Publication date: Available online 6 May 2016
Source:Gait & Posture
Author(s): John Darby, María B. Sánchez, Penelope B. Butler, Ian D. Loram
The Kinect v2 sensor supports real-time non-invasive 3D head pose estimation. Because the sensor is small, widely available and relatively cheap it has great potential as a tool for groups interested in measuring head posture. In this paper we compare the Kinect's head pose estimates with a marker-based record of ground truth in order to establish its accuracy. During movement of the head and neck alone (with static torso), we find average errors in absolute yaw, pitch and roll angles of 2.0±1.2∘, 7.3±3.2∘ and 2.6±0.7∘, and in rotations relative to the rest pose of 1.4±0.5∘, 2.1±0.4∘ and 2.0±0.8∘. Larger head rotations where it becomes difficult to see facial features can cause estimation to fail (10.2±6.1% of all poses in our static torso range of motion tests) but we found no significant changes in performance with the participant standing further away from Kinect – additionally enabling full-body pose estimation – or without performing face shape calibration, something which is not always possible for younger or disabled participants. Where facial features remain visible, the sensor has applications in the non-invasive assessment of postural control, e.g. during a programme of physical therapy. In particular, a multi-Kinect setup covering the full range of head (and body) movement would appear to be a promising way forward.
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Παρασκευή 6 Μαΐου 2016
Center of pressure during stance and gait in subjects with or without persistent complaints after a lateral ankle sprain
Publication date: July 2016
Source:Gait & Posture, Volume 48
Author(s): Wouter Kros, Noël L.W. Keijsers, John. M. van Ochten, Sita. M.A. Bierma-Zeinstra, Marienke van Middelkoop
Study aimTo investigate differences in the center of pressure (COP) during gait and single leg stance between subjects with persistent complaints (PC) and without persistent complaints (NPC) after a lateral ankle sprain.Methods44 patients who consulted the general practitioner, 6–12 months prior to inclusion, with a lateral ankle sprain were included for the current study purpose. Using a 7-point Likert scale patients were divided into the PC or NPC group. All subjects filled out an online questionnaire, walked along a walkway and performed a single leg stance, both on the RSscan. Primary outcomes included the COP displacement, range and percentage used in mediolateral and anterioposterior direction.ResultsThere was a trend (p<0.05) towards a more medially COP trajectory during walking at 34–46% and 83–96% and more anteriorly at 21–31% and 91–100% of the stance phase in the PC group compared to NPC group. Additionally, the COP was more laterally located in the sprained leg compared to the non-sprained leg in the PC group in the loading response phase (p<0.05). An interaction was found for the percentage of anterior–posterior range used in single leg stance without vision.ConclusionThe COP trajectory discriminates between patients with PC and NPC. This indicates that roll off during gait might play an important role in the recovery of patients after a lateral ankle sprain and could be used to monitor treatment.
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Source:Gait & Posture, Volume 48
Author(s): Wouter Kros, Noël L.W. Keijsers, John. M. van Ochten, Sita. M.A. Bierma-Zeinstra, Marienke van Middelkoop
Study aimTo investigate differences in the center of pressure (COP) during gait and single leg stance between subjects with persistent complaints (PC) and without persistent complaints (NPC) after a lateral ankle sprain.Methods44 patients who consulted the general practitioner, 6–12 months prior to inclusion, with a lateral ankle sprain were included for the current study purpose. Using a 7-point Likert scale patients were divided into the PC or NPC group. All subjects filled out an online questionnaire, walked along a walkway and performed a single leg stance, both on the RSscan. Primary outcomes included the COP displacement, range and percentage used in mediolateral and anterioposterior direction.ResultsThere was a trend (p<0.05) towards a more medially COP trajectory during walking at 34–46% and 83–96% and more anteriorly at 21–31% and 91–100% of the stance phase in the PC group compared to NPC group. Additionally, the COP was more laterally located in the sprained leg compared to the non-sprained leg in the PC group in the loading response phase (p<0.05). An interaction was found for the percentage of anterior–posterior range used in single leg stance without vision.ConclusionThe COP trajectory discriminates between patients with PC and NPC. This indicates that roll off during gait might play an important role in the recovery of patients after a lateral ankle sprain and could be used to monitor treatment.
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Validation of hip joint center localization methods during gait analysis using 3D EOS imaging in typically developing and cerebral palsy children
Publication date: July 2016
Source:Gait & Posture, Volume 48
Author(s): Ayman Assi, Christophe Sauret, Abir Massaad, Ziad Bakouny, Hélène Pillet, Wafa Skalli, Ismat Ghanem
Localization of the hip joint center (HJC) is essential in computation of gait data. EOS low dose biplanar X-rays have been shown to be a good reference in evaluating various methods of HJC localization in adults. The aim is to evaluate predictive and functional techniques for HJC localization in typically developing (TD) and cerebral palsy (CP) children, using EOS as an image based reference. Eleven TD and 17 CP children underwent 3D gait analysis. Six HJC localization methods were evaluated in each group bilaterally: 3 predictive (Plug in Gait, Bell and Harrington) and 3 functional methods based on the star arc technique (symmetrical center of rotation estimate, center transformation technique and geometrical sphere fitting). All children then underwent EOS low dose biplanar radiographs. Pelvis, lower limbs and their corresponding external markers were reconstructed in 3D. The center of the femoral head was considered as the reference (HJCEOS). Euclidean distances between HJCs estimated by each of the 6 methods and the HJCEOS were calculated; distances were shown to be lower in predictive compared to functional methods (p<0.0001). Contrarily to findings in adults, functional methods were shown to be less accurate than predictive methods in TD and CP children, which could be mainly due to the shorter thigh segment in children. Harrington method was shown to be the most accurate in the prediction of HJC (mean error≈18mm, SD=9mm) and quasi-equivalent to the Bell method. The bias for each method was quantified, allowing its correction for an improved HJC estimation.
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Source:Gait & Posture, Volume 48
Author(s): Ayman Assi, Christophe Sauret, Abir Massaad, Ziad Bakouny, Hélène Pillet, Wafa Skalli, Ismat Ghanem
Localization of the hip joint center (HJC) is essential in computation of gait data. EOS low dose biplanar X-rays have been shown to be a good reference in evaluating various methods of HJC localization in adults. The aim is to evaluate predictive and functional techniques for HJC localization in typically developing (TD) and cerebral palsy (CP) children, using EOS as an image based reference. Eleven TD and 17 CP children underwent 3D gait analysis. Six HJC localization methods were evaluated in each group bilaterally: 3 predictive (Plug in Gait, Bell and Harrington) and 3 functional methods based on the star arc technique (symmetrical center of rotation estimate, center transformation technique and geometrical sphere fitting). All children then underwent EOS low dose biplanar radiographs. Pelvis, lower limbs and their corresponding external markers were reconstructed in 3D. The center of the femoral head was considered as the reference (HJCEOS). Euclidean distances between HJCs estimated by each of the 6 methods and the HJCEOS were calculated; distances were shown to be lower in predictive compared to functional methods (p<0.0001). Contrarily to findings in adults, functional methods were shown to be less accurate than predictive methods in TD and CP children, which could be mainly due to the shorter thigh segment in children. Harrington method was shown to be the most accurate in the prediction of HJC (mean error≈18mm, SD=9mm) and quasi-equivalent to the Bell method. The bias for each method was quantified, allowing its correction for an improved HJC estimation.
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A simplified marker set to define the center of mass for stability analysis in dynamic situations
Publication date: Available online 6 May 2016
Source:Gait & Posture
Author(s): R. Tisserand, T. Robert, R. Dumas, L. Chèze
The extrapolated center of mass (XCoM), a valuable tool to assess balance stability, involves defining the whole body center of mass (CoMWB). However, accurate three-dimensional estimation of the CoMWB is time consuming, a severe limitation in certain applications. In this study, twenty-four subjects (young and elderly, male and female) performed three different balance tasks: quiet standing, gait and balance recovery. Three different models, based on a segmental method, were used to estimate the three-dimensional CoMWB absolute position during these movements: a reference model based on 38 markers, a simplified 13-marker model and a single marker (sacral) model. CoMWB and XCoM estimations from the proposed simplified model came closer to the reference model than estimations from the sacral marker model. It remained accurate for dynamic tasks, where the sacral marker model proved inappropriate. The simplified model proposed here yields accurate three-dimensional estimation of both the CoMWB and the XCoM with a limited number of markers. Importantly, using this model would reduce the experimental and post-processing times for future balance studies assessing dynamic stability in humans.
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Source:Gait & Posture
Author(s): R. Tisserand, T. Robert, R. Dumas, L. Chèze
The extrapolated center of mass (XCoM), a valuable tool to assess balance stability, involves defining the whole body center of mass (CoMWB). However, accurate three-dimensional estimation of the CoMWB is time consuming, a severe limitation in certain applications. In this study, twenty-four subjects (young and elderly, male and female) performed three different balance tasks: quiet standing, gait and balance recovery. Three different models, based on a segmental method, were used to estimate the three-dimensional CoMWB absolute position during these movements: a reference model based on 38 markers, a simplified 13-marker model and a single marker (sacral) model. CoMWB and XCoM estimations from the proposed simplified model came closer to the reference model than estimations from the sacral marker model. It remained accurate for dynamic tasks, where the sacral marker model proved inappropriate. The simplified model proposed here yields accurate three-dimensional estimation of both the CoMWB and the XCoM with a limited number of markers. Importantly, using this model would reduce the experimental and post-processing times for future balance studies assessing dynamic stability in humans.
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Biomechanical balance response during induced falls under dual task conditions in people with knee osteoarthritis
Publication date: Available online 6 May 2016
Source:Gait & Posture
Author(s): Pazit Levinger, Hanatsu Nagano, Calum Downie, Alan Hayes, Kerrie M Sanders, Flavia Cicuttini, Rezaul Begg
ObjectivePeople with knee osteoarthritis (OA) are at twice the risk of falling compared to older people without knee OA, however the mechanism for this is poorly understood. This study investigated the biomechanical response of the trunk and lower limb joints during a forward induced fall under different task conditions in people with and without knee OA.MethodTwenty four participants with OA (68.6±6.2 years) and fifteen asymptomatic controls (72.4±4.8 years) participated in the study. Forward fall was induced by releasing participants from a static forward leaning position. Participants were required to recover balance during three conditions: normal, physical (obstacle clearance) and cognitive dual tasks (counting backwards). Spatiotemporal parameters, lower limb joint kinematics and kinetics of the recovery limb were compared between the two groups and across the three task conditions.ResultsThe OA group demonstrated slower spatio-temporal characteristics and reduced hip and knee flexion angles, joint moments/powers and reduced muscle negative work at the knee and ankle (p<0.05). Cognitive dual task resulted in reduced centre of mass velocity and step length (p=0.03) compared to the physical dual task condition. Reduced knee (p=0.02) and hip joint powers (p=0.03) were demonstrated in the OA group in the physical task condition.ConclusionWhen simulating a forward fall, participants with OA demonstrated difficulty in absorbing and slowing down the forward momentum of the body during a recovery step. Moreover, poor dynamic postural control was demonstrated as task complexity increased.
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Source:Gait & Posture
Author(s): Pazit Levinger, Hanatsu Nagano, Calum Downie, Alan Hayes, Kerrie M Sanders, Flavia Cicuttini, Rezaul Begg
ObjectivePeople with knee osteoarthritis (OA) are at twice the risk of falling compared to older people without knee OA, however the mechanism for this is poorly understood. This study investigated the biomechanical response of the trunk and lower limb joints during a forward induced fall under different task conditions in people with and without knee OA.MethodTwenty four participants with OA (68.6±6.2 years) and fifteen asymptomatic controls (72.4±4.8 years) participated in the study. Forward fall was induced by releasing participants from a static forward leaning position. Participants were required to recover balance during three conditions: normal, physical (obstacle clearance) and cognitive dual tasks (counting backwards). Spatiotemporal parameters, lower limb joint kinematics and kinetics of the recovery limb were compared between the two groups and across the three task conditions.ResultsThe OA group demonstrated slower spatio-temporal characteristics and reduced hip and knee flexion angles, joint moments/powers and reduced muscle negative work at the knee and ankle (p<0.05). Cognitive dual task resulted in reduced centre of mass velocity and step length (p=0.03) compared to the physical dual task condition. Reduced knee (p=0.02) and hip joint powers (p=0.03) were demonstrated in the OA group in the physical task condition.ConclusionWhen simulating a forward fall, participants with OA demonstrated difficulty in absorbing and slowing down the forward momentum of the body during a recovery step. Moreover, poor dynamic postural control was demonstrated as task complexity increased.
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Disturbances of Automatic Gait Control Mechanisms in Higher Level Gait Disorder
Publication date: Available online 6 May 2016
Source:Gait & Posture
Author(s): Mary Danoudis, Ganga Ganesvaran, Robert Iansek
The underlying mechanisms responsible for the gait changes in frontal gait disorder (FGD), a form of Higher Level Gait Disorders, are poorly understood. We investigated the relationship between stride length and cadence (SLCrel) in people with FGD (n=15) in comparison to healthy older adults (n=21) to improve our understanding of the changes to gait in FGD.Gait data was captured using an electronic walkway system as participants walked at five self-selected speed conditions: preferred, very slow, slow, fast and very fast. Linear regression was used to determine the strength of the relationship (R2), slope and intercept.In the FGD group 9 participants had a strong SLCrel (linear group) (R2>0.8) and 6 a weak relationship (R2<0.8) (nonlinear group). The linear FGD group did not differ to healthy control for slope (p>0.05) but did have a lower intercept (p<0.001). The linear FGD group modulated gait speed by adjusting stride length and cadence similar to controls whereas the nonlinear FGD participants adjusted stride length but not cadence similar to controls. The non-linear FGD group had greater disturbance to their gait, poorer postural control and greater fear of falling compared to the linear FGD group.Investigation of the SLCrel resulted in new insights into the underlying mechanisms responsible for the gait changes found in FGD. The findings suggest stride length regulation was disrupted in milder FGD but as the disorder worsened, cadence control also became disordered resulting in a break down in the relationship between stride length and cadence.
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Source:Gait & Posture
Author(s): Mary Danoudis, Ganga Ganesvaran, Robert Iansek
The underlying mechanisms responsible for the gait changes in frontal gait disorder (FGD), a form of Higher Level Gait Disorders, are poorly understood. We investigated the relationship between stride length and cadence (SLCrel) in people with FGD (n=15) in comparison to healthy older adults (n=21) to improve our understanding of the changes to gait in FGD.Gait data was captured using an electronic walkway system as participants walked at five self-selected speed conditions: preferred, very slow, slow, fast and very fast. Linear regression was used to determine the strength of the relationship (R2), slope and intercept.In the FGD group 9 participants had a strong SLCrel (linear group) (R2>0.8) and 6 a weak relationship (R2<0.8) (nonlinear group). The linear FGD group did not differ to healthy control for slope (p>0.05) but did have a lower intercept (p<0.001). The linear FGD group modulated gait speed by adjusting stride length and cadence similar to controls whereas the nonlinear FGD participants adjusted stride length but not cadence similar to controls. The non-linear FGD group had greater disturbance to their gait, poorer postural control and greater fear of falling compared to the linear FGD group.Investigation of the SLCrel resulted in new insights into the underlying mechanisms responsible for the gait changes found in FGD. The findings suggest stride length regulation was disrupted in milder FGD but as the disorder worsened, cadence control also became disordered resulting in a break down in the relationship between stride length and cadence.
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Developing an assessment approach for perceptual changes to tinnitus sound characteristics for adult cochlear implant recipients
10.3109/14992027.2016.1172391<br/>David Greenberg
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