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Abstract
Traditional motion capture systems are the current standard in the assessment of knee joint kinematics. These systems are, however, very costly, complex to handle, and, in some conditions, fail to estimate the varus/valgus and internal/external rotation accurately due to the camera setup. This paper presents a novel and comprehensive method to infer the full relative motion of the knee joint, including the flexion/extension, varus/valgus, and internal/external rotation, using only low cost inertial measurement units (IMU) connected to the upper and lower leg. Furthermore, sensors can be placed arbitrarily and only require a short calibration, making it an easy-to-use and portable clinical analysis tool. The presented method yields both adequate results and displays the uncertainty band on those results to the user. The proposed method is based on an fixed interval smoother relying on a simple dynamic model of the legs and judicially chosen constraints to estimate the rigid body motion of the leg segments in a world reference frame. In this pilot study, benchmarking of the method on a calibrated robotic manipulator, serving as leg analogue, and comparison with camera-based techniques confirm the method’s accurateness as an easy-to-implement, low-cost clinical tool.
Highlights
In order to diagnose patients, plan surgical procedures and adapt rehabilitation programs, a dedicated movement analysis laboratory equipped with infrared cameras, combined with reflective markers attached on the body, has typically been used as a gold standard for the assessment of human motion [1]
inertial measurement units (IMU) were originally used into aircraft industry in order to calculate altitude and position of the manned or unmanned aircraft or satellite
In order to validate the proposed method, a first test is performed where known angle movements are estimated from measured IMU data
Summary
In order to diagnose patients, plan surgical procedures and adapt rehabilitation programs, a dedicated movement analysis laboratory equipped with infrared cameras, combined with reflective markers attached on the body, has typically been used as a gold standard for the assessment of human motion (e.g., gait analysis or functional movement analysis) [1]. IMUs were originally used into aircraft industry in order to calculate altitude and position of the manned or unmanned aircraft or satellite. The capacities of IMUs to detect positions and accelerations was introduced into biomedical or movement sciences aiming to Sensors 2020, 20, 1683; doi:10.3390/s20061683 www.mdpi.com/journal/sensors
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