Ramakrishna Vivek A S, Chamoli Uphar, Viglione Luke L, Tsafnat Naomi, Diwan Ashish D
Spine Service, Department of Orthopaedic Surgery, St. George & Sutherland Clinical School, University of New South Wales Australia, Kogarah, Sydney NSW, Australia.
School of Biomedical Engineering, University of Technology Sydney, Ultimo NSW, Australia.
Global Spine J. 2018 Aug;8(5):460-470. doi: 10.1177/2192568217735802. Epub 2017 Nov 16.
A biomechanical study using finite element analysis.
The main objective of this study was to investigate the role of sacral slope in the progression of a L5 bilateral spondylolytic defect to spondylolisthesis.
A 3-dimensional model of lumbosacral spine was built using computed tomography (CT) data procured from an anonymized healthy male subject. The segmented CT data was manipulated to generate 3 more models representing L5 bilateral spondylolytic defect with normal sacral slope (SS), sacral slope increased by 10° (SS+10), and sacral slope decreased by 10° (SS-10). The 3D models were imported into finite element modelling software Strand7 for preprocessing, running nonlinear static solves, and postprocessing of the results.
Directional biomechanical instabilities were induced in the lumbosacral spine as a result of changes in the L5-S1 disc shape secondary to the changes in sacral slope. Compared with the normal L5 lytic model, wedging of the L5-S1 disc (SS+10) resulted in a significantly greater range of motion in flexion (18% ↑) but extension motion characteristics were similar. Conversely, flattening of the L5-S1 disc (SS-10) resulted in a significantly greater range of motion in extension (16% ↑) but flexion motion characteristics were similar to that of the normal L5 lytic model.
Variations in sacral slope while preserving the L5-S1 mid-disc height and orientation of the L5 vertebra resulted in variations in the L5-S1 disc shape. The results suggest that for such extremities in the L5-S1 disc shape different pathomechanisms exist for the progression of the L5 lytic defect to spondylolisthesis.
一项使用有限元分析的生物力学研究。
本研究的主要目的是调查骶骨倾斜度在L5双侧峡部裂性缺损进展为腰椎滑脱过程中的作用。
使用从一名匿名健康男性受试者获取的计算机断层扫描（CT）数据构建腰骶椎三维模型。对分割后的CT数据进行处理，以生成另外3个模型，分别代表具有正常骶骨倾斜度（SS）、骶骨倾斜度增加10°（SS+10）和骶骨倾斜度降低10°（SS-10）的L5双侧峡部裂性缺损。将这3D模型导入有限元建模软件Strand7进行预处理、运行非线性静态求解以及结果后处理。
由于骶骨倾斜度变化导致L5-S1椎间盘形状改变，从而在腰骶椎中诱发了方向性生物力学不稳定。与正常L5峡部裂模型相比，L5-S1椎间盘楔形变（SS+10）导致前屈运动范围显著增大（增加18%），但后伸运动特征相似。相反，L5-S1椎间盘变平（SS-10）导致后伸运动范围显著增大（增加16%），但前屈运动特征与正常L5峡部裂模型相似。
在保持L5-S1椎间盘中部高度和L5椎体方向的同时，骶骨倾斜度的变化导致了L5-S1椎间盘形状的改变。结果表明，对于L5-S1椎间盘形状的这种极端情况，L5峡部裂性缺损进展为腰椎滑脱存在不同的病理机制。
