Department of Spine Surgery, Tianjin Hospital, Tianjin University, No. 406 Jiefang South Rd, Hexi District, Tianjin, 300211, China.
The Second Affiliated Hospital of Hainan Medical University, Haikou City, Hainan, China.
BMC Musculoskelet Disord. 2023 Aug 30;24(1):695. doi: 10.1186/s12891-023-06792-1.
This study aimed to compare the biomechanical properties of lumbar interbody fusion involving two types of cages. The study evaluated the effectiveness of the cage spanning the ring apophysis, regardless of the endplate's integrity.
A finite element model of the normal spine was established and validated in this study. The validated model was then utilized to simulate Lateral Lumbar Interbody Fusion (LLIF) with posterior pedicle screw fixation without posterior osteotomy. Two models of interbody fusion cage were placed at the L4/5 level, and the destruction of the bony endplate caused by curetting the cartilaginous endplate during surgery was simulated. Four models were established, including Model 1 with an intact endplate and long cage spanning the ring apophysis, Model 2 with endplate decortication and long cage spanning the ring apophysis, Model 3 with an intact endplate and short cage, and Model 4 with endplate decortication and short cage. Analyzed were the ROM of the fixed and adjacent segments, screw rod system stress, interface stress between cage and L5 endplate, trabecular bone stress on the upper surface of L5, and intervertebral disc pressure (IDP) of adjacent segments.
There were no significant differences in ROM and IDP between adjacent segments in each postoperative model. In the short cage model, the range of motion (ROM), contact pressure between the cage and endplate, stress in L5 cancellous bone, and stress in the screw-rod system all exhibited an increase ranging from 0.4% to 79.9%, 252.9% to 526.9%, 27.3% to 133.3%, and 11.4% to 107%, respectively. This trend was further amplified when the endplate was damaged, resulting in a maximum increase of 88.6%, 676.1%, 516.6%, and 109.3%, respectively. Regardless of the integrity of the endplate, the long cage provided greater support strength compared to the short cage.
Caution should be exercised during endplate preparation and cage placement to maintain the endplate's integrity. Based on preoperative X-ray evaluation, the selection of a cage that exceeds the width of the pedicle by at least 5 mm (ensuring complete coverage of the vertebral ring) has demonstrated remarkable biomechanical performance in lateral lumbar interbody fusion procedures. By opting for such a cage, we expect a reduced occurrence of complications, including cage subsidence, internal fixation system failure, and rod fracture.
本研究旨在比较两种类型的椎间融合笼在腰椎体间融合中的生物力学性能。本研究评估了环突关节融合笼的有效性，无论终板是否完整。
本研究建立并验证了正常脊柱的有限元模型。然后利用该模型模拟了不进行后路截骨的侧方腰椎间融合术（LLIF）并结合后路椎弓根螺钉固定。在 L4/5 水平放置两种椎间融合笼模型，并模拟手术中切除软骨终板时对骨性终板的破坏。建立了 4 种模型，包括 1 型为完整终板和长融合笼跨越环突关节，2 型为终板去皮质化和长融合笼跨越环突关节，3 型为完整终板和短融合笼，4 型为终板去皮质化和短融合笼。分析了固定节段和相邻节段的 ROM、棒系统的应力、 cage 和 L5 终板之间的界面应力、L5 上表面的小梁骨应力以及相邻节段的椎间盘压力（IDP）。
每个术后模型的相邻节段 ROM 和 IDP 无显著差异。在短笼模型中，运动范围（ROM）、 cage 与终板的接触压力、L5 松质骨的应力和螺钉-棒系统的应力分别增加了 0.4%至 79.9%、252.9%至 526.9%、27.3%至 133.3%和 11.4%至 107%。当终板受损时，这种趋势进一步放大，最大增幅分别为 88.6%、676.1%、516.6%和 109.3%。无论终板是否完整，长笼都比短笼提供更大的支撑强度。
在终板准备和 cage 放置过程中应谨慎操作，以保持终板的完整性。基于术前 X 射线评估，选择超出椎弓根宽度至少 5 毫米（确保完全覆盖椎环）的 cage 具有显著的生物力学性能，可降低 cage 下沉、内固定系统失效和棒断裂等并发症的发生。
