Polymeric Reinforcement of Degradable Bone Plates

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Plates for internal fixation fabricated from biodegradable polymers may offer several advantages over metallic devices. They do not corrode; they may be constructed with moduli closer to that of normal bone than metal devices and thus, as a corollary, can reduce stress shielding; and finally, resorbability obviates the need for a second surgical procedure to remove the plate. Promising materials include the polylactides (PLA) and polylactide-co-glycolides (PLGA) that degrade via an autocatalytic route. However, when they are used in bone implants of significant size and thickness, this mode of degradation may lead to hollowing of the implant even though the overall dimensions appear unchanged. Catastrophic failure has been noted in experimental and clinical studies. If a resorbable bone plate can be made such that it contains an internal, supporting structure, the collapse may be prevented and the integrity of the osteosynthesis construct maintained. We propose the use of an unsaturated biodegradable polymer, polypropylene fumarate (PPF), that can be crosslinked in the presence of a host PLA biopolymer. This PPF reinforcement defines a three-dimensional network within the host PLA superstructure. The proposed Phase I project will address the feasibility of preparing a PLA bone plate reinforced with PPF using the hydrophobic crosslinker EDGMA (ethyleneglycol dimethacrylate) that can demonstrate in vitro a temporal mechanical profile that is commensurate with the mechanics of bone healing. The goal is to ameliorate the problems of plate deformation and mechanical collapse. PROPOSED COMMERCIAL APPLICATIONS: Of the more than 1.1 million fractures in the U.S. each year, greater than 470,000 require internal fixation devices to stabilize the fracture during the healing process. While there is significant clinical demand for resorbable devices, available products have not been widely adopted because of problems with dimensional stability. A reinforced, but still resorbable, fixation device that can ameliorate tendencies of plate deformation would address the clinical demand for resorbable orthopedic fixtures.