Nano Scale Experimental Study On The Effects Of Mechanical Vibration With Different Cycles And Low Load On Bone Fracture Healing

Introduction: At present,population structure goes to the aging trend of excessive.With the growth of age and aging of the body,human physiological bone loss,osteoporosis and fractures will become a serious threat to human health.It is very necessary and urgent to develop a simple,safe and effective physical therapy to promote bone formation and fracture healing.This study will focus on the effects of mechanical vibration with different cycles and low load on fracture healing.The lateral and longitudinal nano structure and mechanical properties of the bone tissue near the fracture line were studied in order to obtain the best vibration cycle to promote bone remodeling and promote fracture healing.Methods: A total of 56 12 month old female Small Tail Han sheep were divided into 8 groups: VL1R、VL3R、VL5R、VL7R、VL14R、VLNR、NH and BL.The mechanical vibration of low load(35Hz、0.25g)was applied to the fracture model for 8 weeks,1 times a day,15 min each time.Continuous vibration group received a vibration every day,intermittent vibration X days group with vibration X days,rest X days.Bone samples were collected after vibration,and transverse test samples(2mm thick fan shape)and longitudinal test samples(4mm × 4mm × 2mm)were collected in the vicinity of the fracture line.Using atomic force microscopy(AFM)and the mechanical properties of nano indentation on the proximal external callus,proximal internal callus,distal external callus and distal cortical bone in four regions were observed in bone nano morphology and detection of nanometer level.Results:(1)On the nano topography:1.Transverse and longitudinal grain size,the experimental data of VLXR and VLNR were significantly different from those of natural healing group(P<0.05),the experimental data of VL7 R were significantly different from those of and VLNR(P<0.05),and the particle size of VL7 R was minimum,the particle sizes of VL1R、VL3R、VL5R and VL14 R were larger,the particle size of NH was maximum.2.Transverse and longitudinal surface roughness,the experimental data of VLXR and VLNR were significantly different from those of natural healing group(P<0.05),the experimental data of VL7 R were significantly different from those of and VLNR(P<0.05),and the particle size of VL7 R was maximum,the experimental data of VL1R、VL3R、VL5R and VL14 R were smaller,the particle size of NH was minimum.(2)On the nano mechanical properties: 1.The elastic modulus of transverse and longitudinal samples,no significant difference was found between the experimental data of VLXR 、VLNR and NH(P>0.05),and the elastic modulus of VL7 R was the largest;2.Hardness of transverse and longitudinal samples,no significant difference was found between the experimental data of VLXR 、VLNR and NH(P>0.05),and the hardness of VL7 R was the largest.Conclusions: The analysis results show that the intermittent vibration cycle can improve the nano morphology and the effect of intermittent vibration is better than that of continuous vibration;The best vibration intermittent period was about 7 days.The mechanical properties of the nano scale analysis show that the different intermittent cycle vibration can improve the mechanical properties of nano scale;The maximum of elastic modulus and hardness of intermittent cycle was VL7 R.To sum up,different intermittent vibration cycles are more favorable to promote the healing of fracture,can better promote the bone formation effect,and the optimum intermittent period is 7 days in intermission.