Engineering Center for Orthopedic Research Excellence (E-CORE), Departments of Bioengineering and Orthopaedic Surgery, University of Toledo, Toledo, OH, USA.
Department of Orthopedic Surgery, University of California- San Francisco (UCSF), San Francisco, CA, USA.
Spine J. 2024 Nov;24(11):2191-2203. doi: 10.1016/j.spinee.2024.07.005. Epub 2024 Aug 2.
Pedicle subtraction osteotomy (PSO) is effective for correcting spinal malalignment but is associated with high complication rates. The biomechanical effect of different PSO levels remains unclear, and no finite element (FE) analysis has compared L2-, L3-, L4-, and L5-PSOs.
To assess the effects of PSO level on the spine's global range of motion, stresses on posterior instrumentation, load sharing with the anterior column, and proximal junctional stresses.
A computational biomechanical analysis.
A validated 3D spinopelvic FE model (T10-Pelvis) was used to perform PSOs at L2, L3, L4 and L5. Each model was instrumented with a 4-rod configuration (primary rods + in-line satellite rods) from T11-Pelvis. Simulation included a 2-step analysis; (1) applying 300 N to thoracic, 400 N to lumbar, and 400 N to sacrum, and (2) applying a 7.5 Nm moment to the top endplate of the T10 vertebral body. Acetabulum surfaces were fixed in all degrees of freedom. The range of motion, spinopelvic parameters (lumbar lordosis [LL], sacral slope [SS], pelvic incidence [PI], and pelvic tilt [PT]), PSO force, and von Mises stresses were measured. All models were compared with the L3-PSO model and percentage differences were captured.
Compared to the intact alignment: LL increased by 48%, 45%, 59%, and 56% in the L2-, L3-, L4-, and L5-PSO models; SS increased by 25%, 15%, and 11% while PT decreased by 76%, 53%, and 45% in L2-, L3-, and L4-PSOs (SS and PT approximated intact model in L5-PSO); Lumbar osteotomy did not affect the PI. Compared to L3-PSO: L2-, L4-, and L5-PSOs showed up to 32%, 34%, and 34% lower global ROM. The least T10-T11 ROM was observed in L5-PSO. The left and right SIJ ROM were approximately similar in each model. Amongst all, the L5-PSO model showed the least ROM at the SIJ. Compared to L3-PSO, the L2-, L4-, and L5-PSO models showed up to 67%, 61%, and 78% reduced stresses at the UIV, respectively. Minimum stress at UIV+ was observed in the L3-PSO model. The L2-and L3-PSOs showed the maximum PSO force. The L5-PSO model showed the lowest stresses on the primary rods in all motions.
Our FE investigation indicates that L5-PSO results in the greatest lumbar lordosis and lowest global, SIJ, and T10-T11 ROMs and stresses on the primary rods, suggesting potential mechanical benefits in reducing the risk of rod breakage. However, L4- and L5-PSOs led to the least force across the osteotomy site, which may increase the risk of pseudarthrosis. These findings provide biomechanical insights that may inform surgical planning, though further clinical investigation is essential to determine the optimal PSO level and validate these results.
Understanding the biomechanical impact of PSO level is crucial for optimizing surgical outcomes and minimizing the risks of postoperative complications.
经椎弓根截骨术（PSO）对于矫正脊柱失稳非常有效，但与之相关的并发症发生率较高。不同 PSO 水平的生物力学影响尚不清楚，也没有有限元（FE）分析比较过 L2、L3、L4 和 L5-PSO。
评估 PSO 水平对脊柱整体活动范围、后路内固定物的应力、与前柱的分担以及近端交界区的应力的影响。
计算生物力学分析。
使用经过验证的三维脊柱骨盆 FE 模型（T10-骨盆）进行 L2、L3、L4 和 L5 的 PSO。每个模型均采用 T11-骨盆的 4 杆结构（主杆+在线卫星杆）进行内固定。模拟包括两步分析；（1）在胸椎施加 300 N，在腰椎施加 400 N，在骶骨施加 400 N；（2）在 T10 椎体的顶端施加 7.5 Nm 的力矩。髋臼表面在所有自由度上固定。测量活动范围、脊柱骨盆参数（腰椎前凸[LL]、骶骨倾斜角[SS]、骨盆入射角[PI]和骨盆倾斜角[PT]）、PSO 力和 von Mises 应力。将所有模型与 L3-PSO 模型进行比较，并捕获百分比差异。
与完整对线相比：L2、L3、L4 和 L5-PSO 模型的 LL 分别增加了 48%、45%、59%和 56%；SS 增加了 25%、15%和 11%，而 PT 分别降低了 76%、53%和 45%（L5-PSO 中 SS 和 PT 接近完整模型）；腰椎截骨不影响 PI。与 L3-PSO 相比：L2、L4 和 L5-PSO 显示出高达 32%、34%和 34%的整体 ROM 降低。L5-PSO 中观察到最低的 T10-T11 ROM。每个模型的左右骶髂关节（SIJ）ROM 大致相似。在所有模型中，L5-PSO 模型在 SIJ 处显示出最小的 ROM。与 L3-PSO 相比，L2、L4 和 L5-PSO 模型的 UIV 处的应力分别降低了高达 67%、61%和 78%。在 L3-PSO 模型中观察到 UIV+的最小应力。L2 和 L3-PSO 显示出最大的 PSO 力。L5-PSO 模型在所有运动中表现出初级杆上最低的应力。
我们的 FE 研究表明，L5-PSO 导致最大的腰椎前凸和最低的整体、SIJ 和 T10-T11 ROM 以及初级杆上的应力，这表明在降低杆断裂风险方面可能具有机械优势。然而，L4 和 L5-PSO 导致截骨部位的力最小，这可能增加假关节形成的风险。这些发现提供了生物力学方面的见解，可能有助于指导手术计划，但需要进一步的临床研究来确定最佳的 PSO 水平并验证这些结果。
了解 PSO 水平的生物力学影响对于优化手术结果和最小化术后并发症的风险至关重要。
