Liu Xiaolong, Li Jin, Luan Kuan
College of Intelligent Systems Science and Engineering, Harbin Engineering University, Harbin, Heilongjiang, China.
Front Bioeng Biotechnol. 2023 Mar 31;11:1115473. doi: 10.3389/fbioe.2023.1115473. eCollection 2023.
Internal fixation with intramedullary nails is a gold standard for the treatment of femoral shaft fractures. However, both the mismatch between intramedullary nails and the medullary cavity and inaccurate positioning of entry points will lead to deformation of intramedullary nails after implantation. The study aimed to determine a suitable intramedullary nail with an optimal entry point for a specific patient based on centerline adaptive registration. A homotopic thinning algorithm is employed to extract centerlines of the femoral medullary cavity and the intramedullary nail. The two centerlines are registered to obtain a transformation. The medullary cavity and the intramedullary nail are registered based on the transformation. Next, a plane projection method is employed to calculate the surface points of the intramedullary nail laid outside the medullary cavity. According to the distribution of compenetration points, an iterative adaptive registration strategy is designed to decide an optimal position of the intramedullary nail in medullary cavity. The isthmus centerline is extended to the femur surface, where the entry point of the intramedullary nail is located. The suitability of an intramedullary nail for a specific patient was calculated by measuring the geometric quantities reflecting the interference between the femur and nail, and the suitability values of all nails are compared and the most suitable one is determined. The growth experiment indicated that the bone to nail alignment is indeed affected by the extension of the isthmus centerline, including the extension direction and velocity. The geometrical experiment showed that this method could find the best registration position of intramedullary nails and select the optimal intramedullary nail for a specific patient. In the model experiments, the determined intramedullary nail could be successfully placed into the medullary cavity through the optimal entry point. A pre-screening tool to determine nails which can be successfully used has been given. In addition, the distal hole was accurately located within 14.28 s. These results suggest that the proposed method can select a suitable intramedullary nail with an optimal entry point. The position of the intramedullary nail can be determined in the medullary cavity, while deformation is avoided. The proposed method can determine the largest diameter intramedullary nail with as little damage to the intramedullary tissue as possible. The proposed method provides preparation aid for internal fixation with intramedullary nails guided by navigation systems or extracorporeal aimers.
髓内钉内固定是股骨干骨折治疗的金标准。然而，髓内钉与髓腔不匹配以及进针点定位不准确都会导致植入后髓内钉变形。本研究旨在基于中心线自适应配准为特定患者确定合适的髓内钉及最佳进针点。采用同伦细化算法提取股骨髓腔和髓内钉的中心线。将两条中心线进行配准以获得一个变换。基于该变换对髓腔和髓内钉进行配准。接下来，采用平面投影法计算位于髓腔外的髓内钉的表面点。根据穿透点的分布，设计一种迭代自适应配准策略来确定髓内钉在髓腔内的最佳位置。峡部中心线延伸至股骨表面，髓内钉的进针点即位于此处。通过测量反映股骨与髓内钉之间干涉的几何量来计算特定患者髓内钉的适配性，并比较所有髓内钉的适配值，确定最合适的髓内钉。生长实验表明，峡部中心线的延伸确实会影响骨与钉的对线，包括延伸方向和速度。几何实验表明，该方法能够找到髓内钉的最佳配准位置，并为特定患者选择最佳的髓内钉。在模型实验中，确定的髓内钉能够通过最佳进针点成功置入髓腔。给出了一种用于确定可成功使用的髓内钉的预筛选工具。此外，远端孔在14.28秒内被精确定位。这些结果表明，所提出的方法能够选择合适的髓内钉及最佳进针点。可以在髓腔内确定髓内钉的位置，同时避免变形。所提出的方法能够确定最大直径的髓内钉，同时对髓内组织的损伤尽可能小。所提出的方法为导航系统或体外瞄准器引导下的髓内钉内固定提供了辅助准备。
