Comparative Study about Degradation of High-purity Magnesium Screw in Intact Femoral Intracondyle and in Fixation of Femoral Intracondylar Fracture

Abstract

Bone screws encounter complex mechanical environment in fracture fixation of weight-bearing bone. In the present study, high-purity magnesium (HP Mg) screws were applied in fixation of rabbit femoral intracondylar fracture with 3 mm gap. In the control group, HP Mg screws of the same design were implanted at corresponding position of contralateral leg. At 4, 8 and 16 weeks after surgery, retrieved femurs went through micro-computed tomography (micro-CT) scanning and hard tissue processing. Under mechanical stress involved in fracture fixation, bending of screw bolt was observed at the portion exposed to facture gap at 4 weeks. Then local corrosion at the same portion was detected 16 weeks after surgery, which indicated the accumulation effect of mechanical stress on Mg corrosion. HP Mg screws in the fracture group had no significant difference with the control group in screw volume, surface area, surface-to-volume ratio (S/V). And peri-implant bone volume/tissues volume (BV/TV) and bone volume density (BMD) in the fracture group was comparable to that in the control group. Furthermore, histological analysis showed new formed bone tissues in fracture gap and fracture healing 16 weeks after surgery. Under mechanical stress, HP Mg screw suffered bolt bending and local corrosion at the portion exposed to fracture gap. But it had no influence on the integral corrosion behaviors, osseointegration of HP Mg screw and the fracture healing. Therefore, HP Mg screws possessed good potential in fracture fixation of weight-bearing bones.