Constitutive models for impacted morsellised cortico-cancellous bone.

Constitutive models are developed, based on the results of confined compression testing, to describe the visco-elastic, and non-linear elasto-plastic behaviour of morsellised cortico-cancellous bone (MCB). It is found that the elastic modulus, E of MCB can be expressed as a linear function of the applied pressure, p. E varied from 3 to 30N/mm(2) for pressures up to 1N/mm(2). The visco-elastic behaviour of MCB can be described using a fourth-order Prony series. The plastic behaviour of MCB can be described using a Drucker Prager Cap (DPC) yield criterion, in which consolidation behaviour is described using an exponential function. The developed relationships allow MCB to be included in a realistic manner in finite element models, for example of the acetabular construct, following revision hip arthroplasty, carried out using the Slooff-Ling impaction grafting technique.