Intertransverse Lumbar Fusion Using Calcium Sulfate as a Bone Graft Substitute in Rabbits

Ha, Kee Yong; Han, Chang Whan; Ryoo, Seung Joon

Abstract

STUDY DESIGN: Intertransverse lumbar fusion segments were evaluated in rabbits at 4, 8, 12, and 16 weeks after surgery. The calcium sulfate was used as a bone graft substitute and its fusion rate compared with the fusion rate of autogenous bone graft.
OBJECTIVE
To investigate the efficacy of calcium sulfate as a bone graft substitute in achieving intertransverse fusion in rabbits. SUMMARY OF BACKGROUND: Calcium sulfate is a bone graft substitute made from medical grade calcium sulfate hemihydrate. Preclinical testing and clinical case studies demonstrate the excellent bone healing response and biocompatibility in long bone defect.
MATERIALS AND METHODS
Forty adult New Zealand white rabbits were included in our study. In group I, the 0.8g of the calcium sulfate was grafted on the left inter transverse of L4-5 or L5-6 and the 0.8g of the autogenous iliac bone on the right side at the same level. In group II, the 0.4g of the calcium sulfate mixed with 0.4g of the autogenous graft on the left intertransverse of L4-5 or L5-6 and 0.8g of the autogenous iliac bone on the right side at the same level was grafted. At postoperative 4, 8, 12, 16 weeks, the plain roentgenogram was checked to evaluate the bony union. At 16 weeks, all rabbits were sacrificed and the histologic evidences of the bony union using H&E and trichrome stain were investigated. The molecular-biological study to detect the RNA of TNF-alpha was investigated in nonunion.
RESULTS
Bone graft using calcium sulfate resulted in nonunion radiologically and histologically in all rabbits. 92.5% of calcium sulfate in group I and 80.0% in group II was resorbed within postoperative 12 weeks. There was statistical significance between group I and group II. In contrast, graft using autogenous cancellous bone showed complete bony union in 11 out of 20 rabbits. With molecular-biological study using PCR, the RNA of TNF-alpha was not detected from bony union site, but detected from nonunion site.
CONCLUSION
The results of this study indicate that calcium sulfate is not an effective bone graft substitute for achieving stable intertransverse spinal fusion. TNF-alpha may have direct effects on autogenous graft bone with calcium sulfate resorption