Model-based tracking of the bones of the foot: A biplane fluoroscopy validation study

摘要

Abstract Measuring foot kinematics using optical motion capture is technically challenging due to the depth of the talus, small bone size, and soft tissue artifact. We present a validation of our biplane X-ray system, demonstrating its accuracy in tracking the foot bones directly. Using an experimental linear/rotary stage we imaged pairs of tali, calcanei, and first metatarsals, with embedded beads, through 30 poses. Model- and bead-based algorithms were employed for semi-automatic tracking. Translational and rotational poses were compared to the experimental stage (a reference standard) to determine registration performance. For each bone, 10 frames per pose were analyzed. Model-based: The resulting overall translational bias of the six bones was 0.058?mm with a precision of ±?0.049?mm. The overall rotational bias of the six bones was 0.42° with a precision of ±?0.41°. Bead-based: the overall translational bias was 0.037?mm with a precision of ±?0.032?mm and for rotation was 0.29° with a precision of ±?0.26°. We validated the accuracy of our system to determine the spatial position and orientation of isolated foot bones, including the talus, calcaneus, and first metatarsal over a range of quasi-static poses. Although the accuracy of dynamic motion was not assessed, use of an experimental stage establishes a reference standard. Highlights ? A model-based bone tracking algorithm is validated for foot and ankle bones. ? The translational accuracy of the system was 0.058?mm with a precision of ±0.049?mm. ? The rotational accuracy of the system was 0.42° with a precision of ±0.41°. ? Comparable bead-tracking errors support the use of precision stages in validation.