Preliminary comparison of radiolucent cages containing either autogenous cancellous bone or hydroxyapatite graft in multilevel cervical fusion.

We compared the preliminary outcomes of cervical fusion performed using radiolucent cages containing either cancellous bone or hydroxyapatite graft. From July 2004 to June 2006, 45 consecutive patients presented with a total of 109 levels of degenerative disc disease between the C2 and C7 levels. Each patient underwent anterior cervical discectomy and fusion (ACDF) for each affected cervical disc. The retrospective analysis of the cage fillers was divided into group 1 (23 patients with 56 affected cervical levels) who received cages packed with cancellous bone marrow, and group 2 (22 patients with 53 affected cervical levels) who received cages packed with hydroxyapatite graft. Bone marrow was harvested from the anterior iliac crest. The Prolo scale was used to assess both the economic and functional status postoperatively. The Yates' correction to test independence in a contingency was used to compare the fusion rate of both groups post-operatively at day 1 and at 1, 3 and 6 month follow-up. At a mean follow-up of 12 months, the fusion rates observed in groups 1 and 2, respectively, were 21.4% and 13.2% after 1 month, 76.8% and 64.2% after 3 months, and 98.2% and 96.2% after 6 months. Functional and economic status were better in group 2, with a statistical significance (p<0.05) observed at the 3-month follow-up. Although hydroxyapatite graft is an osteoconductive, rather than osteoinductive, material, when used as a cage filler it is a safe and efficient substitute for cancellous bone.