We evaluated the maturation of grafted bone in cases of successful fusion after a one- or two-level posterior lumbar interbody fusion (PLIF) using interbody carbon cages. We carried out a five-year prospective longitudinal radiological evaluation of patients using plain radiographs and CT scans. One year after surgery, 117 patients with an early successful fusion were selected for inclusion in the study. Radiological evaluation of interbody bone fusion was graded on a 4-point scale. The mean grades of all radiological and CT assessments increased in the five years after surgery, and differences compared to the previous time interval were statistically significant for three or four years after surgery. Because the grafted bone continues to mature for three years after surgery, the success of a fusion should not be assessed until at least three years have elapsed. There were no significant differences in the longitudinal patterns of grafted bone maturity between iliac bone and local bone. However, iliac bone grafting may remodel faster than local bone.
No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.
Supplementary material. Tables showing i) the grading system of interbody bone fusion sites of radiographs and CT scans, ii) the kappa values for inter- and intra-observer agreement for each radiological assessment, and iii) the proportion of grading of levels in the remodelling status of the grafted bone to the trabecular bone on CT scans are available with the electronic version of this article on our website www.jbjs.org.uk