Defining the medial-lateral axis of an anatomical femur coordinate system using freehand 3D ultrasound imaging

Abstract

Hip rotation from gait analysis informs clinical decisions regarding correction of femoral torsional deformities. However, it is among the least repeatable due to discrepancies in determining the medial-lateral axis of the femur. Conventional or functional calibration methods may be used to define the axis but there is no benchmark to evaluate these methods. Freehand 3D ultrasound, the coupling of ultrasound with 3D motion capture, may provide such a benchmark.We measured the accuracy in vitro and repeatability in vivo of determining the femur condylar axis from freehand 3D ultrasound. The condylar axis provided the reference medial-lateral axis of the femur and was used to evaluate one conv..