OBJECTIVETo investigate the tissue toxicity and degradation of ZK60 magnesium alloy with micro-arc oxidation coatings (MAO-ZK60), in order to discuss the possibility of its potential application for orthopedic implantation.

METHODSEighteen Sprague-Dawley rats were randomized equally to three groups of A, B, C. MAO-ZK60 sticks were implanted in the femoral condyles of rats in group A (experimental group). Sticks of ZK60 magnesium alloy without any surface treatment (ZK60) were implanted in the femoral condyles of rats in group B (control group). The poly L-lactic acid (PLLA) sticks were implanted in the femoral condyles of rats in group C (control group). The changes of blood bio-chemical indexes of different groups were observed and compared. All the rats were sacrificed at 12 weeks and histological observation of liver and kidney were carried out to evaluate the hepatic and renal toxicity. Micro-CT was used to evaluate the degradation of the implants and to observe the bone-implant interface. GEHC MicroView software was operated to calculate the volume variation of magnesium alloy.

RESULTSThere was no apparent biochemical index change with time in each group, and there was no significant change among each group. No significant pathology change of liver and kidney was detected among three groups. By using a micro-CT, a gap was found on the bone-implant interface at 4 weeks after implantation in group A, which decreased gradually at 8 weeks after implantation and continued to decrease at 12 weeks after implantation. A good combination between bone and implant formed at 12 weeks after implantation. Group A has less change of volume with time than group B (P < 0.05).

CONCLUSIONZK60 magnesium alloy with micro-arc oxidation coatings is safe in vivo. It has higher corrosion resistance than ZK60 magnesium alloy without any surface treatment.