Department of Orthopedics, Taichung Veterans General Hospital, Taichung, Taiwan, ROC.
Sports Recreation and Health Management Continuing Studies-Bachelor's Degree Completion Program, Tunghai University, Taichung, Taiwan, ROC.
J Chin Med Assoc. 2021 Nov 1;84(11):1038-1047. doi: 10.1097/JCMA.0000000000000625.
Medial displacement calcaneal osteotomy (MDCO) is frequently used for the surgical correction of flatfoot. This study aims to investigate the biomechanical effect of the different diagonal screw design on a novel-designed embedded calcaneal plate for MDCO using finite element analysis (FEA), mechanical test and digital image correlation (DIC) measurement.
Four groups according to the varied implanted plate were set as control group (Group 1), non-diagonal screw (Group 2), one-diagonal screw (Group 3), and two-diagonal screws groups (Group 4). For FEA, A 450 N load was applied to on the anterior process of the calcaneus from top to bottom. Observational indices included the stress on the cortical and cancellous bone of the calcaneus surrounding the implant, the plate itself as well as screws, and the displacement of the overall structure. In addition, this study also used in vitro biomechanics test to investigate the stiffness of the structure after implantation, and used DIC to observe the displacement of the calcaneus structure after external force.
Under a simulated load in FEA, there are significant overall instability and high stress concentration on the calcaneal surrounding host bone and the plate/screws system, respectively, in group 2 compared with other groups. Regard to the mechanical testing with DIC system, significant increased rotation stability, maximum force and stiffness with the addition of diagonal screws. In comparison to Group 2, the increase of 112% and 157% in maximum force as well as 104% and 176% in stiffness were found in Group 3 and 4, respectively.
For reducing stress concentration and enhancing overall stability, more than one-diagonal screw design is recommended and two-diagonal screws design will be superior. This study provided biomechanical references for further calcaneal implants design to prevent clinical failure after MDCO.
内侧移位跟骨截骨术（MDCO）常用于手术矫正扁平足。本研究旨在通过有限元分析（FEA）、力学测试和数字图像相关（DIC）测量，研究新型嵌入式跟骨钢板中不同对角螺钉设计对 MDCO 的生物力学影响。
根据植入钢板的不同，将 4 组分别设为对照组（第 1 组）、非对角螺钉组（第 2 组）、单对角螺钉组（第 3 组）和双对角螺钉组（第 4 组）。在 FEA 中，从顶部到底部在跟骨前突上施加 450N 的负载。观察指标包括植入物周围跟骨皮质和松质骨、钢板本身以及螺钉的应力，以及整体结构的位移。此外，本研究还采用体外生物力学试验研究植入后的结构刚度，并用 DIC 观察外力作用下跟骨结构的位移。
在 FEA 模拟载荷下，与其他组相比，第 2 组跟骨周围宿主骨和钢板/螺钉系统整体不稳定，应力集中明显。在 DIC 系统的力学测试中，随着对角螺钉的增加，旋转稳定性、最大力和刚度显著增加。与第 2 组相比，第 3 组和第 4 组的最大力分别增加了 112%和 157%，刚度分别增加了 104%和 176%。
为了减少应力集中，增强整体稳定性，建议采用多于一个的对角螺钉设计，双对角螺钉设计更优。本研究为进一步的跟骨植入物设计提供了生物力学参考，以防止 MDCO 后临床失败。
