Compressive properties of commercially available polyurethane foams as mechanical models for osteoporotic human cancellous bone

Background: Polyurethane (PU) foam is widely used as a model for cancellous bone. The higher density foams are used as standard biomechanical test materials, but none of the low density PU foams are universally accepted as models for osteoporotic (OP) bone. The aim of this study was to determine whether low density PU foam might be suitable for mimicking human OP cancellous bone. Methods: Quasi-static compression tests were performed on PU foam cylinders of different lengths (3.9 and 7.7 mm) and of different densities (0.09, 0.16 and 0.32 g.cm(-3)), to determine the Young's modulus, yield strength and energy absorbed to yield. Results: Young's modulus values were 0.08-0.93 MPa for the 0.09 g.cm(-3) foam and from 15.1-151.4 MPa for the 0.16 and 0.32 g.cm(-3) foam. Yield strength values were 0.01-0.07 MPa for the 0.09 g.cm(-3) foam and from 0.9-4.5 MPa for the 0.16 and 0.32 g.cm(-3) foam. The energy absorbed to yield was found to be negligible for all foam cylinders. Conclusion: Based on these results, it is concluded that 0.16 g.cm(-3) PU foam may prove to be suitable as an OP cancellous bone model when fracture stress, but not energy dissipation, is of concern.