*Author to whom all correspondence should be addressed. JOURNAL OF MATERIALS SCIENCE: MATERIALS IN MEDICINE 9 (1998) 701 – 706 In vivo skeletal response and biomechanical assessment of two novel polyalkenoate cements following femoral implantation in the female New Zealand White rabbit M. C. BLADES, D. P. MOORE, P. A. REVELL * Royal Free Hospital School of Medicine, Department of Histopathology and Comparative Biology Unit, Rowland Hill Street, London NW3 2PF UK R. HILL Department of Materials Science, University of Limerick Limerick Ireland Glass-ionomer cements (GIC) offer several advantages over the conventional acrylic-based bone cements. The formation of an adhesive bond with bone and metals, a low setting exotherm and no systemic or local toxicity are some of the advantages cited. This study examines the in vivo biological and biomechanical behavior of two polyalkenoate cements (LG26 and LG30) implanted for 6 wk into the submetaphyseal spongiosa of the rabbit femur. Cements were implanted as both set cement rods and unset cement dough. Implantation of set rods resulted in the formation of variably mineralized osteoid/woven bone at the bone—cement interface. Mechanical (push-out) testing revealed the strength of this bone—cement interface was of similar magnitude to control (PMMA-rod implanted) animals. The bone of LG cement-dough implanted animals exhibited demineralization of pre-existing bone local to the site of implantation, accumulation of aluminum both locally and at a distance from the site of implantation, and defective mineralization of newly formed osteoid. The histological picture following LG implantation was strikingly similar to human renal osteodystrophy, in which skeletal accumulation of aluminum is a noted feature. The development of a GIC with low/no aluminum release from the unset cement dough is a priority in the further development of these cements for possible orthopaedic applications.  1998 Kluwer Academic Publishers 1. Introduction Conventional polymethylmethacrylate (PMMA) bone cements have been used extensively in clinical practice for over 30 y. During this time, a range of problems associated with their physical and chemical properties have been identified. The systemic toxicity of methyl- methacrylate monomer has been implicated in acute cardiovascular and respiratory reactions observed during cemented arthroplasty [1], though the patho- logical mechanisms of such reactions remain in debate [2, 3]. Thermal damage to the cortex during the in situ exothermic curing of the cement may lead to local osteonecrosis, thus compromising the bone healing response at the site of implantation [4]. Also, PMMA cements rely on mechanical interlocking with bone and implant rather than adhesive chemical bond formation to form a stable bone—implant union. Glass polyalkenoate (glass-ionomer, GIC) cements are formed by the combination of concentrated poly- meric acid (polyacrylic acid) with an acid degradable fluoro-alumino-silicate glass. The setting reaction re- lies on the glassy phase to contribute cations to cross- link the polymer chains. As the setting reaction is one of neutralization (salification) rather than polymeriz- ation, there is, in contrast to PMMA-based cements, little or no exotherm associated with the reaction. Additionally, GIC’s have been shown to form adhes- ive bonds between bone and metals [5]. Their poten- tial for bioactivity is illustrated by their ability to release osteoconductive ions such as calcium and flu- oride for prolonged periods post-setting [6], an at- tractive characteristic for a surgical bone cement. This study examines the in vivo biological and bi- omechanical behavior of two candidate glass-ionomer cements, LG26 and LG30, implanted as set cement rods and cement dough and compares the tissue reac- tion to that seen following the implantation of conven- tional (PMMA) orthopaedic cement. 0957—4530  1998 Kluwer Academic Publishers 701