| BackgroundAdolescent Idiopathic Scoliosis(AIS),can occur preferentially in young female,is a common type of Scoliosis.If not treated in time,some patients’ scoliosis may develop and worsen,causing severe deformity of the body,which not only affects the neurological and cardiopulmonary functions,but also seriously endangers the mental health of patients.With the innovation of diagnose and treatment technique of AIS and the development of internal fixation,it is of great significance to study the etiology,pathology,pathogenesis and biomechanical changes to improve the efficacy of scoliosis.In order to study the diagnose and treatment of scoliosis,most scholars began to use finite element method to simulate the spine,so as to solve the clinical problem of scoliosis.However,the established models are far from the biomechanical behavior of real individuals,and its process and results are less accurate,which cannot meet the clinical needs.Objectives1.To obtain in vivo biomechanical response characteristic curve in Lenke 1 type adolescent idiopathic scoliosis using the scoliosis measuring apparatus based on the posture sensor combined with longitudinal traction.2.To establish two three-dimensional finite element model of the scoliosis(different flexibility)based on preoperative CT scan data,and use in vivo biomechanical response characteristic curve to optimize and verify the scoliosis model.Methods1.In vivo biomechanical response characteristic curve in Lenke 1 type adolescent idiopathic scoliosisAccording to the experimental standard,the scoliosis measuring apparatus based on the posture sensor was used to evaluate coronary Cobb angle in Lenke type 1 patients who were under longitudinal traction test.Eighteen patients(age from ten to seventeen years old;16 females,2 males)with Lenke type 1 AIS were selected,and the average Cobb angle is 44.50°.Two spine surgeons performed the measurement in every 20 N by longitudinal traction independently and blindly.The measurement were repeated three times under each longitudinal traction,and the average value of data was taken as the evaluation result.Then the line graph was draw to view the trend of biomechanical change.2.Establishment and validation of the biomechanically optimized three-dimensional finite element model of the scoliosis spineTwo patients with different flexibility of Lenke type 1 AIS were selected,and low-dose thin layer(< 1mm)scanning of the spine of the AIS patients were conducted through the three-dimensional spiral CT imaging equipment of our hospital before surgery,so as to obtain the imaging data in DICOM format.Modeling software,such as Mimics17,GeomagicStudio2014 and Hypermesh,were used to establish the three-dimensional finite element model,and the preliminary material parameters of each part of the model were assigned according to the anatomical structure and tissue properties.Comparing the in vivo biomechanical response characteristic curve obtained in the first part,three-dimensional finite element model of the scoliosis were established to simulate the spine vertical traction test.During the process,the material parameters of the intervertebral disc and other soft tissue structures were adjusted to make the three-dimensional finite element model consistent with the in vivo biomechanical response characteristic curve,so as to optimize the model.Finally,the validity of the three-dimensional finite element model was verified.Results1.According to the experimental standard,the scoliosis measuring apparatus based on the posture sensor was used to evaluate coronary Cobb angle in Lenke type 1 patients who were under dynamic longitudinal traction test.The results showed that each patient had a specific in vivo biomechanical response characteristic curve.In patients with Lenke type 1 AIS,the Cobb angle of the main thoracic curve decreased with the increase of longitudinal traction.Comparing the in vivo biomechanical response characteristic curve of different patients,the differences between patients can be mastered dynamically and comprehensively.2.In this study,the three-dimensional finite element model of two patients with Lenke type 1 AIS was successfully established(different flexibility),and the personalized adjustment of biomechanical properties of the model was made according to the in vivo biomechanical response characteristic curve of the spine of the patients.Based on the geometry and the function test,this research has shown that the three-dimensional finite element model of the spine is designed to accurately simulate the anatomical structure and biomechanical performance of the patient’s spine,and to can be used for diagnose and treatment of AIS in the later stages.Conclusions1.In this study,the authors obtained the in vivo biomechanical response characteristic curve through the scoliosis measuring apparatus based on the posture sensor and the longitudinal traction apparatus.In vivo biomechanical response characteristic curve is a new method of assessing the spinal flexibility dynamically and comprehensively,which has the advantage of reducing the patient’s X-ray exposure and related economic expenses.2.In this study,the three-dimensional finite element model of two patients with Lenke type 1 AIS was successfully established(different flexibility),and the personalized adjustment of biomechanical properties of the model was made according to the in vivo biomechanical response characteristic curve of the spine of the patients.Based on the geometry and the function test,this research has shown that the three-dimensional finite element model of the spine is designed to accurately simulate the anatomical structure and biomechanical performance of the patient’s spine,and to can be used for diagnose and treatment of AIS in the later stages. |
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