The absence of a standardized method for defining hindfoot bone coordinate systems makes it difficult to compare kinematics results from different research studies. The purpose of this study was to develop a reliable and robust procedure for defining anatomical coordinate systems for the talus and calcaneus. Four methods were evaluated based upon their anatomic consistency across subjects, repeatability, and their correspondence to functional axes of rotation. The four systems consisted of: 1) interactively identified bony landmarks, 2) a principal component analysis, 3) automatically identified bony landmarks, and 4) translating the tibial coordinate system to the hindfoot bones. The four systems were evaluated on 40 tali and 40 calcanei. The functional axes of rotation were determined using dynamic biplane radiography to image the hindfoot during gait. Systems 2 and 3 were the most repeatable and consistent due to the lack of operator intervention when defining coordinate systems. None of the coordinate systems corresponded well to functional axes of rotation during gait. System 3 is recommended over System 2 because it more closely mimics established bone angles measured clinically, especially for the calcaneus. This study presents an automated method for defining anatomic coordinate systems in the talus and calcaneus that does not rely on manual placement of markers or fitting of spheres to the bone surfaces which are less reliable due to operator-dependent measurements. Using this automated method will make it easier to compare hindfoot kinematics results across research studies.

由于缺乏用于定义后足骨骼坐标系的标准化方法，因此很难比较不同研究的运动学结果。本研究的目的是开发一种可靠且稳健的程序，用于定义距骨和跟骨的解剖坐标系。四种方法的评估基于它们在受试者之间的解剖一致性、可重复性以及它们与功能旋转轴的对应关系。这四个系统包括：1) 交互式识别的骨骼标志，2) 主成分分析，3) 自动识别的骨骼标志，以及 4) 将胫骨坐标系转换为后足骨骼。这四个系统在 40 个跟骨和 40 个跟骨上进行了评估。使用动态双平面射线照相术在步态期间对后足进行成像来确定旋转的功能轴。由于在定义坐标系时缺乏操作员干预，系统 2 和 3 的可重复性和一致性最高。没有一个坐标系与步态期间的功能旋转轴很好地对应。系统 3 优于系统 2，因为它更接近于模拟临床测量的既定骨角度，尤其是跟骨。本研究提出了一种定义距骨和跟骨解剖坐标系的自动化方法，该方法不依赖于手动放置标记或将球体拟合到骨表面，这些方法由于依赖于操作员的测量而不太可靠。