Table 2. Studies comparing inertial sensors with a video-based optoelectronic motion analysis system.
Study | Description of study | Body area | Type of sensor/portability = size | Accuracy of the sensor | Gold standard | Validity | Participants | ||||||
Yaw | Pitch | Roll | Yaw | Pitch | Roll | ||||||||
Plamondon et al. (2007) | The purpose of this study was to evaluate a hybrid system for the 3D measurement of trunk posture in motion. | T (TT, P) | Microstrain 3DM-G, Burlington weight 40 g. 64×64×25 mm | Global angles: P | 2.0±0.5 | 0.5±0.2° | 0.7±0.2° | Optoelectronic system (Optotrak 3020, Northern Digital Inc., Waterloo, Ont,, Canada) | Global angles: P (CMC) | 0.998 | 0.974 | 0.975 | n = 6 (6 male)Age (32±12 years) |
Global angles: TT | 1.9±0.6 | 0.8±0.2° | 0.7±0.1° | Global angles: TT (CMC) | 0.988 | 0.993 | 0.971 | ||||||
Relative angles: P/TT | 2.2±0.4 | 1.1±0.4° | 1.6±0.8° | Relative angles: P/TT (CMC) | 0.657 | 0.987 | 0.953 | ||||||
Jasiewicz et al. (2007)6 | The aim of this study was to determine the accuracy of new generation sensorsof wireless orientation. | T (CT) | Inertial Cube 3 sensor (Intersense, Bedford, MA, USA)/26.2×39.2×14.8 mm | Head mounted sensors | 2.3±0.9 | 2.1±1.1° | 2.5±0.9° | The 3-Space Fastrak (Polhemus, Colchester, VT, USA) | Head mounted sensors (cross-correlation) | 0.97 | 0.98 | 0.97 | n = 10 (mean age 33.4±9.9 SD, range 20–51 years) |
C7/Trunk mounted sensors | 0.9±0.5 | 1.2±0.5° | 0.7±0.7° | C7/Trunk mounted sensors (cross-correlation) | 0.98 | 0.98 | 0.99 | ||||||
Bourke et al. (2008)33 | This study investigates distinguishing falls from normal activities of daily living by thresholding of the vertical velocity of the trunk. | T | ADXRS300 (Gyro) and ADXL210E (accel)/12×12×5 mm | RMS (M±SD): STSI = 0.09±0.05; Kneeling = 0.102±0.04; Object picking = 0.95±0.03; Lying on floor = 0.15±0.05; W = 0.08±0.03; Coughing = 0.06±0.02; Forward fall/knee FLX = 0.13±0.03; Side-fall right/Knee FLX = 0.15±0.09; Backward fall = 0.11±0.05 | Optical motion capture system (6 cameras) | CMC (M±SD): STSI = 0.98±0.02; Kneeling = 0.96±0.03; Object kicking = 0.96±0.02; Lying on floor = 0.96±0.03; W = 0.89±0.07; Coughing = 0.73±0.29; Forward fall/knee FX = 0.98±0.01; Side-fall right/Knee FX = 0.98±0.02; Backward fall = 0.98±0.98 | n = 5 (5 male)Age (25.6±1.9 years) | ||||||
O’Donovan et al. (2007)36 | The technique presented in this paper is concerned with ankle joint angles measurement. | LL (ankle) | ADXL210E (accel) ADXRS150 (Gyro) HMC2003 (mag) 60×40×24 mm | Angular errors in the measurement | 3.33° | 0.49° | – | Optoelectronic system (Evart 3D) | n = 2 (2 males)Age (25 and 23 years) | ||||
Picerno et al. (2008)11 | This paper describes an anatomical calibration technique for three wearable inertial and magnetic sensing modules using palpable anatomical landmarks. | LL (hip, knee, ankle) | MTx (Xsens Technologies, The Netherlands)/weights 30 g. 38×53×21 mm | Hip absolute value (M±SD). | 6.7±6.1 | 1.8±0.7° | 3±2.2° | Optoelectronic system (Vicon Mx cameras, Oxford Metrics, UK) | The correlation coefficient for the FLX/EXT was equal to 1 for all the joints whereas the ÄRoM was less than 0.5°. The lowest R was the knee IER, and it was equal to 0.942 | n = 1 | |||
Knee absolute value (M±SD) | 6.3±3.9 | 1.9±0.7° | 4.6±1.1° | ||||||||||
Ankle absolute value (M±SD) | 8.3±1.6 | 1.3±0.9° | 5.7±1.5° | ||||||||||
Martin-Schepers et al. (2010)9 | This study proposes and evaluates an alternative algorithm for relative position and orientation. A complementary Kalman filter structure was presented. | TT, UL, LL | MTx (Xsens Technologies, The Netherlands)/weights 30 g. 38×53×21 mm | Orientation error: TT | 4.3±0.3 | 4.5±0.7° | – | Optoelectronic system(Vicon, Oxford Metrics, UK) | n = 5 | ||||
Orientation error: UL | – | – | 2.8±0.7° | ||||||||||
Orientation error: LL | – | 3.6±0.9° | – | ||||||||||
Wong and Wong (2008)8 | The aim of this study was to introduce accelerometers and gyroscopes to detect posture in the sagittal and coronal planes. | TT (TT, LT, P) | KXM52-Tri-axis Kionix (Aceel) and Epson gyroscopes (Gyros)/22×9.20×9.12 mm, Weights 6 g | Peak value TT (degrees±SD) | – | 22.8±11.1 | 3.8±1.5 | Optoelectronic system (Vicon 370, Oxford Metrics, UK) | Correlation coefficient TT±SD | – | 0.983±0.014 | 0.829±0.308 | n = 5 (4 female and 5 male, age: 25.2±4.8 years, weight: 50.5±7.2 kg, height: 1.7±0.09 m) |
Peak value LT (degrees±SD) | – | 24.7±7.0 | 6.2±2.2 | ||||||||||
Correlation coefficient LT±SD | – | 0.981±0.014 | 0.984±0.015 | ||||||||||
RMS angular velocity (deg s−1±SD) | – | 6.3±3.0 | 4.5±1.3 | ||||||||||
Zhou et al. (2008)32 | This paper presents a new human motion tracking system that is placed near the wrist and elbow joints. | Upper limb (shoulder, elbow, wrist) | MT9B (Xsens Technologies, The Netherlands)/weights 38 g. 39×54×28 mm | RMS elbow angles (degrees) | 4.83 | 2.41 | – | Optical motion tracker (CODA, Charnwood, UK) | Correlation coefficients in elbow | 0.94 | 0.98 | – | n = 4 (age range: 20–40 years) |
Zhou and Huosheng (2007)13 | A novel motion tracking prototype will be developed on the basis of the previously designed motion detector. | Upper limb (shoulder, elbow, wrist) | MTx (Xsens Technologies, The Netherlands)/weights 30 g. 38×53×21 mm | Arm position RMS (m) | – | 0.004 | 0.005 | Optical motion tracker (CODA, Charnwood, UK) | Correlation coefficients in arm | – | 0.97 | 0.97 | n = 4 (age range: 27–40 years) |
Musić et al. (2008)12 | Model validation was performed on simulated data and on measurements acquired with the Optotrak optical motion analysis system. | T, LL | Average self-selected STSI speed (Shank) | – | 3.6° | – | Optotrak 3010 optical motion capture system (Northern Digital Inc., Waterloo, Ont., Canada), | n = 1 | |||||
Average self-selected STSI speed (Thigh) | – | 5.2° | – | ||||||||||
Average self-selected STSI speed (HAT) | – | 5.8° | – | ||||||||||
Roetenberg et al. (2007)7 | The objective of this study is to design and evaluate a new system for ambulatory measurements of position and orientation on the body. | T (TT), UL | MTx (Xsens Technologies, The Netherlands)/weights 30 g. 38×53×21 mm | Orientation error: TT | 2.6±0.5 | 2.4±0.5° | 2.6±0.5° | Optoelectronic system (Vicon 460, Oxford Metrics, UK) | n = 1 | ||||
Position error (mm): TT | 4.9±1.0 | 4.8±1.1 | 5.0±0.9° | ||||||||||
Orientation error: UL | – | 2.4±0.5° | 2.3±0.5° | ||||||||||
Goodvin et al. (2006)5 | They propose a new method for accurately measuring the real-time orientation and position of the spine in a portable, non-invasive, and clinically meaningful manner. | T (CT, TT, LT) | MT9B (Xsens Technologies, The Netherlands)/weights 38 g. 39×54×28 mm | Cervical average deviation | 0.2° | 0.42° | 0.1° | Optoelectronic system (Vicon 460, Oxford Metrics, UK) | n = 5 | ||||
Torso average deviation | 0.23° | 0.06° | 0.03° | ||||||||||
Hip average deviation | 1.35° | 0.33° | 3.1° | ||||||||||
Zhou and Hu (2010)10 | This paper presents the effects of changes in error reduction by using Kalman filtering. | Upper limb (shoulder, elbow, wrist) | MTx (Xsens sTechnologies, The Netherlands)/weights 30 g. 38×53×21 mm | Statistical error before Kalman filter | – | 14.62° | 14.02° | Optical motion tracker (CODA, Charnwood, UK) | n = 4 | ||||
Statistical error after Kalman filter | – | 2.13° | 2.01° | ||||||||||
Lee et al. (2010)38 | In this study they present sensor nodes (accel) with a goniometer probe. | UL | Freescale MMA7261QT (accel)/6×6×1.45 mm | A linear increasing trend from 0±2.5° at a mean angular speed of 10° s−1 to 3.5±7° at 80° s−1. | Goniometer probe (PS-2137 from PASCO) | n = 1 |
Note: ADL, activities of daily live; CMC, coefficient of multiple correlation; M, mean; SD, standard deviation; STSI, sit-to-stand; FX, flexion-extension; FLX, flexion; EXT, extension; ABD, abduction; ADD, adduction; IER, internal–external rotation; PT, protraction; RT, retraction; MLR, medio-lateral rotation; APT, anterior–posterior tilting; RMS, root mean square; ACRL, angular coefficient of the regression line; IQR, inter-quartile ranges; P, pelvis; LB, lateral bending; R, rotation; TT, thoracic trunk; UL, upper limb; LL, lower limb; G, gait; CT, cervical trunk; LT, lumbar trunk; T, trunk.