Biomechanical changes of the cervical spine in internal fixation with different anterior cervical interbody fusion systems

doi:10.12307/2023.787

Abstract

Abstract: BACKGROUND: Due to the treatment of cervical spondylosis, the Zero-P system of the anterior cervical interbody fusion system will have problems such as screw loosening and fracture after operation, so a novel Low-P system has been developed.
OBJECTIVE: To compare the effects of the novel Low-P and Zero-P anterior cervical intervertebral fusion systems on the biomechanical properties of adjacent segments of the cervical spine and to perform stress analysis on the internal fixation system, so as to provide a theoretical reference for clinical treatment.
METHODS: A complete model of the C1-C7 segment of the cervical spine was established. Based on the effectiveness of the model, a finite element model of Low-P (type Z Low-P and type H Low-P) and Zero-P system implanted in C4-C5 segments was established. The stress distribution of implanted devices and adjacent vertebral nucleus pulposus, fibrous rings and end plates was analyzed under the conditions of forward flexion, posterior extension, lateral bending and rotation.
RESULTS AND CONCLUSION: (1) After implantation of Low-P and Zero-P internal fixation devices, the range of motion of the type H Low-P system was large; the maximum stress value of type Z Low-P system was small; the maximum stress of Zero-P on the nucleus pulposus of adjacent segments was large; the maximum stress of end plate was small. (2) The influence of three internal fixation systems on adjacent segment fiber rings was close. (3) The screw stress of the Zero-P internal fixation system was much greater than that of the Low-P system. (4) It is indicated that compared with Zero-P type internal fixation system, the novel Low-P system reduces the stress value of steel plate and screw, which can reduce screw loosening and internal fixation system failure. The Low-P system has less stress on the nucleus pulposus of adjacent discs and reduces disc degeneration in adjacent segments. This paper provides a theoretical basis for the clinical study of a Low-P type internal fixation system.

Key words: anterior cervical internal fixation system, Low-P type, Zero-P type, cervical spine, biomechanics, finite element analysis

CLC Number:

Wang Qiang, Li Shiyun, Xiong Ying, Li Tiantian. Biomechanical changes of the cervical spine in internal fixation with different anterior cervical interbody fusion systems[J]. Chinese Journal of Tissue Engineering Research, 2024, 28(6): 821-826.

Figures/Tables 9

最大等效应力显示，Zero-P系统在不同工况下的最大应力均大于H型和Z型，其中前屈工况下，Zero-P系统的最大应力值为257.15 MPa，比H型增加了379%，比Z型增加了618%，且H型比Z型增加了63%；后伸工况下，Zero-P系统的最大应力值为69.75 MPa，比H型增加了339%，比Z型增加了219%，且Z型比H型增加了37%；侧弯工况下，Zero-P系统的最大应力值为258.73 MPa，比H型增加了545%，比Z型增加了727%，且H型比Z型增加了33%；旋转工况下，Zero-P系统的最大应力值为792.28 MPa，比H型增加了777%，比Z型增加了963%，且H型比Z型增加了24%。综上所述，H型Low-P系统术后活动度最大，H型Low-P系统与Z型Low-P系统的最大应力均小于Zero-P系统，且Z型Low-P系统所受最大应力更小。 2.4 髓核最大等效应力对比对颈椎模型分别置入H型Low-P、Z型Low-P与Zero-P系统，将病变C4-C5椎体进行融合，施加1.5 N·m载荷。在4种工况下髓核最大等效应力的计算结果见图7。前屈工况下，C3-C4髓核的最大应力相接近；C5-C6髓核最大应力，Zero-P系统比H型增加了53%，比Z型增加了63%。后伸工况下，C3-C4髓核的最大应力Zero-P系统为0.037 MPa，比H型增加了59%，比Z型增加了137%；C5-C6髓核的最大应力Zero-P系统为0.029 MPa，比H型增加了43%，比Z型增加了174%。侧弯工况下，C3-C4髓核的最大应力Zero-P系统为0.186 MPa，比H型增加了95%，比Z型增加了42%；C5-C6髓核的最大应力Zero-P系统为0.117 MPa，比H型增加了32%，比Z型增加了75%。旋转工况下，C3-C4髓核的最大应力Zero-P系统为0.244 MPa，比H型增加了69%，比Z型增加了45%；C5-C6髓核的最大应力Zero-P系统为0.205 MPa，比H型增加了16%，比Z型增加了22%。髓核前屈工况下的应力云图见图8所示，最大应力基本集中于髓核中间和侧面。"

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