Experimental Study And Numerical Simulation On The Effect Of Intercostal Muscle On The Deformation Of Thorax

Nuss surgery as the representative of the minimally invasive surgery has been widely used in the treatment of pectus excavatum with scoliosis.The smaller wound is conducive to the recovery of patients,but there are few biomechanical studies on the postoperative deformity of the sternum and ribs.At present,most of the methods of numerical simulation are used to predict the results of orthopedic surgery.The advantage of numerical simulation is that it can get results faster and facilitate the study of parameters,but its calculation model and calculation method also need experimental and clinical test.The numerical simulation model of the study of the pectus excavatum combined with scoliosis orthopedic model includes the solid model based on 3D reconstruction and the calculation model based on the beam element.The two models obtained the superior displacement of the sternum consistent with the clinical results,but the results of the scoliosis there is a big difference.The existing experimental and numerical simulations did not take into account the effect of intercostal muscle on thoracic deformity.The mechanism of intercostal muscle on thoracic deformity was studied.The reasonable numerical model was used to predict the minimally invasive Orthopedic effect and the development of minimally invasive surgery program has a very important clinical significance.At present,the study on the process of pectus excavatum surgery is still lack of experimental research work.Although the displacement field at the thorax position after orthopedic surgery can be obtained from the preoperative and postoperative images,the correctness of the computational model and calculation method used to test the numerical simulation can only be obtained by comparing the results of the displacement field,But also the lack of strain result of ribs and costal cartilage.The main problem in the experimental study of thorax deformation is that it can not be used to measure strain in vivo model and in vitro model by the method of electrical measurement.Although the artificial thorax model has the same structure as the human thorax,but the aritificial thorax model has no intercostal muscle,there are still many difficulties in the selection of materials,the preparation of models and the assembly of thorax models.In the selection of thoracic experimental model,the author found that animal model of porcine thorax model and sheep thoracic model can be used as an experimental model to study the effect of intercostal muscle on thorax deformation.However,affected by slaughtering and processing methods,it is difficult to obtain intact porcine thorax model.Taking into account the easy access to the integrity of the sheep thoracic model,this paper uses the sheep model as experimental thorax animal model.In this paper,the load displacement curve of the thorax in the sagittal plane and the strain distribution of the ribs and costal cartilage were obtained by electrical experiment.The intercostal muscle resection wasdesigned,and the animal thorax model of partial and total intercostal muscle was measured.The effect of intercostal muscle on thorax deformation was studied by repeated experiments.Based on the thorax CT images of the minimally invasive cases of the pectus excavatum,and using the Mimics and NX software,the thorax three-dimensional simplified calculation model including the sternum,vertebral body,rib and intervertebral disc and intercostal muscle was created based on the thorax model.The displacement field and stress-strain field of human thorax model were obtained by numerical simulation.The influence of intercostal muscle on thorax deformation was considered in the parameter study.Research results show that the intercostal muscles will affect the thorax deformation,the influence of different positions of the intercostal muscles is different,the influence between the fifth to ninth ribs of the intercostal muscles on the thoracic deformation is obvious.This paper first studies the impact of different positions of intercostal muscle on thorax deformation,and puts forward the modeling method to facilitate the establishment of thorax intercostal muscles.It is useful to predict the effect of minimally invasive correction of infundibulum with scoliosis by using three-dimensional solid model including intercostal muscles and to determine the factors that affect the effect of minimally invasive correction.