension images were considered a successful fusion (16 (link)).