An Experimental–Numerical Methodology for a Rapid Prototyped Application Combined with Finite Element Models in Vertebral Trabecular Bone

Abstract

In the present study, a novel evaluation method involving rapid prototyped (RP) technology and finite element (FE) analysis was used to study the elastic mechanical characteristics of human vertebral trabecular bone. Three-dimensional (3D) geometries of the RP and FE models were obtained from the central area of vertebral bones of female cadavers, age 70 and 85. RP and FE models were generated from the same high-resolution micro-computed tomography (μCT) scan data. We utilized RP technology along with FE analysis based on μCT for high-resolution vertebral trabecular bone specimens. RP models were used to fabricate complex 3D objects of vertebral trabecular bone that were created in a fused deposition modeling machine. RP models of vertebral trabecular bone are advantageous, particularly considering the repetition, risks, and ethical issues involved in using real bone from cadaveric specimens. A cubic specimen with a side length of 6.5 mm or a cylindrical specimen with a 7 mm diameter and 5 mm length proved better than a universal cubic specimen with a side length of 4 mm for the evaluation of elastic mechanical characteristics of vertebral trabecular bones through experimental and simulated compression tests. The results from the experimental compression tests of RP models closely matched those predicted by the FE models, and thus provided substantive corroboration of all three approaches (experimental tests using RP models and simulated tests using FE models with ABS and trabecular bone material properties). The RP technique combined with FE analysis has potential for widespread biomechanical use, such as the fabrication of dummy human skeleton systems for the investigation of elastic mechanical characteristics of various bones.

Experimental and simulated studies on the plastic mechanical characteristics of osteoporotic vertebral trabecular bone

“…Material properties of trabecular bones and acrylonitrile-butadiene-styrene (ABS) copolymer ( [12,22] lated compression test with FE analysis also provided important insights into the failure pattern of internal bone structures which could not be exactly investigated in experimental test (Fig. 1b); we found that thin central area of trabeculae was destroyed before everything else in stress distribution.…”

“…Based on the widespread use of ABS in FDM-RP&M processes [19][20][21], we selected ABS plastic to produce a realistic functional model of human vertebral trabecular bone for experimental compression tests. In previous work [22], we determined the material properties of ABS copolymer in three-point bending tests performed with an IN-STRON testing machine (8874 series, Instron, UK) ( Table 2). Trabecular bone specimens of actual size were too small to reproduce by RP-FDM modeling; therefore, we first scaled up the architectural replicas by a factor of 20 [22].…”

“…In previous work [22], we determined the material properties of ABS copolymer in three-point bending tests performed with an IN-STRON testing machine (8874 series, Instron, UK) ( Table 2). Trabecular bone specimens of actual size were too small to reproduce by RP-FDM modeling; therefore, we first scaled up the architectural replicas by a factor of 20 [22]. Two types of RP-FDM specimen were produced [(a) a cubic specimen with sides of 6.5 mm; and (b) a cylindrical specimen 7 mm in diameter and 5 mm long], using lCT data obtained at two different voxel resolutions (42 lm and 84 lm) for each specimen type.…”

“…The 42 lm voxel resolution consisted of 2 Â 2 Â 2 voxels in 21 lm voxel resolutions, and the 84 lm voxel resolution consisted of 4 Â 4 Â 4 voxels. Table 2 shows the values we used for Young's modulus, strength, and Poisson's ratio [12,22]. The trabecular material in this FE analysis was assumed to be isotropic and perfectly elastic plastic.…”

The Evolution of the Field of Biomechanics Through the Lens of Experimental Mechanics

“…Other recent works have conducted in-depth investigations into the biomechanics of the femur in fracture fixation and into the phenomena of strain shielding [22,23]. The mechanics of trabecular bone, which is of tremendous interest due to its role in osteoporosis, has been investigated using a novel non-destructive method based on micro-computed tomography technology [24] and was also the subject of a nanoscale biomechanical study by Gao et al [25].…”