Investigation on the Potential of Magnesium Alloy AZ31 as a Bone Implant

Abstract

Degradable implants have been in use for bone surgery for decades. However, degradable metal implants are one of the new research areas of biomaterials science. There is a potential for application of degradable metal implants as screws and plates in bones. Magnesium alloys are one of the new candidate materials for degradable implants. Magnesium has good biocompatibility due to its low toxicity, and it is a corroding, i.e. dissolvable, metal. Furthermore, magnesium is needed in human body, and naturally found in bone tissue. Mechanical properties of magnesium alloys are dimensionally comparable to the cortical bone substance. In this study, corrosion behavior of magnesium metal at the bone interface and the possibility of new bone cell formation have been investigated. Cortical bone screws were machined from magnesium alloy AZ31 extruded rod and implanted to hip-bones of sheep via surgery. Three months after surgery, the bone segments carrying these screws were removed from the sacrificed animals. Samples were sectioned to reveal Mg/bone interfaces and investigated using optical microscope, SEM-EDS and radiography. Optical and SEM images showed that there was a significant amount of corrosion on the magnesium screw. The elemental mapping results indicate, due to the presence of calcium and phosphorus elements, that there exists new bone formation at the interface. From the results of this study, it may be stated that the potential for using magnesium alloys as a bone implant material is expected to be significant.