Study On The Interaction Between Scoliosis And Pectus Excavatum During Surgical Correction

Part I: Clinical Study of Pediatric Pectus Excavatum Combined with Idiopathic ScoliosisBackground: Pectus excavatum has a high associated rate with idiopathic scoliosis,both of them have a negative effect on the cardiopulmonary function and development.However,there is few study on the interaction effect for pectus excavatum associated scoliosis.Purpose: To evaluate the prevelance and progression of idiopathic scoliosis in pectus excavatum after Nuss procedure.Method: 171 pectus excavatum cases were retrospectively reviewed.Chest and spine radiography have been undertook before Nuss procedure and after the bar removed,Parameters including thoracic kyphosis,sternum rotation,thoracic rotation,thoracic assymetric ratio and Haller index were compared between scoliosis and non-scoliosis group;the change of scoliosis were compared between symmetric and asymmetric chest group.Results: The prevelance of scoliosis in pectus excavatum is 21.1%(36/171)with average cobb angle 16.87°.In scoliosis group,patients have a higher sternum rotation and thoracic rotation(p<0.05),and there is no difference between the Haller index.The scoliosis patient were treated as observation/brace/surgery due to their curve angle.After 35.73 months follow-up the bar is removed,14 scoliosis improve to normal and another 13 normal case progress to scoliosis;the scoliosis change is more likely occoured in assymetric chest patients(p<0.01).Conclusion: there is a high prevelance of idiopathic scoliosis in pectus excavatum patients,and the scoliosismay change after Nuss procedure.The pediatric chest surgeon and orthopedics surgeon need to work together to deal this situation.Part II: The Effect of Surgical Treatment on The Spine in Asymmetric Pectus ExcavatumPurpose: To evaluate the effect of surgical treatment on the spine in the pectus excavatum patient with asymmetric thoraces.Method: From CT data,typical finite-element model of asymmetric pectus excavatum was produced by mimics and 3-matic software.The model was divided to2 types due to the fix point: in type a the top of cartilage rib and the front edge of vertebral canal were fixed,in type b only the convex side of cartilage rib and the back edge of vertebral canal were fixed.The surgical treatments were simulated in abaqus software in 2 steps: first step aimed to uplift the sternum,second step was to uplift the depressed side of asymmetric thorax.The two--step surgical correction was stimulated and the effect on the spine and the vertebral was evaluated.37 asymmetric pectus excavatum cases were retrospective reviewed and divided into 3group: In Group 1(n=9),patient has scoliosis with convex of scoliosis and concave of thorax were in both side.In Group 2(n=5),patients have scoliosis with convex of scoliosis and concave of thorax were in opposite side.In Group 3(n=23),patient has no scoliosis.The morphology change of spine was evaluated after surgical treatment and the results were compared with the finite-element model simulation to validate.Results: The result of finite-element model simulation show there is limited effect on the spine in step 1 correction.However the spine was effected in step 2 correction: the vertebra were forced to rotate to the convex side of thorax,in type a the average rotation angle is 10°,in type b the angle is 4.8°.The clinical cases show in Group 1 there were 7 cases scoliosis improved with 2 cases changeless.In Group 2 there were 4 cases scoliosis progressed with 1 cases changeless.In Group 3 there were 14 cases unchanged with 8 cases progressed to scoliosis and 1 case improved.There is significant difference between the 3 groups(p<0.001).Conclusion: There is a mechanical effect on the spine after the asymmetric pectus excavatum were surgical corrected.The change of spine could be predicted due to the morphological characteristics between the thorax and spine.