Chinese Journal of Tissue Engineering Research ›› 2024, Vol. 28 ›› Issue (12): 1842-1848.doi: 10.12307/2024.012

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Biomechanical features of posterior “Y” osteotomy and fixation in treatment of ankylosing spondylitis based on finite element simulation analysis

Zhang Le1, 2, Cao Zhenhua3, 4, Zhang Yunfeng3, Xu Yangyang4, Jin Feng5, Su Baoke6, Wang Lidong7, Wang Xing1, Tong Ling1, Liu Qinghua1, Fang Yuan1, Sha Lirong1, Wang Haiyan1, Li Xiaohe1, Li Zhijun1   

  1. 1Department of Human Anatomy, School of Basic Medicine, Inner Mongolia Medical University (Inner Mongolia Digital Transformation Medical Engineering Technology Research Center), Hohhot 010000, Inner Mongolia Autonomous Region, China; 2Bayannur City Hospital, Bayannur 015000, Inner Mongolia Autonomous Region, China; 3Department of Imaging, Second Affiliated Hospital of Inner Mongolia Medical University, Hohhot 010000, Inner Mongolia Autonomous Region, China; 
  • Received:2022-12-01 Accepted:2023-03-09 Online:2024-04-28 Published:2023-08-22
  • Contact: Zhang Yunfeng, Associate chief physician, Department of Imaging, Second Affiliated Hospital of Inner Mongolia Medical University, Hohhot 010000, Inner Mongolia Autonomous Region, China Li Xiaohe, Professor, Doctoral supervisor, Department of Human Anatomy, School of Basic Medicine, Inner Mongolia Medical University (Inner Mongolia Digital Transformation Medical Engineering Technology Research Center), Hohhot 010000, Inner Mongolia Autonomous Region, China
  • About author:Zhang Le, Master candidate, Department of Human Anatomy, School of Basic Medicine, Inner Mongolia Medical University (Inner Mongolia Digital Transformation Medical Engineering Technology Research Center), Hohhot 010000, Inner Mongolia Autonomous Region, China; Bayannur City Hospital, Bayannur 015000, Inner Mongolia Autonomous Region, China Cao Zhenhua, MD, Associate chief physician, Department of Imaging, Second Affiliated Hospital of Inner Mongolia Medical University, Hohhot 010000, Inner Mongolia Autonomous Region, China; School of Biological and Medical Engineering, Beihang University, Beijing 100083, China
  • Supported by:
    Natural Science Foundation of Inner Mongolia Autonomous Region, No. 2021MS08086 (to WHY); 2022 Inner Mongolia Autonomous Region Health Science and Technology Plan Project, No. 202201188 (to WHY); “Achievement Transformation” Project of Inner Mongolia Medical University in 2020, No. YKD2020CGZH009 (to WHY); Inner Mongolia Natural Science Foundation, No. 2020MS08124 (to LXH); “Grassland Talents” Project Youth Innovation and Entrepreneurship Talent Program of Inner Mongolia Autonomous Region, No. 2020 (to LXH); Follow-Up Scientific Research Project of Inner Mongolia Medical University, No. 2020 (to LXH); Inner Mongolia Science and Technology Plan Project, No. 2019GG115 (to LZJ); 2021 Mongolian Medicine Collaborative Innovation Center Scientific Research Project of Inner Mongolia Autonomous Region (to LXH); 2021 Zhiyuan Talent Project of Inner Mongolia Medical University (to LXH); 2021 School-Level Key Scientific Research Project of Inner Mongolia Medical University, No. YKD2021ZD001 (to LXH); Higher Education Innovation Team Development Plan of Inner Mongolia Education Department, No. NMGIRT2227 (to LXH)

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Abstract: BACKGROUND: Ankylosing spondylitis is a progressive inflammation of spinal stiffness deformity caused by tissue ossification and fibrosis. The posture of ankylosing spondylitis patients is abnormal and their activities are limited that minor injuries can lead to thoracolumbar fractures. Traditional medical image observation limits doctors’ preoperative decision planning and postoperative disease prevention for ankylosing spondylitis treatment.
OBJECTIVE: Based on the spinal model of ankylosing spondylitis patients before and after posterior spinal cancellous ossification osteotomy (“Y” osteotomy for short), to explore the biomechanical changes of “Y” osteotomy and fixation in the treatment of ankylosing spondylitis.
METHODS: Based on the preoperative and postoperative CT images of an ankylosing spondylitis patient who went to the Second Affiliated Hospital of Inner Mongolia Medical University, a three-dimensional spine model (T11-S1) before and after “Y” osteotomy (L3 osteotomy) was reconstructed in Mimics 19.0 software. A 7.5 Nm torque was applied to the top of T11 vertebral body to simulate the movement of the spine under six conditions: flexion, extension, left bending, right bending, left rotation and right rotation. Finally, the range of motion of each vertebral body, the stress of each intervertebral disc, and the stress of the screw rod system were simulated. 
RESULTS AND CONCLUSION: (1) After “Y” type osteotomy and posterior fixation, the range of motion of all vertebrae in the spine decreased, and the loss rate of upper vertebrae was large (L1: 77.95%). (2) The maximum stress of the spinal intervertebral disc before operation occurred at the L1-L2 segment (0.55 MPa), and the maximum stress of the spinal intervertebral disc after operation occurred at the T11-T12 segment (0.50 MPa), and the stress of intervertebral disc below T12 was far less than that before operation. (3) The maximum stress of the screw rod system (166.67 MPa) occurred in the upper and middle segments of the rod body and the root of the pedicle screw. (4) In conclusion, the “Y” type posterior fixation operation enhances the stability of the spine and reduces the range of motion of the spine. The vertebral body decompression of the fixed segment is great and the stress-shielding phenomenon of the lower vertebral body is significant. The stiffness of the rod body and the stress concentration area of the pedicle screw should be strengthened to avoid the fracture of the rod caused by stress fatigue. 

Key words: ankylosing spondylitis, posterior fixation surgery, three-dimensional reconstruction model, Y-shaped osteotomy, spinal biomechanics

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