Evaluation of a short glass fibre-reinforced tube as a model for cat femur for biomechanical testing of orthopedic implants

This thesis investigated the suitability of a third generation short glass fiber-reinforced (SGFR) material as a surrogate to feline cadaveric femurs for biomechanical testing of surgical implants. In phase one, the biomechanical properties of feline femurs were determined. Femurs obtained from mature cat cadavers, were tested in compression, three-point bending, screw pullout strength and notch sensitivity after drilling a 2 mm hole in the cortex. Similar biomechanical testing was then performed on SGFR tubes with material properties approximating that of cat femurs to determine their suitability as cat femur surrogates for biomechanical testing of orthopedic implants.;Thin-walled tubes (B1-tubes) were manufactured with approximate dimensions of feline femurs. B1-tubes had a 13% lower maximum load to failure, a 19% higher maximum stress and a 13% lower elastic modulus compared to cat femurs tested in compression. B1-tubes maximum load to failure in three-point bending and screw pullout strength were considerably lower compared to cat femurs (29% and 63% respectively). Thicker walled (B2-tubes) had a 23% higher maximum load to failure, a 10% higher maximum stress and a 21% lower elastic modulus compared to cat femurs tested in compression. Comparing B2-tubes and cat femurs in three-point bending revealed a 7% increase in maximum load to failure for the B2-tubes. Drilled B2-tubes were weaker with a 30% lower load to failure compared to cat femurs. Screw pullout comparison of B2-tubes and cat femurs revealed a 2% increase in maximum load to failure for the B2-tubes. The testing of SGFR tubes revealed results in compression, bending and screw pullout strength that were well within acceptable limits when compared to the biomechanical properties of cat femur. However, the fracture toughness of the SGFR material, as tested in this study, was much lower than that of feline femurs similarly tested. Tubes were intended to provide a suitable surrogate for cat femurs for testing the bending strength of various orthopedic constructs involving plates and screws. Testing revealed that third generation SGFR tubes were not suitable for these purposes and emphasizes the need to carefully evaluate the suitability of any model.