AUTHOR=Guo Zehao , Peng Yongjun , Shen Qiling , Li Jian , He Peng , Yuan Peng , Liu Yulei , Que Yukang , Guo Wei , Hu Yong , Xu Shenglin 

TITLE=Reconstruction with 3D-printed prostheses after type I + II + III internal hemipelvectomy: Finite element analysis and preliminary outcomes

JOURNAL=Frontiers in Bioengineering and Biotechnology

VOLUME=Volume 10 - 2022

YEAR=2023

URL=https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2022.1036882

DOI=10.3389/fbioe.2022.1036882

ISSN=2296-4185

ABSTRACT=Background: The prosthetic reconstruction after type Ⅰ+Ⅱ+Ⅲ internal hemipelvectomy remains challenging due to the lack of osseointegration and giant shear force at the sacroiliac joint. The purpose of this study was to evaluate the biomechanical properties of the novel 3D-printed, custom-made prosthesis with pedicle screw-rod system and sacral tray using finite element analysis. 
Methods: Four models including one intact pelvis for validation were established. Forces of 500 N and 2000N were applied respectively to simulate static bipedal standing and extreme positions during a gait cycle. Biomechanical analysis was performed and results were compared. And the preliminary outcomes of four patients were recorded.
Results: For the reconstructed hemipelvis, stress mainly concentrated on the sacral screws and the bone/prosthesis interface, and the upper endplate of the L5 vertebra. The optimization of the design with the sacral tray structure could decrease the peak stress of the sacral screws by 18.6%, while the maximal stress of the prosthesis increased by 60.7%. The addition of the lumbosacral pedicle-rod system could further alleviate the stress of sacral screws and prosthesis by 30.2% and 19.4% respectively. The site of peak stress was contemporaneously transferred to the connecting rods within an elastic range. In the retrospective clinical study, four patients who had been reconstructed with the prosthesis were included. During a follow-up of 16.6 ± 7.5 months, walking ability was preserved in all patients who are still alive and no prosthesis-related complications occurred except one hip dislocation. The MSTS score was 19.5 ±2.9. 
Conclusion: The novel reconstructive system yielded favorable biomechanical characteristics and demonstrated promising preliminary outcomes. The method can provide a reference for the reconstruction after type Ⅰ+Ⅱ+Ⅲ hemipelvectomy.