Mechanical Engineering Department, Sharif University of Technology, Azadi Avenue, Tehran, Iran.
Mechanical Engineering Department, Sharif University of Technology, Azadi Avenue, Tehran, Iran; RCBTR, Tehran University of Medical Sciences, Tehran, Iran.
Med Eng Phys. 2019 Dec;74:172-179. doi: 10.1016/j.medengphy.2019.09.012. Epub 2019 Sep 19.
Inserting the distal locking screws is a challenging step of the intramedullary nailing procedures due to the nail deformation that makes the proximally mounted targeting systems ineffective. A pre-planning methodology is proposed, based on an analytical model of the nail-bone construct, to predict the nail deformation during surgery using orthogonal preoperative radiographs. Each of the femoral shaft and the nail was modeled as a curved tubular Euler-Bernoulli beam. The unknown positions and forces of the nail-bone interaction were found using a systematic trial and error approach, which minimized the total strain energy of the system while satisfying the force and geometrical constraints. The predictions of the model for the nail deformation were compared with the experimental results of five cadaver specimens in 15 test conditions. Relatively large displacements (up to 13 mm) were found for the distal hole in sagittal plane only. The model predictions were in close agreement with the experimental results, with a root mean square error of 1.2 mm. It was concluded that the proposed pre-planning methodology is promising for practical clinical use in intramedullary nailing operations, in order to provide the compensatory information that is required for tuning of proximally mounted targeting systems.
由于钉变形导致近端安装的瞄准系统失效，插入远端锁定螺钉是髓内钉手术的一个具有挑战性的步骤。提出了一种基于钉-骨结构分析模型的术前规划方法，使用正交术前 X 射线预测手术过程中的钉变形。股骨和钉都被建模为弯曲的管状 Euler-Bernoulli 梁。使用系统的反复试验方法找到钉-骨相互作用的未知位置和力，该方法使系统的总应变能最小化，同时满足力和几何约束。将模型对钉变形的预测与五个尸体标本在 15 种测试条件下的实验结果进行了比较。仅在矢状面发现了较大的远端孔位移（高达 13mm）。模型预测与实验结果非常吻合，均方根误差为 1.2mm。结论是，所提出的术前规划方法有望在髓内钉手术中实际临床应用，以提供近端安装的瞄准系统所需的补偿信息。
