基于深度回归的骨折锁钉孔三维空间定位方法

Three-dimensional Spatial Location Method for Inter-locking Holes of Fracture Bones Based on Deep Regression

人体长骨发生骨折后,需要将髓内钉插入髓腔之中以固定骨折区域,之后将螺钉置入髓内钉远端孔中以固定髓内钉,该手术难点在于远端孔位姿会随髓腔形状发生变化,因此传统徒手锁钉方法难以准确定位远端孔的空间位姿。为解决此问题,提出一种基于单张术中X线片精准定位髓内钉远端孔的方法。首先通过对比虚拟髓内钉与真实术中髓内钉的轮廓相似性确定远端孔的初始位姿;之后利用位姿修正算法对齐髓内钉轮廓特征,驱动虚拟髓内钉位姿迭代优化;最后确定远端孔的精确位姿。此外,为了准确提取X线片中的轮廓特征,结合目标检测算法,提出一种由粗到精的两阶段髓内钉轮廓提取方法。分别在模拟环境与真实临床环境中进行实验,将本方法计算得到的远端孔轴线与真实远端孔轴线进行比较,模拟环境中2个轴线的距离、角度误差为0.42 mm、0.46°,临床环境中2个轴线的距离、角度误差为0.75 mm、0.81°。本方法能满足髓内钉手术中远端孔定位的实际需求,有效提高髓内钉远端锁钉术中定位与规划效率。

After the fracture of the human long bone,the intramedullary nail needs to be inserted into the medullary cavity to fix the fracture area.Then the screw is required to be placed in the distal hole of the nail.The difficulty of this operation is that the distal hole’s pose will change with the shape of the medullary cavity.Therefore,it is difficult to accurately locate the distal hole’s pose by the traditional manual method.To solve this problem,a three-dimensional spatial location method using single intraop⁃erative X-ray image for distal hole is proposed.Firstly,the initial pose of the distal hole is determined by comparing the contour similarity between the virtual and real nails.Then,the nail’s contour is aligned using a correction algorithm to drive the iterative optimization of the virtual nail pose.Finally,the accurate pose of distal hole is determined.In addition,in order to extract the contour features of X-ray film accurately,a two-stage extraction method from coarse to fine intramedullary nail contour is pro⁃posed combined with the target detection algorithm.The experiments are carried out in simulated and clinical environments.Com⁃parison is drawn between the calculated distal hole’s axis and the real hole’s axis.The distance and angle errors in the simulated environment are 0.42 mm,0.46°,and the errors in the clinical environment are 0.75 mm,0.81°.The proposed method can meet the actual surgical needs and improves the efficiency and planning in the distal locking nail surgery.