Bone cement compositions comprising fused fibrous compounds

#The invention is directed to improved bone cement and dental cement systems comprising fused fibrous compounds and methods of making the same. The invention is further directed to bone cement and dental cement system kits for bone or teeth repair or other treatment of bone and teeth.

#In joint surgery it is common practice today to anchor components of replacement joints by using as bone cement a two-component resin which polymerizes during the operation at normal temperatures and which, on account of its plastic properties leads to an interlocking of the prosthesis component in the bony sheath. Because of its physical properties, the bone cement shrinks onto the prosthesis resulting in a closed metal-to-cement contact.

#The bone cements commonly used are polymethylmethacrylate (PMMA) consisting of powdery bead polymers which are superficially dissolved by liquid monomers and embedded during the polymerization process. During mixing the polymer is immersed in the monomers. The PMMA beads are superficially dissolved and embedded in a composite manner. Despite their widespread use PMMA and related bone cements tend to represent the “weak link” in prosthesis fixation.

#FIG. 1 is a plot or graph of the density versus the porosity of the fused fibrous compound of the present invention.

#FIG. 2 is a bar graph illustrating the flexural strength of various bone cement compositions reinforced with the fused fibrous compound of the present invention.

#FIG. 3 is a bar graph illustrating the flexural modulus of various bone cement compositions reinforced with the fused fibrous compound of the present invention.

#In this invention, the terms “(meth)acrylate” and “poly(meth)acrylate” include the monomers and polymers, respectively, of methacrylic acid esters and acrylic acid esters, and the polymers also include the co-polymers of the compounds named.

#The preferred bone cement material to which the fused fibrous compound is added includes a solid finely divided powdery or granular polymer component and a liquid reactive or polymerizable monomer component which is also a solvent or swelling agent for the polymer component. The polymer and monomer components can be based on the acrylic, e.g., (meth)acrylate system, however, other polymeric systems can also be used. For convenience, the cement system may at times be broadly referred to as an acrylic polymer, or as based on PMMA (polymethylmethacrylate), the preferred polymer component. While the invention is described herein in terms of a preferred embodiment, i.e., bone cement, it is to be understood that the invention is also directed to dental/tooth cements.

#More generally, the polymer component of the composition can be any methyl(meth)acrylate polymer such as methyl(meth)acrylate homopolymers and copolymers of methyl(meth)acrylate with alpha, beta-ethylenically unsaturated compounds such as vinyl acetate, alkyl (e.g., C2-C6) (meth)acrylates and multi-functional acrylic monomers such as alkylene dimethacrylate and alkylene diacrylates and triacrylates. These polymers generally have a molecular weight between 500,000 and 2,000,000. Methylmethacrylate homopolymers and copolymers are preferred. The reactive monomer component is preferably methyl acrylate or methyl methacrylate although the C2-C4 alkyl(meth)acrylates, such as ethyl(meth)acrylate, propyl(meth)acrylate or (n-, or iso-)butyl(meth)acrylate, can also be used. These bone cement materials, which are themselves well known and commercially available, are usually provided with 2 parts by weight of the finely divided polymer and 1 part by weight of liquid monomer, although higher or lower ratios can also be used, and are characterized as being self-polymerizable substances which are mixed, together with a polymerization catalyst, such as dibenzoyl peroxide, and polymerization accelerator, such as dimethyl-p-toluidine, immediately prior to the operation to form a viscous liquid or pasty mass. The pasty mass is introduced into the appropriate body cavity and/or to the surgical implant, device, and will harden in situ, at room temperature (via an exothermic reaction) within a few minutes.