Bioactive glass can potentially reinforce large bone defects

Introduction: Bioactive glass (BAG) has been studied widely and seems to be a very promising biomaterial in regeneration of large bone defects and osteomyelitis treatment, because of its bone bonding and antibacterial properties[1]-[5]. Potentially, it could also mechanically reinforce large defects, thus making it suitable for load-bearing applications. However, the mechanical properties of the reconstructive layer and its dependence on BAG:bone allograft mixture composition are unknown.
In this study, we measured the mechanical properties of different impacted BAG/bone graft mixtures. Then these properties were used in micro-Finite Element (FE) patient-specific models to investigate whether these mixtures could restore mechanical properties of large bone defects.
Materials and Methods: Five different S53P4 BAG/bone graft mixtures were impacted in a cylindrical holder, mechanically tested in confined compression and scanned with micro-CT. From these images, the mixture was identified by its three phases: bone, glass or interface region. Micro-Finite-Element (FE) models of the composites were made using a Young’s modulus of 2.5 GPa for bone and 35 GPa for BAG. The Young’s modulus for the interface region was determined by fitting experimental and micro-FE results for the same specimens.
High-Resolution peripheral quantitative CT scans of a 9 mm region of the distal tibia of seven subjects were used for studying the reinforcement potential. Micro-FE models of this region were made to determine its stiffness in the original state, with a simulated cortical defect, and after that a mixture of BAG/bone or BAG alone was simulated in the defect.
Results: The confined compression tests showed a strong dependence of the Young’s modulus of the BAG/bone composite on the amount of BAG, ranging from 116.7±18.2 to 654.2±35.2 MPa. The micro-FE results could fairly reproduce these measured moduli, when using a stiffness of 25 MPa for the interface layer (R2=0.678, see Figure 1).