Baleani Massimiliano, Fraterrigo Giulia, Erani Paolo, Rota Giulia, Berni Matteo, Taddei Fulvia, Schileo Enrico
IRCCS Istituto Ortopedico Rizzoli, Laboratorio di Tecnologia Medica, Bologna, Italy.
IRCCS Istituto Ortopedico Rizzoli, Laboratorio di Bioingegneria Computazionale, Bologna, Italy.
J Mech Behav Biomed Mater. 2023 Apr;140:105706. doi: 10.1016/j.jmbbm.2023.105706. Epub 2023 Feb 2.
Image-based personalized Finite Element Models (pFEM) could detect alterations in physiological deformation of human vertebral bodies, but their accuracy has been seldom reported. Meaningful validation experiments should allow vertebral endplate deformability and ensure well-controlled boundary conditions. This study aimed to (i) validate a new loading system to apply a homogeneous pressure on the vertebral endplate during vertebral body compression regardless of endplate deformation; (ii) perform a pilot study on human vertebral bodies measuring surface displacements and strains with Digital Image Correlation (DIC); (iii) determine the accuracy of pFEM of the vertebral bodies. Homogeneous pressure application was achieved by pressurizing a fluid silicone encased in a rubber silicone film acting on the cranial endplate. The loading system was validated by comparing DIC-measured longitudinal strains and lower-end contact pressures, measured on three homogeneous pseudovertebrae of constant transversal section at 2.0 kN, against theoretically calculated values. Longitudinal strains and contact pressures were rather homogeneous, and their mean values close to theoretical calculations (5% underestimation). DIC measurements of surface longitudinal and circumferential displacements and strains were obtained on three human vertebral bodies at 2.0 kN. Complete displacement and strain maps were achieved for anterolateral aspects with random errors ≤0.2 μm and ≤30 μstrain, respectively. Venous plexus and double curvatures limited the completeness and accuracy of DIC data in posterior aspects. pFEM of vertebral bodies, including cortical bone mapping, were built from computed tomography images. In anterolateral aspects, pFEM accuracy of the three vertebrae was: (i) comparable to literature in terms of longitudinal displacements (R2>0.8); (ii) extended to circumferential displacements (pooled data: R2>0.9) and longitudinal strains (zero median error, 95% error: <27%). Circumferential strains were overestimated (median error: 39%). The new methods presented may permit to study how physiological and pathologic conditions influence the ability of vertebral endplates/bodies to sustain loads.
基于图像的个性化有限元模型（pFEM）能够检测人体椎体生理变形的变化，但其准确性鲜有报道。有意义的验证实验应考虑椎体终板的可变形性，并确保边界条件得到良好控制。本研究旨在：（i）验证一种新的加载系统，该系统可在椎体压缩过程中对椎体终板施加均匀压力，而不受终板变形的影响；（ii）对人体椎体进行初步研究，使用数字图像相关技术（DIC）测量表面位移和应变；（iii）确定椎体pFEM的准确性。通过对包裹在橡胶硅胶膜中的流体硅胶加压，使其作用于颅端终板，从而实现均匀压力的施加。通过比较在2.0 kN下对三个具有恒定横截面的均匀假椎体测量的DIC纵向应变和下端接触压力与理论计算值，对加载系统进行了验证。纵向应变和接触压力相当均匀，其平均值接近理论计算值（低估5%）。在2.0 kN下对三个人体椎体进行了DIC表面纵向和周向位移及应变测量。在前外侧方面获得了完整的位移和应变图，随机误差分别≤0.2μm和≤30微应变。静脉丛和双曲率限制了后侧DIC数据的完整性和准确性。从计算机断层扫描图像构建了包括皮质骨映射的椎体pFEM。在前外侧方面，三个椎体的pFEM准确性为：（i）在纵向位移方面与文献相当（R2>0.8）；（ii）扩展到周向位移（汇总数据：R2>0.9）和纵向应变（中位数误差为零，95%误差：<27%）。周向应变被高估（中位数误差：39%）。所提出的新方法可能有助于研究生理和病理状况如何影响椎体终板/椎体承受负荷的能力。
