Grade | Definition | CT imaging (Fig. 4) |
---|---|---|
I—complete fusion | Bone bridging is visible bilaterally on CT scans in the coronal plane, eventually ventrally or dorsally of a cage in the sagittal plane | A, B |
II—incomplete bipolar fusion | Fusion in the area of a cage is presented bilaterally, but it is not completed. Eventually, radiological signs of bone consolidation between the vertebra endplate and the surface of a cage are presented bipolarly | C, D |
III—unipolar fusion | Fusion is presented, but only unilaterally or ventrally or dorsally, not all-around the cage | E, F |
IV—no fusion (non-union) | No signs of fusion in the area of the cage observed | G, H |