Gait quality assessed by trunk accelerometry after total knee arthroplasty and its association with patient related outcome measures

BackgroundWith an increasingly younger population and more active patients, assessment of functional outcome is more important than ever in patients undergoing total knee arthroplasty. Accelerometers have been used successfully to objectively evaluate gait quality in other fields. The aim of this study was to assess gait quality with accelerometers before and after surgery, and to assess added value of resulting parameters to patient reported outcome measures scores.MethodsSixty-five patients (mean age 65 years (range 41–75)) who underwent primary total knee arthroplasty were evaluated using a tri-axial trunk accelerometer preoperatively and 1 year after surgery. Gait quality parameters derived from the accelerometry data were evaluated in three dimensions at both time points. Factor analysis was performed on all outcome variables and changes from before to 1 year after surgery in the most representative variable for each factor were studied.FindingsFactor analysis identified three separate gait quality factors, with questionnaire and gait quality parameters loading on different factors. Both gait quality factor scores and questionnaire factor scores improved significantly 1 year after surgery. As expected based on the factor analysis, only weak to moderate associations were found between patient reported outcome measures and gait quality before surgery, after surgery and in change scores.InterpretationThe independence of patient reported outcome measures and gait quality parameters measured with trunk accelerometry indicates that gait quality parameters provide additional information on functional outcome after total knee arthroplasty. Providing caretakers with objectively measurable targets using accelerometry could help improve outcome of these patients.     

The association of leg length and offset reconstruction after total hip arthroplasty with clinical outcomes

BackgroundRestoring native hip anatomy and biomechanics is important to create a well-functioning hip arthroplasty. This study investigated the association of hip offset and leg length after hip arthroplasty with clinical outcomes, including patient reported outcome measures, the Trendelenburg Test and gait analysis.MethodsIn 77 patients undergoing primary hip arthroplasty for osteoarthritis (age mean = 65 SD = 11 years; BMI mean = 27 SD = 5 kg/m²), hip offset and leg length discrepancy were measured on anteroposterior radiographs. The Western Ontario & McMaster Universities Osteoarthritis Index, the Trendelenburg Test and gait were assessed preoperatively, and at 3 and 12 months postoperatively. An inertial measurement unit was used to derive biomechanical parameters, including spatiotemporal gait parameters and tilt angles of the pelvis. Relationships between radiographic and functional outcomes were investigated, and subgroups of patients with >15% decreased and increased femoral offset were analysed separately.FindingsPatient-reported function scores and clinical tests demonstrated a few significant, weak correlations with radiographic outcomes (Spearman's ρ range = 0.26–0.32; p < 0.05). Undercorrection of femoral offset was associated with lower patient-reported function scores and with more step irregularity as well as step asymmetry during gait. Postoperative leg length inequality was associated with increased frontal plane tilt angle of the pelvis during the Trendelenburg Test and increased sagittal plane motion of the pelvis during gait. Femoral offset subgroups demonstrated no significant differences for patient-reported function scores and outcomes of the Trendelenburg Test and gait analysis.InterpretationReduced hip offset and leg length discrepancy following hip arthroplasty seem to be marginally associated with worse clinical outcomes.     

Automated detection and explainability of pathological gait patterns using a one-class support vector machine trained on inertial measurement unit based gait data

BackgroundMachine learning approaches for the classification of pathological gait based on kinematic data, e.g. derived from inertial sensors, are commonly used in terms of a multi-class classification problem. However, there is a lack of research regarding one-class classifiers that are independent of certain pathologies. Therefore, it was the aim of this work to design a one-class classifier based on healthy norm-data that provides not only a prediction probability but rather an explanation of the classification decision, increasing the acceptance of this machine learning approach.MethodsThe inertial sensor based gait kinematics of 25 healthy subjects was employed to train a one-class support vector machine. 25 healthy subjects, 20 patients after total hip arthroplasty and one transfemoral amputee served to validate the classifier. Prediction probabilities and feature importance scores were estimated for each subject.FindingsThe support vector machine predicted 100% of the patients as outliers from the healthy group. Three healthy subjects were predicted as outliers. The feature importance calculation revealed the hip in the sagittal plane as most relevant feature concerning the group after total hip arthroplasty. For the misclassified healthy subject with the lowest probability score the knee flexion and the pelvis obliquity were identified.InterpretationThe support vector machine seems a useful tool to identify outliers from a healthy norm-group. The feature importance examination proved to provide valuable information on the musculoskeletal status of the subjects. In this combination, the present approach could be employed in various disciplines to identify abnormal gait and suggest subsequent training.     

A kinematic and kinetic analysis of walking after total knee arthroplasty with and without patellar resurfacing

BACKGROUND: Clarification of the indications for patellar resurfacing in total knee arthroplasty (TKA) is still necessary. Few studies of adequate power have evaluated functional differences between total knee arthroplasty with and without patellar resurfacing, in particular walking gait. This study aimed to identify clinically relevant differences in knee kinematic or kinetic parameters during level walking between total knee arthroplasty with and without patellar resurfacing, after controlling for pre-surgery gait parameters. METHODS: Kinematic and kinetic gait analysis of level walking was performed on 34 subjects (41 knees) before and 12-18 months after total knee arthroplasty with patellar resurfacing performed randomly. Linear regression analysis was used to examine the influence of patellar resurfacing upon gait variables whilst controlling for the corresponding pre-surgery measure. FINDINGS: The pre-surgery value was a moderate to strong significant predictor of all post-surgery temporal-spatial and kinetic gait parameters (p < 0.001-0.008), and most kinematic parameters (p < 0.001-0.066). The addition of patellar resurfacing to the regression models did not improve the predictive power in any case. Only one parameter, knee flexion at heel-strike, displayed a difference near statistical significance between total knee arthroplasty with and without patellar resurfacing (10 degrees versus 7 degrees respectively, p = 0.023). INTERPRETATION: Pre-surgery gait patterns are an important determinant of post-surgery gait. There are no clinically relevant differences in walking gait between total knee arthroplasty performed with or without patellar resurfacing, using the Profix design.     

Inertial measurement unit compared to an optical motion capturing system in post-stroke individuals with foot-drop syndrome

BackgroundFunctional electrical stimulation (FES) can be used for compensation of foot-drop for post-stroke individuals by pre-programmed fixed stimulation; however, this stimulation seems no more effective than mechanical ankle foot orthoses.ObjectiveWe evaluated the metrological quality of inertial sensors for movement reconstruction as compared with the gold-standard motion capturing system, to couple FES with inertial sensors to improve dorsiflexion on the paretic side, by using an adaptive stimulation taking into account individuals’ performance post-stroke.MethodsAdults with ischemic or hemorrhagic stroke presenting foot-drop and able to walk 10 m, were included from May 2016 to June 2017. Those with passive ankle dorsiflexion < 0° with the knee stretched were excluded. Synchronous gait was analyzed with the VICON© system as the gold standard and inertial measurement units (IMUs) worn by participants. The main outcome was the dorsiflexion angle at the heel strike and mid-swing phase obtained from IMUs and the VICON system. Secondary outcomes were: stride length, walking speed, maximal ankle dorsiflexion velocity and fatigue detection.ResultsWe included 26 participants [18 males; mean age 58 (range 45–84) years]. During heel strike, the dorsiflexion angle measurements demonstrated a root mean square error (RMSE) of 5.5°; a mean average error (MAE) of 3.9°; Bland-Altman bias of  − 0.1° with limits of agreement  − 10.9° to + 10.7° and good intra-class correlation coefficient (ICC) at 0.87 between the 2 techniques. During the mid-swing phase, the RMSE was 5.6; MAE 3.7°; Bland-Altman bias  − 0.9° with limits of agreement  − 11.7° to + 9.8° and ICC 0.88. Good agreement was demonstrated for secondary outcomes and fatigue detection.ConclusionsIMU-based reconstruction algorithms were effective in measuring ankle dorsiflexion with small biases and good ICCs in adults with ischemic or hemorrhagic stroke presenting foot-drop. The precision obtained is sufficient to observe the fatigue influence on the dorsiflexion and therefore to use IMUs to adapt FES.     

Reliability of Bluetooth inertial sensors for assessing lower limb segment angles and stride length during gait

[Purpose] To assess the agreement between our custom Bluetooth IS system and the gold standard MOCAP system during gait. Bluetooth inertial movement sensors (IS) allow for real-time movement analysis with fewer restrictions than optoelectrical motion capture systems (MOCAP) and more accessibility than wireless IS systems. [Participants and Methods] We collected simultaneous Bluetooth IS and MOCAP data for 16 young participants walking at a self-selected speed. Sensors were placed on the right thigh and shank. Segment angles and stride length were calculated and compared between systems using Pearson’s correlation coefficients (R), intra-class correlation coefficients (ICC), root mean square errors (RMSE), limits of agreement (LOA), and Bland-Altman plots. [Results] R values ranged from 0.371–0.715; ICC values ranged from 0.263–0.770. RMSE was 0.369 m for stride length and ranged from 6.85–13.07° in segment angles. Limits of agreement were −0.01–0.66 m for stride length and ranged from −27.71–20.53° in segment angles. [Conclusion] The Bluetooth IS system showed moderate agreement with MOCAP. Bluetooth IS could be used for reliable gait analysis with fewer space requirements and more portability than wireless IS or MOCAP systems. Bluetooth IS could be used outside of the clinic for real-time monitoring of gait during daily life.     

A multiple regression normalization approach to evaluation of gait in total knee arthroplasty patients

BackgroundGait features characteristic of a cohort may be difficult to evaluate due to differences in subjects' demographic factors and walking speed. The aim of this study was to employ a multiple regression normalization method that accounts for subject age, height, body mass, gender, and self-selected walking speed in the evaluation of gait in unilateral total knee arthroplasty patients.MethodsThree-dimensional gait analysis was performed on 45 total knee arthroplasty patients and 31 aged-matched controls walking at their self-selected speed. Gait data peaks including joint angles, ground reaction forces, net joint moments, and net joint powers were normalized using subject body mass, standard dimensionless equations, and a multiple regression approach that modeled subject age, height, body mass, gender, and self-selected walking speed.FindingsNormalizing gait data using subject body mass, dimensionless equations, and multiple regression approach resulted in a significantly lower knee adduction moment and knee extensor power in total knee arthroplasty patients compared to controls (p < 0.05). In contrast to normalization using body mass and dimensionless equations, multiple regression normalization greatly reduced variance in gait data by minimizing correlations with subject demographic factors and walking speed, resulting in significantly higher peak hip extension angles and peak hip flexion powers in total knee arthroplasty patients (p < 0.05).InterpretationTotal knee arthroplasty patients generate greater hip extension angles and hip flexor power and have a lower knee adduction moment than healthy controls. This gait pattern may be a strategy to reduce muscle and joint loading at the knee.     

Concurrent Validity and Test-retest Reliability of the OPTOGait Photoelectric Cell System for the Assessment of Spatio-temporal Parameters of the Gait of Young Adults

[Purpose] The purpose of this study was to investigate the concurrent validity and test-retest reliability of the recently introduced OPTOGait Photoelectric Cell System for the assessment of spatio-temporal parameters of gait. [Subjects] Twenty healthy young adults (mean age = 27.35, SD = 7.4) were asked to walk 3 times on walkway at a comfortable speed. [Methods] Concurrent validity was assessed by comparing data obtained using the OPTOGait and GAITRite systems, and reliability was assessed by comparing data from the first and third OPTOGait sessions. [Results] Concurrent validity, as identified by intra-class correlation coefficients (ICC (2, 1) = 0.929–0.998), coefficients of variation (CV_ME = 0.32–11.30%), and 95% limits of agreement, showed high levels of correlation. In addition, the test-retest reliability of the OPTOGait Photoelectric Cell System was demonstrated as showing a high level of correlation with all spatio-temporal parameters by intra-class correlation coefficients (ICC (3, 1) = 0.785–0.952), coefficients of variation (CV_ME = 1.66–4.06%), 95% limits of agreement, standard error of measurement (SEM = 2.17–5.96%), and minimum detectable change (MDC₉₅% = 6.01–16.52%). [Conclusion] The OPTOGait Photoelectric Cell System has strong concurrent validity along with relative and absolute test-retest reliabilities. This portable system with easy-to-use features can be used for clinical assessments or research purposes as an objective means of assessing gait.Key words: Locomotion, Measurement, Analysis     

Consistent femoral external rotation during weight-bearing knee flexion is associated with better patient-reported pain and mediolateral balance after total knee arthroplasty

BackgroundNormal knees generally show consistent femoral external rotation during knee flexion, although knees that have had total knee arthroplasty exhibit various rotational patterns with less rotational angle. This study aimed to determine whether consistent femoral external rotation during weight-bearing knee flexion after total knee arthroplasty is associated with better patient-reported outcomes and mediolateral joint balance.MethodsA total of 40 total knee arthroplasty knees with a high-flexion posterior-stabilized prosthesis were divided into two groups based on their axial rotational kinematic pattern during squatting activity, and the clinical results including patient-reported outcomes and joint laxity were compared between the consistent external rotation group (20 knees) and the inconsistent external rotation group (20 knees). The unpaired Student's t-test or Welch's test were used for group comparison, and Fisher's exact test was applied for categorical data.Findings“Pain at rest” and “Pain at first gait in the morning” measured using a numerical rating scale (/10) were significantly lower in the consistent external rotation group compared with those in the inconsistent external rotation group. “Pain during gait on flat surface” tended to be lower in the consistent external rotation group. Medial stability was obtained in both groups with significantly greater lateral laxity in extension in the inconsistent external rotation group.InterpretationTotal knee arthroplasty knees with consistent femoral external rotation during weight-bearing knee flexion exhibited better patient-reported pain and mediolateral soft tissue balance. Surgical procedures that control the mediolateral balance with medial stability would induce consistent femoral external rotation and improve patient-reported pain.     

Assessing the knee flexion range of motion after total knee arthroplasty: Technology versus senses

IntroductionFollowing total knee arthroplasty surgery, attention should be paid to post-operative knee range of motion to achieve daily activities. Goniometer assessment is widely used to assess the range of motion in the post-operative period. This study aimed to determine the inter-rater ability of a smartphone application and visual estimation of the knee joint after total knee arthroplasty among different professions that commonly work together and compare whether any method is superior to another.MethodRange of motion measurements was performed by four clinicians as two physiotherapists and two orthopedic fellows. They utilized the Goniometer Reports application for smartphones, universal goniometer, and visual estimation to measure angles of knees which was operated. A two-way mixed model of intra-class correlation coefficient (ICC) with a 95% confidence level was used to assess inter-rater reliability.ResultsThirteen patients (11 female) and 20 knees (10 right) were assessed. The ICCs were found excellent both for between methods and between raters.ConclusionOur results show that technology seems a more accurate way to determine the knee range of motion after knee arthroplasty compared to senses. However, in lack of technological resources or time, or to avoid possible infection, visual estimation also could provide useful information.     

Quantifying varus thrust in knee osteoarthritis using wearable inertial sensors: A proof of concept

BackgroundVarus thrust during walking, visualized as excessive frontal plane knee motion during weight acceptance, is a modifiable risk factor for progression of knee osteoarthritis. However, visual assessment does not capture thrust severity and quantification with optical motion capture is often not feasible. Inertial sensors may provide a convenient alternative to optical motion capture. This proof-of-concept study sought to compare wearable inertial sensors to optical motion capture for the quantification of varus thrust.MethodsTwenty-six participants with medial knee osteoarthritis underwent gait analysis at self-selected and fast speeds. Linear regression with generalized estimating equations assessed associations between peak knee adduction velocity or knee adduction excursion from optical motion capture and peak thigh or shank adduction velocity from two inertial sensors on the lower limb. Relationships between inertial measures and peak external knee adduction moment were assessed as a secondary aim.FindingsBoth thigh and shank inertial sensor measures were associated with the optical motion capture measures for both speeds (P < 0.001 to P = 0.020), with the thigh measures having less variability than the shank. After accounting for age, sex, body mass index, radiographic severity, and limb alignment, thigh adduction velocity was also associated with knee adduction moment at both speeds (both P < 0.001).InterpretationAn inertial sensor placed on the mid-thigh can quantify varus thrust in people with medial knee osteoarthritis without the need for optical motion capture. This single sensor may be useful for risk screening or evaluating the effects of interventions in large samples.     

Wearable inertial sensors provide reliable biomarkers of disease severity in multiple sclerosis: A systematic review and meta-analysis

BackgroundGait impairment is a hallmark of multiple sclerosis (MS). InertiaLocoGraphy, the quantification of gait with inertial measurement units (IMUs), has been found useful to detect early changes in gait in MS. Still, the potential use of IMUs as a reliable biomarker of disease severity in MS remains unknown.ObjectiveThis systematic review and meta-analysis of observational studies aimed to describe IMU protocols used to assess gait in MS patients and calculate the effect sizes of IMU features associated with disease severity scale measures.MethodsWe searched MEDLINE, Cochrane Central, EMBASE and grey literature to identify articles published before May 2, 2018 that measured gait in MS patients by using IMUs and correlated IMU parameters with disease severity scale measures. We excluded from the meta-analysis articles that did not provide enough data to evaluate the association between IMU parameters and disease severity scale measures. The study was registered with the International Prospective Register of Systematic Reviews on May 2, 2018 (Registration: CRD42018092651) and the protocol was published in Systematic Reviews on January 8, 2019.ResultsWe included 36 articles in the systematic review and pooled 12 for the meta-analysis. The risk of bias was moderate, with only 2 articles (none included in the meta-analysis) showing a bias score < 50%. Among protocols tested, 2 were predominant (the Timed Up and Go test and 6-min walk test). Speed, step length and step time with IMUs were significantly correlated with the Expanded Disability Status Scale (EDSS) score, and speed and step length were significantly correlated with the Multiple Sclerosis Walking Scale-12 score.ConclusionIMU measurement has the potential to increase the sensitivity of clinical and performance tests to identify evolution in gait alteration in MS. Kinematic parameters easily accessible with IMUs, such as speed, step length and step duration, can help follow up disease severity in MS individuals with low to medium EDSS score (1.0–4.5).     

Are there different gait profiles in patients with advanced knee osteoarthritis? A machine learning approach

BackgroundDetermine whether knee kinematics features analyzed using machine-learning algorithms can identify different gait profiles in knee OA patients.Methods3D gait kinematic data were recorded from 42 patients (Kellgren-Lawrence stages III and IV) walking barefoot at individual maximal gait speed (0.98 ± 0.34 m/s). Principal component analysis, self-organizing maps, and k-means were applied to the data to identify the most relevant and discriminative knee kinematic features and to identify gait profiles.FindingsFour different gait profiles were identified and clinically characterized as type 1: gait with the knee in excessive varus and flexion (n = 6, 14%, increased knee adduction and increased maximum and minimum knee flexion, p < 0.01); type 2: gait with knee external rotation, either in varus or valgus (n = 11, 26%, excessive maximum and minimum external rotation, p < 0.001); type 3: gait with a stiff knee (n = 17, 40%, decreased knee flexion range of motion, p < 0.001); and type 4: gait with knee varus ‘thrust’ and decreased rotation (n = 8, 19%, increased and reduced range of motion in the coronal and transverse plane, respectively, p < 0.05).InterpretationIn a group of patients with homogeneous Kellgren-Lawrence classification of knee OA, gait kinematics data permitted to identify four different gait profiles. These gait profiles can be a valuable tool for helping surgical decisions and treatment. To allow generalization, further studies should be carried with a larger and heterogeneous population.     

Changes in plantar pressure,contact area and contact time symmetry during the gait 4 weeks before and 12 and 24 weeks after unilateral total hip arthroplasty

BackgroundFoot to ground pressure changes in total hip arthroplasty patients' gait are not widely described, although they are sensitive to gait abnormalities and the distribution of plantar pressures may differ before and after the surgery. This study aimed to analyse longitudinally differences in plantar pressure during gait in total hip arthroplasty patients compared to healthy controls.MethodsEighteen males participated in this study. Eight males, who underwent unilateral total hip arthroplasty, participated at the data collection three times: 4 weeks before the surgery, 12 and 24 weeks after, and ten healthy controls. All participants were asked to walk over Emed platform. To compare differences between the affected and unaffected limbs, Kolmogorov-Smirnov test was used. Kruskal-Wallis test was used to compare the difference between total hip arthroplasty patients and healthy controls.FindingsStatistically significant differences between the affected and unaffected limb were observed only during the preoperative measurement in peak pressure at MH4 area and in the contact area at MH4 and big toe. When comparing total hip arthroplasty patients and controls, a difference in the contact time at MH2, MH3 and MH4 areas 12 weeks after surgery and at MH2 and MH4 24 weeks after the surgery were observed.InterpretationThe shorter contact time at forefoot areas may indicate an alteration in the propulsive phase of the gait of both the affected limb and unaffected limb in total hip arthroplasty patients as a result of decreased terminal hip extension during the stance phase described in previous studies.     

Joint loading asymmetries in knee replacement patients observed both pre- and six months post-operation

Background

Studies have highlighted asymmetries in knee joint moments in individuals with osteoarthritis and joint replacements. However, there is a need to investigate the forces at the knee joints to establish the extent of loading asymmetries.

Methods

Twenty healthy (mean age, 62; range, 55–79 years) and 34 pre- to post-knee arthroplasty (mean age, 64; range, 39–79 years) participants performed gait and sit–stand activities in a motion capture laboratory. Knee joint forces and moments were predicted using inverse dynamics and used to calculate peak loading and impulse data which were normalized to body weight. Comparisons were made between affected and contralateral limbs, and changes from pre- to post-knee arthroplasty.

Findings

Pre-knee arthroplasty peak vertical knee forces were greater in the contralateral limb compared to the affected limb during both gait 3.5 vs. 3.2 ∗ body weight and sit–stand 1.8 vs. 1.5 ∗ body weight. During gait, peak knee adduction moment asymmetries significantly changed from pre- to post-knee arthroplasty (− 0.3 to 0.8 ∗ % body weight ∗ m ∗ height), although differences in vertical knee forces remained. There were no significant changes in loading during sit-stand from pre- to post-knee arthroplasty. The healthy participants showed no noteworthy asymmetries.

Interpretation

This study showed loading asymmetries in knee forces between affected and contralateral limbs both pre- and post-knee arthroplasty. Continued over reliance of the contralateral limb could lead to pathology.     

Relative phase measures of intersegmental coordination describe motor control impairments in children with cerebral palsy who exhibit stiff-knee gait

BackgroundThe purpose of this retrospective study was to explore lower limb intersegmental coordination as a clinically important indicator of motor control mechanisms in individuals with cerebral palsy exhibiting stiff-knee gait. We used the relative phase of thigh and foot segments around foot-off to describe motor control, given the relevance of the pre-swing phase of gait to the existence of stiff-knee gait.MethodsTraditional gait parameters and thigh/foot intersegmental coordination were calculated using pre-and postoperative kinematic data from a cohort of 54 subjects (92 legs) with spastic cerebral palsy. All participants had stiff-knee gait, walked without assistive devices, and underwent rectus femoris transfer surgery to improve swing period knee flexion. Analyses included correlations between a) preoperative intersegmental coordination and gait variables (knee flexion range, rate and gait performance) and b) pre-to-postoperative intersegmental coordination change and change in gait variables.FindingsThigh/foot intersegmental coordination significantly (P < 0.001) correlated with knee flexion range, rate and walking speed. Postoperative intersegmental coordination was significantly more uncoupled than preoperative. Pre-to-postoperative intersegmental coordination improvement also significantly correlated with improvements in knee flexion range, rate and walking speed. Pre-to-postoperative changes in intersegmental coordination accounted for 43% and 36% of variance in knee flexion range change and knee flexion rate change respectively.InterpretationIntersegmental coordination is a clinically important factor in knee flexion limitations associated with stiff-knee gait for individuals with cerebral palsy. These findings are a foundation for further study of intersegmental coordination measures as complements to traditional instrumented gait analysis.     

Anticipatory and reactive responses to underfoot perturbations during gait in healthy adults and individuals with a recent mild traumatic brain injury

BackgroundFollowing mild traumatic brain injury, individuals often exhibit quantifiable gait deficits over flat surfaces, but little is known about how they control gait over complex surfaces. Such complex surfaces require precise neuromotor control to anticipate and react to small disturbances in walking surfaces, and mild traumatic brain injury-related balance deficits may adversely affect these gait adjustments.MethodsThis study investigates anticipatory and reactive gait adjustments for expected and unexpected underfoot perturbations in healthy adults (n = 5) and individuals with mild traumatic brain injury (n = 5). Participants completed walking trials with random unexpected or expected underfoot perturbations from a mechanized shoe and inertial measurement units collected kinematic data from the feet and sternum. Linear mixed-effects models assessed the effects of segment, group, and their interaction on standardized difference of accelerations between perturbation and non-perturbation trials.FindingsBoth groups demonstrated similar gait strategies when perturbations were unexpected. During late swing phase before expected perturbations, persons with mild traumatic brain injury exhibited greater lateral acceleration of their perturbed foot and less lateral movement of their trunk compared with unperturbed gait. Control participants exhibited less lateral foot acceleration and no difference in mediolateral trunk acceleration compared with unperturbed gait during the same period. A significant group*segment interaction (p < 0.001) during this part of the gait cycle suggests the groups adopted different anticipatory strategies for the perturbation.InterpretationIndividuals with mild traumatic brain injury may be adopting cautious strategies for expected perturbations due to persistent neuromechanical deficits stemming from their injury.     

Dual-channel cascade pose estimation network trained on infrared thermal image and groundtruth annotation for real-time gait measurement

Real-time spatiotemporal parameter measurement for gait analysis is challenging. Previous techniques for 3D motion analysis, such as inertial measurement units, marker based motion analysis or the use of depth cameras, require expensive equipment, highly skilled staff and limits feasibility for sustainable applications. In this paper a dual-channel cascaded network to perform contactless real-time 3D human pose estimation using a single infrared thermal video as an input is proposed. An algorithm to calculate gait spatiotemporal parameters is presented by tracking estimated joint locations. Additionally, a training dataset composed of infrared thermal images and groundtruth annotations has been developed. The annotation represents a set of 3D joint locations from infrared optical trackers, which is considered to be the gold standard in clinical applications. On the proposed dataset, our pose estimation framework achieved a 3D human pose mean error of below 21 mm and outperforms state-of-the-art methods. The results reveal that the proposed system achieves competitive skeleton tracking performance on par with the other motion capture devices and exhibited good agreement with a marker-based three-dimensional motion analysis system (3DMA) over a range of spatiotemporal parameters. Moreover, the process is shown to distinguish differences in over-ground gait parameters of older adults with and without Hemiplegia’s disease. We believe that the proposed approaches can measure selected spatiotemporal gait parameters and could be effectively used in clinical or home settings.     

The validity and usability of an eight marker model for avatar-based biofeedback gait training

BackgroundVirtual reality presents a platform for therapeutic gaming, and incorporation of immersive biofeedback on gait may enhance outcomes in rehabilitation. Time is limited in therapeutic practice, therefore any potential gait training tool requires a short set up time, while maintaining clinical relevance and accuracy. The aim of this study was to develop, validate, and establish the usability of an avatar-based application for biofeedback-enhanced gait training with minimal set up time.MethodsA simplified, eight marker model was developed using eight passive markers placed on anatomical landmarks. This allowed for visualisation of avatar-based biofeedback on pelvis kinematics, hip and knee sagittal angles in real-time. Retrospective gait analysis data from typically developing children (n = 41) and children with cerebral palsy (n = 25), were used to validate eight marker model. Gait outcomes were compared to the Human Body Model using statistical parametric mapping. Usability for use in clinical practice was tested in five clinical rehabilitation centers with the system usability score.FindingsGait outcomes of Human Body Model and eight marker model were comparable, with small differences in gait parameters. The discrepancies between models were <5°, except for knee extension where eight marker model showed significantly less knee extension, especially towards full extension. The application was considered of ‘high marginal acceptability’ (system usability score, mean 68 (SD 13)).InterpretationGait biofeedback can be achieved, to acceptable accuracy for within-session gait training, using an eight marker model. The application may be considered usable and implemented for use in patient populations undergoing gait training.     

Concurrent validity and within-session reliability of gait kinematics measured using an inertial motion capture system with repeated calibration

IntroductionWearable 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.MethodsCalibration 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.ResultsConcurrent validity for gait revealed clinically significant between-system differences for sagittal angles (root-mean-square error [RMSE] 6.7°–15.0°; bias −9.3°–3.0°) and hip rotation (RMSE 7.9°; bias −4.2°). 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°–2.2°). Pose accuracy revealed mean absolute differences (MAD) < 5° for all angles except sagittal ankle, hip and pelvis. IMU tracking accuracy demonstrated RMSE ≤ 2.0°.ConclusionA 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.