Using 3D‐Printing to Evaluate Trabecular Bone Mechanical Properties

Abstract

IntroductionTrabecular bone structure is essential to the normal mechanical behavior of whole bones. Studies have shown that osteoporosis negatively affects trabecular bone structure, mostly by reducing trabecular number and decreasing the thickness of the remaining trabeculae. The end effect of these phenomena is an increase in fracture risk. A major difficulty in assessing and quantifying the effect of trabecular structural deterioration on the mechanical behavior of whole bones is that no two trabecular structures are identical. Thus, when we compare a group of healthy vs. osteoporotic samples we only get the general trend. 3D‐printing is a new technology that can assist in overcoming this issue. Here we present a preliminary study that compares a healthy 3D‐printed trabecular bone model with the same model after osteoporosis was simulated (i.e. trabecular number and thickness were reduced). Since the osteoporotic model is derived from the healthy one, it is possible for the first time to directly estimate (percentage wise) the decrease of tissue stiffness and strength as a result of trabecular bone structural deterioration.MethodsA cubical volume of interest (4.5×4.5×4.5 mm) was cropped and segmented from a micro‐CT scan of a chimpanzee's metacarpal head using Amira 6.0. To simulate the onset of osteoporosis (loss of about 10% of bone mass), a second model was created by raising the gray‐scale threshold during segmentation. Next, the “healthy” and “osteoporotic” models were printed in scale (1:1 to real life size) 30 times each, using a 3D‐printer (ProJet 1200). Finally, all samples were tested in compression until failure (Instron 5942) and trabecular bone tissue strength and stiffness was calculated.Results and discussionOur results demonstrate that the “osteoporotic” trabecular structure was significantly less strong and stiff than the original intact (healthy) structure (P<0.01). Structural strength decreased by 47%, from an average of 4.13±2.04 MPa to 2.19±0.77 MPa, while structural stiffness decreased by 35% from an average of 71.82±20.30 MPa to 45.36±12.73 MPa. Despite the fact that these 3D models are made of printing resin and not bone, they enable us to compare the exact same trabecular structure before and after the onset of trabecular tissue structural damage. Our results demonstrate that a relatively small decrease in bone volume (about 10% of bone mass) leads to a dramatic decrease in structural strength (47%) and stiffness (35%).ConclusionsThis study demonstrates that 3D‐printing is a valuable tool for estimating the mechanical properties of trabecular structures. In the future, 3D‐printing may help us to attain better personal fracture risk assessments and consequently improve life quality for people suffering from Osteopenia and osteoporosis.Support or Funding InformationThe study was supported by the Winthrop University Research Council Grant (SC15014).