An Experiment For Selecting The Optimum Period Concerning The Effect Of Low-Magnitude Mechanical Vibration On Fracture Healing

Purpose: In this experiment,low-magnitude continuous and intermittent mechanical vibration were investigated respectively to explore the effects of macro biomechanical property and bone mineral elements on the process of fracture healing,thus seeking the optimum vibrational period for fracture healing.Materials and methods: A total of 63 twelve-month old female Small Tailed Han Sheep were randomly divided into seven groups,namely,basic control group(n=7),continuous vibration group(n=7),and the continuous vibration groups with N days rest(N=1,3,5,7 and 14;n=7 for each group).A surgery for metatarsal fracture was performed for all groups except the basic vibration group.Two weeks after the surgery,vibrational experiment was conducted(F=35Hz,a=0.25 g,and T=15min).After six-week vibrationalexperiment,metatarsals were obtained for all groups.The test of macro biomechanical property was performed on metatarsals in the continuous vibration groups with N days rest(N=1,3,5,7 and 14;n=7 for each group).The test of bone mineral elements was conducted for all groups.Results:(1)Macro biomechanical property: 1.Failure stress: at fracture line,maximum failure stress was found in intermittent one-day vibration group,and no statistical difference was found between all groups(p>0.05);At the interval of 15 mm from the fracture line,there was maximum failure stress in intermittent one-day vibration group,and there was no statistical difference between all groups(p>0.05);At the interval of 25 mm from the fracture line,intermittent five-day vibration group showed maximum failure stress,and there was no statistical difference between all groups(p>0.05).(2)Ultimate strain: at fracture line,maximum ultimate strain was found in intermittent one-day vibration group,and no statistical difference was found between all groups(p>0.05);At the interval of 15 mm from the fracture line,there was maximum ultimatestrain in intermittent one-day vibration group,and there was no statistical difference between all groups(p>0.05);At the interval of 25 mm from the fracture line,intermittent one-day vibration group showed maximum ultimate stain,and there was no statistical difference between all groups(p>0.05).(3)Elastic modulus:at fracture line,maximum elastic modulus was found in intermittent one-day vibration group,and no statistical difference was found between all groups(p>0.05);At the interval of 15 mm from the fracture line,there was maximum elastic modulus in intermittent three-day vibration group,and there was no statistical difference between all groups(p>0.05);At the interval of 25 mm from the fracture line,intermittent five-day vibration group showed maximum elastic modulus,and there was no statistical difference between all groups(p>0.05).In addition,compared with basic vibration group,continuous vibration group,and intermittent seven-day vibration group performed by previous researchers,andtaken together from the three aspects,continuous vibration group showed the best data.The data from intermittent seven-day vibration group were best at the interval of 15 mm and 25 mm from the fracture line.(1)The test of bone mineral elements: 1.At fracture line,compared with basic control group,the content of bone mineral elements changed in other groups to some extent,and generally indicated statistical difference(p<0.05).The content of Ca and P increased compared with basic control group(p>0.05),and between all the groups except the basic vibration group,there was statistical difference(p<0.05).The content of Ca and P was the highest in continuous vibration group.The ratio of Ca to P(Ca/P)wasin addition the highest in continuous vibration group.(2)At the interval of 15 mm from the fracture line,compared with basic control group,the content of bone mineral elements changed in other groups to some extent,and generally indicated statistical difference(p<0.05).The content of Ca and P increased compared with basic control group(p<0.05),and between all the groups except the basic vibration group,there was statistical difference(p<0.05).The content of Ca and P was the highest in intermittent seven-day vibration group.Ca/P was in addition maximum in continuous vibration group.(3)At the interval of 25 mm from the fracture line,compared with basic control group,the content of bone mineral elements changed in other groups to some extent,and generally indicated statistical difference(p<0.05).The content of Ca and P increased compared with basic control group(p<0.05),and between all the groups except the basic vibration group,there was statistical difference(p<0.05).The content of Ca and P was the highest in intermittent seven-day vibration group.Ca/P was in additionmaximum in intermittent seven-day vibration group.Conclusion:Continuous and intermittent low-magnitude mechanical vibration are able to benefit fracture healing and serve to bone growth.Continuous vibration with 7 days rest was found to produce the best effect,thus making it the optimum period for fracture healing.