Two-year fusion rate equivalency between Grafton® DBM gel and autograft in posterolateral spine fusion

Study Design. Multicenter, prospective equivalency trial with each patient serving as his/her own control. Objectives. To compare the effectiveness of a Grafton(R) DBM gel composite with iliac crest autograft in posterolateral spine fusion. Summary of Background Data. While autograft remains the preferred graft material to facilitate spine fusion, the supply is limited and harvesting produces undesirable clinical consequences. Methods. A total of 120 patients underwent posterolateral spine fusion with pedicle screw fixation and bone grafting. Iliac crest autograft was implanted on one side of the spine and a Grafton(R) DBM/autograft composite was implanted on the contralateral side in the same patient. An independent, blinded reviewer evaluated anteroposterior and lateral flexion-extension radiographs. The fusion mass lateral to the instrumentation on each side was judged fused or not, and the mineralization of the graft was rated absent, mild, moderate, or extensive. The degree of correspondence in outcomes between sides was estimated by computing the percentage agreement and kappa statistic. Results. Nearly 70% of patients ( 81 of 120) provided complete 24-month radiographic studies. The bone graft mass was fused in 42 cases (52%) on the Grafton(R) DBM side and in 44 cases ( 54%) on the autograft side. The overall percentage agreement for fusion status between sides was approximately 75% ( 61 of 81), indicating moderately strong statistical correspondence ( kappa = 0.51, P < 0.0001). Bone mineralization ratings also were similar between treated sides. Perfect agreement was realized in almost 60% of patients ( 48 of 81) with moderate statistical correspondence ( weighted kappa = 0.54, P < 0.0001). Conclusions. Grafton(R) DBM can extend a smaller quantity of autograft than is normally required to achieve a solid spinal arthrodesis. Consequently, a reduced amount of harvested autograft may be required, potentially diminishing the risk and severity of donor site complications.