Introduction. Radio-opaque additives for Orthopaedic Bone Cement, like BaSO4 or ZrO2, are now routinely used because of the valuable help in identifying cement location around an implant on the x-ray films. A new bone cement formulation was devised with the aim to improve the reparative response of bone tissue surrounding a cemented implant, soon after the operation: a 6% NaF 6% BaSO4 preparation “Fluoride Bone Cement©” (Tecres, I) was tested in-vivo versus a 9% BaSO4 preparation “CemexRX©” (Tecres, I). NaF stimulating action towards bone repair is prompt by the formation of fluoroapatite and the stimulation of osteoblast differentiation. NaF-added cement acts like a “drug-release device” for fluoride ions.

Materials & Methods. Eighteen outbred male New Zealand White rabbits of approximately 3,2 kg of weight have been used. They were divided into six groups of three units. Gropus A1, A2, A3 were implanted with cement without fluoride “CemexRX©” while groups B1, B2, B3 had “Fluoride Bone Cement©”. Retrieval occurred after 17 days (A1, B1); 33 days (A2, B2); 60 days (A3, B3). The surgical implantation site selected was the distal femural canal (meta-epiphyseal region). The canal in the right femur was filled with cement while the canal in the left femur was used as a surgical control (“sham” operation). Sections of 100 micron of thickness were taken by a rotating diamond-saw microtome (Leitz Wetzlar) and analyzed by polarized light and ultra-violet fluorescence microscopy (Nikon Miscroscope). One hundred and twenty sections were obtained for each femur.

Results. Calcein green fluorescent labelling showed that no real endosteal osteogenic response was evidenced the day after surgery, for both cement preparations, while periosteal response was normal. This was the consequence of the biological insult of the intramedullary polymerization of the cement. Xylenol orange showed that all the contra-lateral femurs (“sham”) had a normal endosteal and periosteal osteogenesis at all times. Both cement preparations continued to show a limited end-osteal response after 17 days and a slow recovery after 33 days, with better pictures in favour of NaF cement. After 60 days recovery in endosteal osteogenesis was adequate but, again, NaF cement showed the highst number of good pictures.

Conclusions. Adding NaF promoted the better recovery in endosteal osteogenic response observed in comparison with NaF-free cement. To differentiate the biological response it was essential to compare a high number of sections (120) in comparable locations, in a contralateral “sham” operated control in the very same animal. This procedure, costly and demanding, seems to be a right methodological approach.

A new class of soybean-based biomaterials has been presented to the scientific community (patent PCT/GB01/03464) that shows good mechanical properties and an intrinsic anti-inflammatory potential, probably related to the phyto-hormone Genistein. This plant iso-flavone is also reported to inhibit osteoclastic activity.

De-fatted soybean curd was prepared into granules which were subsequently implanted in a cylindrical cavity drilled into the femoral canal of New Zealand White rabbits. Retrieved femurs were embedded in polymethyl-meta-acrylate and samples were analysed by back-scattered electron microscopy (BSEM). Retrieved, operated femurs showed a macroscopic appearance similar to the non-operated controls. BSEM showed that granules were still present at the site of implantation after 8 weeks, but a clear progressive degradation took place from the periphery to the centre of the femural canal already after 3 weeks. The degradation of the granule was accompanied by the production of new trabeculae apposed to the surface of the material.

It can be hypothesised that the released Genistein shifts the metabolic balance towards bone production by inhibiting the macrophagic and osteoclastic activities and that the material degrading surface supports the apposition and mineralisation of the newly formed bone.

The rationale for a degradable bioactive glass coating is to lead the bone to appose gradually to the metal without the release of non-degradable particles. Two formulations of bioactive glasses, already described in the literature, have been studied: bg A and bg F. A non-bioactive glass (glass H) was sprayed as a control. Glass-coated Ti6Al4V cylinders were implanted in the femoral canal of New Zealand White rabbits. Samples were analysed by back scattered electron microscopy (BSEM) and electron dispersive analysis (EDX).

Bone was in tight apposition with the coating. As time progressed, images were found where bone showed features of physiological remodelling (newly formed bone filling areas of bone resorption) close to the coating. At the interface the apposition was so tight that it was not possible to discern a clear demarcation, even at higher magnification (more than 2500x). There was a gradual degradation during time and at 10 months bone was found apposed directly to the metal in more than half of the samples. In contrast, the non-bioactive glass coating showed complete integrity at any time examined and a clear demarcation with the coating was evident. Two peculiar features of the behaviour of bioactive glass coatings in vivo are: (a) degradation during time; and (b) promotion of a tight apposition with the newly formed bone.

Aims: A new class of soybean-based biomaterials has been presented (patent PCT/GB01/03464) which shows good mechanical properties and an intrinsic anti-inflammatory potential, probably related to the phyto-hormone Genistein. This plant isoflavone is also reported to inhibit osteoclastic activity. Aim of this study is to evaluate in-vivo the bone response to such soybean-based biomaterials.

Methods: De-fatted soybean curd was prepared into granules which were subsequently implanted in a cylindrical cavity drilled into the femural canal of New Zealand White rabbits. Retrieved femurs were embedded in poly-methyl-methacrylate and samples were analyzed by back-scattered electron microscopy (BSEM).

Results: Retrieved operated femurs showed a macroscopic appearance similar to the non-operated controls. BSEM showed that granules were still present at the site of implantation after 8 weeks, but a clear progressive degradation took place from the periphery to the centre of the femural canal already after 3 weeks. The degradation of the granule was accompanied by the production of new trabeculae apposed to the surface of the material.

Conclusions: It can be hypothesised that the released Genistein shifts the metabolic balance towards bone production by inhibiting the macrophagic and osteo-clastic activities and that the material degrading surface supports the apposition and mineralization of newly-formed bone.