Biomechanical comparison of a 3D-printed sacrum prosthesis versus rod-screw systems for reconstruction after total sacrectomy: A finite element analysis

Abstract Background Reconstruction after total sacrectomy is a difficult problem in the field of orthopedic oncology. Current reconstruction methods have not completely solved the problems associated with instrumentation failure. The purpose of this study was to evaluate the biomechanical properties of a 3D-printed total sacrum prosthesis and to conduct biomechanical comparisons between the total sacrum prosthesis and rod-screw systems for lumbosacral reconstruction after total sacrectomy. Methods Three types of reconstruction were explored, and corresponding finite element models were simulated: four-rod reconstruction, four-rod plus anterior column reconstruction, and 3D-printed total sacrum prosthesis reconstruction. A vertical load of 600 N was applied to the L4 vertebra, and the bilateral acetabula were set as the boundary with six degrees of freedom fixed, simulating the bipedal standing position. Findings The order of the reconstructions according to decreasing maximum von Mises stress was as follows: four-rod reconstruction > four-rod plus anterior column reconstruction >3D-printed total sacrum prosthesis reconstruction. The order of reconstructions according to decreasing L5 shift-down displacement was as follows: four-rod reconstruction >3D-printed total sacrum prosthesis reconstruction > four-rod plus anterior column reconstruction. Interpretation Compared with the rod-screw systems, the total sacrum prosthesis reconstruction has the biomechanical advantages of a more uniform stress distribution, a lower peak stress and better stability and can thus serve as an alternative choice for reconstruction after total sacrectomy.