The Human Body Model versus conventional gait models for kinematic gait analysis in children with cerebral palsy

With the rise of biofeedback in gait training in cerebral palsy there is a need for real-time measurements of gait kinematics. The Human Body Model (HBM) is a recently developed model, optimized for the real-time computing of kinematics. This study evaluated differences between HBM and two commonly used models for clinical gait analysis: the Newington Model, also known as Plug-in-Gait (PiG), and the calibrated anatomical system technique (CAST). Twenty-five children with cerebral palsy participated. 3D instrumented gait analyses were performed in three laboratories across Europe, using a comprehensive retroreflective marker set comprising three models: HBM, PiG and CAST. Gait kinematics from the three models were compared using statistical parametric mapping, and RMSE values were used to quantify differences. The minimal clinically significant difference was set at 5°. Sagittal plane differences were mostly less than 5°. For frontal and transverse planes, differences between all three models for almost all segment and joint angles exceeded the value of minimal clinical significance. Which model holds the most accurate information remains undecided since none of the three models represents a ground truth. Meanwhile, it can be concluded that all three models are equivalent in representing sagittal plane gait kinematics in clinical gait analysis.     

A Note on Motor Learning Without Post-Response Knowledge of Results

The authors studied the adjustment of the 2 distinct known expressions of gait velocity, the velocity of the center of gravity (CG) and the velocity of the center of foot pressure (CP) at the end of the 1st step in 2 experimental situations: natural gait initiation (the control situation, CS) and heel-off gait initiation (the test situation, TS). Gait was initiated by 7 healthy participants, from an erect spontaneous posture in the CS and from a posture with heels raised in the TS, on a force platform at 3 self-selected speed conditions. Biomechanical data from the force platform were collected in both experimental situations, and the authors used a particular gait analysis based on the differential method of Y. Brenière (2003) in order to approach velocity modulation by means of step length and frequency. Results showed that CG and CP velocities were adjusted differently during heel-off gait initiation than during natural gait initiation. CP velocity, as compared with CG velocity, was overestimated in TS. Results also established the relevance of the expression of step velocity by means of step length and frequency: The central nervous system, taking into account the specific postural constraints of each experimental situation, uses a reference value and a regulating parameter to modulate step velocity. Moreover, the contributions of 1st step length and frequency to the expression of step velocity in TS and CS were different. Thus, a specific locomotor behavior corresponds to a given experimental situation that is characterized by its own initial biomechanical constraints.     

Comparison of balance and gait in visually or hearing impaired children

The study was planned to evaluate the effect of loss of hearing and vision on balance and gait in 60 children, 20 of whom had hearing loss (M age = 9.3 yr., SD = 0.9), 20 who were visually impaired (M age = 12.2 yr., SD = 2.5), and 20 controls with no disability (M age = 9.4 yr., SD = 0.6). Standing Balance subtests of the Southern California Sensory Integration Tests were used. Gait analysis was conducted on a powdered surface. When the gait analysis results of the three groups of children were compared, statistically significant differences were noted. Scores for the hearing impaired group were more like those of the control group than those of the visually impaired group. Results show that children with visual impairment had more problems with balance and gait than controls.     

Gait training facilitates push-off and improves gait symmetry in children with cerebral palsy

BackgroundHuman walking involves a rapid and powerful contraction of ankle plantar flexors during push-off in late stance.ObjectiveHere we investigated whether impaired push-off force contributes to gait problems in children with cerebral palsy (CP) and whether it may be improved by intensive gait training.MethodsSixteen children with CP (6–15 years) and fourteen typically developing (TD) children (4–15 years) were recruited. Foot pressure was measured by insoles and gait kinematics were recorded by 3-dimensional video analysis during treadmill and overground walking. The peak derivative of ground reaction force at push off (dPF) was calculated from the foot pressure measurements. Maximal voluntary plantar flexion (MVC) was measured while seated. Measurements were performed before and after a control period and after 4 weeks of 30 minutes daily inclined treadmill training.ResultsdPF and MVC were significantly lower in children with CP on the most affected (MA) as compared to TD children (p < .001). dPF was lower on the MA leg as compared to the less affected (LA) leg in children with CP (p < .05). Following gait training, increases in dPF (p < .001) and MVC (p < .01) were observed for the MA leg. Following gait training children with CP showed similar timing of dPF and similar stance phase duration on both legs indicating improved symmetry of gait. These effects were also shown during overground walking.ConclusionImpaired ability to voluntarily activate ankle plantar flexors and produce a rapid and powerful push-off during late stance are of importance for impaired gait function in children with CP. Intensive treadmill training may facilitate the drive to ankle plantar flexors and reduce gait asymmetry during both treadmill and overground walking.     

Strength Training Effects on Muscle Forces and Contributions to Whole-Body Movement in Cerebral Palsy

Strength training is often prescribed for children with cerebral palsy (CP); however, links between strength gains and mobility are unclear. Nine children (age 14?±?3?years; GMFCS I-III) with spastic CP completed a 6-week strength-training program. Musculoskeletal gait simulations were generated for four children to assess training effects on muscle forces and function. There were increases in isometric joint strength, but no statistical changes in fast-as-possible walking speed or endurance after training. The walking simulations revealed changes in muscle forces and contributions to body center of mass acceleration, with greater forces from the hip muscles during walking most commonly observed. A progressive strength-training program can result in isometric and dynamic strength gains in children with CP, associated with variable mobility outcomes.     

Comparison and evaluation of two common methods to measure center of mass displacement in three dimensions during gait

Center of mass displacement during gait has frequently been used as an indicator of gait efficiency or as a complement to standard gait analysis. With technological advances, measuring the center of mass as the centroid of a multi-segment system is practical and feasible, but must first be compared to the well-established Newtonian computation of double-integrating the ground reaction force. This study aims to verify that the kinematic centroid obtained from a commonly-used model (Vicon Peak Plug-In-Gait) provides at least as reliable measurements of center of mass displacement as those obtained from the ground reaction forces. Gait data was collected for able-bodied children and children with myelomeningocele who use larger lateral center of mass excursions during gait. Reasonable agreement between methods was found in fore-aft and vertical directions, where the methods' excursions differed by an average of less than 10 mm in either direction, and the average RMS differences between methods' computed curves were 6 and 13 mm. Particularly good agreement was observed in the lateral direction, where the calculated excursions differed by an average of less than 2 mm and the RMS difference was 5 mm. Error analyses in computing the center of mass displacement from ground reaction forces were performed. A 5% deviation in mass estimation increased the computed vertical excursion twofold, and a 5% deviation in the integration constant of initial velocity increased the computed fore-aft excursions by 10%. The suitability of calculating center of mass displacement using ground reaction forces in a patient population is questioned. The kinematic centroid is susceptible to errors in segment parameters and marker placement, but results in plausible results that are at least within the range of doubt of the better-established ground reaction force integration, and are more useful when interpreting 3-D gait data.     

Are there common walking gait characteristics in patients diagnosed with late-onset Pompe disease?

Late-onset Pompe disease (LOPD) is a rare disease, defined as a progressive accumulation of lysosomal glycogen resulting in muscle weakness and respiratory problems. Anecdotally, individuals often have difficulties walking, yet, there is no three-dimensional data supporting these claims. We aimed to assess walking patterns in individuals with LOPD and compare with healthy individuals. Kinematic, kinetic and spatiotemporal data were compared during walking at a self-selected speed between individuals with LOPD (n = 12) and healthy controls (n = 12). Gait profile scores and movement analysis profiles were also determined to indicate gait quality. In comparison with healthy individuals, the LOPD group demonstrated greater thoracic sway (96%), hip adduction angles (56%) and pelvic range of motion (77%) and reduced hip extensor moments (36%). Greater group variance for the LOPD group were also observed. Individuals with LOPD had a slower (15%) walking speed and reduced cadence (7%). Gait profile scores were 37% greater in the LOPD group compared to the healthy group. Proximal muscular weakness associated with LOPD disease is likely to have resulted in a myopathic gait pattern, slower selected walking speeds and deviations in gait patterns. Although individuals with LOPD presented with some common characteristics, greater variability in gait patterns is likely to be a result of wide variability in phenotype spectrum observed with LOPD. This is the first study to examine walking in individuals with LOPD using instrumented gait analysis and provides an understanding of LOPD on walking function which can help orientate physiotherapy treatment for individuals with LOPD.     

How does the heel-off posture modify gait initiation parameter programming?

The authors studied the adjustment of the 2 distinct known expressions of gait velocity, the velocity of the center of gravity (CG) and the velocity of the center of foot pressure (CP) at the end of the 1st step in 2 experimental situations: natural gait initiation (the control situation, CS) and heel-off gait initiation (the test situation, TS). Gait was initiated by 7 healthy participants, from an erect spontaneous posture in the CS and from a posture with heels raised in the TS, on a force platform at 3 self-selected speed conditions. Biomechanical data from the force platform were collected in both experimental situations, and the authors used a particular gait analysis based on the differential method of Y. Brenière (2003) in order to approach velocity modulation by means of step length and frequency. Results showed that CG and CP velocities were adjusted differently during heel-off gait initiation than during natural gait initiation. CP velocity, as compared with CG velocity, was overestimated in TS. Results also established the relevance of the expression of step velocity by means of step length and frequency: The central nervous system, taking into account the specific postural constraints of each experimental situation, uses a reference value and a regulating parameter to modulate step velocity. Moreover, the contributions of 1st step length and frequency to the expression of step velocity in TS and CS were different. Thus, a specific locomotor behavior corresponds to a given experimental situation that is characterized by its own initial biomechanical constraints.     

Parallel Factor Analysis of gait waveform data: A multimode extension of Principal Component Analysis

Gait data are typically collected in multivariate form, so some multivariate analysis is often used to understand interrelationships between observed data. Principal Component Analysis (PCA), a data reduction technique for correlated multivariate data, has been widely applied by gait analysts to investigate patterns of association in gait waveform data (e.g., interrelationships between joint angle waveforms from different subjects and/or joints). Despite its widespread use in gait analysis, PCA is for two-mode data, whereas gait data are often collected in higher-mode form. In this paper, we present the benefits of analyzing gait data via Parallel Factor Analysis (Parafac), which is a component analysis model designed for three- or higher-mode data. Using three-mode joint angle waveform data (subjects×time×joints), we demonstrate Parafac's ability to (a) determine interpretable components revealing the primary interrelationships between lower-limb joints in healthy gait and (b) identify interpretable components revealing the fundamental differences between normal and perturbed subjects' gait patterns across multiple joints. Our results offer evidence of the complex interconnections that exist between lower-limb joints and limb segments in both normal and abnormal gaits, confirming the need for the simultaneous analysis of multi-joint gait waveform data (especially when studying perturbed gait patterns).     

Gait measurement in chronic mild traumatic brain injury: A model approach

IntroductionMild traumatic brain injury (mTBI) can impact gait, with deficits linked to underlying neural disturbances in cognitive, motor and sensory systems. Gait is complex as it is comprised of multiple characteristics that are sensitive to underlying neural deficits. However, there is currently no clear framework to guide selection of gait characteristics in mTBI. This study developed a model of gait in chronic mTBI and replicated this in a separate group of controls, to provide a comprehensive and structured methodology on which to base gait assessment and analysis.MethodsFifty-two people with chronic mTBI and 59 controls completed a controlled laboratory gait assessment; walking for two minutes back and forth over a 13 m distance while wearing five wirelessly synchronized inertial sensors. Thirteen gait characteristics derived from the inertial sensors were selected for entry into the principle component analysis based on previous literature, robustness and novelty. Principle component analysis was then used to derive domains (components) of gait.ResultsFour gait domains were derived for our chronic mTBI group (variability, rhythm, pace and turning) and this was replicated in a separate control cohort. Domains totaled 80.8% and 77.4% of variance in gait for chronic mTBI and controls, respectively. Gait characteristic loading was unambiguous for all features, with the exception of gait speed in controls that loaded on pace and rhythm domains.ConclusionThis study contributes a four component model of gait in chronic mTBI and controls that can be used to comprehensively assess and analyze gait and underlying mechanisms involved in impairment, or examine the influence of interventions.     

Dynamic balance assessment during gait in children with Down and Prader-Willi syndromes using inertial sensors

Down (DS) and Prader-Willi (PWS) syndromes are chromosomal disorders both characterized by obesity, ligament laxity, and hypotonia, the latter associated with gait instability. Although these shared features may justify a common rehabilitation approach, evidence exists that adults with DS and PWS adopt different postural and walking strategies. The development of an instrumented protocol able to describe these strategies and quantify patients’ gait stability in the current clinical routine would be of great benefit for health professionals, allowing them to design personalized rehabilitation programs. This is particularly true for children with DS and PWS, where motor development is dramatically constrained by severe hypotonia and muscle weakness. The aim of this study was, thus, to propose an instrumented protocol, integrated with the clinical routine and based on the use of wearable inertial sensors, to assess gait stability in DS and PWS children.Fifteen children with DS, 11 children with PWS, and 12 typically developing children (CG) were involved in the study. Participants performed a 10-meter walking test while wearing four inertial sensors located at pelvis, sternum, and both distal tibiae levels. Spatiotemporal parameters (walking speed, stride frequency, and stride length) and a set of indices related to gait symmetry and upper-body stability (Root Mean Square, Attenuation Coefficient and Improved Harmonic Ratio) were estimated from pelvis and sternum accelerations. The Gross Motor Functional Measures (GMFM-88) and Intelligence Quotient (IQ Wechsler) were also assessed for each patient. A correlation analysis among the GMFM-88 and IQ scales and the estimated parameters was then performed.Children with DS and PWS exhibit reduced gait symmetry and higher accelerations at pelvis level than CG. While these accelerations are attenuated by about 40% at sternum level in CG and DS, PWS children display significant smaller attenuations, thus reporting reduced gait stability, most likely due to their typical “Trendelenburg gait”. Significant correlations were found between the estimated parameters and the GMFM-88 scale when considering the whole PWS and DS group and the PWS group alone.These results promote the adoption of wearable technology in clinical routines to monitor gait patterns in children with DS and PWS: the proposed protocol allows to markedly characterize patient-specific motor limitations even when clinical assessment scores provide similar results in terms of pathology severity. This protocol could be adopted to support health professionals in designing personalized treatments that, in turn, could help improving patients’ quality of life in terms of both physical and social perspectives.     

Evaluation of gait transitional phases using neuromechanical outputs and somatosensory inputs in an overground walk

In a bipedal walk, the human body experiences continuous changes in stability especially during weight loading and unloading transitions which are reported crucial to avoid fall. Prior stability assessment methods are unclear to quantify stabilities during these gait transitions due to methodological and/or measurement limitations. This study introduces Nyquist and Bode methods to quantify stability gait transitional stabilities using the neuromechanical output (CoP) and somatosensory input (GRF) responses. These methods are implemented for five different walking conditions grouped into walking speed and imitated rotational impairments. The trials were recorded with eleven healthy subjects using motion cameras and force platforms. The time rate of change in O/Is illustrated impulsive responses and modelled in the frequency domain. Nyquist and Bode stability methods are applied to quantify stability margins. Stability margins from outputs illustrated loading phases as stable and unloading phases as unstable in all walking conditions. There was a strong intralimb compensatory interaction (p < .001, Spearman correlation) found between opposite limbs. Overall, both walking groups illustrated a decrease (p < .05, Wilcoxon signed-rank test) in stability margins compared with normal/preferred speed walk. Further, stabilities quantified from outputs were found greater in magnitudes than the instability quantified from inputs illustrating the neuromotor balance control ability. These stability outcomes were also compared by applying extrapolated-CoM method. These methods of investigating gait dynamic stability are considered as having important implications for the assessment of ankle-foot impairments, rehabilitation effectiveness, and wearable orthoses.     

A cheap telemetric system for analyzing gait.

This study presents a technique for gait analysis, developed for the assessment of footfall timing and speed. The system in question consists of a transmitter, a receiver, a conductive walkway and a PC with the appropriate software.The technique was first tested for accuracy and repeatability with known signals, and was validated with a group of 20 healthy male adults (mean age = 34 years, S.D. = 5.5). The results thus obtained were similar to those reported in the literature for corresponding groups. Then, measurements on 10 children suffering from cerebral palsy (spastic hemiplegia) were performed. Gait analysis was carried out just before surgery and one year post-operatively. The results confirm the validity of the technique for measurements on orthopedic patients and its efficiency for functional evaluation of gait improvement after surgery.     

Investigation of factors impacting mobility and gait in Parkinson disease

Mobility and gait limitations are major issues for people with Parkinson disease (PD). Identification of factors that contribute to these impairments may inform treatment and intervention strategies. In this study we investigated factors that predict mobility and gait impairment in PD. Participants with mild to moderate PD and without dementia (n = 114) were tested in one session ‘off’ medication. Mobility measures included the 6-Minute Walk test and Timed-Up-and-Go. Gait velocity was collected in four conditions: forward preferred speed, forward dual task, forward fast as possible and backward walking. The predictors analyzed were age, gender, disease severity, balance, balance confidence, fall history, self-reported physical activity, and executive function. Multiple regression models were used to assess the relationships between predictors and outcomes. The predictors, in different combinations for each outcome measure, explained 55.7% to 66.9% of variability for mobility and 39.5% to 52.8% for gait velocity. Balance was the most relevant factor (explaining up to 54.1% of variance in mobility and up to 45.6% in gait velocity). Balance confidence contributed to a lesser extent (2.0% to 8.2% of variance) in all models. Age explained a small percentage of variance in mobility and gait velocity (up to 2.9%). Executive function explained 3.0% of variance during forward walking only. The strong predictive relationships between balance deficits and mobility and gait impairment suggest targeting balance deficits may be particularly important for improving mobility and gait in people with PD, regardless of an individual’s age, disease severity, fall history, or other demographic features.     

Validity of Functional Ambulation Performance Score for the evaluation of spatiotemporal parameters of children's gait

Gait characteristics of a healthy adult population have been used to develop the Functional Ambulation Profile (FAP) score to evaluate gait in patients with neuromuscular or musculoskeletal involvement (A. J. Nelson, 1974). Further technological progress allowed a more precise recording of walk parameters and propitiated the development of the Functional Ambulation Performance Score (FAPS). The authors aimed to explore the evolution of the FAPS in healthy children to determine what the lower limit of age would be to ensure reliability of this score. Participants were 32 children with normal development. A GAITRite? walkway was used to log the spatiotemporal parameters. Compared with values obtained in adults, the average FAPS was significantly lower for children under 12 years old. The interparticipant variability was particularly high for the younger children and decreased with age. Similar trends were observed regarding the intraparticipant variability. In conclusion, the authors observed that the FAPS is not suitable to compare the gait of different children younger than 12 years old. At least, the adult standards used to calculate FAPS would need to be modified if the score has to be applied to a pediatric population.     

A modified surface EMG biomarker for gait assessment in spastic cerebral palsy

ObjectiveMuscle clinical metrics are crucial for spastic cocontraction management in children with Cerebral Palsy (CP). We investigated whether the ankle plantar flexors cocontraction index (CCI) normalized with respect to the bipedal heel rise (BHR) approach provides more robust spastic cocontraction estimates during gait than those obtained through the widely accepted standard maximal isometric plantar flexion (IPF).MethodsTen control and 10 CP children with equinus gait pattern performed the BHR and IPF testing and walked barefoot 10-m distance. We compared agonist medial gastrocnemius EMG during both testing and CCIs obtained as the ratios of antagonist EMG during swing phase of gait and either BHR or IPF agonist EMG.ResultsAgonist EMG values from the BHR were: (i) internally reliable (Cronbach's α = 0.993), (ii) ~50 ± 0.4% larger than IPF, (iii) and positively correlated. Derived CCIs were significantly smaller (p < 0.05) in both populations.ConclusionThe bipedal heel rise approach may be accurate enough to reveal greater agonist activity of plantar flexors than the maximal isometric plantar flexion and seems to be more appropriate to obtain cocontraction estimates during swing of gait.SignificanceThis modified biomarker may represent a step forward towards improved accuracy of spastic gait management in pediatric.     

Why We Walk the Way We Do

By using inverse dynamics and forceplate recordings, this study established the principle of oscillating systems and the influence of gravity and body parameters on the programming of the gait parameters, step frequency and length. Calculation of the ratio of the amplitude of the center of mass (CM) and the center of foot pressure (CP) oscillations yielded an equation and established a biomechanical constant, the natural body frequency (NBF). NBF appears to be an absolute invariant parameter, specific to human standing posture and gait in terrestrial gravity, which influences the relative positions of CM and CP and whose value separates the frequency bands of standing posture from those for gait. This equation was tested by using the experimental paradigm of stepping in place and then used in calculating the magnitude of CM oscillations during gait. The biomechanical analysis of the experimental observations allows one to establish the relationships between body parameters and gravity and the central programming of locomotor parameters.     

Reliability of gait parameters in children under two years of age

The walking movement of children of school age and adults can be regarded as very consistent. However, few studies have reported reliability of gait parameters in very young children that may be used as normative data for the clinical assessment of gait. In the present study, nine normal children of ages 10 to 21 mo. were assessed cross-sectionally using three-dimensional video analysis and digitization to assess within-day reliability of gait kinematics. Between-subject differences in gait kinematics were also examined. In addition, one child was assessed at the onset of independent walking and at monthly intervals thereafter to assess changes in gait kinematics during the first 8 mo. of autonomous walking. The case study allowed the acquisition of pilot data for longitudinal studies of this age group. 10 kinematics variables regarded as indicators of efficient walking were measured, and reliability was assessed using one-way analysis of variance and coefficient of variation. The study showed that all children produced reliable within-day results; however, the gait of each child was unique. In the case study, the between-month differences in gait kinematics were significant. The findings may be of clinical interest for pediatricians and child neurologists given the lack of normative data for this age group.