Dukkipati Siril Teja, Driscoll Mark
Musculoskeletal Biomechanics Research Lab, Department of Mechanical Engineering, McGill University, 845 Sherbrooke St. W (163), Montréal, QC, H3A 0C3, Canada.
Orthopaedic Research Lab, Montreal General Hospital, 1650 Cedar Ave (LS1.409), Montréal, QC, H3G 1A4, Canada.
3D Print Med. 2025 Jan 23;11(1):3. doi: 10.1186/s41205-025-00249-y.
There exists a need for validated lumbar spine models in spine biomechanics research. Although cadaveric testing is the current gold standard for spinal implant development, it poses significant issues related to reliability and repeatability due to the wide variability in cadaveric physiologies. Moreover, there are increasing ethical concerns with human dissection practices. Analogue models can act as cost saving alternatives to human tissue with better repeatability. The current study proposes a new methodology of spinal biomechanics testing using 3D printable surrogates and characterized its multi-dimensional stiffness in displacement-controlled loading scenarios.
The model consisted of L1 to S1 vertebrae, intervertebral discs (IVD), intertransverse, interspinous, anterior and posterior longitudinal ligaments. The vertebrae and the IVDs were derived from an open-source 3D MRI anatomography database, while the ligaments were modeled based on literature incorporating mounting points on the spinous and transverse processes. Stereolithography 3D printing along with a combination of stiff and soft photopolymer resins were used to manufacture the vertebrae and the soft tissues in the model. Thereafter, displacement-controlled pure moments were applied in the range of ± 15° at 0.5°/sec in all bending modes using a torsion testing machine and a custom pure bending jig. Model rotation and resisting moment under loading were recorded to quantify the rotational stiffness and hysteresis in the model.
The model reached a maximum of 5.66Nm and 3.53Nm at 15° flexion-extension, 3.84Nm and 3.93Nm at 15° right and left lateral bending, and 2.45Nm and 2.59Nm at 15° right and left axial rotation respectively. Model RMS error against ex vivo human response was estimated to be 1.57°, 1.64°, 0.82° in flexion-extension, lateral bending and axial rotation respectively. Bilateral symmetry in model stiffness was observed in lateral bending and axial rotation directions.
This study presents a reproducible 3D printable L1-S1 lumbar spine and validated it in all three orthogonal bending modes in the range of ± 15° against ex vivo and in silico data. The 3D printed analogue spine model described herein shows promising results, suggesting this model, with further validation, could have potential as a human cadaveric tissue substitute within the explored contexts of use.
脊柱生物力学研究中需要经过验证的腰椎模型。尽管尸体测试是目前脊柱植入物开发的金标准，但由于尸体生理特征差异很大，它在可靠性和可重复性方面存在重大问题。此外，人体解剖实践引发的伦理问题也日益增多。模拟模型可以作为人体组织的低成本替代方案，且具有更好的可重复性。本研究提出了一种使用3D可打印替代物进行脊柱生物力学测试的新方法，并在位移控制加载场景中对其多维刚度进行了表征。
该模型由L1至S1椎体、椎间盘（IVD）、横突间、棘突间、前纵和后纵韧带组成。椎体和椎间盘源自一个开源3D MRI解剖数据库，而韧带则根据文献进行建模，并结合了棘突和横突上的固定点。使用立体光刻3D打印技术以及硬软光聚合物树脂的组合来制造模型中的椎体和软组织。此后，使用扭转试验机和定制的纯弯曲夹具，在所有弯曲模式下以0.5°/秒的速度在±15°范围内施加位移控制的纯力矩。记录加载过程中模型的旋转和抗力矩，以量化模型中的旋转刚度和滞后现象。
该模型在15°屈伸时最大力矩分别达到5.66Nm和3.53Nm，在15°左右侧弯曲时分别为3.84Nm和3.93Nm，在15°左右轴向旋转时分别为2.45Nm和2.59Nm。模型相对于离体人体反应的均方根误差在屈伸、侧弯和轴向旋转时分别估计为1.57°、1.64°、0.82°。在侧弯和轴向旋转方向观察到模型刚度的双侧对称性。
本研究展示了一种可重复的3D可打印L1-S1腰椎，并在±15°范围内的所有三种正交弯曲模式下针对离体和计算机模拟数据对其进行了验证。本文所述的3D打印模拟脊柱模型显示出了有前景的结果，表明该模型经过进一步验证后，在探索的使用场景中可能有潜力作为人体尸体组织的替代品。
