Table 2.

Classification of fusion results (Brantigan and Steffee 1991)

	Overall
A	Obvious collapse of construct due to pseudoarthrosis, loss of disc height, vertebral slip, broken screws, displacement of the cage, resorption of bone graft
B	Probable significant resorption of the bone graft due to pseudoarthrosis, major lucency, or gap visible in fusion area (2 mm around the entire periphery of graft)
C	Uncertain non-union, bone graft visible in the fusion area at approximately the density originally achieved at surgery. A small lucency or gap may be visible involving a portion of the fusion area with at least half of the flat area
D	Probable fusion bone bridges entire fusion area with at least the density achieved at surgery. There should be no lucency between the door and vertebral bone. Fusion bone in the fusion area is radiographically more dense and mature than originally achieved by surgery
E	Optimally, there is no interface between the donor and vertebral bone, although a sclerotic line between the graft and vertebral bone indicates fusion. Other signs of the solid fusion include mature bony trabeculae bridging the fusion area, resorption of the anterior traction spur, anterior progression of the graft within disc space, and fusion of facet joints