Polymethyl methacrylate bone cement is a commonly used grouting material for the in vivo fixation of orthopaedic joint replacement implants. Void reduction and fiber reinforcement are two possible methods of improving bone cement properties. The fundamental hypothesis of this study was that the fracture toughness of bone cement could be elevated by void reduction and by optimizing the fiber-matrix interface strength in fiber reinforced bone cement.
The effect of the voids in PMMA bone cement on the plane strain fracture toughness was examined experimentally. Air mixed cement was compared to reduced porosity PMMA bone cement. In contradiction to the results of other investigators but in agreement with theoretical expectations, the fracture toughness of bone cement was significantly increased by a reduction in porosity.
The effect of fiber reinforcement and especially the fiber-matrix interface strength on fracture toughness was examined both experimentally and analytically. Fracture toughness tests were performed on PMMA bone cement samples reinforced with PET chopped fibers of different fiber-matrix bonding strength potential. The composite bone cement was significantly tougher than neat cement. The strength of the fiber-matrix interface bond did affect toughness. A simple finite element model was developed which simulated the effect of fiber bridging and fiber-matrix interface strength on fracture properties of the composite. The results of this modei suggest that an intermediate fibermatrix interface strength is most effective in improving fracture properties.