Finite element analysis of idealised unit cell cancellous structure based on morphological indices of cancellous bone

Human bones can be categorised into one of two types—the compact cortical and the porous cancellous. Whilst the cortical is a solid structure macroscopically, the structure of cancellous bone is highly complex with plate-like and strut-like structures of various sizes and shapes depending on the anatomical site. Reconstructing the actual structure of cancellous bone for defect filling is highly unfeasible. However, the complex structure can be simplified into an idealised structure with similar properties. In this study, two idealised architectures were developed based on morphological indices of cancellous bone: the tetrakaidecahedral and the prismatic. The two architectures were further subdivided into two types of microstructure, the first consists of struts only and the second consists of a combination of plates and struts. The microstructures were transformed into finite element models and displacement boundary condition was applied to all four idealised cancellous models with periodic boundary conditions. Eight unit cells extracted from the actual cancellous bone obtained from micro-computed tomography were also analysed with the same boundary conditions. Young’s modulus values were calculated and comparison was made between the idealised and real cancellous structures. Results showed that all models with a combination of plates and struts have higher rigidity compared to the one with struts only. Values of Young’s modulus from eight unit cells of cancellous bone varied from 42 to 479 MPa with an average of 234 MPa. The prismatic architecture with plates and rods closely resemble the average stiffness of a unit cell of cancellous bone

Bone tissue stiffness in the mandibular condyle is dependent on the direction and density of the cancellous structure.

Contains fulltext : 57238.pdf (publisher's version ) (Closed access)Variation in the apparent stiffness of cancellous bone is generally ascribed to variation in cancellous structure and density, while the bone tissue stiffness is assumed to be constant. The purpose of the present study was to examine whether the bone tissue stiffness is dependent on the direction and density of the cancellous structure. Bone tissue stiffness was estimated by combining mechanical testing and micro-finite element (micro-FE) modeling on cylindrical bone specimens obtained from the human mandibular condyle. One set of specimens was tested in the vertical direction of the condyle (n = 39) and another set in the transverse direction (n = 30). The cancellous structure of the specimens was characterized by micro-CT. The apparent bone stiffnesses predicted by the FE model correlated strongly (r2 = 0.91) with the measured apparent bone stiffnesses. Apparent bone stiffness in the transverse direction was considerably smaller than that in the vertical direction. In contrast, the predicted bone tissue stiffness was significantly larger in the transverse direction (E = 13.70 GPa) than in the vertical direction (E = 11.87 GPa). In addition, bone tissue stiffness correlated negatively with the bone volume fraction and directional sensitivity of the bone tissue stiffness increased with a decrease of bone volume fraction. The results suggest that the transversely oriented trabeculae in the mandibular condyle are stiffer and more mineralized than the vertically oriented trabeculae and that bone loss is compensated by an increase in the degree of mineralization