Kim Cheol-Jeong, Son Seung Min, Choi Sung Hoon, Ryu Dongman, Lee Chiseung
Department of Biomedical Engineering, Graduate School, Pusan National University, Busan, South Korea.
Department of Orthopaedic Surgery, Pusan National University Yangsan Hospital, Yangsan, South Korea.
Front Bioeng Biotechnol. 2022 Oct 7;10:1002276. doi: 10.3389/fbioe.2022.1002276. eCollection 2022.
Recently, the objectives of lumbar interbody fusion (LIF) have been extended to include the correction of broader/relative indications in addition to spinal fixation. Accordingly, LIF must be optimized for sagittal alignment while simultaneously achieving decompression. Therefore, a representative model classified into three pelvic types, i.e., neutral pelvis (NP), anterior pelvis (AP), and retroverted pelvis (RP), was selected according to the pelvic index, and LIF was performed on each representative model to analyze Lumbar lordosis (LL) and the corresponding equivalent stress. The finite element (FE) model was based on a sagittal 2D X-ray image. The calculation efficiency and convergence were improved by simplifying the modeling of the vertebral body in general and its posterior portion in particular. Based on the position of the pelvis, according to the pelvic shape, images of patients were classified into three types: AP, RP, and NP. Subsequently, representative images were selected for each type. The fixation device used in the fusion model was a pedicle screw and a spinal rod of a general type. PEEK was used as the cage material, and the cage shape was varied by using three different cage angles: 0°, 4°, and 8°. Spinal mobility: The pelvic type with the highest range of motion (ROM) for the spine was the NP type; the AP type had the highest LL. Under a combination load, the NP type exhibited the highest lumbar flexibility (LF), which was 2.46° lower on average compared to the case where a pure moment was applied. Equivalent stress on the spinal fixation device: The equivalent stress acting on the vertebrae was lowest when cage 0 was used for the NP and AP type. For the RP type, the lowest equivalent stress on the vertebrae was observed when cage 4 was used. Finally, for the L5 upper endplate, the stress did not vary significantly for a given type of cage. In conclusion, there was no significant difference in ROM according to cage angle, and the highest ROM, LL and LF were shown in the pelvic shape of NP type. However, when comparing the results with other pelvic types, it was not possible to confirm that LF is completely dependent on LL and ROM.
最近，腰椎椎间融合术（LIF）的目标已扩展到除脊柱固定外，还包括纠正更广泛的/相对适应证。因此，LIF必须在矢状位对线方面进行优化，同时实现减压。因此，根据骨盆指数选择了一种代表性模型，分为三种骨盆类型，即中立骨盆（NP）、前骨盆（AP）和后倾骨盆（RP），并在每个代表性模型上进行LIF，以分析腰椎前凸（LL）和相应的等效应力。有限元（FE）模型基于矢状面二维X线图像。通过简化椎体尤其是其后部的建模，提高了计算效率和收敛性。根据骨盆的位置，按照骨盆形状将患者图像分为三种类型：AP、RP和NP。随后，为每种类型选择代表性图像。融合模型中使用的固定装置是普通类型的椎弓根螺钉和脊柱棒。聚醚醚酮（PEEK）用作椎间融合器材料，通过使用三种不同的椎间融合器角度（0°、4°和8°）来改变椎间融合器的形状。脊柱活动度：脊柱活动范围（ROM）最高的骨盆类型是NP型；AP型的LL最高。在联合载荷下，NP型表现出最高的腰椎灵活性（LF），与施加纯力矩的情况相比，平均低2.46°。脊柱固定装置上的等效应力：对于NP型和AP型，使用椎间融合器0时，作用于椎体的等效应力最低。对于RP型，使用椎间融合器4时，观察到椎体上的等效应力最低。最后，对于L5上终板，给定类型的椎间融合器的应力没有显著变化。总之，根据椎间融合器角度，ROM没有显著差异，NP型骨盆形状的ROM、LL和LF最高。然而，当将结果与其他骨盆类型进行比较时，无法确定LF完全依赖于LL和ROM。
