Eltes Peter Endre, Bartos Marton, Hajnal Benjamin, Pokorni Agoston Jakab, Kiss Laszlo, Lacroix Damien, Varga Peter Pal, Lazary Aron
National Center for Spinal Disorders, Buda Health Center, Budapest, Hungary.
In Silico Biomechanics Laboratory, National Center for Spinal Disorders, Buda Health Center, Budapest, Hungary.
Front Surg. 2021 Jan 25;7:583386. doi: 10.3389/fsurg.2020.583386. eCollection 2020.
Revision surgery of a previous lumbosacral non-union is highly challenging, especially in case of complications, such as a broken screw at the first sacral level (S1). Here, we propose the implementation of a new method based on the CT scan of a clinical case using 3D reconstruction, combined with finite element analysis (FEA), computer-assisted design (CAD), and 3D-printing technology to provide accurate surgical navigation to aid the surgeon in performing the optimal surgical technique by inserting a pedicle screw at the S1 level. A step-by-step approach was developed and performed as follows: (1) Quantitative CT based patient-specific FE model of the sacrum was created. (2) The CAD model of the pedicle screw was inserted into the sacrum model in a bicortical convergent and a monocortical divergent position, by overcoming the geometrical difficulty caused by the broken screw. (3) Static FEAs (Abaqus, Dassault Systemes) were performed using 500 N tensile load applied to the screw head. (4) A template with two screw guiding structures for the sacrum was designed and manufactured using CAD design and 3D-printing technologies, and investment casting. (5) The proposed surgical technique was performed on the patient-specific physical model created with the FDM printing technology. The patient-specific model was CT scanned and a comparison with the virtual plan was performed to evaluate the template accuracy FEA results proved that the modified bicortical convergent insertion is stiffer (6,617.23 N/mm) compared to monocortical divergent placement (2,989.07 N/mm). The final template was created via investment casting from cobalt-chrome. The template design concept was shown to be accurate (grade A, Gertzbein-Robbins scale) based on the comparison of the simulated surgery using the patient-specific physical model and the 3D virtual surgical plan. Compared to the conventional surgical navigation techniques, the presented method allows the consideration of the patient-specific biomechanical parameters; is more affordable, and the intraoperative X-ray exposure can be reduced. This new patient- and condition-specific approach may be widely used in revision spine surgeries or in challenging primary cases after its further clinical validation.
既往腰骶部骨不连的翻修手术极具挑战性，尤其是在出现并发症的情况下，比如第一骶椎水平（S1）的螺钉断裂。在此，我们提出一种新方法，该方法基于一个临床病例的CT扫描，运用三维重建，并结合有限元分析（FEA）、计算机辅助设计（CAD）和3D打印技术，以提供精确的手术导航，帮助外科医生通过在S1水平置入椎弓根螺钉来实施最佳手术技术。具体步骤如下：（1）基于定量CT创建患者特异性的骶骨有限元模型。（2）通过克服因螺钉断裂造成的几何难题，将椎弓根螺钉的CAD模型以双皮质汇聚和单皮质发散的位置插入骶骨模型。（3）使用施加于螺钉头部的500N拉伸载荷进行静态有限元分析（Abaqus，达索系统公司）。（4）运用CAD设计、3D打印技术和熔模铸造设计并制造一个带有两个用于骶骨的螺钉导向结构的模板。（5）在所创建的患者特异性物理模型上运用熔融沉积成型（FDM）打印技术实施所提出的手术技术。对患者特异性模型进行CT扫描，并与虚拟计划进行比较，以评估模板的准确性。有限元分析结果证明，改良的双皮质汇聚置入方式（6617.23N/mm）比单皮质发散置入方式（2989.07N/mm）更具刚性。最终模板通过钴铬合金熔模铸造制成。基于使用患者特异性物理模型的模拟手术与三维虚拟手术计划的比较，模板设计理念显示准确无误（A级，格茨贝恩 - 罗宾斯量表）。与传统手术导航技术相比，所提出的方法能够考虑患者特异性生物力学参数；成本更低，并且可以减少术中X线暴露。这种新的针对患者和病情的方法在经过进一步临床验证后，可能会广泛应用于脊柱翻修手术或具有挑战性的初次手术病例。
