Study On The Effect Of Pulsed Electromagnetic Fields Combined With A Static Magnetic Intramedullary Implant On The Repair Of Bone And Cartilage Defects

Objective In order to explore the feasible application of magnetic field loading methods,this study was to evaluate the effect of pulsed electromagnetic fields combined with a static magnetic intramedullary implant on bone and cartilage tissue.Methods 1.According to the foundation of previous research in magnetic field and the related literature reports and with the help of experts in bio-engineering,this study selected the Nd Fe B permanent magnet materials as the basic component to format a static magnetic intramedullary implant.And the external was made by titanium alloy which possess excellent biocompatibility and strength;2.Effect of pulsed electromagnetic fields combined with a static magnetic intramedullary implant on the repair of bone defects: All experimental animal were established of femoral condyle bone defect.And divided into the combined magnetic field group,pulse electromagnetic field group and control group.The combined magneticfields group:a static magnetic intramedullary implant was implanted in the right side of the rabbit femoral shaft distal and combined with pulsed electromagnetic fields(1h/d);The pulse electromagnetic field group and the control group implanted a non magnetic titanium alloy rod in the same position respective.Meanwhile,the pulse electromagnetic field group also combined with pulsed electromagnetic fields(1h/d).Main outcome measures would be done at the fifth weeks after operation.3.Effect of pulsed electromagnetic fields combined with a static magnetic intramedullary implant on the repair of cartilage defects: All experimental animal were established cartilage defect on femoral trochlear cartilage surface and also divided into the combined magnetic field group,pulse electromagnetic field group and control group.The experimental methods of each group are the same as above.The main results was measures at the fourth and tenth weeks after operation.Result 1.The static magnetic intramedullary implant showed an overall length of 25 mm and diameter of 7 mm.The internal consists of Nd-Fe-B permanent magnet and polyethylene gasket which are arranged at intervals.The external sealed by titanium alloy(Ti6Al4V).The maximum magnetic induction was 40+5 m T;2.Fifth weeks after operation,micro-CT outcome showed that the combined magnetic field group has a better result in bone mass compared with PEMFs group and control group.Quantitative analysis of Micro-CT in bone defect region showed that the combined magnetic field group were significantly increased in BV/TV and Tb.N(P<0.05),while decreased in Tb.Sp(P<0.01).Compared with the PEMFs group,the combined magnetic field group were increased in Tb.N(P<0.05)and decreased in Tb.Sp(P<0.01);3.On morphology results,fourth weeks after operation,cartilage tissue repair of combined with magnetic field group is better than that of control group(P < 0.05),while there was no significant difference in the pulse electromagnetic field group(P > 0.05).Tenth weeks after operation,the combined magnetic field group repair the gross morphological score was significantly better than the control group(P < 0.01)and pulsed magnetic field group(P < 0.05).On pathology results,fourth weeks after operation,the combined magnetic field group was significantly better than the control group(P < 0.05),and had no significant difference with the electromagnetic field group(P > 0.05).Tenth weeks after the operation,combined magnetic field group was significantly better than the control group(P < 0.01),and had no significant difference with the electromagnetic field group(P > 0.05).Glycosaminoglycan(GAG)quantitative comparison shows that the GAG content of the combined magnetic field group,the pulsed electromagnetic field group and the control group were respectively 12.26±4.43μg、12.48±3.91μg and 13.02±2.83μg,there was no statistically significant difference among groups;After tenth weeks,the GAG content of three groups were respectively 15.54±3.66μg、20.45±2.9μg and 19.84±2.21μg.The content of GAG of pulse electromagnetic fields group and the combined fields group was significantly higher than the control group(P < 0.05).there was no statistical significance of this two groups(P > 0.05).Conclusion In this study,compared with single pulse electromagnetic field and control group,combined magnetic fields has better results in promoting bone formation and improving the bone microstructure under the same tissue trauma condition.At the same time,the combined magnetic fields can enhance the early process of articular cartilage repair and interface integration and improving the synthesis of cartilage glycosaminoglycan matrix.The results of this study confirmed the feasibility of a static magnetic intramedullary implant and combined magnetic fields.