Neuromuscular disorders often lead to ankle plantar flexor muscle weakness, which impairs ankle push-off power and forward propulsion during gait. To improve walking speed and reduce metabolic cost of transport (mCoT), patients with plantar flexor weakness are provided dorsal-leaf spring ankle-foot orthoses (AFOs). It is widely believed that mCoT during gait depends on the AFO stiffness and an optimal AFO stiffness that minimizes mCoT exists. The biomechanics behind why and how an optimal stiffness exists and benefits individuals with plantar flexor weakness are not well understood. We hypothesized that the AFO would reduce the required support moment and, hence, metabolic cost contributions of the ankle plantar flexor and knee extensor muscles during stance, and reduce hip flexor metabolic cost to initiate swing. To test these hypotheses, we generated neuromusculoskeletal simulations to represent gait of an individual with bilateral plantar flexor weakness wearing an AFO with varying stiffness. Predictions were based on the objective of minimizing mCoT, loading rates at impact and head accelerations at each stiffness level, and the motor patterns were determined via dynamic optimization. The predictive gait simulation results were compared to experimental data from subjects with bilateral plantar flexor weakness walking with varying AFO stiffness. Our simulations demonstrated that reductions in mCoT with increasing stiffness were attributed to reductions in quadriceps metabolic cost during midstance. Increases in mCoT above optimum stiffness were attributed to the increasing metabolic cost of both hip flexor and hamstrings muscles. The insights gained from our predictive gait simulations could inform clinicians on the prescription of personalized AFOs. With further model individualization, simulations based on mCoT minimization may sufficiently predict adaptations to an AFO in individuals with plantar flexor weakness.@en

People with spasticity, i.e., stretch hyperreflexia, have a limited functional independence and mobility. While a broad range of spasticity treatments is available, many treatments are invasive, non-specific, or temporary and might have negative side effects. Operant conditioning of the stretch reflex is a promising non-invasive paradigm with potential long-term sustained effects. Within this conditioning paradigm, seated participants have to reduce the mechanically elicited reflex response using biofeedback of reflex magnitude quantified using electromyography (EMG). Before clinical application of the conditioning paradigm, improvements are needed regarding the time-intensiveness and slow learning curve. Previous studies have shown that gamification of biofeedback can improve participant motivation and long-term engagement. Moreover, quantification of reflex magnitude for biofeedback using reflexive joint impedance may obtain similar effectiveness within fewer sessions. Nine healthy volunteers participated in the study, split in three groups. First, as a reference the “Conventional” group received EMG- and bar-based biofeedback similar to previous research. Second, we explored feasibility of game-based biofeedback with the “Gaming” group receiving EMG- and game-based biofeedback. Third, we explored feasibility of game- and impedance-based biofeedback with the “Impedance” group receiving impedance and game-based biofeedback. Participants completed five baseline sessions (without reflex biofeedback) and six conditioning sessions (with reflex biofeedback). Participants were instructed to reduce reflex magnitude without modulating background activity. The Conventional and Gaming groups showed feasibility of the protocol in 2 and 3 out of 3 participants, respectively. These participants achieved a significant Soleus short-latency (M1) within-session reduction in at least –15% in the 4th–6th conditioning session. None of the Impedance group participants showed any within-session decrease in Soleus reflex magnitude. The feasibility in the EMG- and game-based biofeedback calls for further research on gamification of the conditioning paradigm to obtain improved participant motivation and engagement, while achieving long-term conditioning effects. Before clinical application, the time-intensiveness and slow learning curve of the conditioning paradigm remain an open challenge.@en

Objective: To identify factors associated with long-term improvement in gait in children after selective dorsal rhizotomy (SDR). Design: Retrospective cohort study. Setting: University medical center. Participants: Children (N=36) (age 4-13y) with spastic diplegia of Gross Motor Function Classification System (GMFCS) level I (n=14), II (n=15), and III (n=7) were included retrospectively from the database of our hospital. Children underwent SDR between January 1999 and May 2011. Patients were included if they received clinical gait analysis before and 5 years post-SDR, age >4 years at time of SDR and if brain magnetic resonance imaging (MRI) scan was available. Intervention: Selective dorsal rhizotomy. Main Outcome Measures: Overall gait quality was assessed with Edinburgh visual gait score (EVGS), before and 5 years after SDR. In addition, knee and ankle angles at initial contact and midstance were evaluated. To identify predictors for gait improvement, several factors were evaluated including functional mobility level GMFCS, presence of white matter abnormalities on brain MRI, and selective motor control during gait (synergy analysis). Results: Overall gait quality improved after SDR, with a large variation between patients. Multiple linear regression analysis revealed that worse score on EVGS and better GMFCS were independently related to gait improvement. Gait improved more in children with GMFCS I and II compared to III. No differences were observed between children with or without white matter abnormalities on brain MRI. Selective motor control during gait was predictive for improvement of knee angle at initial contact and midstance, but not for EVGS. Conclusion: Functional mobility level and baseline gait quality are both important factors to predict gait outcomes after SDR. If candidates are well selected, SDR can be a successful intervention to improve gait both in children with brain MRI abnormalities as well as other causes of spastic diplegia.

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Objective: To investigate the immediate response to avatar-based biofeedback on 3 clinically important gait parameters: step length, knee extension, and ankle power in children with cerebral palsy (CP). Design: Repeated measures design. Setting: Rehabilitation clinic. Participants: Children with spastic paresis (N=22; 10.5±3.1y), able to walk without assistive devices. Intervention: Children walked on a treadmill with a virtual reality environment. Following baseline gait analysis, they were challenged to improve aspects of gait. Children visualized themselves as an avatar, representing movement in real time. They underwent a series of 2-minute trials receiving avatar-based biofeedback on step length, knee extension, and ankle power. To investigate optimization of biofeedback visualization, additional trials in which knee extension was visualized as a simple bar with no avatar; and avatar alone with no specific biofeedback were carried out. Main Outcome Measures: Gait pattern, as measured by joint angles, powers, and spatiotemporal parameters, were compared between baseline and biofeedback trials. Results: Participants were able to adapt gait pattern with biofeedback, in an immediate response, reaching large increases in ankle power generation at push-off (37.7%) and clinically important improvements in knee extension (7.4^o) and step length (12.7%). Biofeedback on one parameter had indirect influence on other aspects of gait. Conclusion: Children with CP show capacity in motor function to achieve improvements in clinically important aspects of gait. Visualizing biofeedback with an avatar was subjectively preferential compared to a simplified bar presentation of knee angle. Future studies are required to investigate if observed transient effects of biofeedback can be retained with prolonged training to test whether biofeedback-based gait training may be implemented as a therapy tool.

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Computational modelling of the neuromusculoskeletal system (NMSS) can potentially provide detailed insight into muscle function to optimize treatment planning and evaluation in cerebral palsy (CP). Commonly, static optimization is used to solve the redundancy problem in estimating muscle forces, assuming, for example, minimization of the muscle activation squared. However, since the primary problem in children with CP is an aberrant motor control [1], it is questionable if using this criterion is applicable in this clinical population. Electromyography (EMG) might be used to further inform optimization procedures and improve model performance.@en

Individuals with cerebral palsy often walk with atypical gait patterns like equinus or crouch gait. Several multi-segment foot models have been developed [1] to measure the abnormal foot kinematics of these gait patterns. The Oxford Foot Model [2] (OFM) and Rizzoli Foot Model [3,4] (RFM) are used most frequently in both clinical practice and research [1]. Their different model characteristics (e.g. marker placement and axis definitions) will likely result in different kinematic output. However, these differences have not yet been extensively compared, especially not in pathological gait patterns.@en

Children with cerebral palsy (CP) often have gait limitations and this is a key target of rehabilitation. Gait training can be an effective intervention to improve functional outcomes such as walking speed and endurance [1]. Virtual reality (VR) is a valuable tool in gait training to increase engagement, however, games must be therapeutically principled. One advantage of VR is that it allows for addition of augmented biofeedback. Biofeedback can improve communication between patient and therapist, while the implementation of gamification and motor learning principles may increase motivation and skill retention. Therapy may target gait parameters, such as step length, knee extension or ankle power generation, with a functional goal to increase walking speed. These gait parameters are interlinked and the most effective target for biofeedback is unknown.@en

Real-time feedback may be useful for enhancing information gained from clinical gait analysis of children with cerebral palsy (CP). It may also be effective in functional gait training, however, it is not known if children with CP can adapt gait in response to real-time feedback of kinematic parameters. Sixteen children with cerebral palsy (age 6–16; GMFCS I–III), walking with a flexed-knee gait pattern, walked on an instrumented treadmill with virtual reality in three conditions: regular walking without feedback (NF), feedback on hip angle (FH) and feedback on knee angle (FK). Clinically relevant gait parameters were calculated and the gait profile score (GPS) was used as a measure of overall gait changes between conditions. All children, except one, were able to improve hip and/or knee extension during gait in response to feedback, with nine achieving a clinically relevant improvement. Peak hip extension improved significantly by 5.1 ± 5.9° (NF: 8.9 ± 12.8°, FH: 3.8 ± 10.4°, p = 0.01). Peak knee extension improved significantly by 7.7 ± 7.1° (NF: 22.2 ± 12.0°, FK: 14.5 ± 12.7°, p < 0.01). GPS did not change between conditions due to increased deviations in other gait parameters. Responders to feedback were shown to have worse initial gait as measured by GPS (p = 0.005) and functional selectivity score (p = 0.049). In conclusion, ambulatory children with CP show adaptability in gait and are able to respond to real-time feedback, resulting in significant and clinically relevant improvements in peak hip and knee extension. These findings show the potential of real-time feedback as a tool for functional gait training and advanced gait analysis in CP.

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Background and purpose: To support clinical decision-making in central neurological disorders, a physical examination is used to assess responses to passive muscle stretch. However, what exactly is being assessed is expressed and interpreted in different ways. A clear diagnostic framework is lacking. Therefore, the aim was to arrive at unambiguous terminology about the concepts and measurement around pathophysiological neuromuscular response to passive muscle stretch. Methods: During two consensus meetings, 37 experts from 12 European countries filled online questionnaires based on a Delphi approach, followed by plenary discussion after rounds. Consensus was reached for agreement ≥75%. Results: The term hyper-resistance should be used to describe the phenomenon of impaired neuromuscular response during passive stretch, instead of for example ‘spasticity’ or ‘hypertonia’. From there, it is essential to distinguish non-neural (tissue-related) from neural (central nervous system related) contributions to hyper-resistance. Tissue contributions are elasticity, viscosity and muscle shortening. Neural contributions are velocity dependent stretch hyperreflexia and non-velocity dependent involuntary background activation. The term ‘spasticity’ should only be used next to stretch hyperreflexia, and ‘stiffness’ next to passive tissue contributions. When joint angle, moment and electromyography are recorded, components of hyper-resistance within the framework can be quantitatively assessed. Conclusions: A conceptual framework of pathophysiological responses to passive muscle stretch is defined. This framework can be used in clinical assessment of hyper-resistance and will improve communication between clinicians. Components within the framework are defined by objective parameters from instrumented assessment. These parameters need experimental validation in order to develop treatment algorithms based on the aetiology of the clinical phenomena.

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The process of clinical gait analysis interpretation is complex and subject to the experience and professional background of the gait analyst. Here we present a novel, systematic way of reasoning, to bridge the critical gap between identifying abnormal gait features and finding their underlying impairments [1], to be addressed by a therapeutic intervention. The method is illustrated using a clinical case of a 7yo girl M. with spastic diplegic cerebral palsy, GMFCS level II, due to periventricular leucomalacia associated with prematurity (26+2 weeks).@en

Selective dorsal rhizotomy (SDR) is a neurosurgical treatment to reduce spasticity in children with cerebral palsy (CP). Where some children show large improvements on domains of motor function and mobility, others do not [1–3]. Since SDR is a highly invasive and irreversible treatment, it is important to select only those candidates who are most likely to benefit from the procedure.@en

Gait analysis is used for the assessment of walking ability of children with cerebral palsy (CP), to inform clinical decision making and to quantify changes after treatment. To simplify gait analysis interpretation and to quantify deviations from normality, some quantitative synthetic descriptors were developed over the years, such as the Movement Analysis Profile (MAP) and the Linear Fit Method (LFM), but their interpretation is not always straightforward. The aims of this work were to: (i) study gait changes, by means of synthetic descriptors, in children with CP that underwent Single Event Multilevel Surgery; (ii) compare the MAP and the LFM on these patients; (iii) design a new index that may overcome the limitations of the previous methods, i.e. the lack of information about the direction of deviation or its source. Gait analysis exams of 10 children with CP, pre- and post-surgery, were collected and MAP and LFM were computed. A new index was designed as a modified version of the MAP by separating out changes in offset (named OC-MAP). MAP documented an improvement in the gait pattern after surgery. The highest effect was observed for the knee flexion/extension angle. However, a worsening was observed as an increase in anterior pelvic tilt. An important source of gait deviation was recognized in the offset between observed tracks and reference. OC-MAP allowed the assessment of the offset component versus the shape component of deviation. LFM provided results similar to OC-MAP offset analysis but could not be considered reliable due to intrinsic limitations. As offset in gait features played an important role in gait deviation, OC-MAP synthetic analysis was proposed as a novel approach to a meaningful parameterisation of global deviations in gait patterns of subjects with CP and gait changes after treatment.

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Multiple marker protocols exist for analysing gait kinematics, however most models show crosstalk, particularly in the knee joint due to difficulties in aligning the flexion/extension (F/E) axis. These difficulties are enlarged in patient groups, such as children with cerebral palsy (CP) due to difficulties in palpation and deviations from model assumptions. Functional calibration might be effective in improving knee axes alignment [1], but is time consuming and difficult to perform. Therefore post hoc optimisation methods are preferable. The aim of this study is to outline the effects of a newly proposed post hoc method based on principal component analysis (PCA) to reduce crosstalk [2] in commonly used models for gait analysis.@en

Gait Analysis (GA) allows the quantitative assessment of walking. Over the years, several descriptors have been developed with the aim to derive an overall GA assessment based on a synthetic score. Examples are the Gait Deviation Index (GDI) [1], and the Movement Analysis Profile (MAP) [2]. These indices are useful to assess the overall quality of gait patterns, but inherently do not provide information about the nature of the deviation (offset, scaling, time shift) or about the direction of the deviation (too much flexion or extension). It was observed that certain gait abnormalities corresponded to specific deviations in kinematic angles [3]. E.g. crouch gait is characterized by a persistent knee flexion that can be observed as a shift in the baseline of the knee flexion/extension angle.@en

A common gait limitation in cerebral palsy (CP) is a reduced ability to generate power at the ankle during push off. This may be due a number of factors, such as muscle weakness or disrupted neuromuscular control. It has been shown that with the use real-time feedback, children with CP can improve key gait parameters such as knee and hip extension [1]. However, it is not known if children can improve ankle power, or, how they would achieve this change at the neuromuscular level. The use of synergy analysis to describe dynamic motor control (DMC) in CP is growing and has been shown to be predictive of treatment outcomes [2].@en

Spasticity, i.e. exaggerated velocity-dependent stretch reflex activity, is one of the key impairments in neurological diseases, but its effect on gait is unclear [1]. To quantify spastic reflexes during gait, ankle rotations have been applied by mechanical devices [2,3], but these are cumbersome and can affect gait. Recently, it has been shown that treadmill accelerations can be used to evoke stretch reflexes during gait in the calf muscles of healthy adults [4]. However, the applicability of this approach in children and in patients with neurological diseases has yet to be demonstrated.@en