Bone plate applications

Aydin E, Planell JA, Hasirci V. Hydroxyapatite nanorod-reinforced biodegradable poly(L-lactic acid) composites for bone plate applications. J Mater Sci Mater Med 2011 22(ll) 2413-27. 

A rapidly growing use in the medical field is for surgical implants as either bone plates and screws, joint replacements, or for the repair of cranial injuries. Here, titanium and its alloys have the advantages of complete compatibility with body fluids, low density, and low modulus. Applications also exist in dentistry. 

The mechanical properties of these materials are too weak to use them in places in the body where much pressure is exerted. It is virtually impossible to achieve 100% polymerisation during the production process. Consequently the material contains impurities which may lead to toxic, allergic or carcinogenic processes. In future so-called biodegradable plastics will be used in applications such as artificial skin, synthetic blood, bone plates and in the controlled release of medication. 

FIGURE 45.1 Radiographs of (a) tibial fracture fixed with four pins and an external bar (b) a total hip joint replacement in a patient who sustained a femoral fracture and was treated with double bone plates, screws, and surgical wire (arrows) (c) application of wires, screws, and plates in the spine. 

P(3HB-co-4HB) copolymers are known to be biocompatible material. The biocompatible nature of these copolymers allows it to be utilized for various medical applications. These PHA polymers have been tested in tissue engineering applications as surgical sutures, bone plates, implants, gauzes, osteosynthetic materials, and also as matrix material assisting slow release of drugs and hormones (Zinn et al. 2001 Williams and Martin 2002 Sudesh 2004 Chen and Wu 2005 Freier 2006). Recently, electrospun nanofibers of P(3HB-co-4HB) have been evaluated as scaffolds in vivo and in vitro (Ying et al. 2008). 

Examples of medical applications include controlled drug release,surgical sutures, lubricant powders for surgical gloves, bone plates and wound care. All of these potential uses, however, depend upon the biocompatibility and slow resorption of PHB in vivo. 

There are important medical applications for polylactides prepared from the lactide dimer as well as for lactide-glycolide copolymers synthesized from lactide and glycolide dimers. These polymers are used for procedures requiring surgical sutures, implants, bone plates, and controlled drug release, inasmuch as they are biocompatible, biodegradable, and resorbable materials. 

Several types of classification of biocomposites are known, though Fig. 21.32 presents the main kinds of biocomposites based on type the of the reinforcement used. The first group includes short fiber biocomposites, whisker and blade-reinforced biocomposites, for example carbon fibers, which are used for hip replacement stems or producing high-tech performance products. Continuous fiber biocomposites found their applications in military aircraft, orthopedic bone plates, etc. The last category, particulate and powder biocomposites, may be used in field of dentistry, packaging, and many other fields [2]. 

The plate dryer is limited in its scope of apphcations only in the consistency of the feed material (the products must be friable, free flowing, and not undergo phase changes) and diying temperatures up to 320°C. Applications include speci ty chemicals, pharmaceuticals, foods, polymers, pigments, etc. Initial moisture or volatile level can be as high as 65 percent and the unit is often used as a final dryer to take materials to a bone-dry state, if necessary. The plate dryer can also be used for heat treatment, removal of waters of hydration (bound moisture), solvent removal, and as a product cooler. 

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