Table 1 CT-based Classification of Spinal Fusion

Grade I

Complete fusion

Cortical union of the allograft at bone cranial and caudal ends and continuity of trabecular pattern between the autograft within the medullary canal of the allograft and the adjacent cranial and caudal vertebral bodies

Grade II

Partial fusion

Cortical union of the allograft to the endplates at each end however with partial or absent trabecular continuity between the medullary autograft and the adjacent vertebral body bone at one or either end.

Grade III

Unipolar pseudarthrosis

Cranial or caudal cortical nonunion of the allograft with associated central trabecular discontinuity

Grade IV

Bipolar pseudarthrosis

Both superior and inferior cortical nonunion with a complete lack of central trabecular continuity