STTR Phase I: Mechanical Surface Treatment for High Performance Biodegradable Implants

The broader impact/commercial potential of this Small Business Technology Transfer (STTR) Phase I project is to shift current practices in bone fracture fixation care from using permanent metal implants to biodegradable metal implants (screws, plates, pins, rods, etc.). A promising biodegradable metal that is gaining widespread attention is magnesium. This project will advance magnesium implant technology towards becoming a viable alternative biomaterial for fracture fixation care. A magnesium implant?s biodegradation can be customized to an individual patient or application by modifying surface properties of an implant through surface treatments. If successful, patients will no longer have to rely on off-the-shelf permanent implants for treating bone fractures or require secondary removal surgeries to prevent the long-term complications with these devices. A senior patient with osteoporosis can have an implant that degrades slowly since his/her bones heal slowly, while a younger patient can have an implant that degrades quickly since his/her bones heal quickly. The commercial impact will be an unprecedented shift in the orthopedic industry towards customizable healthcare. The use of biodegradable metal implants will not only improve the quality of life of the affected individuals but also boost the competitiveness of the US medical device industry. The proposed project will demonstrate the feasibility of using surface treatments, such as laser shock peening or burnishing, on the surface of a magnesium implant to control the biodegradation while maintaining necessary mechanical integrity. Permanent metal implants made of titanium or stainless steel have unsatisfactory performance such as stress shielding. In addition, they are often removed with a secondary surgery after the bone heals. An alternative biodegradable material is needed that avoids the complications inherent to permanent metals. Magnesium is a promising biodegradable metal. The critical issue that hinders the adoption of this material for orthopedic applications is its high corrosion rate in the human body. Surface treatments are an effective method to slow the corrosion rate. The research objectives are to (1) create a surface layer on a magnesium alloy that degrades in 3 weeks to 3 months while maintaining structural integrity and (2) develop a model that designs a surface treatment procedure to meet the degradation and structural integrity needs of a patient. These objectives will be accomplished by (a) determining corrosion rate and mechanical degradation rate over time for different surface treatments and (b) understanding the relationships between surface treatment, surface integrity, and performance.