基于三维图像的髓内针钉孔定位方法

研究基于三维图像的髓内针钉孔定位导航方法.首先，使用CT扫描髓内针，获得其三维图像.其次，在髓内针尾部安装空间定位传感器，通过坐标系配准使得髓内针三维图像模型注册到空间定位仪所在坐标系，实现空间中的髓内针与导航系统中的髓内针的联动.最后，使用安装有定位传感器的骨钻来对准钉孔.两个阈值用于判断骨钻与钉孔间的位置关系：距离阈值用于判断骨钻尖端与髓内针钉孔中轴线之间的距离，角度阈值用于判断骨钻轴线与髓内针钉孔中轴线之间的角度.两个阈值全部满足时，按照导航指示骨钻钻入骨壁.仿真结果表明，该方法在髓内针钉孔不可见情况下，能够准确定位钉孔位置及方向，导航用于判断可定位器械与钉孔的空间位置，以不同颜色标识引导骨钻到达钉孔，能够满足髓内针整复手术的要求.

Localization of Holes on Intramedullary Nail Based on Three Dimensional Images

Localization algorithm for holes on intramedullary nail based on three dimensional images was proposed. Firstly, intramedullary nail was scanned by CT, and a three dimensional (3D) model was obtained according to the CT images. Secondly, a positioning sensor was mounted on the intramedullary nail. The 3D model was registered into the coordinate frame of a positioning system for the intramedullary nail tracking. Finally, a bone drill mounted with a positioning sensor was used to aim at the holes on the intramedullary nail. Two thresholds, the distance threshold and angle threshold, were used to estimate the location relationship of the bone drill and nail hole. The distance threshold was used to determine the distance between the bone drill tip and the center axes of nail hole. The angle threshold was employed to determine the intersection angle between the bone drill and the hole. When the two thresholds were full satisfaction, the bone drill could be allowed to execute bone surgery according to the navigation instruction. Test results show the accuracy and validity of the proposed method. The drill can be placed into the holes on the intramedullary nail accurately, satisfying the need of reconstructive surgery.