Department of Spine Surgery, Tongji Hospital, Tongji University School of Medicine, Shanghai, 200065, China; College of Civil Engineering, Tongji University, Shanghai, 200082, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration (Tongji University), Ministry of Education, Tongji University School of Medicine, Shanghai, 200065, China.
Department of Spine Surgery, Tongji Hospital, Tongji University School of Medicine, Shanghai, 200065, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration (Tongji University), Ministry of Education, Tongji University School of Medicine, Shanghai, 200065, China.
Comput Biol Med. 2021 Apr;131:104291. doi: 10.1016/j.compbiomed.2021.104291. Epub 2021 Feb 19.
Transforaminal lumbar interbody fusion (TLIF) is a well-established surgical treatment for patients with lumbar degenerative disc disease; however, the optimal position for the interbody fusion cage in TLIF procedures for reducing cage-related complications remains uncertain. The present study aims to compare the biomechanical effects between different cage positions in TLIF and percutaneous endoscopic-TLIF (PE-TLIF).
An intact finite element model of L3-L5 from computed tomography images of a 25-year-old healthy male without any lumbar disease was reconstructed and validated. TLIF and PE-TLIF were performed on L4-L5 with bilateral pedicle screws fixation. Two surgical finite element models were subjected to loads with six degrees of freedom. The range of motion (ROM) and von Mises stress of the implantations and endplates were measured for the anterior, middle, and posterior district and the traverse or oblique direction of the cage respectively.
As the cage was implanted forward, the ROMs in the fused L4-L5 segments and the von Mises stress of the cage and endplates decreased while the von Mises stress of the screws increased; this was also shown in the traverse cage when compared with the oblique cage (A-90-compared with A-45- had a 31.3%, 1.7%, 12.6%, and 5.7% decrease in FL, EX, LB and AR). The ROMs (TLIF A-45 increase of 80.8%, 23.8%, and 12.2% in FL, EX, and LB when compared with PE-TLIF), cage stress, and endplate stress of PE-TLIF were lower than those of TLIF.
Considering the ROM of the fusion segments, implanting the cage in the anterior district in the traverse direction can effectively enhance the fusion segment stiffness, thus contributing to the stability of the lumbar spine after fusion. It can also cause less cage stress and endplate stress, which indicates its beneficial effect in avoiding cage injury or subsidence. However, the higher stress of the pedicle screws and rods indicates higher failure risk. PE-TLIF had better biomechanical performance than TLIF. Therefore, it is recommended that the surgeon implant the cage in the anterior district of the L5 vertebra's upper endplate in the traverse direction using the PE-TLIF technique.
经椎间孔腰椎体间融合术（TLIF）是治疗腰椎退行性疾病患者的一种成熟的手术治疗方法；然而，TLIF 手术中椎间融合器的最佳位置以减少与融合器相关的并发症仍不确定。本研究旨在比较 TLIF 和经皮内镜 TLIF（PE-TLIF）中不同融合器位置的生物力学效应。
从一位 25 岁无腰椎疾病的健康男性的 CT 图像中重建并验证了 L3-L5 的完整有限元模型。在 L4-L5 双侧椎弓根螺钉固定下进行 TLIF 和 PE-TLIF。对两个手术有限元模型施加六个自由度的载荷。测量植入物和终板在前、中、后区以及融合器的横切或斜向方向的运动范围（ROM）和 von Mises 应力。
随着融合器向前植入，融合的 L4-L5 节段的 ROM 和融合器及终板的 von Mises 应力减小，而螺钉的 von Mises 应力增加；与斜向融合器相比，横切融合器也表现出同样的结果（A-90 与 A-45 相比，FL、EX、LB 和 AR 的 ROM 分别减少 31.3%、1.7%、12.6%和 5.7%）。与 TLIF 相比，PE-TLIF 的 ROM（TLIF A-45 的增加幅度为 FL、EX 和 LB 的 80.8%、23.8%和 12.2%）、融合器应力和终板应力较低。
考虑到融合节段的 ROM，将融合器从前部以横切方向植入可以有效地增强融合节段的刚度，从而有助于融合后腰椎的稳定性。它还可以减少融合器和终板的应力，表明其在避免融合器损伤或下沉方面具有有益的效果。然而，椎弓根螺钉和棒的较高应力表明更高的失效风险。PE-TLIF 的生物力学性能优于 TLIF。因此，建议外科医生使用 PE-TLIF 技术，将融合器从前部植入 L5 椎体上终板的横切方向。
