Simulation of Nuss Orthopedic for Pectus Excavatum

Abstract

Nuss Orthopedic of Pectus Excavatum(PE) is a novel minimal invasive surgical technique for the treatment of PE, however, the surgery will fail as the Nuss bar is slipped or rotated. A 3D model for thorax is built according to the helical CT images of PE, the process of Nuss orthopedic was simulated by finite element analysis. The results show as the depressed sternum was jacking to normal position gradually by Nuss bar, the sternum, the ribs and the rib cartilages will all move upward which make the Nuss bar support the sternum at the location lower about 1~6 mm than the end of depressed sternum end. However, original plan is that the bar should be supported just at the end of depressed sternum. After the bar is fixed, there is a torque on the bar for the pressure imposed by sternum and the force produced by the fixed place of bar forms a pair of torque. This torque may be the reason for the failure of surgery. The improvement is that the fix place of bar should be move upward 1~6mm or a distance of one rib. Keywords-pectus excavatum; Nuss orthopedic; 3D modeling; finite element; simulation