In vitro degradation of a poly(propylene fumarate)/beta-tricalcium phosphate composite orthopaedic scaffold

This study involves investigating the in vitro degradation of a poly(propylene fumarate) (PPF) based composite material for orthopaedic applications. The effects of PPF molecular weight, PPF to vinyl monomer ratio, and solid phase content were studied. Mechanical properties, pore morphology, and sample mass loss were analyzed over a 12-week period of degradation. An initial increase in both compressive modulus and strength was seen for all formulations incorporating high molecular weight PPF. The PPF/monomer ratio was not seen to have a significant effect on any observations. Incorporation of beta-tricalcium phosphate (beta-TCP) resulted in an increase in mechanical properties and had no effect on weight loss. A composite formulation with an initial PPF/beta-TCP ratio of 1.0 g/0.66 g exhibited an initial compressive strength of 2.60 MPa, which rose to 9.38 MPa at 3 weeks, and fell to 3.24 MPa at 7 weeks into the study. The initial modulus of 62.0 MPa for the same formulation increased to 250 MPa at 3 weeks, and fell to 63.7 MPa at 7 weeks. These studies further show that PPF/beta-TCP composite scaffolds can be fabricated exhibiting initial mechanical properties similar to human trabecular bone and maintain these properties over several weeks of degradation.