The biomechanical analysis for biodegradable pure magnesium bone screws under three point bending and torsional test

Recently, magnesium and its alloys have been used as the raw material of degradable implants. In the orthopedic implant group, it is used in the production of medical tools due to its close modulus of elasticity and mechanical behavior suitable for bone tissue. In addition, magnesium is completely biodegradable both in biocompatible and living organisms. The purpose of using a degradable implant within the living organism is both to perform biomedical functions. It has become even more attractive to use the biodegradable magnesium screws due to the use of the temporary (non-biodegradable) implant in the living organism, the need for a secondary surgical operation to remove it from the body, and the increased risk of complications for the patient. However, the degradation times of magnesium screws; It is difficult to control the biological environment, the age and gender of the patients and the implant geometry Determination of the degradation stage is important for mechanical performance due to loss of mass and volume in the implant. Furthermore, loss of adhesion performance due to deterioration of bone screws weakens the mechanical properties of the implant system. Considering this feature of magnesium screws, pure magnesium screws of different origin were kept in phosphate buffer solution (pH = 7.4) for 1 day, 1,4,12 and 26 weeks. Then, three-point bending and torsion tests were performed according to ASTM F2502-11 standard to examine the mechanical properties of the screws. In the mechanical tests applied for both groups, when the three-point bending test and force-displacement curves were examined, it was observed that the mechanical properties of the 26th week decreased by about half compared to the 1st day. In the same way, when the torsion-torsion angle curves were examined in the torsion test, it was observed that the mechanical properties of the 26th week decreased for both groups.