Design of patient specific implants for amputee prostheses using porous titanium and development of antimicrobial silver coating for implant materials

This thesis presents research for two projects. The first project is based on designing and fabricating porous Ti-based metal implants for amputation prostheses. The implants are patient specific and are based on a computed tomography scan of the patient's bone. The efficient fill and porous structure of the implant has potential to improve load transfer from the prosthesis to the bone, the bone in-growth, and reduce premature loosening, thus decreasing the rehabilitation period for the amputees. Three iterations of this process have been completed. The first design is based on patient bone geometry but uses an elliptical geometric shape as the implant stem. The second design employs a model of the bone cavity as the implant stem, with a sloping area connecting the stem and head. The third design also utilizes the bone cavity as the implant stem, and incorporates a flange where the implant head meets bone. The second design greatly improved on the fit of the implant by using the patient geometry as the implant itself. The third design added further value by increasing the maximum compressive loads the designs could endure. The second project is research into a coating that can be used on implants to reduce the risk of infection. Silver has been utilized for many years as an antimicrobial agent. With an increasing amount of antibiotic-resistant bacteria, silver-coatings and treatments are again being noticed as an effective way to prevent infection. This is especially crucial when surgeries are performed in environments where sanitation is not ensured as well as environments in North American Hospitals. This research presents methods and feasibility of silver coatings on stainless steel (SS) which is a practical material for low cost implants. Parameters have been adjusted in order to optimize the efficacy of the coating. A post deposition heat treat has also been incorporated to increase coating adhesion. The coating has been shown to be safe for use with human cells and to create a 13 fold reduction in bacteria. This coating could also be applied to other implant materials or cases to limit the possibility of infection

Antimicrobial particulate silver coatings on stainless steel implants for fracture management

We have used particulate silver coating on stainless steel to prevent in vivo bacterial infection. Stainless steel is commonly used as an implant material for fracture management. The antimicrobial use of silver has been well documented and studied, therefore the novelty of this research is the use of a particulate coating as well as facing the real world challenges of a fracture repair implant. The variable parameters for applying the coating were time of deposition, silver solution concentration, voltage applied, heat treatment temperature between 400 and 500°C and time. The resultant coating is shown to be non-toxic to human osteoblasts using an MTT assay for proliferation and SEM images for morphology. In vitro silver release studies of various treatments were done using simulated body fluid. The bactericidal effects were tested by challenging the coatings with Pseudomonas aeruginosa in a bioreactor and compared against uncoated stainless steel. A 13-fold reduction in bacteria was observed at 24h and proved to be statistically significant. ► Processing of particulate silver coating that are strongly adherent on SS surface. ► Optimized the amount of silver that is sufficient to reduce bacterial colonization but non-toxic to human bone tissue. ► The adhesion strength of silver was sufficient to survive industrial sterilization steps used for fracture management devices

Antimicrobial particulate silver coatings on stainless steel implants for fracture management

We have used particulate silver coating on stainless steel to prevent in vivo bacterial infection. Stainless steel is commonly used as an implant material for fracture management. The antimicrobial use of silver has been well documented and studied, therefore the novelty of this research is the use of a particulate coating as well as facing the real world challenges of a fracture repair implant. The variable parameters for applying the coating were time of deposition, silver solution concentration, voltage applied, heat treatment temperature between 400 to 500 °C and time. The resultant coating is shown to be non-toxic to human osteoblasts using an MTT assay for proliferation and SEM images for morphology. In vitro silver release studies of various treatments were done using simulated body fluid. The bactericidal effects were tested by challenging the coatings with P. aeruginosa in a bioreactor and compared against uncoated stainless steel. A 13-fold reduction in bacteria was observed at 24 hours and proved to be statistically significant