Comparison of Fusion Rates between Autologous Iliac Bone Graft and Calcium Sulfate with Laminectomy Bone Chips in Multilevel Posterolateral Spine Fusion

Multilevel lumbar fusion usually requires a large quantity of iliac crest bone graft but the supply is usually insufficient, so an alternative bone graft substitute for autograft is needed. This prospective study investigated the efficacy of calcium sulfate by comparing the fusion rates between the experimental material (calcium sulfate pellets with bone chips from laminectomy) and autologous iliac bone graft in long segment (three-or four-level) lumbar and lumbosacral posterolateral fusion. Forty-five patients with degenerative scoliosis or spondylolisthesis received multilevel spine fusion and decompression. The experimental material of calcium sulfate pellets with decompression bone chips was placed on the experimental side and the iliac crest bone graft was placed on the control side. The fusion status was assessed radiographically at three-month intervals, and solid fusion was defined as a clear continuous intertransverse bony bridge at all levels. The average follow-up period was 34.4 months. Twenty-nine (64.4%) patients showed solid fusion on the experimental side and 39 (86.7%) patients on the control side. The overall fusion rate was 86.7%. A statistically significant relation was found between the two sides with the Kappa coefficient of agreement of 0.436. Compared to the control side, the fusion rate of experimental side is significantly reduced (p = 0.014). The fusion ability of autograft is higher than the experimental material in multilevel lumbar posterolateral fusion. However, the overall fusion rate of calcium sulfate pellets is improved, compared with previously reported rates, which suggested that such material may be considered as an acceptable bone graft extender.