2024, Vol. 28 ›› Issue (36): 5747-5752

Finite element analysis of biomechanical effect of lumbar range of motion on the implants after lumbar fusion

Li Ke1, Cao Shuai2, Zhang Qiongchi1, He Xijing1, Li Haopeng1, Li Jie1   

Abstract: BACKGROUND: At present, lumbar interbody fusion is widely used in the treatment of a variety of lumbar diseases. However, how to reduce postoperative complications such as pseudarthrosis formation, screw loosening and fracture, and cage failure remains a serious challenge.
OBJECTIVE: To analyze the effect of total lumbar range of motion on the stress or strain of bone grafts, cage, and screw-rod system, so as to better guide patients to carry out lumbar activities to reduce the risks of pseudarthrosis formation and instrumentation failure.
METHODS: An intact human L1-S1 finite element model was constructed using Mimics, 3-Matic, HyperMesh, and Abaqus software and the transforaminal lumbar interbody fusion was simulated. The average strain of the interbody bone grafts and the peak stresses of the cage and screw-rod system were compared before and after applying the bending moment, and the changing trend with the total range of motion was analyzed. The stress nephogram was drawn to observe the stress distribution.  
RESULTS AND CONCLUSION: (1) Compared with applying the vertical compression load alone, the average strain of the interbody bone grafts, peak stresses of the cage and screw-rod system after applying bending moment increased by 2.6%-55.3%, 65.6%-166.8%, and 36.0%-353.4%, respectively. (2) With the increase of total range of motion, the average strain of the interbody bone grafts increased nonlinearly and produced the maximum value under left and right axial rotation, while the peak stresses of the cage and screw-rod system increased linearly and produced the maximum value under left and right lateral bending. (3) The stress distribution of the interbody bone grafts and cage was related to the loading condition. The stress of the screw-rod system was mainly concentrated in the interfaces of the screw-bone and screw-rod. (4) Therefore, increasing axial rotation activity after operation may reduce the risk of pseudarthrosis formation, while reducing lateral bending activity may reduce the failure of the cage and screw-rod system.

Key words: transforaminal lumbar interbody fusion, range of motion, pseudarthrosis, instrumentation failure, finite element analysis