Polyethylene, implant material

Polyethylene, implant material, 145 Polymer-mediated synthesis, dendrimers, 14-15... 

Bohner M, Lemaitre J, van Landnyt P, Zambelli PY, Merkle HP, Gander B (1997) Gentamicin-loaded hydranUc calcium phosphate bone cement as antibiotic delivery system. J Pharmaceut Sci 86 565-572 Bonfield W, Grynpas MD, Tally AE, Bowman J, Abram J (1981) Hydroxylapatite reinforced polyethylene —a mechanically compatible implant material for bone replacement. Biomaterials 2 185-186 Bonyer E, Gitzhofer F, Bonlos MI (1997) The snspension plasma spraying of bioceramics by induction plasma. J Metals 58-62... 

W. Bonfield, M.D. Grynpas, A.E. Tully, Hydroxyapatite reinforced polyethylene—a mechanically compatible implant material for bone replacement. Biomaterials 2, 185-186 (1981)... 

Li S., and A.H. Burstein. 1994. Ultra-high molecular weight polyethylene. The material and its use in total joint implants. / Bone Joint Surg Am 76 1080-1090. 

Our next foray into this field, in collaboration with Rowena Crockett at the Empa (Swiss Federal Laboratories for Materials Science and Technology), took a broader look at the proteins in synovial fluid. We came to the conclusion that albumin actually increases friction in comparison to saline, while glycoproteins, in general, lubricated implant-material sliding surfaces effectively. Despite the massive excess of albumin in synovial fluid, we could show, by fluorescence spectroscopy, that the glycoproteins made it to the surface and lubricated the materials (2.41). Fluorescence microscopy also proved useful for monitoring the transfer of polyethylene to inorganic countersurfaces, and it was found, contrary to conventional wisdom, that this transfer also occurs in the presence of proteins or even synovial fluid (2.42). 

Polymers are widely used as implant materials because they have physical properties that are similar to those of natural tissues. Examples are long-term and shortterm implants such as blood vessels, heart valves, membranes, mesh prostheses, corneas, tracheal prostheses, dental materials, parts of the nose and ear, knee and hip joints, and others. The synthetic polymers used include polyethylene (PE), particularly ultrahigh molecular weight PE (UHMWPE), poly(ethylene terephthal-ate) (PET), poly(tetrafluoroethylene) (PTFE), polyurethane (PU), and poly(methyl methacrylate) (PMMA). The necessary sterilization before implantation can be performed by y-irradiation, heat (steam), or chemical treatment (ethylene oxide), which should not cause any structural degradation of the polymers. Current challenges in research include the development of biomimetic materials that match both the mechanical and biological properties of their natural counterparts. 

TABLE 6 Properties of ultra high molecular weight polyethylene as an implant material... 

High-density polyethylene (HDPE)-hydroxyapatite (HA)-aluminum oxide (AI2O3) composite-based implant materials showed great biocompatibility for orthopedic appUcations, especially for bone replacement (Tripathi et al 2013) (Table 4.1). 

Berzen J. Luketic D. Stabilised polyethylene moulding materials, esp. for implants containing polyethylene with molecular wt. 10 5-10 7. antioxidant, and toco[4ierol, esp. alpha- tocopherol or vitamin E. as stabiliser. European Patent 613,923 1994. 

The materials used in a total joint replacement ate designed to enable the joint to function normally. The artificial components ate generally composed of a metal piece that fits closely into bone tissue. The metals ate varied and include stainless steel or alloys of cobalt, chrome, and titanium. The plastic material used in implants is a polyethylene that is extremely durable and wear-resistant. Also, a bone cement, a methacrylate, is often used to anchor the artificial joint materials into the bone. Cementiess joint replacements have mote tecentiy been developed. In these replacements, the prosthesis and the bone ate made to fit together without the need for bone cement. The implants ate press-fit into the bone. 

Goma K and Gogolewski S. Biodegradable polyurethane implants U in vitro degradadon and calcification of materials from poly (e-caprolactone)-polyethylene) diols and various chain extenders. J Biomater Res, 2002, 60, 592-606. 

Although the single amino acids cannot bind the adhesion receptors on cells, they provide other ehemieal functional groups which may improve the adsorption of eell adhesion-mediating molecules on the material surface. Similar efifeet was observed on ion-implanted polyethylene grafted with the Arg-Gly-Asp (RGD)... 

Coagulation is not the only problem with materials intended for implantation, however. Cardiac pacemakers are intended to correct arrhythmias. Insulating materials for a pacemaker lead must be tough and long lasting. The first leads were insulated with polyethylene or silicone rubber. Neither material was considered ideal because of endocardial reactions (polyethylene) and limited durability (silicone rubber). The strength and flexibility of polyurethanes led to their introduction in 1978 as lead insulators. 

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