Institute of Biomedical Engineering, Polytechnique Montréal, PO Box 6079, Montreal, QC H3C 3A7, Canada; Sainte-Justine University Hospital Center, Montreal, Canada.
Department of Surgery, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada.
Clin Biomech (Bristol). 2024 Dec;120:106352. doi: 10.1016/j.clinbiomech.2024.106352. Epub 2024 Sep 20.
Oblique lumbar intervertebral fusion aims to decompress spinal nerves via an interbody fusion cage, but the optimal surgical strategy, including implant selection for specific patient characteristics, remains unclear. A biomechanical model was developed to assess how pathophysiological characteristics and instrumentation impact spinal realignment, indirect decompression, and cage subsidence risk.
A finite element model of the L4-L5 segment was derived from a validated asymptomatic T1-S1 spine model. Five cases of grade I spondylolisthesis with normal or osteoporotic bone densities and initial disc heights of 4.3 to 8.3 mm were simulated. Oblique lumbar intervertebral fusion with cage heights of 10, 12, and 14 mm (12° lordosis) was examined. Postoperative changes in disc height, foraminal and spinal canal dimensions, segmental lordosis, and vertebral slip were assessed. Vertebral stresses and displacements under 10 Nm flexion and 400 N gravitational load were compared between stand-alone constructs and bilateral pedicle screw fixation using rods of 4.75, 5.5, and 6 mm diameters.
Oblique lumbar intervertebral fusion significantly improved postoperative disc height, foraminal and spinal canal dimensions, with the greatest enhancements observed with 14 mm cages. Bilateral pedicle screw fixation markedly reduced cortical endplate stresses and displacements compared to stand-alone constructs, with added benefits from larger rod diameters. Low bone density increased displacements by 63 %.
Thicker cages achieve better decompression but increase subsidence risk. Bilateral pedicle screw fixation with 6 mm rods minimizes endplate stresses and displacements, especially in osteoporotic cases. Future research will validate these findings and explore the model's potential for surgical planning.
斜向腰椎椎间融合术旨在通过椎间融合 cage 来对脊髓神经进行减压，但对于特定患者特征的最佳手术策略，包括植入物选择，仍不清楚。建立了生物力学模型来评估病理生理特征和器械如何影响脊柱对线、间接减压和 cage 下沉风险。
从一个经过验证的无症状 T1-S1 脊柱模型中推导出 L4-L5 节段的有限元模型。模拟了 5 例具有正常或骨质疏松骨密度和初始椎间盘高度为 4.3 至 8.3 毫米的 I 度脊椎滑脱。研究了斜向腰椎椎间融合，使用 10、12 和 14 毫米高的 cage（12°前凸）。评估了术后椎间盘高度、椎间孔和椎管尺寸、节段前凸和椎体滑移的变化。在 10 Nm 前屈和 400 N 重力载荷下，比较了独立结构和双侧椎弓根螺钉固定（使用 4.75、5.5 和 6 毫米直径的棒）的椎骨应力和位移。
斜向腰椎椎间融合术显著改善了术后椎间盘高度、椎间孔和椎管尺寸，14 毫米 cage 的改善最大。双侧椎弓根螺钉固定与独立结构相比，显著降低了皮质终板的应力和位移，而更大的棒直径则增加了额外的益处。低骨密度增加了 63%的位移。
较厚的 cage 可实现更好的减压，但增加了下沉的风险。双侧椎弓根螺钉固定使用 6 毫米棒可最大程度地减少终板的应力和位移，特别是在骨质疏松病例中。未来的研究将验证这些发现，并探讨该模型在手术规划中的潜力。
