Biomechanical Finite Element Analysis Of Nuss Procedure And Wang Procedure

Objective1.To establish a three-dimensional finite element analysis model of Wang procedure to provide a basis for future basic research of Wang procedure biomechanics.2.To investigate the biomechanics of Nuss procedure and Wang procedure during surgery.3.To investigate the biomechanics of Nuss procedure and postoperative Wang procedure.4.To compare the biomechanical differences between Nuss procedure and Wang procedure.MethodsThree patients with pectus excavatum before operation(one patient each with mild,moderate and severe pectus excavatum)and one patient after pectus excavatum correction were selected to obtain their CT data.A 3D model of the thorax was constructed from the CT data using the 3D reconstruction software Mimics.The model was further refined and smoothed in the reverse engineering software Geomagic,and the surfaces were fitted to construct the solids.Use Solidworks software to construct the intervertebral disc and spinal joints,segment the thoracic structure,and assemble the steel plate to the thorax.The material was given elastic modulus and Poisson’s ratio in the finite element analysis software,the spinal ligaments were constructed,meshing was performed,and contact conditions and constraints were set.Displacement loads of 1.5 cm,3 cm,and 6 cm were applied to the three preoperative models,respectively.A sternal force of 0-180N perpendicular to the plane was applied to the lower sternal surface in the postoperative model.Finally,finite element analysis of the model was performed to derive the displacement and stresses in each part of the thorax.Results1.A more complete three-dimensional finite element model of the thorax was established in this study.2.Simulation results of the surgical procedure:sternal displacement and stress situation:both Nuss procedure and Wang procedure elevated the depressed sternum to the expected value,and the stress generated during Nuss procedure was less than that of Wang procedure;rib cartilage displacement and stress situation:both had similar displacement in mild and moderate pectus excavatum,and the displacement generated by Wang procedure in severe pectus excavatum was less than that of Nuss procedure,and the stress Wang procedure was greater than Nuss procedure.Rib displacement and stress:the intraoperative displacement and stress of Wang procedure on the ribs were greater than those of Nuss procedure.Spinal displacement and stress:the effect of Wang procedure on spinal displacement and stress on mild and moderate pectus excavatum spine during Wang procedure was less than that of Nuss procedure,and the stress on severe pectus excavatum spine by Nuss procedure was less than that of Wang procedure.3.postoperative simulation results:the displacement of each part of the thorax during Nuss procedure and Wang procedure was smaller than that without plate fixation,and the Nuss procedure was smaller than that of Wang procedure,but the difference between them was not significant.In terms of stress,the rib cartilage and rib stress of Nuss procedure was smaller than that of Wang procedure;the sternal and spinal stress of Wang procedure was smaller than that of Nuss procedure.Conclusion1.In this study,a variety of Nuss procedure finite element models were referred to construct a more complete and refined model.2.In this study,the first complete intraoperative and postoperative simulation of Wang procedure using finite element analysis method was performed,and the displacement and stress results were obtained.It provides theoretical basis for future Wang procedure improvement and biomechanical analysis.3.Both Nuss procedure and Wang procedure can effectively elevate the depression of the lower sternum,and Wang procedure can effectively limit the over-expansion of the thorax and reduce the displacement of the spine during the correction of severe pectus excavatum.Wang procedure causes more stress on the anterior chest wall,and the intraoperative stress on the spine of patients with mild and moderate pectus excavatum is less than that of Nuss procedure.4.Both Nuss procedure and Wang procedure can effectively prevent sternal depression after surgery;Nuss procedure has advantages in postoperative reduction of rib cartilage and rib stress forces;Wang procedure has advantages in postoperative reduction of sternal and spinal stresses.