Numerous musculoskeletal applications would benefit from recent advances in the development of safe, strong, easily fashioned and degradable polymers. For example, treatment of fractures through fixation requires the use of materials with sufficient strength to allow fixation, good tissue/material compatibility, and facile molding (into potentially complex shapes) for easy placement by the surgeon. In addition, controlled degradation is imperative to restore optimum bone function upon healing. The material must initially re-establish the mechanical integrity of the bone and subsequently degrade to allow new bone formation to bear load and remodel. This property is a major advantage of degradable polymeric materials over metallic orthopedic devices, which shield stresses during healing and can lead to bone atrophy. Degradable polymer implants also eliminate the need for implant retrieval and can be used simultaneously to deliver therapeutic drugs or growth factors. The objective of the proposed research is to develop a new class of degradable polymers that is photopolymerizable and exhibits the desired mechanical properties (particularly as the sample degrades) necessary for orthopedic applications. Development of a photopolymerizable system is beneficial for many reasons, including fast curing rates at room temperature, spatial control of the polymerization, and complete ease of fashioning and flexibility during implantation. The polymers will be produced from novel multifunctional monomers (with 3 or more methacrylate groups) that react to produce densely cross-linked networks. The networks will remain biodegradable because the cross-links will contain either anhydride or ester linkages, and the rate of degradation will be controlled by changes in the network composition and cross-linking density. With these new materials, studies will be performed to optimize the polymer composition to produce the desired mechanical properties and degradation rates, to attain maximum functional group conversion and minimize volume shrinkage during in vivo curing, and to allow easy placement and handling by the surgeon.
