Characterization of the quasi-static and viscoelastic properties of orthopaedic bone cement at the macro and nanoscale

Acrylic bone cement is often used in total joint replacement procedures to anchor an orthopaedic implant to bone. Bone cement is a viscoelastic material that exhibits creep and stress relaxation properties, which have been previously characterized using a variety of techniques such as flexural testing. Nanoindentation has become a popular method to characterize polymer mechanical properties at the nanoscale due to the technique's high sensitivity and the small sample volume required for testing. The purpose of the present work therefore was to determine the mechanical properties of bone cement using traditional macroscale techniques and compare the results to those obtained from nanoindentation. To this end, the quasi-static and viscoelastic properties of two commercially available cements, Palacos and Simplex, were assessed using a combination of three-point bending and nanoindentation. Quasi-static properties obtained from nanoindentation tended to be higher relative to three-point bending. The general displacement and creep compliance trends were similar for the two methods. These findings suggest that nanoindentation is an attractive characterization technique for bone cement, due to the small sample volumes required for testing. This may prove particularly useful in testing failed/retrieved cement samples from patients where material availability is typically limited.