Simulation Analyses Of Fracture Load And Implant Treatment Of Osteoporotic Vertebral Compressive Fractures

As a common orthopedic disease,osteoporotic vertebral compressive fractures have significantly affected patients' normal life,which have also added great burdens to the patients' familily and our society.This thesis performs a study on fracture loads and biomechanical effects of implants on osteoporotic vertebraes.Present studies about fracture loads of osteoporotic vertebras are limited on analyzing osteoporotic vertebraes with specific osteoporotic degrees,however different osteoporotic vertebraes own different osteoporotic degrees.Hence,this thesis invertigates fracture loads of osteoporotic vertebraes with different osteoporotic degrees,with the aim of determining the relationship between fracture loads and bone density.The bone density of cancellous bone and cortical bone have been reduced to 67% and 34% of their normal density at the rates of 3% and 6%,respectively.Then,12 finite element models of osteoporotic vertebrae L1 with different osteoporotic degrees have been built.Applying axial compression loads to the finite element models,the corresponding fracutre loads and fracture sites of vertebrae L1 were obtained.The results show that the fracture sites appear in the posterior of vertebrae L1.In addition,the fracture loads show the exponential relationship with the density of cancellous bone and cortical bone.The results can help provide theoretical guidance for preventing osteoporotic vertebral compressive fractures.Percutaneous vertebroplasty is one of the most common treatment methods for osteoporotic vertebral compressive fractures.However,there is not a universally accepted standard for the usage of bone cement volume at present.Therefore,the effects of bone cement volume on the biomechanics of vertebrae are explored in this thesis,in order to provide theoretical guidance and clinical advice for choosing the proper usuage of bone cement volume.Twelve finite element models of osteoporotic vertebrae T11~L3 without bone cement,12 finite element models of osteoporotic vertebrae T11~L3 with 1.8 mL bone cement,and 12 finite element models of osteoporotic vertebraes T11~L3 with 3.6 mL bone cement have been built to investigate the stress and displacement of vertebraes under stand load,extension load,antexion load,lateral side bending load and axial rotational load.The results indicate that the stress of vertebraes with 1.8 mL bone cement is much less while the displacement is larger.Therefore,it is clinically suggested that the low dosage of bone cement should be used to treat osteoporotic vertebral compressive fractures,under the condition that the vetebraes could obtain the enough stiffness.In light of the risks of leakage of bone cement and reoccurrence of fractures,the influences of a novel implant called n-HA/PA66 bone column on the biomehcnics of vertebrae are explored to offer the theoretical support for its clicinical application.First,four kinds of finite element models of vertebraes T11~L3 with n-HA/PA66 bone column,and 2 kinds of controlled models have been built.In the following,the stress and displacement of vertebraes that strengened by bone cement and strengthened by bone column were compared to figure out the influences of these two methods on vertebraes.The results show that the bone cement method results in larger stress and displacement of vertebraes,which proves that the n-HA/PA66 bone column method has more advantages on biomechanics.Then,the numbers and inserting ways of bone column have been further explored.The calculation results show that inserting only one bone column through psoas major leads to the minimum stress of vertebraes.Hence,we should give priority to inserting one n-HA/PA66 bone column into vertebraes through psoas major to treat osteoporotic vertebral compressive fractures.In this thesis,the finite element models of vertebrae T11~L3 have been built and verified.The relationship between fracture loads and bone density as well as the biomechanical effects of bone cement and bone column on osteoporotic vertebraes have been investigated.All the results are listed as follows:(1)the fracture loads exhibit an exponential relationship with bone density;(2)when adopting percutaneous vertebroplasty,the low volume of bone cement should be used if it can help recover the enough stiffness of fractured vertebrae;(3)the stress of vertrbraes with bone column is lower than that of vertrbraes with bone cement,and thus inserting a bone column through psoas major is recommended.The outcomes this thesis obtained can provide useful guidance and feasible suggestions for preventing and treating osteoporotic vertebral compressive fractures.