FLOW INTRUSION CHARACTERISTICS AND FRACTURE PROPERTIES OF TITANIUM-FIBER-REINFORCED BONE-CEMENT

Two clinically relevant considerations for a new bone cement are its f racture properties and flow intrusion characteristics. We present data for a titanium-fibre-reinforced poly(methyl methacrylate) (Ti-PMMA). The fracture properties presented are a concise review of previously p ublished material, while the flow intrusion observations are new. We p erformed fracture toughness and fatigue fracture experiments. Two type s of fatigue specimens were designed and tested. A 'smooth' specimen r epresented the extreme case of minimum surface flaws. The lifetime of a 'smooth' specimen incorporates fatigue crack initiation (FCI) and fa tigue crack propagation (FCP). 'Notched' specimens were created by mac hining a sharp notch into cylindrical specimens. The sharp notch effec tively eliminated FCI from a random surface flaw and thus we made the assumption that the lifetime of the notched specimen was a function of FCP only. Fatigue testing was performed on rotating-bending fatigue m achines until failure. Fibre addition resulted in a significant increa se in fracture toughness over the control bone cement. Fibre addition and the combination of fibre addition and centrifugation increased the fatigue crack initiation and propagation resistance of the bone cemen t. For the intrusion studies, eight femurs were obtained from four dog s. The femurs were prepared following a procedure similar to that in h uman hip replacement surgery. One of the pair of femurs from each dog was filled with non-reinforced bone cement and the other was filled wi th Ti-PMMA. A stainless-steel rod was inserted into the cement to simu late the insertion of a prosthesis stem. The cemented bones were secti oned and then stained with Alizarin Red S to distinguish the bone from the PMMA or Ti-PMMA. Because of the irregular bone morphology, it was not practical to quantify intrusion depth, but instead to make genera l observations on the intrusion characteristics. The Ti fibres did not generally flow into the small openings; however, fibre addition did n ot hinder the bone cement's ability to penetrate into bone interstices . (C) 1998 Elsevier Science Ltd. All rights reserved.