TY - GEN

T1 - A Method for Lower Back Motion Assessment Using Wearable 6D Inertial Sensors

AU - Molnar, Marco

AU - Kok, Manon

AU - Engel, Tilman

AU - Kaplick, Hannes

AU - Mayer, Frank

AU - Seel, Thomas

N1 - Funding Information: This research was financially supported by the EPSRC grant Autonomous behaviour and learning in an uncertain world (Grant number: EP/J012300/1) and by the German Federal Institute of Sport Science under the auspices of MiSpEx – the National Research Network for Medicine in Spine Exercise (Grant number: BISp IIA1-080102A/11-14).

PY - 2018/9/5

Y1 - 2018/9/5

N2 - Low back pain (LBP) is a leading cause of activity limitation. Objective assessment of the spinal motion plays a key role in diagnosis and treatment of LBP. We propose a method that facilitates clinical assessment of lower back motions by means of a wireless inertial sensor network. The sensor units are attached to the right and left side of the lumbar region, the pelvis and the thighs, respectively. Since magnetometers are known to be unreliable in indoor environments, we use only 3D accelerometer and 3D gyroscope readings. Compensation of integration drift in the horizontal plane is achieved by estimating the gyroscope biases from automatically detected initial rest phases. For the estimation of sensor orientations, both a smoothing algorithm and a filtering algorithm are presented. From these orientations, we determine three-dimensional joint angles between the thighs and the pelvis and between the pelvis and the lumbar region. We compare the orientations and joint angles to measurements of an optical motion tracking system that tracks each skin-mounted sensor by means of reflective markers. Eight subjects perform a neutral initial pose, then flexion/extension, lateral flexion, and rotation of the trunk. The root mean square deviation between inertial and optical angles is about one degree for angles in the frontal and sagittal plane and about two degrees for angles in the transverse plane (both values averaged over all trials). We choose five features that characterize the initial pose and the three motions. Interindividual differences of all features are found to be clearly larger than the observed measurement deviations. These results indicate that the proposed inertial sensor-based method is a promising tool for lower back motion assessment.

AB - Low back pain (LBP) is a leading cause of activity limitation. Objective assessment of the spinal motion plays a key role in diagnosis and treatment of LBP. We propose a method that facilitates clinical assessment of lower back motions by means of a wireless inertial sensor network. The sensor units are attached to the right and left side of the lumbar region, the pelvis and the thighs, respectively. Since magnetometers are known to be unreliable in indoor environments, we use only 3D accelerometer and 3D gyroscope readings. Compensation of integration drift in the horizontal plane is achieved by estimating the gyroscope biases from automatically detected initial rest phases. For the estimation of sensor orientations, both a smoothing algorithm and a filtering algorithm are presented. From these orientations, we determine three-dimensional joint angles between the thighs and the pelvis and between the pelvis and the lumbar region. We compare the orientations and joint angles to measurements of an optical motion tracking system that tracks each skin-mounted sensor by means of reflective markers. Eight subjects perform a neutral initial pose, then flexion/extension, lateral flexion, and rotation of the trunk. The root mean square deviation between inertial and optical angles is about one degree for angles in the frontal and sagittal plane and about two degrees for angles in the transverse plane (both values averaged over all trials). We choose five features that characterize the initial pose and the three motions. Interindividual differences of all features are found to be clearly larger than the observed measurement deviations. These results indicate that the proposed inertial sensor-based method is a promising tool for lower back motion assessment.

KW - avoid magnetometers

KW - back motion assessment

KW - drift correction

KW - human motion analysis

KW - Inertial measurement units

KW - joint angle estimation

KW - low back pain

KW - validation against optical motion capture

UR - http://www.scopus.com/inward/record.url?scp=85054073974&partnerID=8YFLogxK

U2 - 10.23919/ICIF.2018.8455828

DO - 10.23919/ICIF.2018.8455828

M3 - Conference contribution

AN - SCOPUS:85054073974

SN - 9780996452762

T3 - 2018 21st International Conference on Information Fusion, FUSION 2018

SP - 799

EP - 806

BT - 2018 21st International Conference on Information Fusion, FUSION 2018

PB - Institute of Electrical and Electronics Engineers Inc.

T2 - 21st International Conference on Information Fusion, FUSION 2018

Y2 - 10 July 2018 through 13 July 2018

ER -