• An IMU-to-Body Alignment Method Applied to Human Gait Analysis
"This paper presents a novel calibration procedure as a simple, yet powerful, method to place and align inertial sensors with body segments. The calibration can be easily replicated without the need of any additional tools. The proposed method is validated in three different applications: a computer mathematical simulation; a simplified joint composed of two semi-spheres interconnected by a universal goniometer; and a real gait test with five able-bodied subjects."
• First in vivo assessment of "Outwalk"
First in vivo assessment of "Outwalk": a novel protocol for clinical gait analysis based on
inertial and magnetic sensors

"A protocol named "Outwalk" was recently proposed to measure the thorax-pelvis and lower-limb kinematics during gait in free-living conditions, by means of an inertial and magnetic measurement system (IMMS). The aim of this study was to validate Outwalk on four healthy subjects when it is used in combination with a specific IMMS (Xsens Technologies, NL), against a reference protocol (CAST) and measurement system (optoelectronic system; Vicon, Oxford Metrics Group, UK)."


• Gait analysis in children with cerebral palsy via inertial and magnetic sensors
"3D kinematic measurements in children with cerebral palsy (CP) to assess gait deviations can only be performed in gait laboratories using optoelectronic systems. Alternatively, an inertial and magnetic measurement system (IMMS) can be applied for ambulatory motion-tracking. A protocol named Outwalk has recently been developed to measure the 3D kinematics during gait with IMMS. This study preliminary validated the application of IMMS, based on the Outwalk protocol, in gait analysis of six children with CP and one typically developing child. Reference joint kinematics were simultaneously obtained from a laboratory-based system and protocol."
• IMU-Based Joint Angle Measurement for Gait Analysis
"This contribution is concerned with joint angle calculation based on inertial measurement data in the context of human motion analysis. Unlike most robotic devices, the human body lacks even surfaces and right angles. Therefore, we focus on methods that avoid assuming certain orientations in which the sensors are mounted with respect to the body segments. After a review of available methods that may cope with this challenge, we present a set of new methods for: (1) joint axis and position identification; and (2) flexion/extension joint angle measurement. In particular, we propose methods that use only gyroscopes and accelerometers and, therefore, do not rely on a homogeneous magnetic field. We provide results from gait trials of a transfemoral amputee in which we compare the inertial measurement unit (IMU)-based methods to an optical 3D motion capture system."
• Measurement of scapular dyskinesis
Measurement of scapular dyskinesis using wireless inertial and magnetic sensors:
Importance of scapula calibration

"Measurement of 3D scapular kinematics is meaningful in patients with shoulder pathologies showing scapular dyskinesis. This study evaluates the effect of single and double anatomical calibration
(0° and 120°) with a scapula locator compared to standard calibration (using sensor alignment with the spina scapulae and static upright posture, ISEO-protocol) on 3D scapular kinematics measured with an inertial and magnetic measurement system (IMMS)."


• "Outwalk": a protocol for clinical gait analysis based on inertial and magnetic sensors
"A protocol named Outwalk was developed to easily measure the thorax-pelvis and lower-limb 3D kinematics on children with cerebral palsy (CP) and amputees during gait in free-living conditions, by means of an Inertial and Magnetic Measurement System (IMMS). Outwalk defines the anatomical/functional coordinate systems (CS) for each body segment through three steps: (1) positioning the sensing units (SUs) of the IMMS on the subjects' thorax, pelvis, thighs, shanks and feet, following simple rules; (2) computing the orientation of the mean flexion-extension axis of the knees; (3) measuring the SUs' orientation while the subject's body is oriented in a predefined posture, either upright or supine."
• Validation of inertial measurement units with optical tracking system
Validation of inertial measurement units with optical tracking system in patients operated with
total hip arthroplasty

BMC Musculoskelet Disord. 2019 Feb 6;20(1):52. doi: 10.1186/s12891-019-2416-4.

"BACKGROUND:
Patient reported outcome measurement (PROMs) will not capture in detail the functional joint motion before and after total hip arthroplasty (THA). Therefore, methods more specifically aimed to analyse joint movements may be of interest. An analysis method that addresses these issues should be readily accessible and easy to use especially if applied to large groups of patients, who you want to study both before and after a surgical intervention such as THA. Our aim was to evaluate the accuracy of inertial measurement units (IMU) by comparison with an optical tracking system (OTS) to record pelvic tilt, hip and knee flexion in patients who had undergone THA.
METHODS:
49 subjects, 25 males 24 females, mean age of 73 years (range 51-80) with THA participated. All patients were measured with a portable IMU system, with sensors attached lateral to the pelvis, the thigh and the lower leg. For validation, a 12-camera motion capture system was used to determine the positions of 15 skin markers (Oqus 4, Qualisys AB, Sweden). Comparison of sagittal pelvic rotations, and hip and knee flexion-extension motions measured with the two systems was performed. The mean values of the IMU's on the left and right sides were compared with OTS data.
RESULTS:
The comparison between the two gait analysis methods showed no significant difference for mean pelvic tilt range (4.9-5.4 degrees) or mean knee flexion range (54.4-55.1 degrees) on either side (p>0.7). The IMU system did however record slightly less hip flexion on both sides (36.7-37.7 degrees for the OTS compared to 34.0-34.4 degrees for the IMU, p<0.001).
CONCLUSIONS:
We found that inertial measurement units can produce valid kinematic data of pelvis- and knee flexion-extension range. Slightly less hip flexion was however recorded with the inertial measurement units which may be due to the difference in the modelling of the pelvis, soft tissue artefacts, and malalignment between the two methods or misplacement of the inertial measurement units."