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Background: Polio survivors often exhibit plantarflexor weakness, which impairs gait stability, and increases energy cost of walking. Quantifying gait stability could provide insights in the control mechanisms polio survivors use to maintain gait stability and in whether impaired gait stability is related to the increased energy cost of walking., Research Question: Is gait stability impaired in polio survivors with plantarflexor weakness compared to able-bodied individuals, and does gait stability relate to energy cost of walking?, Methods: We retrospectively analyzed barefoot biomechanical gait data of 31 polio survivors with unilateral plantarflexor weakness and of 24 able-bodied individuals. We estimated gait stability by calculating variability (SD) of step width, step length, double support time, and stance time, and by the mean and variability (SD) of the mediolateral and anteroposterior margin of stability (MoS ML and MoS AP ). In addition, energy cost of walking (polio survivors only) at comfortable speed was analyzed., Results: Comfortable speed was 31% lower in polio survivors compared to able-bodied individuals (p < 0.001). Corrected for speed differences, step width variability was significantly larger in polio survivors (+41%), double support time variability was significantly smaller (-27%), MoS ML (affected leg) was significantly larger (+80%), and MoS AP was significantly smaller (affected leg:-17% and non-affected leg:-15%). Step width and step length variability (affected leg) were positively correlated with energy cost of walking (r = 0.502 and r = 0.552). MoS AP (non-affected leg) was negatively correlated with energy cost of walking (r = -0.530)., Significance: Polio survivors with unilateral plantarflexor weakness demonstrated an impaired gait stability. Increased step width and step length variability and lower MoS AP could be factors related to the elevated energy cost of walking in polio survivors. These findings increase our understanding of stability problems due to plantarflexor weakness, which could be used for the improvement of (orthotic) interventions to enhance gait stability and reduce energy cost in polio survivors., Competing Interests: Declaration of Competing Interest The authors report no conflicts of interest., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: The C-Mill interactive treadmill allows for a safe walking-adaptability assessment, unveiling reduced walking adaptability in polio survivors compared to healthy individuals, possibly related to their high fall rate. However, evidence on its validity and reproducibility is scarce., Research Question: What is the validity and reproducibility of C-Mill walking-adaptability assessment in polio survivors?, Methods: Polio survivors with a history and/or fear of falling (n = 46) performed two walking-adaptability assessments, 1-2 weeks apart, including target-stepping tests (with 0%, 20% and 30% inter-target variance) and obstacle-avoidance tests (anticipatory and reactive). We examined (1) face validity by determining Group effects (for subgroups stratified for fall frequency, fear of falling and leg muscle weakness) and Condition effects (for difficulty level) on walking-adaptability outcomes, (2) construct validity by correlating walking-adaptability and balance outcomes, and (3) content validity by establishing possible ceiling effects. We determined whether face-validity findings were reproducible over test occasions and calculated Intraclass Correlation Coefficients (ICC) and the 95% Limits of Agreement (LoA) for walking-adaptability outcomes., Results: Walking-adaptability outcomes differed in to-be-expected directions for subgroups stratified for fall frequency and leg muscle weakness and for difficulty levels, all reproducible over test occasions. Correlations between walking-adaptability and balance outcomes were mainly low (r < 0.587). Ceiling effects were present for anticipatory obstacle-avoidance and balance outcomes, but not for reactive obstacle avoidance. ICCs [95% confidence intervals] were good for the challenging 20% (0.80[0.67-0.88]) and 30% target-stepping conditions (0.74[0.57-0.85]) and for the reactive obstacle-avoidance (0.76[0.59-0.86]) condition, but not for 0% target-stepping and anticipatory obstacle-avoidance (ICC<0.62) conditions. Likewise, the narrowest LoA were observed for the 20% and 30% target-stepping conditions., Significance: We proved face, construct and content validity of C-Mill walking-adaptability assessment in polio survivors with a history of falls and/or fear of falling. Adding walking-adaptability assessment, particularly the more challenging tests given their superior reproducibility, to currently used clinical tests could improve fall-risk evaluation in this population., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: To improve gait, persons with calf muscle weakness can be provided with a dorsal leaf spring ankle foot orthosis (DLS-AFO). These AFOs can store energy during stance and return this energy during push-off, which, in turn, reduces walking energy cost. Simulations indicate that the effect of the DLS-AFO on walking energy cost and gait biomechanics depends on its stiffness and on patient characteristics. We therefore studied the effect of varying DLS-AFO stiffness on reducing walking energy cost, and improving gait biomechanics and AFO generated power in persons with non-spastic calf muscle weakness, and whether the optimal AFO stiffness for maximally reducing walking energy cost varies between persons., Methods: Thirty-seven individuals with neuromuscular disorders and non-spastic calf muscle weakness were included. Participants were provided with a DLS-AFO of which the stiffness could be varied. For 5 stiffness configurations (ranging from 2.8 to 6.6 Nm/degree), walking energy cost (J/kg/m) was assessed using a 6-min comfortable walk test. Selected gait parameters, e.g. maximal dorsiflexion angle, ankle power, knee angle, knee moment and AFO generated power, were derived from 3D gait analysis., Results: On group level, no significant effect of DLS-AFO stiffness on reducing walking energy cost was found (p = 0.059, largest difference: 0.14 J/kg/m). The AFO stiffness that reduced energy cost the most varied between persons. The difference in energy cost between the least and most efficient AFO stiffness was on average 10.7%. Regarding gait biomechanics, increasing AFO stiffness significantly decreased maximal ankle dorsiflexion angle (- 1.1 ± 0.1 degrees per 1 Nm/degree, p < 0.001) and peak ankle power (- 0.09 ± 0.01 W/kg, p < 0.001). The reduction in minimal knee angle (- 0.3 ± 0.1 degrees, p = 0.034), and increment in external knee extension moment in stance (- 0.01 ± 0.01 Nm/kg, p = 0.016) were small, although all stiffness' substantially affected knee angle and knee moment compared to shoes only. No effect of stiffness on AFO generated power was found (p = 0.900)., Conclusions: The optimal efficient DLS-AFO stiffness varied largely between persons with non-spastic calf muscle weakness. Results indicate this is caused by an individual trade-off between ankle angle and ankle power affected differently by AFO stiffness. We therefore recommend that the AFO stiffness should be individually optimized to best improve gait., Trial Registration Number: Nederlands Trial Register 5170. Registration date: May 7th 2015. http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=5170.

Background: Patients with calf muscle weakness due to neuromuscular disorders have a reduced ankle push-off work, which leads to increased energy dissipation at contralateral heel-strike. Consequently, compensatory positive work needs to be generated, which is mechanically less efficient. It is unknown whether neuromuscular disorder patients compensate with their ipsilateral hip and/or contralateral leg; and if such compensatory joint work is related to walking energy cost., Research Question: Do patients with calf muscle weakness compensate for the increase in negative joint work by increasing positive ipsilateral hip work and/or positive contralateral leg work? And is the total mechanical work related with walking energy cost?, Methods: Seventeen patients with unilateral flaccid calf muscle weakness and 10 healthy individuals performed the following two tests: i) a barefoot 3D gait analysis at comfortable speed and matched control speed (i.e. 0.4 non-dimensional) to assess lower limb joint work and ii) a 6-minute walk test at comfortable speed to assess walking energy cost., Results: Patients had a lower comfortable walking speed compared to healthy individuals (1.05 vs 1.36 m/s, p < 0.001) and did not increase positive lower limb joint work at comfortable speed. At matched speed (1.25 m/s), patients showed increased positive work at their ipsilateral hip (0.38 ± 0.08 vs 0.27 ± 0.07, p = 0.001) and/or contralateral leg (0.99 ± 0.14 vs 0.69 ± 0.14, p < 0.001). Patients with weakest plantar flexors used both strategies. No relation between total positive work and walking energy cost was found (r = 0.43, p = 0.122)., Significance: Patients with unilateral calf muscle weakness compensated for reduced ankle push-off work by lowering their comfortable walking speed or, at matched speed, by generating additional positive joint work at the ipsilateral hip and/or contralateral leg. The additional positive joint work at matched speed did not explain the elevated walking energy cost at comfortable speed, which needs further exploration., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The objective was to identify gait patterns in polio survivors with calf muscle weakness and associate them to underlying lower extremity impairments, which are expected to help in the search for an optimal orthosis. Unilaterally affected patients underwent barefoot 3D-gait analyses. Gait pattern clusters were created based on the ankle and knee angle and ankle moment shown in midstance of the affected limb. Impairment clusters were created based on plantarflexor and knee-extensor strength, and ankle and knee joint range-of-motion. The association between gait patterns and underlying impairments were examined descriptively. The Random Forest Algorithm and regression analyses were used to predict gait patterns and parameters. Seven gait patterns in 73 polio survivors were identified, with two dominant patterns: one with a mildly/non-deviant ankle angle, ankle moment and knee angle (n=23), and one with a strongly deviant ankle angle and a mildly/non-deviant ankle moment and knee angle (n=18). Gait pattern prediction from underlying impairments was 49% accurate with best prediction performance for the second dominant gait pattern (sensitivity 78% and positive predictive value 74%). The underlying impairments explained between 20 and 32% of the variance in individual gait parameters. Polio survivors with calf muscle weakness who present a similar impairment profile do not necessarily walk the same. From physical examination alone, the gait pattern nor the individual gait parameters could be accurately predicted. The patient's gait should therefore be measured to help in the prescription and evaluation of orthoses for these patients., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Introduction: In patients with neuromuscular disorders and subsequent calf muscle weakness, metabolic walking energy cost (EC) is nearly always increased, which may restrict walking activity in daily life. To reduce walking EC, a spring-like ankle-foot-orthosis (AFO) can be prescribed. However, the reduction in EC that can be obtained from these AFOs is stiffness dependent, and it is unknown which AFO stiffness would optimally support calf muscle weakness. The PROOF-AFO study aims to determine the effectiveness of stiffness-optimised AFOs on reducing walking EC, and improving gait biomechanics and walking speed in patients with calf muscle weakness, compared to standard, non-optimised AFOs. A second aim is to build a model to predict optimal AFO stiffness., Methods and Analysis: A prospective intervention study will be conducted. In total, 37 patients with calf muscle weakness who already use an AFO will be recruited. At study entry, participants will receive a new custom-made spring-like AFO of which the stiffness can be varied. For each patient, walking EC (primary outcome), gait biomechanics and walking speed (secondary outcomes) will be assessed for five stiffness configurations and the patient's own (standard) AFO. On the basis of walking EC and gait biomechanics outcomes, the optimal AFO stiffness will be determined. After wearing this optimal AFO for 3 months, walking EC, gait biomechanics and walking speed will be assessed again and compared to the standard AFO., Ethics and Dissemination: The Medical Ethics Committee of the Academic Medical Centre in Amsterdam has approved the study protocol. The study is registered at the Dutch trial register (NTR 5170). The PROOF-AFO study is the first to compare stiffness-optimised AFOs with usual care AFOs in patients with calf muscle weakness. The results will also provide insight into factors that influence optimal AFO stiffness in these patients. The results are necessary for improving orthotic treatment and will be disseminated through international peer-reviewed journals and scientific conferences., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.)

Introduction: Rigid Ankle-Foot Orthoses (AFOs) are commonly prescribed to counteract excessive knee flexion during the stance phase of gait in children with cerebral palsy (CP). While rigid AFOs may normalize knee kinematics and kinetics effectively, it has the disadvantage of impeding push-off power. A spring-like AFO may enhance push-off power, which may come at the cost of reducing the knee flexion less effectively. Optimizing this trade-off between enhancing push-off power and normalizing knee flexion in stance is expected to maximize gait efficiency. This study investigated the effects of varying AFO stiffness on gait biomechanics and efficiency in children with CP who walk with excessive knee flexion in stance. Fifteen children with spastic CP (11 boys, 10±2 years) were prescribed with a ventral shell spring-hinged AFO (vAFO). The hinge was set into a rigid, or spring-like setting, using both a stiff and flexible performance. At baseline (i.e. shoes-only) and for each vAFO, a 3D-gait analysis and 6-minute walk test with breath-gas analysis were performed at comfortable speed. Lower limb joint kinematics and kinetics were calculated. From the 6-minute walk test, walking speed and the net energy cost were determined. A generalized estimation equation (p<0.05) was used to analyze the effects of different conditions. Compared to shoes-only, all vAFOs improved the knee angle and net moment similarly. Ankle power generation and work were preserved only by the spring-like vAFOs. All vAFOs decreased the net energy cost compared to shoes-only, but no differences were found between vAFOs, showing that the effects of spring-like vAFOs to promote push-off power did not lead to greater reductions in walking energy cost. These findings suggest that, in this specific group of children with spastic CP, the vAFO stiffness that maximizes gait efficiency is primarily determined by its effect on knee kinematics and kinetics rather than by its effect on push-off power., Trial Registration: Dutch Trial Register NTR3418.

Objective: To determine the effect of ankle-foot orthoses on walking efficiency and gait in a heterogeneous group of children with cerebral palsy, using barefoot walking as the control condition., Design: A retrospective study., Methods: Barefoot and ankle-foot orthosis data for 172 children with spastic cerebral palsy (mean age 9 years; hemiplegia: 21, diplegia: 97, and quadriplegia: 54) were compared. These data consisted of non-dimensional speed, net non- dimensional energy cost of walking (NN-cost), and NN-cost as a percentage of speed-matched controls (NN-cost(pct)). For 80 of these children the Gillette Gait Index and data for 3D gait kinematics and kinetics were also analyzed., Results: Speed was 9% faster (p<0.001), NN-cost was 6% lower (p=0.007), and NN-cost(pct) was 9% lower (p=0.022) when walking with an ankle-foot orthosis. The Gillette Gait Index remained unchanged (p=0.607). Secondary subgroup analysis for involvement pattern showed a significant improvement in NN-cost(pct) only for quadriplegics (20%, p=0.004), whereas it remained unchanged for patients with hemiplegia and diplegia. Changes in the minimum knee flexion angle in stance phase and in terminal swing were found to be significantly related to the change in NN-cost(pct) (p=0.013 and p=0.022, respectively)., Conclusion: The use of an ankle-foot orthosis resulted in a significant decrease in the energy cost of walking of quadriplegic children with cerebral palsy, compared with barefoot walking, whereas it remained unchanged in hemiplegic and diplegic children with cerebral palsy. Energy cost reduction was related to both a faster and more efficient walking pattern. The improvements in efficiency were reflected in changes of stance and swing phase knee motion, i.e. those children whose knee flexion angle improved toward the typical normal range demonstrated a decrease in energy cost of walking, and vice versa.

Abstract Background Ankle-Foot-Orthoses with a ventral shell, also known as Floor Reaction Orthoses (FROs), are often used to reduce gait-related problems in children with spastic cerebral palsy (SCP), walking with excessive knee flexion. However, current evidence for the effectiveness (e.g. in terms of walking energy cost) of FROs is both limited and inconclusive. Much of this ambiguity may be due to a mismatch between the FRO ankle stiffness and the patient’s gait deviations. The primary aim of this study is to evaluate the effect of FROs optimised for ankle stiffness on the walking energy cost in children with SCP, compared to walking with shoes alone. In addition, effects on various secondary outcome measures will be evaluated in order to identify possible working mechanisms and potential predictors of FRO treatment success. Method/Design A pre-post experimental study design will include 32 children with SCP, walking with excessive knee flexion in midstance, recruited from our university hospital and affiliated rehabilitation centres. All participants will receive a newly designed FRO, allowing ankle stiffness to be varied into three configurations by means of a hinge. Gait biomechanics will be assessed for each FRO configuration. The FRO that results in the greatest reduction in knee flexion during the single stance phase will be selected as the subject’s optimal FRO. Subsequently, the effects of wearing this optimal FRO will be evaluated after 12–20 weeks. The primary study parameter will be walking energy cost, with the most important secondary outcomes being intensity of participation, daily activity, walking speed and gait biomechanics. Discussion The AFO-CP trial will be the first experimental study to evaluate the effect of individually optimised FROs on mobility and participation. The evaluation will include outcome measures at all levels of the International Classification of Functioning, Disability and Health, providing a unique set of data with which to assess relationships between outcome measures. This will give insights into working mechanisms of FROs and will help to identify predictors of treatment success, both of which will contribute to improving FRO treatment in SCP in term. Trial registration This study is registered in the Dutch Trial Register as NTR3418.

A rigid ventral shelf ankle foot orthosis (AFO) may improve gait in children with spastic cerebral palsy (SCP) whose gait is characterized by excessive knee flexion in stance. However, these AFOs can also impede ankle range of motion (ROM) and thereby inhibit push-off power. A more spring-like AFO can enhance push-off and may potentially reduce walking energy cost. The recent development of an adjustable spring-hinged AFO now allows adjustment of AFO stiffness, enabling tuning toward optimal gait performance. This study aims to quantify the mechanical properties of this spring-hinged AFO for each of its springs and settings. Using an AFO stiffness tester, two AFO hinges and their accompanying springs were measured. The springs showed a stiffness range of 0.01-1.82 N·m·deg-1. The moment-threshold increased with increasing stiffness (1.13-12.1 N·m), while ROM decreased (4.91-16.5°). Energy was returned by all springs (11.5-116.3 J). These results suggest that the two stiffest available springs should improve joint kinematics and enhance push-off in children with SCP walking with excessive knee flexion. [ABSTRACT FROM AUTHOR]

The effectiveness of an Ankle-Foot Orthosis footwear combination (AFO-FC) may be partly dependent on the alignment of the ground reaction force with respect to lower limb joint rotation centers, reflected by joint angles and moments. Adjusting (i.e. tuning) the AFO-FC's properties could affect this alignment, which may be guided by monitoring the Shank-to-Vertical-Angle. This study aimed to investigate whether the Shank-to-Vertical-Angle during walking responds to variations in heel height and footplate stiffness, and if this would reflect changes in joint angles and net moments in healthy adults. Ten subjects walked on an instrumented treadmill and performed six trials while walking with bilateral rigid Ankle-Foot Orthoses. The AFO-FC heel height was increased, aiming to impose a Shank-to-Vertical-Angle of 5°, 11° and 20°, and combined with a flexible or stiff footplate. For each trial, the Shank-to-Vertical-Angle, joint flexion-extension angles and net joint moments of the right leg at midstance were averaged over 25 gait cycles. The Shank-to-Vertical-Angle significantly increased with increasing heel height (p<0.001), resulting in an increase in knee flexion angle and internal knee extensor moment (p<0.001). The stiff footplate reduced the effect of heel height on the internal knee extensor moment (p=0.030), while the internal ankle plantar flexion moment increased (p=0.035). Effects of heel height and footplate stiffness on the hip joint were limited. Our results support the potential to use the Shank-to-Vertical-Angle as a parameter to evaluate AFO-FC tuning, as it is responsive to changes in heel height and reflects concomitant changes in the lower limb angles and moments. [ABSTRACT FROM AUTHOR]

Abstract: Purpose: To determine the reproducibility and validity of video screen measurement (VSM) of sagittal plane joint angles during gait. Methods: 17 children with spastic cerebral palsy walked on a 10m walkway. Videos were recorded and 3d-instrumented gait analysis was performed. Two investigators measured six sagittal joint/segment angles (shank, ankle, knee, hip, pelvis, and trunk) using a custom-made software package. The intra- and interrater reproducibility were expressed by the intraclass correlation coefficient (ICC), standard error of measurements (SEM) and smallest detectable difference (SDD). The agreement between VSM and 3d joint angles was illustrated by Bland–Altman plots and limits of agreement (LoA). Results: Regarding the intrarater reproducibility of VSM, the ICC ranged from 0.99 (shank) to 0.58 (trunk), the SEM from 0.81° (shank) to 5.97° (trunk) and the SDD from 1.80° (shank) to 16.55° (trunk). Regarding the interrater reproducibility, the ICC ranged from 0.99 (shank) to 0.48 (trunk), the SEM from 0.70° (shank) to 6.78° (trunk) and the SDD from 1.95° (shank) to 18.8° (trunk). The LoA between VSM and 3d data ranged from 0.4±13.4° (knee extension stance) to 12.0±14.6° (ankle dorsiflexion swing). Conclusion: When performed by the same observer, VSM mostly allows the detection of relevant changes after an intervention. However, VSM angles differ from 3d-IGA and do not reflect the real sagittal joint position, probably due to the additional movements in the other planes. [Copyright &y& Elsevier]