Predicting the Failure Response of Cement-Bone Constructs Using a Non-Linear Fracture Mechanics Approach

A non-linear fracture mechanics approach was used to predict the failure response of complex cement-bone constructs. A series of eight mechanical tests with a combination of tensile and shear loading along the cement-bone interface was performed. Each experiment was modeled using the finite element method with non-linear constitutive models at the cement-bone interface. Interface constitutive parameters were assigned based on the quantity of bone interdigitated with the cement. There was a strong correlation $r2=0.80$ between experimentally measured and finite element predicted ultimate loads. The average error in predicted ultimate load was 23.9 percent. In comparison to the ultimate load predictions, correlations and errors for total energy to failure $(r2=0.24,$ avg. error=38.2 percent) and displacement at 50 percent of the ultimate load $(r2=0.27,$ avg. error=52.2 percent) were poor. The results indicate that the non-linear constitutive laws could be useful in predicting the initiation and progression of interface failure of cemented bone-implant systems. However, improvements in the estimation of post-yield interface properties from the quantity of bone interdigitated with cement are needed to enhance predictions of the overall failure response.