Han Lin, Li Yongheng, Li Zhiyong, Ma Hongdao, Wang Chenfeng, Chen Qiang, Lu Xuhua
Department of Orthopaedics, Shanghai Changzheng Hospital, Second Military Medical University, Shanghai, China.
Biomechanics Laboratory, School of Biological Science and Medical Engineering, Southeast University, Nanjing, China.
Front Bioeng Biotechnol. 2022 Mar 3;10:824688. doi: 10.3389/fbioe.2022.824688. eCollection 2022.
Pedicle screw fixation is a common technique used in posterior lumbar interbody fusion (PLIF) surgery for lumbar disorders. During operation, rod contouring is often subjective and not satisfactory, but only few studies focused on the rod-contouring issue previously. The aim of the study was to explore the effect of the rod contouring on the single-segment PLIF by the finite element (FE) method and retrospective study. A FE model of the lumbosacral vertebrae was first reconstructed, and subsequently single-segmental (L4/5) PLIF surgeries with four rod curvatures (RCs) were simulated. Herein, three RCs were designed by referring to centroid, Cobb, and posterior tangent methods applied in the lumbar lordosis measurement, and zero RC indicating straight rods was included as well. Clinical data of patients subjected to L4/5 segmental PLIF were also analyzed to verify the correlation between RCs and clinical outcome. No difference was observed among the four RC models in the range of motion (ROM), intersegmental rotation angle (IRA), and intradiscal pressure (IDP) under four actions. The posterior tangent model had less maximum stress in fixation (MSF) in flexion, extension, and axial rotation than the other RC models. Patients with favorable prognosis had larger RC and positive RC minus posterior tangent angle (RC-PTA) of fused segments with respect to those who had poor prognosis and received revision surgery. All RC models had similar biomechanical behaviors under four actions. The posterior tangent-based RC model was superior in fixation stress distribution compared to centroid, Cobb, and straight models. The retrospective study demonstrated that moderate RC and positive RC-PTA were associated with better postoperative results.
椎弓根螺钉固定是腰椎后路椎间融合术（PLIF）治疗腰椎疾病的常用技术。手术过程中，棒材塑形往往主观且不尽人意，但此前仅有少数研究关注棒材塑形问题。本研究旨在通过有限元（FE）方法和回顾性研究探讨棒材塑形对单节段PLIF的影响。首先重建腰骶椎的有限元模型，随后模拟了具有四种棒材曲率（RC）的单节段（L4/5）PLIF手术。在此，参照腰椎前凸测量中应用的质心、Cobb和后切线方法设计了三种RC，还包括表示直棒的零RC。对接受L4/5节段PLIF的患者的临床数据也进行了分析，以验证RC与临床结果之间的相关性。在四种动作下，四种RC模型在活动范围（ROM）、节段间旋转角度（IRA）和椎间盘内压力（IDP）方面未观察到差异。后切线模型在屈曲、伸展和轴向旋转时的固定最大应力（MSF）低于其他RC模型。预后良好的患者与预后不良并接受翻修手术的患者相比，融合节段的RC和正RC减去后切线角度（RC-PTA）更大。所有RC模型在四种动作下具有相似的生物力学行为。与质心、Cobb和直棒模型相比，基于后切线的RC模型在固定应力分布方面更优。回顾性研究表明，适度的RC和正RC-PTA与更好的术后结果相关。
