Development of Porous Polymeric Implants for Use in Orthopedic Research and Development Applications
Current orthopedic implants comprised of plastic, ceramic, or metal alloys are susceptible to surface degradation at the implant-implant interface. The resulting microscopic fragments cause tissue irritation that can lead to osteolysis. In addition, existing percutaneous implants, such as pins used to stabilize fractures, are prone to bacterial infections due to the inability of the surrounding soft tissue to adhere to the implant and form a biologic seal. The goal of this Honors Thesis was to develop porous polymeric implants for orthopedic research and development applications that improve upon current designs in an attempt to remedy the issues detailed above. A novel approach was taken to produce the implants, using an Objet30® Desktop 3D printer to create porous structures comprised of open rhombic dodecahedra. The hypothesis of this study was that a porous polymeric material will behave much like trabecular bone and allow for bone, soft tissue, nerve, and vascular in-growth. Thus, degradation of subcutaneous (osseointegrated) implants and infection associated with percutaneous implants would be minimized due to increased compatibility with the respective implant site. In addition, the use of 3D technology will allow for rapid design and production, thus resulting in a quicker and more economical research and development process. A cell culture experiment was performed by seeding implants with Buffalo Rat Liver cells. The results of this experiment showed that the polymeric material used was cytotoxic, with almost no cell attachment. To test the effectiveness of the porous implants in vivo, both subcutaneous and percutaneous implants were placed on the dorsa of six New Zealand White rabbits. The results of this project demonstrated the ability to achieve tissue in-growth and vascularization of both subcutaneous and percutaneous implants with a dodecahedral pore size of greater than or equal to 800 microns.