Reconstruction of Bone Defect with a Novel Injectable Bio-Cement Bone Substitute-Mechanical Study and Histological Research

Various synthetic materials for bone substitute have been tested with unreliable clinical application. A bone graft substitute, calcium phosphate bio-glass with titanium ions was developed. Reagent grade of hydro-phosphate acid, tri-calcium phosphate (TCP) and titanium oxide (TiO2) were prepared to be TiO2-calcium phosphate bioglass (TCPG). The ready TCPG and calcium sulfate (CS) were mixed to form an injectable form and then solidified to be a bio-cement bone substitute (TCPG-CS). Immersion test, differential thermal analysis, X-ray defraction, scanning electronic microscopy, and compressive loading test were examined to determine physical and mechanical properties. In vivo study, adult New Zealand white rabbits were used for evaluation of bone healing process. At 4 weeks, osteoblasts appeared adjacent to the osteoclasts indicating initiation of bone ingrowth. At 8 weeks, the filling material showed evidence of vascular invasion associated with resorption and new-bone formation. At 12 weeks, the calcium sulfate in the bone defect revealed complete resorption with replacement of trabecular bone ingrowths. TCPG could be identified within the new-formed trabecular bone. This TCPG-CS bio-cement has the injectable property that made it possible to fill bone gap easily and efficiently and could provide instant mechanical support. The biodegrading rate could be reduced with the adding of TCPG. Addition of TiO2 can achieve good biocompatibility and form strong bioglass structure, and induce microelectronic current to promote bone healing.