A Novel Use of 3D-Printing Demonstrates Structural Effects of Osteoporosis on Cancellous Bone Stiffness and Strength

Previously, we performed a study using a 3D-printer to test the effect of cancellous bone deterioration on tissue strength and stiffness. In this study, 3D-printing enabled, for the first time, accurate mechanical testing of the same cancellous structure in both healthy and osteoporotic states. Our results demonstrated a 20% decrease in stiffness and a 24% decrease in strength in the osteoporotic structure. Our current study aims to confirm that the 3D material (VisiJet FTX green resin) achieves constant material stiffness in repeated printings, and that the 3D printer (ProJet 1200) is capable of accurately printing trabecular bone samples in real size. Sixty 3D-printed cubes were cropped and segmented (Amira6.0) from a chimpanzee’s metacarpal head micro-CT scan. Thirty of the cubes were identical to the original scan and thirty were the same structure after osteoporosis was simulated (10% loss of bone tissue). Results demonstrated that Young’s modulus values (i.e., material stiffness) for the healthy and osteoporotic models were not significantly different (171.0 ± 41.1 versus 169.3 ± 40.6MPa; p \u3e 0.05). These results confirmed that the 3D-material achieves constant stiffness in repeated printings. Thus, any difference between the models is due to structural, not material differences. Thirty-six 3D-printed cubes ranging in size from 4.5 to 21 mm (in increments of 1.5 mm) were analyzed by calculating the predicted volume (i.e., bone pixels; Amira 6.0) and measuring actual weight. In a scatterplot, this demonstrated a strong correlation(R2 = 0.9997), indicating that our 3D-printer is capable of accurately printing realistic replicas of the original structure. This study demonstrates that 3D-printing is a novel tool for testing cancellous structures in order to estimate their mechanical properties