Vosoughi Ardalan Seyed, Shekouhi Niloufar, Joukar Amin, Zavatsky Michael, Goel Vijay K, Zavatsky Joseph M
Engineering Center for Orthopedic Research Excellence (E-CORE), Departments of Bioengineering and Orthopaedic Surgery, University of Toledo, Toledo, OH, USA.
Spine & Scoliosis Specialists, Tampa, FL, USA.
Global Spine J. 2023 Oct;13(8):2336-2344. doi: 10.1177/21925682221081797. Epub 2022 Feb 26.
Finite element (FE) study.
Pedicle subtraction osteotomy (PSO) is a surgical method to correct sagittal plane deformities. In this study, we aimed to investigate the biomechanical effects of lumbar disc degeneration on the instrumentation following PSO and assess the effects of using interbody spacers adjacent to the PSO level in a long instrumented spinal construct.
A spinopelvic model (T10-pelvis) with PSO at the L3 level was used to generate 3 different simplified grades of degenerated lumbar discs (mild (Pfirrmann grade III), moderate (Pfirrmann grade IV), and severe (Pfirrmann grade V)). Instrumentation included eighteen pedicle screws and bilateral primary rods. To investigate the effect of interbody spacers, the model with normal disc height was modified to accommodate 2 interbody spacers adjacent to the PSO level through a lateral approach. For the models, the rods' stress distribution, PSO site force values, and the spine range of motion (ROM) were recorded.
The mildly, moderately, and severely degenerated models indicated approximately 10%, 26%, and 40% decrease in flexion/extension motion, respectively. Supplementing the instrumented spinopelvic PSO model using interbody spacers reduced the ROM by 22%, 21%, 4%, and 11% in flexion, extension, lateral bending, and axial rotation, respectively. The FE results illustrated lower von Mises stress on the rods and higher forces at the PSO site at higher degeneration grades and while using the interbody spacers.
Larger and less degenerated discs adjacent to the PSO site may warrant consideration for interbody cage instrumentation to decrease the risk of rod fracture and PSO site non-union.
有限元研究。
椎弓根截骨术（PSO）是一种矫正矢状面畸形的手术方法。在本研究中，我们旨在探讨腰椎间盘退变对PSO术后内固定器械的生物力学影响，并评估在长节段脊柱内固定结构中，在PSO节段相邻位置使用椎间融合器的效果。
使用在L3水平行PSO的脊柱骨盆模型（T10 - 骨盆），生成3种不同简化程度的退变腰椎间盘（轻度（Pfirrmann III级）、中度（Pfirrmann IV级）和重度（Pfirrmann V级））。内固定包括18枚椎弓根螺钉和双侧主棒。为研究椎间融合器的作用，将椎间盘高度正常的模型进行修改，通过外侧入路在PSO节段相邻位置置入2个椎间融合器。记录各模型中棒的应力分布、PSO部位的力值以及脊柱活动度（ROM）。
轻度、中度和重度退变模型的屈伸活动度分别降低约10%、26%和40%。在置入椎间融合器的脊柱骨盆PSO内固定模型中，屈伸、侧屈和轴向旋转的ROM分别降低了22%、21%、4%和11%。有限元结果表明，在退变程度较高以及使用椎间融合器时，棒上的von Mises应力较低，而PSO部位的力较高。
PSO部位相邻的椎间盘较大且退变程度较低时，可能需要考虑使用椎间融合器内固定，以降低棒断裂和PSO部位不愈合的风险。
