Quantifying Antalgic Gait Knee Function Using Inertial Sensor Technology

The use of body-fixed inertial sensors to analyze human movement may prove useful in the medical field. Improving orthopaedic device design, diagnosing musculoskeletal disorders, and rehabilitation assessment could all benefit from a mobile gait analysis system based on inertial sensors. More specifically, patients recovering from lower limb corrective surgeries tend to adjust gait patterns to accommodate pain, a condition referred to as antalgic gait. Currently there is no quantitative method available to assess recovery for this patient population during post-operative management. A comparison of the inertial sensor system with the camera-based industry standard has confirmed it as a viable method for lower limb motion analysis during normal gait. The inertial sensors consist of multiple accelerometers, gyroscopes and magnetometers used to obtain raw data, which is manipulated to calculate dynamic parameters. By comparing kinematic parameters between affected and unaffected limbs, it is possible to deduce a set of unique knee functionality ratios for recovering fracture patients. A control population was used to verify no significant difference (p \u3e 0.05) of seven kinematic parameters between limbs during normal gait. Parameters included peak knee flexion-extension angles at 15±5% and 75±5% gait cycle. These parameters were then analyzed in a group of patients recovering from lower limb fractures, using the unaffected limb as a control/reference. The goal of this project is to use inertial sensor technology to pinpoint specific kinematic parameters of the lower limb that are clinically appropriate in assessing knee function of lower limb fracture patients during the post-operative time span critical in normal gait recovery

Are tibial angles measured with inertial sensors useful surrogates for frontal plane projection angles using 2-dimensional video analysis during single leg squat tasks? A reliability and agreement analysis in elite football (soccer) players

During single leg squats (SLS), tibial angle (TA) quantification using inertial measurement units (IMU) may offer a practical alternative to frontal plane projection angle (FPPA) measurement using 2-dimensional (2D) video analysis. This study determined: (i) the reliability of IMUs and 2D video analysis for TA measurement, and 2D video analysis for FPPA measurement; (ii) the agreement between IMU TA and both 2D video TA and FPPA measurements during single leg squats in elite footballers. 18 players were tested on consecutive days. Absolute TA (ATA) and relative TA (RTA) were measured with IMUs. ATA and FPPA were measured concurrently using 2D video analysis. Within-session reliability for all measurements varied across days (intraclass correlation coefficient (ICC) range=0.27–0.83, standard error of measurement (SEM) range=2.12–6.23°, minimal detectable change (MDC) range=5.87–17.26°). Between-sessions, ATA reliability was good for both systems (ICCs=0.70–0.74, SEMs=1.64–7.53°, MDCs=4.55–7.01°), while IMU RTA and 2D FPPA reliability ranged from poor to good (ICCs=0.39–0.72, SEMs=2.60–5.99°, MDCs=7.20–16.61°). All limits of agreement exceeded a 5° acceptability threshold. Both systems were reliable for between-session ATA, although agreement was poor. IMU RTA and 2D video FPPA reliability was variable. For SLS assessment, IMU derived TAs are not useful surrogates for 2D video FPPA measures in this population

Varus/valgus and internal/external rotational knee joint stiffness in males and females

"The purpose of this investigation was to establish day to day reliability of varus/valgus and internal/external rotational stiffness measures and then compare stiffnesses between males and females. Twenty healthy college students underwent varus/valgus (non-weightbearing) and internal/external (non-weight and weightbearing) applied torques to 10, and 5 Nm, respectively. Ten subjects returned a second day to establish reliability measures. Stiffness constants were calculated for each displacement created by a .5 Nm incrementally applied torque. Results revealed mean female stiffness was significantly less than males for valgus, varus, and weightbearing external rotational stiffness. Interactions demonstrated that female knees were less stiff during initial loading. Female knee joint stiffness increased to equal male stiffness during internal rotation, external rotation, and weightbearing internal rotation. These results suggest that with respect to males, females are in different joint positions as loads are applied, potentially causing a need for alternate strategies to control joint orientation. "--Abstract from author supplied metadata

Wearable sensors and total knee arthroplasty: Assessing quantitative function to improve the patient experience

Osteoarthritis (OA) is a chronic degenerative disease for which the only long-term solution is total knee arthroplasty (TKA), though many patients are not satisfied with their TKA. Satisfaction in TKA patients is not well understood. Subjective questionnaires and objective functional tests have been previously used to assess TKA outcomes, but both have disadvantages. Wearable sensors have facilitated affordable biomechanical measurement in OA and TKA populations. The objective of this work was to use wearable sensors alongside functional tests with TKA patients to identify quantitative function that related to subjective function and satisfaction. A wearable sensor-setup was validated before implementation in a TKA population. Quantitative sensor metrics describing the motion of individual leg segments was found to correlate with subjective function and satisfaction. This study provided strong evidence towards the connection between quantitative function and patient experience and may be able to identify functional deficiencies for targeted therapy to improve satisfaction

Evaluation of Angular Velocity Data from Inertial Measurement Units for Use in Clinical Settings

Evaluating the human gait cycle with inertial measurement units (IMU) may prove beneficial for applications such as diagnoses of musculoskeletal diseases and assessment of rehabilitation regimes. An IMU system is potentially applicable for diagnosing and assessing rehabilitation outcomes for a variety of neuromuscular diseases since it is small, portable, and less expensive than a camera system. IMUs directly measure angular velocity, whereas position data from a camera system must be processed twice to obtain this information. The purpose of this research is to determine repeatability of IMU angular velocity data, and agreement between angular velocity data from an IMU system and a camera system during normal gait. From this data, the feasibility of using IMU systems in clinical or rehabilitative settings for obtaining reliable angular velocity data will be determined. Lower limb motion data was collected simultaneously from six XSens MTx IMUs (XSens Technologies, Enschede, The Netherlands) and an 8-camera Qualisys Motion Capture system (Pro-Reflex, 240 Hz system). Each IMU consists of three orthogonal accelerometers, gyroscopes, and magnetometers. Data from 4 subjects (3 males, 2 females) were collected after an initialization technique before each trial to reduce effects of electro-magnetic interference with the IMUs. Knee joint angular velocities (Gx, Gy, Gz) corresponding to appropriate knee joint angles (flexion/extension, adduction/abduction, and internal/external rotations) from both systems were used in this analysis. Coefficients of variation (COV) were calculated for both IMU and camera data to determine variability of data from both systems. Knee joint Average angular velocities from both systems for each subject and limb were plotted together to visually evaluate correlation between data sets. F-test analyses were performed on linear models of the data to determine areas of co-linearity within the gait cycle, and at different intervals of angular velocities. The IMUs had lower COV\u27s than the camera system, likely due to the fact that the IMUs directly measure angular velocity, and camera system derives angular velocity from position data. However, these differences were not statistically different, likely due to variability within trials for individual subjects. Linearity between camera system and IMU angular velocity was visually observed only about the flexion/extension axis during segments of the gait cycle occurring from 0-4% (heel strike) and 65-100% (swing phase) of the gait cycle. Comparisons about the adduction/abduction and internal/external axes showed evidence of linearity for lower angular velocities. Linear regression statistics showed that the only correlational trend between the two systems was around 8-12% of the gait cycle for all three rotational axes. This may be due to drift of the IMU data. Although the camera system is the \u27gold standard\u27 in motion analysis, IMUs may be used for applications in which angular velocity for a flexion-extension movement at low joint angles is being evaluated. Future studies will include a larger sample population, and evaluate specific movements within human gait that affect drift of the IMUs. In addition, other IMU system designs could be evaluated for clinical use, and other algorithms that further reduce the effects of drift should be implemented

Evaluation of Validity and Reliability of Inertial Measurement Unit-Based Gait Analysis Systems

Objective To replace camera-based three-dimensional motion analyzers which are widely used to analyze body movements and gait but are also costly and require a large dedicated space, this study evaluates the validity and reliability of inertial measurement unit (IMU)-based systems by analyzing their spatio-temporal and kinematic measurement parameters. Methods The investigation was conducted in three separate hospitals with three healthy participants. IMUs were attached to the abdomen as well as the thigh, shank, and foot of both legs of each participant. Each participant then completed a 10-m gait course 10 times. During each gait cycle, the hips, knees, and ankle joints were observed from the sagittal, frontal, and transverse planes. The experiments were conducted with both a camerabased system and an IMU-based system. The measured gait analysis data were evaluated for validity and reliability using root mean square error (RMSE) and intraclass correlation coefficient (ICC) analyses. Results The differences between the RMSE values of the two systems determined through kinematic parameters ranged from a minimum of 1.83 to a maximum of 3.98 with a tolerance close to 1%. The results of this study also confirmed the reliability of the IMU-based system, and all of the variables showed a statistically high ICC. Conclusion These results confirmed that IMU-based systems can reliably replace camera-based systems for clinical body motion and gait analyses

Wearable inertial sensors and range of motion metrics in physical therapy remote support

Abstract. The practice of physiotherapy diagnoses patient ailments which are often treated by the daily repetition of prescribed physiotherapeutic exercise. The effectiveness of the exercise regime is dependent on regular daily repetition of the regime and the correct execution of the prescribed exercises. Patients often have issues learning unfamiliar exercises and performing the exercise with good technique. This design science research study examines a back squat classifier design to appraise patient exercise regime away from the physiotherapy practice. The scope of the exercise appraisal is limited to one exercise, the back squat. Kinematic data captured with commercial inertial sensors is presented to a small group of physiotherapists to illustrate the potential of the technology to measure range of motion (ROM) for back squat appraisal. Opinions are considered from two fields of physiotherapy, general musculoskeletal and post-operative rehabilitation. While the exercise classifier is considered not suitable for post-operative rehabilitation, the opinions expressed for use in general musculoskeletal physiotherapy are positive. Kinematic data captured with gyroscope sensors in the sagittal plane is analysed with Matlab to develop a method for back squat exercise recognition and appraisal. The artefact, a back squat classifier with appraisal features is constructed from Matlab scripts which are proven to be effective with kinematic data from a novice athlete

Gait measurements in the transverse plane using a wearable system: An experimental study of test-retest reliability

3D gait analysis comprises the study of kinematics in the sagittal, coronal, and transverse planes. The transverse plane measurements are usually less used and generally show the lowest reliability. Nevertheless, the knee and ankle joint center trajectories, in the transverse plane, provide new parameters that may be important in clinical gait analysis. The aim of this study is to analyze the test-retest variability of these parameters. Gait measurements were performed using H-Gait, a wearable system based on magnetic and inertial sensors. A normal weight and an overweight subject were recruited and were asked to walk at their preferred speed for 6 trials. For both of them, the angle between the right and left knee and ankle joint center trajectories were analyzed. Overall, results showed a standard deviation across trials always lower than 2°. This small standard deviation was found also in the overweight subject, for whom it is usually challenging to obtain reliable gait measurements. In addition, a greater knee angle between the right and left joint center trajectories was found in the overweight subject compared to the normal weight. The promising results of this study suggest that the new parameters introduced might be suitable to assess gait of subjects with different anthropometric characteristics

Assessment of Normal Knee Kinematics Using High-Speed Stereo-Radiography System

The measurement of dynamic joint kinematics in vivo is important in order to understand the effects of joint injuries and diseases as well as for evaluating the treatment effectiveness. Quantification of knee motion is essential for assessment of joint function for diagnosis of pathology, such as tracking and progression of osteoarthritis and evaluation of outcome following conservative or surgical treatment. Total knee arthroplasty (TKA) is an invasive treatment for arthritic pain and functional disability and it is used for deformed joint replacement with implants in order to restore joint alignment. It is important to describe knee kinematics in healthy individuals for comparison in diagnosis of pathology and understanding treatment to restore normal function. However measuring the in vivo dynamic biomechanics in 6 degrees of freedom with an accuracy that is acceptable has been shown to be technically challenging. Skin marker based methods, commonly used in human movement analysis, are still prone to large errors produced by soft tissue artifacts. Thus, great deal of research has been done to obtain more accurate data of the knee joint by using other measuring techniques like dual plane fluoroscopy. The goal of this thesis is to use high-speed stereo radiography (HSSR) system for measuring joint kinematics in healthy older adults performing common movements of daily living such as straight walking and during higher demand activities of pivoting and step descending in order to establish a useful baseline for the envelope of healthy knee motion for subsequent comparison with patients with TKA. Prior to data collection, validation and calibration techniques as well as dose estimations were mandatory for the successful accomplishment of this study

Design of a new approach to register biomechanical gait data, when combining lower limb powered exoskeletons controlled by neural machine interfaces and transcutaneous spinal current stimulation

To analyze the effect of robotic-aided gait rehabilitation controlled with brain-machine interfaces, it is necessary to ensure a strategy to assess gait biomechanics recording data that is not disturbed by the rehabilitation technologies. To this end, a protocol to measure the kinematics of the lower extremities on the three planes based on Inertial Measurement Units (IMUs) is developed. To evaluate the IMUs system accuracy and reliability, it is validated with a high-precision reference device, an optoelectronic system. The validation of the protocol is performed in one healthy subject in two steps: 1) testing four different configurations of the IMUs to identify the optimal gait data registration model, including the number and location of sensors, since these affect the system's output, and 2) validation of IMUs with Vicon through synchronously walking records (Condition 1) and exoskeleton-assisted walking (Condition 2). The within-day multiple correlation coefficients (CMCw) from Kadaba and its reformulation, the inter-protocol CMC (CMCp), are used respectively for Part 1 and Part 2 to assess the waveform similarity of each lower limb joint angle, removing the between-gait-cycle variability. In addition, other parameters are studied to assess the technological error and the differences between the biomechanical models, such as Pearson's correlation, range of motion, offset, and the Root Mean Square Error. For Part 1, it is concluded that the optimal configuration for the rest of the project is Model 2, showing good CMCw values for every joint angle (CMCw ≥ 0.8). During the walking test (Part 2, Condition 1) the CMCp shows that gait kinematics measured by both systems for the right limb are equivalent, demonstrating IMUs accuracy, for the hip and the knee flexion/extension (CMCp = 1), and for the knee adduction/abduction (CMCp = 0.91). For exoskeleton-assisted walking (Part 2, Condition 2), after adjusting the position of the IMUs located at the ankles, the gait kinematics for the right limb are equivalent for every joint in the sagittal plane (CMCp ≥ 0.9), for the knee and the ankle in frontal plane (CMCp ≥ 0.95), and for the hip in transversal plane (CMCp = 0.99)Para analizar el efecto de la rehabilitación de la marcha asistida por robots controlada con interfaces cerebro-máquina, es necesario garantizar una estrategia para evaluar los datos de registro de la biomecánica de la marcha de forma que no estén alterados por las tecnologías de rehabilitación. Para ello, se desarrolla un protocolo para medir la cinemática de las extremidades inferiores en los tres planos basado en Unidades de Medición Inercial (IMUs). Para evaluar la precisión y fiabilidad del sistema de IMUs, se valida con un dispositivo de referencia de alta precisión, un sistema optoelectrónico. La validación del protocolo se realiza en un sujeto sano en dos pasos: 1) prueba de cuatro configuraciones diferentes de las IMUs para identificar el modelo óptimo de registro de datos de la marcha, incluyendo el número y la ubicación de los sensores, ya que estos afectan a la salida del sistema, y 2) validación de las IMUs con Vicon a través de registros sincronizados de marcha (Condición 1) y marcha asistida por exoesqueleto (Condición 2). Los coeficientes de correlación múltiple dentro del día (CMCw) de Kadaba y su reformulación, el CMC interprotocolo (CMCp), se utilizan respectivamente en la Parte 1 y la Parte 2 para evaluar la similitud de la forma de onda de cada ángulo articular de la extremidad inferior, eliminando la variabilidad entre ciclos de la marcha. Además, se estudian otros parámetros para evaluar el error tecnológico y las diferencias entre los modelos biomecánicos, como la correlación de Pearson, el rango de movimiento, el desplazamiento y el error cuadrático medio. Para la Parte 1, se concluye que la configuración óptima para el resto del proyecto es el Modelo 2, mostrando buenos valores de CMCw para cada ángulo articular (CMCw ≥ 0.8). Durante la prueba de marcha (Parte 2, Condición 1), el CMCp muestra que la cinemática de la marcha medida por ambos sistemas para la extremidad derecha es equivalente, demostrando la precisión de las IMUs, para la flexo-extensión de la cadera y la rodilla (CMCp = 1), y para la aducción/abducción de la rodilla (CMCp = 0.91). Para la marcha asistida por exoesqueleto (Parte 2, Condición 2), tras ajustar la posición de las IMUs situadas en los tobillos, la cinemática de la marcha para la extremidad derecha es equivalente para cada articulación en el plano sagital (CMCp ≥ 0.9), para la rodilla y el tobillo en el plano frontal (CMCp ≥ 0.95), y para la cadera en el plano transversal (CMCp = 0.99)Per analitzar l'efecte de la rehabilitació de la marxa assistida per robòtica controlada amb interfícies cervell-màquina, cal garantir una estratègia per avaluar la biomecànica de la marxa registrant dades que no es vegi alterada per les tecnologies de rehabilitació. Amb aquesta finalitat, es desenvolupa un protocol per mesurar la cinemàtica de les extremitats inferiors en els tres plans basat en Unitats de Mesurament Inercial (IMU). Per avaluar la precisió i la fiabilitat del sistema IMU, es valida amb un dispositiu de referència d'alta precisió, un sistema optoelectrònic. La validació del protocol es realitza en un subjecte sa en dos passos: 1) provant quatre configuracions diferents de les IMU per identificar el model òptim de registre de dades de la marxa, inclòs el nombre i la ubicació dels sensors, ja que aquests afecten la sortida del sistema, i 2 ) validació de les IMU amb Vicon mitjançant registres de marxa sincrònica (Condició 1) i caminada assistida per exoesquelet (Condició 2). Els coeficients de correlació múltiple d'un dia (CMCw) de Kadaba i la seva reformulació, el CMC interprotocol (CMCp), s'utilitzen respectivament per a la part 1 i la part 2 per avaluar la similitud de la forma d'ona de cada angle d'articulació de l'extremitat inferior, eliminant l'entre- variabilitat del cicle de la marxa. A més, s'estudien altres paràmetres per avaluar l'error tecnològic i les diferències entre els models biomecànics, com ara la correlació de Pearson, el rang de moviment, l'offset i l'error quadràtic mitjà. Per a la part 1, es conclou que la configuració òptima per a la resta del projecte és el model 2, que mostra bons valors de CMCw per a cada angle d'articulació (CMCw ≥ 0,8). Durant la prova de marxa (part 2, condició 1), el CMCp mostra que la cinemàtica de la marxa mesurada pels dos sistemes per a l'extremitat dreta és equivalent, demostrant la precisió de les IMU, per al maluc i la flexió/extensió del genoll (CMCp = 1) i per a la adducció/abducció del genoll (CMCp = 0,91). Per a la marxa assistida per exoesquelet (Part 2, Condició 2), després d'ajustar la posició de les IMU situades als turmells, la cinemàtica de la marxa de l'extremitat dreta és equivalent per a cada articulació del pla sagital (CMCp ≥ 0,9), per al genoll. i el turmell en pla frontal (CMCp ≥ 0,95), i per al maluc en pla transversal (CMCp = 0,99