Validation of an Inertial-Measurement-Unit System for Calculating Hip and Knee Flexion Angles During Gait (original) (raw)
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IEEE Journal of Translational Engineering in Health and Medicine
Background: Hip and knee flexion joint motions are frequently examined in clinical practice using camera based motion capture (CBMC) systems; however, these systems require elaborate setups and dedicated space. Inertial measurement unit (IMU) based systems avoid these disadvantages but require validation before widespread adoption. Moreover, it is important for clinical practice to determine the stability of these systems for prolonged evaluation periods. The purpose of this study was to assess the validity of a three-sensor inertial measurement unit system for calculating hip and knee flexion angles during gait by comparing with a gold standard CBMC system. Validity was also examined before and after a treadmill walking session. Methods: Twenty healthy participants were tested. Twenty seconds of gait at preferred walking speed were analyzed before and after thirty-two minutes of treadmill walking using previously validated CBMC methods and with a custom IMU model. Measurement validity for the IMU system was evaluated using Bland & Altman 95 percent limits of agreement, linear regression, mean absolute error and root mean square error. The effects of a measurement zeroing calibration strategy were also investigated. Results: Strong measurement agreement was observed for both hip and knee flexion angles, although overall agreement for the hip exceeded that for the knee. Linear regressions between the datasets for each participant illustrated strong (> 0.94) relationships between IMU and CBMC measurements. More significant changes between timepoints were observed for the knee than for the hip. Error values were generally reduced when zeroing calibration was implemented. Conclusion: The IMU system presented in this study is a convenient and accessible technique to measure joint angles. The protocol described in the current study can be easily applied in the clinical setting for evaluation of clinical populations. Additional development work on sensor placement and calibration methods may further increase the accuracy of such methods.
Journal of Bodywork and Movement Therapies, 2020
Introduction: Wearable inertial measurement units (IMUs) enable gait analysis in the clinic, but require calibrations that may affect subsequent gait measurements. This study assessed concurrent validity and within-session reliability of gait kinematics measured by a frequently calibrated IMU-based system. Calibration pose accuracy and intra-rater repeatability, and IMU orientation tracking accuracy, were additionally quantified. Methods: Calibration poses and gait were recorded in 15 women using IMUs and optical motion capture (OMC) (reference standard) simultaneously. Participants performed six consecutive trials: each comprising a calibration pose and a walk. IMU tracking was assessed separately (once-off) using technical static and dynamic tests. Differences of > 5 constituted clinical significance. Results: Concurrent validity for gait revealed clinically significant between-system differences for sagittal angles (root-mean-square error [RMSE] 6.7 e15.0 ; bias À9.3 e3.0) and hip rotation (RMSE 7.9 ; bias À4.2). After removing modelling offsets, differences for all angles (except hip rotation) were < 5. Gait curves correlated highly between systems (r > 0.8), except hip rotation, pelvic tilt and-obliquity. Within-session reliability of IMU-measured gait angles was clinically acceptable (standard error of measurement [SEM] < 5). Calibration poses were repeatable (SEM 0.3 e2.2). Pose accuracy revealed mean absolute differences (MAD) < 5 for all angles except sagittal ankle, hip and pelvis. IMU tracking accuracy demonstrated RMSE 2.0. Conclusion: A frequently calibrated IMU system provides reliable gait measurements; comparing highly to OMC after removing modelling differences. Calibration poses can be implemented accurately for most angles and consistently. IMU-measured gait data are clinically useful and comparable within participants, but should not be compared to OMC-measured data.
Cogent Medicine
To examine the concurrent validity and test-retest repeatability of the RehaWatch® system for the assessment of spatiotemporal parameters of gait. Methods: Spatiotemporal gait parameters were recorded using the RehaWatch® and GAITRite® systems among 17 healthy young adults (mean age = 21.5 years, SD = 1.9). Concurrent validity was assessed by comparing data obtained using both gait measurement systems, and repeatability of the RehaWatch® measurements was assessed between the six measurement trials. Results: The level of agreement between both measurement systems was strong as for the velocity, cadence, and double support time of the left side (r = 0.73-0.95) and moderate for double support time of the right side, and swing and stance time of both sides (r = 0.46-0.69). The hierarchical linear mixed model showed mostly good repeatability for gait parameters between the six trials. Despite some ABOUT THE AUTHORS
Journal of Biomechanical Science and Engineering, 2021
This study describes a new calibration procedure that provides a simple and accurate method to place and align an inertial measurement unit (IMU) sensor with the relative clinical bone frame on a developed lower limb skeletal model. The calibration can be easily replicated without the need for additional tools and, more importantly, it is independent of the joint attachment position. The proposed method was validated under realistic gait tests using eight healthy subjects in a motion capture system environment. Calculated results showed that the joint angles were correctly measured after applying the calibration method. Therefore, the proposed calibration procedure is an interesting alternative to solve the alignment problem when using IMU sensors for gait analysis.
Validity and repeatability of inertial measurement units for measuring gait parameters
Gait & posture, 2017
Inertial measurement units (IMUs) are small wearable sensors that have tremendous potential to be applied to clinical gait analysis. They allow objective evaluation of gait and movement disorders outside the clinic and research laboratory, and permit evaluation on large numbers of steps. However, repeatability and validity data of these systems are sparse for gait metrics. The purpose of this study was to determine the validity and between-day repeatability of spatiotemporal metrics (gait speed, stance percent, swing percent, gait cycle time, stride length, cadence, and step duration) as measured with the APDM Opal IMUs and Mobility Lab system. We collected data on 39 healthy subjects. Subjects were tested over two days while walking on a standard treadmill, split-belt treadmill, or overground, with IMUs placed in two locations: both feet and both ankles. The spatiotemporal measurements taken with the IMU system were validated against data from an instrumented treadmill, or using st...
Gait & Posture, 2020
Background: Osteoarthritis (OA) is one of the main causes of disability and its frequent hip and knee joint localization requires surgical joint replacement treatment. Patients after total hip (THA) or knee (TKA) arthroplasty often show gait abnormalities, whose comprehension is crucial in order to plan an appropriate rehabilitative treatment. Wearable sensor devices can be a valid tool for gait assessment in clinical practice, being relatively inexpensive and easy to use. Research question: Does the use of crutches influence the ability of a single inertial measurement unit (IMU), placed on the lower trunk, to correctly record the spatial-temporal gait parameters in patients after recent THA or TKA? Methods: 20 patients walking with crutches after recent THA or TKA and 10 healthy subjects were recruited. Each participant was recorded simultaneously with an IMU and with an optoelectronic motion capture system during 5 consecutive walking tests. Results: Intraclass correlation index of spatial-temporal parameters recorded with the IMU showed moderate to excellent reliability results both for healthy subjects (ICC range 0.626-0.897) and for patients (ICC range 0.596-0.951). In terms of concurrent validity, Pearson's r coefficient of healthy subjects, showed strong to very strong levels of correlations for some spatial-temporal parameters (speed, mean cadence, left and right stride length and stride duration) (r range 0.646-0.977) and very week to moderately week levels of correlation for gait cycle phases (swing, stance, single support and double support) (r range 0.390-0.633). Patients' data analysis showed similar results for general spatial-temporal parameters (r range 0.704-0.986) and slightly lower values for gait cycle phases (r range 0.077-0.464). Significance: We can consider the single IMU as a reliable tool for the detection of some spatial-temporal gait parameters. Crutches seem to interfere with the detection of the gait cycle phases.
Validation of a Knee Angle Measurement System Based on Imus
Human-Centric Robotics, 2017
Inertial Measurements Unit (IMU) based systems are a purposeful and alternative tool to monitor human gait mainly because they are cheaper, smaller and can be used without space restrictions compared to other gait analysis methods. In the scientific community, there are well-known studies that test the accuracy and efficiency of this method compared to ground truth systems. Gait parameters such as stride length, distance, velocity, cadence, gait phases duration and detection, or joint angles are tested and validated in these studies in order to study and improve this technology. In this article, knee joint angles were calculated from IMUs' data and they were compared with DARwIn OP knee joint angles. IMUs were attached to the left leg of the robot and left knee flexion-extension (F-E) was evaluated. The RMSE values were less than 6 • when DARwIn OP was walking, and less than 5 • when the robot kept the left leg stretched and performed an angle of-30 • .
Validation of a Device to Measure Knee Joint Angles for a Dynamic Movement
2020
Participation in sports has risen in the United States over the last few years, increasing the risk of injuries such as tears to the anterior cruciate ligament (ACL) in the knee. Previous studies have shown a correlation between knee kinematics when landing from a jump and this injury. The purpose of this study was to validate the ability of a commercially available inertial measurement units (IMUs) to accurately measure knee joint angles during a dynamic movement. Eight healthy subjects participated in the study. Validation was performed by comparing the angles measured by the wearable device to those obtained through the gold standard motion capture system when landing from a jump. Root mean square, linear regression analysis, and Bland–Altman plots were performed/constructed. The mean difference between the wearable device and the motion capture data was 8.4° (flexion/extension), 4.9° (ab/adduction), and 3.9° (rotation). In addition, the device was more accurate at smaller knee a...
Inertial sensor-based knee flexion/extension angle estimation
Journal of Biomechanics, 2009
A new method for estimating knee joint flexion/extension angles from segment acceleration and angular velocity data is described. The approach uses a combination of Kalman filters and biomechanical constraints based on anatomical knowledge. In contrast to many recently published methods, the proposed approach does not make use of the earth's magnetic field and hence is insensitive to the complex field distortions commonly found in modern buildings. The method was validated experimentally by calculating knee angle from measurements taken from two IMUs placed on adjacent body segments. In contrast to many previous studies which have validated their approach during relatively slow activities or over short durations, the performance of the algorithm was evaluated during both walking and running over 5 minute periods. Seven healthy subjects were tested at various speeds from 1 to 5 miles/hour. Errors were estimated by comparing the results against data obtained simultaneously from a 10 camera motion tracking system (Qualysis). The average measurement error ranged from 0.7 degrees for slow walking (1 mph) to 3.4 degrees for running (5mph). The joint constraint used in the IMU analysis was derived from the Qualysis data.
Inertial Measurement Units for Clinical Movement Analysis: Reliability and Concurrent Validity
Sensors (Basel, Switzerland), 2018
The aim of this study was to investigate the reliability and concurrent validity of a commercially available Xsens MVN BIOMECH inertial-sensor-based motion capture system during clinically relevant functional activities. A clinician with no prior experience of motion capture technologies and an experienced clinical movement scientist each assessed 26 healthy participants within each of two sessions using a camera-based motion capture system and the MVN BIOMECH system. Participants performed overground walking, squatting, and jumping. Sessions were separated by 4 ± 3 days. Reliability was evaluated using intraclass correlation coefficient and standard error of measurement, and validity was evaluated using the coefficient of multiple correlation and the linear fit method. Day-to-day reliability was generally fair-to-excellent in all three planes for hip, knee, and ankle joint angles in all three tasks. Within-day (between-rater) reliability was fair-to-excellent in all three planes du...