Finite Element Analysis And Health Assessment Of The Child’s Hip Joint Based On MRI Images

The hip joint is one of the important joints that maintain the normal activities of the human body,but it is a vulnerable to disease.Developmental dysplasia of the hip(abbreviation:DDH)is the most common developmental disorders of children’s hip joint.Early detection,early diagnosis,and early treatment can help affected hip restore normal function.However,the structure of hip joint is complex,and there are still many deficiencies in many aspects of DDH studyo,which affects the normal life of patients seriously.In recent years,the rapid development of magnetic resonance imaging(abbreviation:MRI)technology,three-dimensional reconstruction and 3D printing technology has provided new ideas and technologies for the research and treatment of DDH.Based on MRI images,this thesis establishes a complete finite element model of the hip joints on both healthy hip and affected hip of the child with DDH and conducts biomechanical studies.By comparing the mechanical indicators of the healthy hip joint and the affected hip joint in the state of standing on one leg and standing on both legs,the harmfulness of DDH is analyzed and health assessment is performed.In addition,the deficient acetabular repair plan is designed for the affected hip.All of these works provide a theoretical basis and reference for doctors’ clinical treatment.The main research contents include:(1)The best modeling method based on MRI images is explored.Using Mimics software to extract MRI images of the child’s hip joint,and initially establishing a three-dimensional model of the affected and unhealthy hip joints including bone tissue and soft tissue,the established model become more realistic,appropriate and conforms to the human anatomical structure.(2)Optimal processing method of the initial model based on Mimics is studied.Top removing,noise reduction and smoothing at polygon stage and contour line extracting,surface patch constructing and surface fitting processing at surface stage are executed by using Geomagic Studio software,an accurate surface model and divided cancellous bone model generating.Using SolidWorks to the combining each model,segmenting the cortical bone model and checking interference,then high-quality solid model is obtained,which lays the foundation for the subsequent finite element analysis.(3)Finite element model of hip joint is established.According to human anatomy,selecting appropriate unit types and material attributes for each hip joint tissue,determining the contact type between the hip joint tissues,the loading and constraint conditions of the hip joint in different states,such as standing on one leg and standing on both legs,a finite element model of the hip joint is established that fits the real situation of the patients.(4)Mechanical characteristics of hip joint in different states are analyzed.Health is assessed by carrying out the mechanical analysis of both affected side and healthy side of the hip joint in different states to obtain the changes in the mechanical characteristics of the hip joint.The research results show that the maximum displacement,maximum stress and maximum contact pressure of the healthy hip and affected hip tissues when standing on one leg are about 2.5 times that of standing on both legs.Due to the defect of the acetabulum,the contact area is reduced and the stress distribution is abnormal on the affected hip.The stress and peak displacement under the same condition are much higher than those of the healthy hip.Therefore,early detection and treatment should be carried out to restore the structure and function of the patient’s hip joint as soon as possible.(5)Affected hip joint is simulated.Personalized repair patch and repaired finite element model of the affected hip are established,analyzed by finite element method,and then the effect of repair is evaluated.Due to repairing the deficient acetabulum in structure accurately,the establishment of repair patch can improve the mechanical environment of the affected hip and solve the harm caused by acetabular deficiency.The establishment and analysis of the finite element model of hip joint reflects the structural and mechanical environment differences between the affected and healthy hip joint.Doctors can more accurately evaluate and judge the condition of hip joint in the child with DDH,and provide biomechanical basis for the treatment of the disease.Simulation repairing and analyzing established personalized strengthening blocks of the part of deficient acetabular and simulating the mechanical characteristics of the affected hip after DDH repair provides a new method and approach for the formulation of clinical treatment plan.