In Vitro Biomechanical and in Vivo Animal Study on the Strength-Enhanced Biodegradable Polylactic Acid Fabricated Magnesium Bone Screw for Ultrasonic Welding Implantation

Magnesium is a lightweight metal with properties similar to bone. The degradation behavior of magnesium makes them very promising for biodegradable implants. However, the pure magnesium corrodes too quickly in the physiological systems. Consequently, the implant will lose its mechanical integrity before the tissues sufficiently heal. Many studies attempted to overcome these difficulties with alloying or surface modification. Among them, Polylactic acid (PLA)-based composites were researched extensively as medical applications for many years. Recently, the ultrasonic activated PLA implants were highly noted for its shorter insertion times and higher stability. Accordingly, the aim of this study is to develop a novel PLA-fabricated magnesium implant. This implant was manufactured for ultrasonic welding technology to not only reduce the operation times but apply to any weight bearing bone defects. The parametric optimization of implant design will be achieved by Taguchi method coupled with finite elements analysis. Once the novel implant was produced, the mechanical characteristic including heat transduction, torsion, and shear-strength are going to be evaluated by simulated model. Then, the cytotoxicity and in vitro biocompability test will be performed to assure the safety of this novel implant. In addition, Animal studies will be used to test the in vivo stability, biocompability and osteoinductive activity. The applicability and superiority of this novel implant will be evaluated and determinated through in vitro and in vivo testing. Accordingly, after finishing this study, we will provide the biodegradable novel implant which the mechanical properties and degradation rate are controllable to apply for any bone defects especially weight bearing areas. This novel ultrasonic-welded PLA-fabricated magnesium implant will launch a full-scale expansion into the field of medical devices.