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Abstract
The addition of a plasticizer to synthetic bone graft substitutes can improve handling characteristics, injectability, and the ability to uniformly fill defects. Restoration of large medullary bone defects using an injectable calcium sulfate-based putty using hydroxypropylmethylcellose as the plasticizer was compared to conventional calcium sulfate paste in a canine model. Beginning 2 weeks following implantation, serial clinical and specimen radiographs demonstrated a similar progressive resorption of the implanted materials and replacement with new bone for both the putty and paste forms of calcium sulfate. The area fraction of new bone and remaining implant material in bone defects treated with the putty were not significantly different from defects treated with conventional calcium sulfate paste after ? 3 and 26 weeks. In addition to its handling characteristics, the putty was biocompatible and as effective as conventional calcium sulfate paste in achieving substantial bony restoration of a large, critical-size bone defect.
Synthetic bone graft substitute materials are in demand because of their ability to eliminate the morbidity related to harvesting of autogenous bone graft.1 Calcium sulfate has been used extensively as a bone graft substitute since 1892, when Dreesman2 proposed its use. In later years, Peltier3 summarized the usage of calcium sulfate, which acts primarily as a space filler and prevents the ingrowth of soft tissue into defects. Calcium sulfate is osteoconductive, allowing the ingrowth of blood vessels and osteogenic cells. In recent publications, the successful use of a surgical grade of calcium sulfate as a bone graft substitute in research and clinical settings has been discussed.4-7
Surgical-grade calcium sulfate is available in pellet form (OsteoSet pellets, Wright Medical Technology, Ine, Arlington, Tenn) and as kits that can be used to make beads or a paste-like form that can be injected directly into a defect site (OsteoSet Resorbable Bead Kit and Minimally Invasive Injectable Graft, Wright Medical Technology, Ine). In these products, calcium sulfate hemihydrate powder is mixed with water to form a paste-like material that hardens into a calcium sulfate dihydrate solid. The handling properties of the paste or the pellet form, although adequate, are not optimal for some applications. For this reason, calcium sulfate has been made available in the form of putties (AlloMatrix, Wright Medical Technology, Ine), and these contain demineralized bone matrix.