Biomechanics and Imaging Group, Department of Orthopaedics, Leiden University Medical Center, The Netherlands.
J Biomech. 2010 Mar 3;43(4):694-700. doi: 10.1016/j.jbiomech.2009.10.023. Epub 2009 Dec 11.
Fluoroscopic analysis is an important tool for assessing in vivo kinematics of knee prostheses. Most commonly, a single-plane fluoroscopic setup is used to capture the motion of prostheses during a particular task. Unfortunately, single-plane fluoroscopic analysis is imprecise in the out-of-plane direction. This can result in reconstructing physically impossible poses, in which--for example--the femoral component intersects with the insert, as the normal pose estimation process does not take into account the relation between the components. In the proposed method, the poses of both components are estimated simultaneously, while preventing femur-insert collisions. In a phantom study, the accuracy and precision of the new method in estimating the relative pose of the femoral component were compared to those of the original method. With reverse engineered models, the errors in estimating the out-of-plane position decreased from 2.0+/-0.7 to 0.1+/-0.1 mm, without effects on the errors in rotations and the in-plane positions. With CAD models, the errors in estimating the out-of-plane position decreased from 5.3+/-0.7 mm (mean+/-SD) to 0.0+/-0.4 mm, at the expense of a decreased precision for the other position or orientation parameters. In conclusion, collision detection can prevent reconstructing impossible poses and it improves the position and motion estimation in the out-of-plane direction.
荧光分析是评估膝关节假体体内运动学的重要工具。最常用的是单平面荧光透视设置，用于捕获在特定任务期间假体的运动。不幸的是，单平面荧光透视分析在非平面方向上不够精确。这可能导致重建物理上不可能的姿势，例如股骨组件与插入物相交，因为正常的姿势估计过程没有考虑到组件之间的关系。在提出的方法中，同时估计两个组件的姿势，同时防止股骨-插入物碰撞。在一项体模研究中，将新方法估计股骨组件相对姿势的准确性和精度与原始方法进行了比较。使用逆向工程模型，估计的外位置误差从 2.0+/-0.7 毫米减小到 0.1+/-0.1 毫米，而旋转和平面内位置的误差没有影响。使用 CAD 模型，估计外位置误差从 5.3+/-0.7 毫米（平均值+/-SD）减小到 0.0+/-0.4 毫米，代价是其他位置或定向参数的精度降低。总之，碰撞检测可以防止重建不可能的姿势，并改善非平面方向的位置和运动估计。
