Gait deviations in Duchenne muscular dystrophy-Part 1. A systematic review

Effects of cycling training on balance and gait in children with Duchenne muscular dystrophy: A randomized controlled study

BACKGROUND AND AIMS

Although aerobic exercises such as cycling and swimming are increasingly being recommended in Duchenne muscular dystrophy (DMD), their effect on gait and balance parameters is unclear. This study was aimed to investigate the effect of cycling training on balance and spatio-temporal gait parameters in children with DMD.

METHODS

Ambulant children (age range: 6.17-11.33 years) were randomly divided into two groups: home-based exercise training applied in the control group (n = 12) while 12 weeks of supervised submaximal lower extremity cycling training in addition to home-based exercise training performed in the study group (n = 11). Gait and balance parameters were evaluated using the GAITRite electronic walkway system and the Bertec Balance Check Screener™, respectively. Assessments were applied before and after 12 weeks of training.

RESULTS

The mean ages of the children in the study and control groups were 8.20 (SD:1.34) and 8.86 (SD:1.30) years, consecutively (p > 0.05). Considering the baseline values, the balance and spatio-temporal gait parameters of the children were similar except for the antero-posterior postural sway on the perturbed surface with eyes open (p > 0.05). There was a significant time x group interaction effect in favor of the study group for the antero-posterior postural sway of children on the normal surface with eyes open (F (1,58) = 12.62, p = 0.002). It was found that the antero-posterior postural sway on the normal surface with eyes open was improved in the study group within group comparison (F (1,10) = 8.50, p = 0.015).

CONCLUSIONS

The study showed that both the cycling and the home-based exercise training groups may maintain gait and balance parameters during the study. Adding a cycling training to the rehabilitation program can also provide additional contribution to improve antero-posterior balance.

Gait classification for growing children with Duchenne muscular dystrophy

Classifying gait patterns into homogeneous groups could enhance communication among healthcare providers, clinical decision making and clinical trial designs in boys with Duchenne muscular dystrophy (DMD). Sutherland's classification has been developed 40 years ago. Ever since, the state-of-the-art medical care has improved and boys with DMD are now longer ambulatory. Therefore, the gait classification requires an update. The overall aim was to develop an up-to-date, valid DMD gait classification. A total of 137 three-dimensional gait analysis sessions were collected in 30 boys with DMD, aged 4.6-17 years. Three classes were distinguished, which only partly aligned with increasing severity of gait deviations. Apart from the mildly affected pattern, two more severely affected gait patterns were found, namely the tiptoeing pattern and the flexion pattern with distinct anterior pelvic tilt and posterior trunk leaning, which showed most severe deviations at the ankle or at the proximal segments/joints, respectively. The agreement between Sutherland's and the current classification was low, suggesting that gait pathology with the current state-of-the-art medical care has changed. However, overlap between classes, especially between the two more affected classes, highlights the complexity of the continuous gait changes. Therefore, caution is required when classifying individual boys with DMD into classes.

Population longitudinal analysis of Gait Profile Score and North Star Ambulatory Assessment in children with Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a rare X-linked recessive disorder characterized by loss-of-function mutations in the gene encoding dystrophin. These mutations lead to progressive functional deterioration including muscle weakness, respiratory insufficiency, and musculoskeletal deformities. Three-dimensional gait analysis (3DGA) has been used as a tool to analyze gait pathology through the quantification of altered joint kinematics, kinetics, and muscle activity patterns. Among 3DGA indices, the Gait Profile Score (GPS), has been used as a sensitive overall measure to detect clinically relevant changes in gait patterns in children with DMD. To enhance our understanding of the clinical translation of 3DGA, we report here the development of a population nonlinear mixed-effect model that jointly describes the disease progression of the 3DGA index, GPS, and the functional endpoint, North Star Ambulatory Assessment (NSAA). The final model consists of a quadratic structure for GPS progression and a linear structure for GPS-NSAA correlation. Our model was able to capture the improvement in function in GPS and NSAA in younger subjects, as well as the decline of function in older subjects. Furthermore, the model predicted NSAA (CFB) at 1 year reasonably well for DMD subjects ≤7 years old at baseline. The model tended to slightly underpredict the decline in NSAA after 1 year for those >7 years old at baseline, but the prediction summary statistics were well maintained within the standard deviation of observed data. Quantitative models such as this may help answer clinically relevant questions to facilitate the development of novel therapies in DMD.

Children with Duchenne muscular dystrophy display specific kinematic strategies during obstacle-crossing

Duchenne muscular dystrophy (DMD) is a genetic disease characterized by progressive muscle weakness with increased neuromechanical challenge and fall risks, especially during obstructed locomotion. This study aimed to identify the kinematic strategies for obstacle-crossing in DMD via synthesizing the changes in the joint kinematics and associated end-point control. Fourteen boys with DMD (age: 9.0 ± 2.5 years) and fourteen typically developed controls (age: 9.0 ± 2.8 years) each crossed obstacles of three different heights (10%, 20% and 30% of leg length) while the angular motions of the trunk-pelvis-leg apparatus and foot-obstacle clearances were measured. Two-way analyses of variance were used to analyze group and obstacle height effects. Compared to the controls, the DMD group crossed obstacles with significantly increased step width, but decreased crossing speed, crossing step length, trailing toe-obstacle clearance and leading heel-obstacle horizontal distance (p < 0.05). When the leading toe was above the obstacle, the patients showed significantly increased pelvic hiking, pelvic and trunk anterior tilt and ankle plantarflexion, but decreased hip flexion in both limbs (p < 0.05). Similar kinematic changes were found during trailing-limb crossing, except for an additional increase in swing-hip abduction and decrease in contralateral trunk side-bending and stance-knee flexion. Patients with DMD crossed obstacles via a specific kinematic strategy with altered end-point control, predisposing them to a greater risk of tripping during trailing-limb crossing. These results suggest that crossing kinematics in DMD should be monitored-especially in the proximal segments of the pelvis-leg apparatus-that may lead to an increased risk of falling.

Development of a new instrument to evaluate gait characteristics of individuals with Duchenne Muscular Dystrophy: Gait Assessment Scale for Duchenne Muscular Dystrophy, and its validity and reliability

BACKGROUND

Patients with Duchenne Muscular Dystrophy (DMD) have gait disorders. Therefore, specific gait assessment tools are needed.

AIMS

The aim of this study was to develop a gait assessment instrument for DMD patients (DMD-GAS), and investigate its validity and reliability.

STUDY DESIGN

The scale was developed considering the expert opinions which included 10 physiotherapists who had experience in the management of patients with DMD, and the Content Validity Index (CVI) was calculated. The final version of the DMD-GAS that was agreed upon the experts consisted of 10 items, and each item scored between 0 and 2. The intra-rater reliability was established by the video analysis of children with a 1-month interval and inter-rater reliability was determined by the scores of 3 physiotherapists.

SUBJECTS

The study included 56 patients with DMD.

OUTCOME MEASURES

The criterion validity was determined by investigating the relationship between the total score of the DMD-GAS and Motor Function Measure (MFM), 6 Minute Walk Test (6MWT), and the data obtained from GAITRite.

RESULTS

The CVI of the DMD-GAS was 0.90 (p < 0.05). The construct validity and internal consistency of the DMD-GAS were excellent as well as the intra- and inter-rater reliability (>0.90). Moderate-to-very strong correlations were found between the total score of the DMD-GAS and the MFM-total score (r = 0.78), 6MWT (r = 0.71), gait speed (r = 0.50), stride length (r = 0.56), and base of support (r = -0.70) (p < 0.01).

CONCLUSIONS

The results indicated that DMD-GAS was a reliable and valid instrument to determine gait characteristics of the patients with DMD in clinical settings.

CLINICAL TRIAL NUMBER

NCT05244395.

Gait asymmetry in children with Duchenne muscular dystrophy: evaluated through kinematic synergies and muscle synergies of lower limbs

BACKGROUND

Gait is a complex, whole-body movement that requires the coordinated action of multiple joints and muscles of our musculoskeletal system. In the context of Duchenne muscular dystrophy (DMD), a disease characterized by progressive muscle weakness and joint contractures, previous studies have generally assumed symmetrical behavior of the lower limbs during gait. However, such a symmetric gait pattern of DMD was controversial. One aspect of this is criticized, because most of these studies have primarily focused on univariate variables, rather than on the coordination of multiple body segments and even less investigate gait symmetry under a motor synergy of view.

METHODS

We investigated the gait pattern of 20 patients with DMD, compared to 18 typical developing children (TD) through 3D Gait Analysis. Kinematic and muscle synergies were extracted with principal component analysis (PCA) and non-negative matrix factorization (NNMF), respectively. The synergies extracted from the left and right sides were compared with each other to obtain a symmetry value. In addition, bilateral spatiotemporal variables of gait, such as stride length, percentage of stance and swing phase, step length, and percentage of double support phase, were used for calculating the symmetry index (SI) to evaluate gait symmetry as well.

RESULTS

Compared with the TD group, the DMD group walked with decreased gait velocity (both p < 0.01), stride length (both p < 0.01), and step length (both p < 0.001). No significant difference was found between groups in SI of all spatiotemporal parameters extracted between the left and right lower limbs. In addition, the DMD group exhibited lower kinematic synergy symmetry values compared to the TD group (p < 0.001), while no such significant group difference was observed in symmetry values of muscle synergy.

CONCLUSIONS

The findings of this study suggest that DMD influences, to some extent, the symmetry of synergistic movement of multiple segments of lower limbs, and thus kinematic synergy appears capable of discriminating gait asymmetry in children with DMD when conventional spatiotemporal parameters are unchanged.

Kinematic changes in gait in boys with Duchenne Muscular Dystrophy: Utility of the Gait Deviation Index, the Gait Profile Score and the Gait Variable Scores

BACKGROUND

Duchenne Muscular Dystrophy (DMD) is an X-linked muscle disorder caused by a mutation or deletion in the dystrophin gene. In boys with DMD, muscle weakness progresses in a proximal to distal pattern, leading to gait abnormalities at all joints, in all planes of motion. Longitudinal studies are imperative to quantify changes in gait function due to DMD and are of particular importance when examining the efficacy of treatment interventions.

RESEARCH QUESTION

The purpose of this study was to examine the sensitivity of the Gait Deviation Index (GDI) and Movement Analysis Profile (Gait Profile Score (GPS) and Gait Variable Score (GVS)) to quantify the longitudinal ambulatory decline in boys with DMD. A secondary aim was to quantify the effect of corticosteroid (CS) treatment.

METHODS

The gait patterns of 75 boys were assessed longitudinally, 11 were steroid naïve (SN), and 64 received CS treatment. Joint kinematics were collected using either a VICON 612 or a Motion Analysis Corporation 3-D system. Representative trials were used to compute the GDI, GPS and the nine GVS for each boy for each visit.

RESULTS

At baseline, GVS for the boys with DMD revealed abnormalities in all lower extremity joints and in all planes of movement compared to TD peers. GDI and GPS indices verified that the overall quality of gait in boys with DMD decreases at a significant rate with age. Boys who were steroid naïve changed at a rate 3 times greater than boys on CS in coronal plane hip motion.

SIGNIFICANCE

The gait indices of GDI and GPS are able to identify changes in the quality of gait patterns in boys with DMD. Although boys on steroids had greater gait deviations than boys who were SN at baseline, the rate of decline in gait quality was slower in boys on CS.

Characterising gait in paediatric neuromuscular disorders: an observational study of spatio-temporal gait in a clinical cohort

AIM

Few studies have characterised the relationship between disease and gait function in children and young people with rare neuromuscular disorders (NMDs). This study aimed to describe the relationship between disease and gait in a large paediatric cohort from a neuromuscular outpatient clinic.

METHODS

A prospective, cross-sectional study of gait in independently ambulant children and young people aged 4-21 years with a clinical or genetically confirmed NMD. Participants traversed an electronic walkway barefoot and in footwear at self-selected and fast pace. Analysis of disease included a typically developing (TD) reference group.

RESULTS

A sample of 113 participants with NMD, mean age 9.5 years (SD 3.1), 28% female, grouped into nine diagnostic subgroups. Eighty percent reported limitations to functional mobility. Children with NMD walked slower, with a shorter and wider step compared to a TD reference group, with moderate to large effect sizes for each of these gait parameters indicative of the clinical significance of these gait deviations. Children with Duchenne muscular dystrophy (DMD) walked slowest with a markedly wide gait pattern. Footwear had little overall effect on gait in children with NMDs. All children could accelerate over short distances.

CONCLUSIONS

Gait, notably speed, step length, and width are clinically significant biomarkers of disease in paediatric NMDs, affording objective functional measures in clinical settings and research.Implications for rehabilitationGait should be considered a functional biomarker of disease in children and young people with neuromuscular disorders (NMDs).Comparison of gait in a paediatric neuromuscular cohort indicates that children with Duchenne muscular dystrophy (DMD) walk slowest with a shorter step length and a wider step width which increases with age and disease progression.Measurement of gait speed is a simple, pragmatic tool to monitor disease progression in the outpatient clinical environment and relates to everyday function.In clinical research, gait can be measured as a functional outcome to demonstrate change from disease-modifying interventions and treatments in NMDs.

Influence of sagittal pelvic attitude on gait pattern in normally developed people and interactions with neurological pathologies: A pilot study

Background

Gait Analysis of healthy people, imitating pathological conditions while walking, has increased our understanding of biomechanical factors. The influence of the pelvis as a biomechanical constraint during gait is not specifically studied. How could mimicking a pelvic attitude influence the dynamic mechanical interaction of the body segments? We proposed an investigation of the pelvic attitude role on the gait pattern of typically developed people when they mimicked pelvic anteversion and posteroversion.

Materials and methods

Seventeen healthy volunteers were enrolled in this study (mean age 24.4 ± 5.5). They simulated a pelvic anteversion and posteroversion during walking, exaggerating these postures as much as possible. 3D gait analysis was conducted using an optoelectronic system with eight cameras (Vicon MX, Oxford, United Kingdom) and two force plates (AMTI, Or-6, Watertown, MA, United States). The kinematic, kinetic, and spatio-temporal parameters were compared between the three walking conditions (anteversion, posteroversion, and normal gait).

Results

In Pelvic Anteversion gait (PA) we found: increased hip flexion (p < 0.0001), increased knee flexion during stance (p = 0.02), and reduction of ankle flexion-extension Range of Motion (RoM) compared with Pelvic Normal gait (PN). In Pelvic Posteroversion gait (PP) compared with PN, we found: decreased hip flexion-extension RoM (p < 0.01) with a tendency to hip extension, decreased knee maximum extension in stance (p = 0.033), and increased ankle maximum dorsiflexion in stance (p = 0.002).

Conclusion

The configuration of PA contains gait similarities and differences when compared with pathologic gait where there is an anteversion as seen in children with Cerebral Palsy (CP) or Duchenne Muscular Dystrophy (DMD). Similarly, attitudes of PP have been described in patients with Charcot-Marie-Tooth Syndrome (CMT) or patients who have undergone Pelvic Osteotomy (PO). Understanding the dynamic biomechanical constraints is essential to the assessment of pathological behavior. The central nervous system adapts motor behavior in interaction with body constraints and available resources.

Longitudinal Alterations in Gait Features in Growing Children With Duchenne Muscular Dystrophy

Prolonging ambulation is an important treatment goal in children with Duchenne muscular dystrophy (DMD). Three-dimensional gait analysis (3DGA) could provide sensitive parameters to study the efficacy of clinical trials aiming to preserve ambulation. However, quantitative descriptions of the natural history of gait features in DMD are first required. The overall goal was to provide a full delineation of the progressive gait pathology in children with DMD, covering the entire period of ambulation, by performing a so-called mixed cross-sectional longitudinal study. Firstly, to make our results comparable with previous literature, we aimed to cross-sectionally compare 31 predefined gait features between children with DMD and a typically developing (TD) database (1). Secondly, we aimed to explore the longitudinal changes in the 31 predefined gait features in growing boys with DMD using follow-up 3DGA sessions (2). 3DGA-sessions (n = 124) at self-selected speed were collected in 27 boys with DMD (baseline age: 4.6-15 years). They were repeatedly measured over a varying follow-up period (range: 6 months-5 years). The TD group consisted of 27 children (age: 5.4-15.6 years). Per measurement session, the spatiotemporal parameters, and the kinematic and kinetic waveforms were averaged over the selected gait cycles. From the averaged waveforms, discrete gait features (e.g., maxima and minima) were extracted. Mann-Whitney U tests were performed to cross-sectionally analyze the differences between DMD at baseline and TD (1). Linear mixed effect models were performed to assess the changes in gait features in the same group of children with DMD from both a longitudinal (i.e., increasing time) as well as a cross-sectional perspective (i.e., increasing baseline age) (2). At baseline, the boys with DMD differed from the TD children in 17 gait features. Additionally, 21 gait features evolved longitudinally when following-up the same boys with DMD and 25 gait features presented a significant cross-sectional baseline age-effect. The current study quantitatively described the longitudinal alterations in gait features in boys with DMD, thereby providing detailed insight into how DMD gait deteriorates. Additionally, our results highlight that gait features extracted from 3DGA are promising outcome measures for future clinical trials to quantify the efficacy of novel therapeutic strategies.

Comparison of the Gait Biomechanical Constraints in Three Different Type of Neuromotor Damages

Background and Objective

Absolute angle represents the inclination of a body segment relative to a fixed reference in space. This work compares the absolute and relative angles for exploring biomechanical gait constraints.

Methods

Gait patterns of different neuromotor conditions were analyzed using 3D gait analysis: normal gait (healthy, H), Cerebral Palsy (CP), Charcot Marie Tooth (CMT) and Duchenne Muscular Dystrophy (DMD), representing central and peripheral nervous system and muscular disorders, respectively. Forty-two children underwent gait analysis: 10 children affected by CP, 10 children by CMT, 10 children by DMD and 12 healthy children. The kinematic and kinetic parameters were collected to describe the biomechanical pattern of participants’ lower limbs. The absolute angles of thigh, leg and foot were calculated using the trigonometric relationship of the tangent. For each absolute series, the mean, range, maximum, minimum and initial contact were calculated. Kinematic and kinetic gait data were studied, and the results were compared with the literature.

Results

Statistical analysis of the absolute angles showed how, at the local level, the single segments (thigh, leg and foot) behave differently depending on the pathology. However, if the lower limb is studied globally (sum of the kinematics of the three segments: thigh, leg and foot), a biomechanical constraint emerges.

Conclusion

Each segment compensates separately for the disease deficit so as to maintain a global biomechanical invariance. Using a model of inter-joint co-variation could improve the interpretation of the clinical gait pattern.

Four-limb wireless IMU sensor system for automatic gait detection in canines

This study aims to develop a 4-limb canine gait analysis system using wireless inertial measurement units (IMUs). 3D printed sensor holders were designed to ensure quick and consistent sensor mounting. Signal analysis algorithms were developed to automatically determine the timing of swing start and end in a stride. To evaluate the accuracy of the new system, a synchronized study was conducted in which stride parameters in four dogs were measured simultaneously using the 4-limb IMU system and a pressure-sensor based walkway gait system. The results showed that stride parameters measured in both systems were highly correlated. Bland-Altman analyses revealed a nominal mean measurement bias between the two systems in both forelimbs and hindlimbs. Overall, the disagreement between the two systems was less than 10% of the mean value in over 92% of the data points acquired from forelimbs. The same performance was observed in hindlimbs except for one parameter due to small mean values. We demonstrated that this 4-limb system could successfully visualize the overall gait types and identify rapid gait changes in dogs. This method provides an effective, low-cost tool for gait studies in veterinary applications or in translational studies using dog models of neuromuscular diseases.

Ankle contractures and functional motor decline in Duchenne muscular dystrophy

INTRODUCTION

This prospective, correlational pilot study investigated the relationship between ankle plantar flexion contractures and motor function in boys with Duchenne muscular dystrophy in British Columbia (BC), Canada.

PARTICIPANTS

Ambulatory boys with Duchenne muscular dystrophy were recruited from BC Children's Hospital, which follows everyone with Duchenne muscular dystrophy in BC ≤ 18 years of age (n = 14).

METHODS

Spearman and Pearson correlation coefficients were estimated to examine the association between the degree of ankle dorsiflexion range of motion and North Star Ambulatory Assessment scores and the degree of ankle dorsiflexion range and six-minute walk test distances.

RESULTS

Our analysis showed a moderate correlation between the degree of ankle dorsiflexion range and North Star Ambulatory Assessment scores [rho (14) = 0.50; p = 0.070] and a weak correlation between ankle dorsiflexion range of motion and six-minute walk test distances [rho (13) = 0.08; p = 0.747], however neither result was statistically significant.

DISCUSSION

Although a significant relationship between ankle dorsiflexion range of motion and motor function was not found, the variability of ankle dorsiflexion range suggests challenges with preventing ankle contracture. This reinforces the importance of assessing ankle range of motion in boys with Duchenne muscular dystrophy with sufficient frequency to identify a need for additional interventions.

Stride Velocity 95th Centile: Insights into Gaining Regulatory Qualification of the First Wearable-Derived Digital Endpoint for use in Duchenne Muscular Dystrophy Trials

In 2019, stride velocity 95th centile (SV95C) became the first wearable-derived digital clinical outcome assessment (COA) qualified by the European Medicines Agency (EMA) for use as a secondary endpoint in trials for Duchenne muscular dystrophy. SV95C was approved via the EMA's qualification pathway for novel methodologies for medicine development, which is a voluntary procedure for assessing the regulatory acceptability of innovative methods used in pharmaceutical research and development. SV95C is an objective, real-world digital ambulation measure of peak performance, representing the speed of the fastest strides taken by the wearer over a recording period of 180 hours. SV95C is correlated with traditional clinic-based assessments of motor function and has greater sensitivity to clinical change over 6 months than other wearable-derived stride variables, for example, median stride length or velocity. SV95C overcomes many limitations of episodic, clinic-based motor function testing, allowing the assessment of ambulation ability between clinic visits and under free-living conditions. Here we highlight considerations and challenges in developing SV95C using evidence generated by a high-performance wearable sensor. We also provide a commentary of the device's technical capabilities, which were a determining factor in the regulatory approval of SV95C. This article aims to provide insights into the methods employed, and the challenges faced, during the regulatory approval process for researchers developing new digital tools for patients with diseases that affect motor function.

Complexity of skeletal muscle degeneration: multi-systems pathophysiology and organ crosstalk in dystrophinopathy

Duchenne muscular dystrophy is a highly progressive muscle wasting disorder due to primary abnormalities in one of the largest genes in the human genome, the DMD gene, which encodes various tissue-specific isoforms of the protein dystrophin. Although dystrophinopathies are classified as primary neuromuscular disorders, the body-wide abnormalities that are associated with this disorder and the occurrence of organ crosstalk suggest that a multi-systems pathophysiological view should be taken for a better overall understanding of the complex aetiology of X-linked muscular dystrophy. This article reviews the molecular and cellular effects of deficiency in dystrophin isoforms in relation to voluntary striated muscles, the cardio-respiratory system, the kidney, the liver, the gastrointestinal tract, the nervous system and the immune system. Based on the establishment of comprehensive biomarker signatures of X-linked muscular dystrophy using large-scale screening of both patient specimens and genetic animal models, this article also discusses the potential usefulness of novel disease markers for more inclusive approaches to differential diagnosis, prognosis and therapy monitoring that also take into account multi-systems aspects of dystrophinopathy. Current therapeutic approaches to combat muscular dystrophy are summarised.

Muscle Eccentric Contractions Increase in Downhill and High-Grade Uphill Walking

In Duchenne muscular dystrophy (DMD), one of the most severe and frequent genetic diseases in humans, dystrophic muscles are prone to damage caused by mechanical stresses during eccentric contractions. Eccentric contraction during walking on level ground likely contributes to the progression of degeneration in lower limb muscles. However, little is known about how the amount of muscle eccentric contractions is affected by uphill/downhill sloped walking, which is often encountered in patients’ daily lives and poses different biomechanical demands than level walking. By recreating the dynamic musculoskeletal simulations of downhill (−9°, −6°, and −3°), uphill (+3°, +6°, and +9°) and level walking (0°) from a published study of healthy participants, negative muscle mechanical work, as a measure of eccentric contraction, of 35 lower limb muscles was quantified and compared. Our results indicated that downhill walking overall induced more (32% at −9°, 19% at −6°, and 13% at −3°) eccentric contractions in lower limb muscles compared to level walking. In contrast, uphill walking led to eccentric contractions similar to level walking at low grades (+3° and +6°), but 17% more eccentric contraction at high grades (+9°). The changes of muscle eccentric contraction were largely predicted by the changes in both joint negative work and muscle coactivation in sloped walking. As muscle eccentric contractions play a critical role in the disease progression in DMD, this study provides an important baseline for future studies to safely improve rehabilitation strategies and exercise management for patients with DMD and other similar conditions.

A novel ex vivo protocol to mimic human walking gait: implications for Duchenne muscular dystrophy

We developed a novel ex vivo mouse protocol to mimic in vivo human soleus muscle function predicted by musculoskeletal simulations to better understand eccentric contractions during gait and ultimately to better understand their effects in Duchenne muscular dystrophy (DMD) muscles. DMD muscles are susceptible to eccentric injury because the protein dystrophin is absent. The mdx mouse, a DMD model that also lacks dystrophin, is often subjected to ex vivo acute but nonphysiological eccentric injury protocols. It is possible these acute protocols either over- or underestimate eccentric stresses and strains compared with those from humans during gait. To explore this possibility, healthy human soleus excitation, force, and length change profiles during a single walking stride (gait cycle) were simulated using OpenSim and then scaled to an ex vivo mouse soleus preparation based on muscle architectural measurements. Aurora Scientific, Inc., software and a 701C electrical stimulator were modified to discretely modulate muscle stimulation voltage at constant frequency and finely control muscle length changes to produce a force pattern that correctly mimicked the gait cycle from simulations. In a proof-of-principle study, wild-type and mdx mice soleus muscles were subjected to 25 gait cycles. Modest fatigue was evident in the muscles at the 25th versus first gait cycle for both genotypes, but both rapidly recovered isometric force within 1 min of the last cycle. These data indicate that the ex vivo gait protocol was well tolerated. More important, this protocol provides a novel assessment tool to determine the effects of physiological eccentric contractions on dystrophic muscle.NEW & NOTEWORTHY A novel ex vivo mouse soleus protocol that mimics scaled length change and excitation profiles predicted by a mathematical model of human soleus during gait is presented. A custom stimulator was developed that enabled an innovative muscle stimulation technique to modulate voltage to closely match the excitation pattern of human soleus during gait. This ex vivo protocol provides assessment of simulated human movement in mouse muscle, including components of eccentric contractions.

Progression of muscular co-activation and gait variability in children with Duchenne muscular dystrophy: A 2-year follow-up study

BACKGROUND

Duchenne muscular dystrophy is an X-linked muscle disease caused by dystrophin absence. Muscle weakness is a major determinant of the gait impairments in patients with Duchenne muscular dystrophy and it affects lower limbs more often than upper limbs. Monitoring progression of motor symptoms is key to plan treatments for prolonging ambulation.

METHODS

The progression of gait impairment in a group of ten patients with Duchenne muscular dystrophy was observed longitudinally three times over a period of 2 years by computerized gait analysis system. Spatio-temporal parameters of gait, and variability indicators were extracted from kinematics, while lower limb muscles coactivation were measured at the baseline and at each follow-up evaluation. The 6-min walk test was used to evaluate functional capacity at each time session.

FINDINGS

We found a significant increase in stride width and in both stride width and stride length variability at the 1-and 2-year follow-up evaluations. Furthermore, significant higher values in proximal muscle coactivation and significant lower values in both distal muscle coactivation and functional capacity were found at the 2-year follow-up evaluation. Significant negative correlations between muscle coactivation at proximal level and functional capacity and between muscle coactivation at distal level and gait variability were observed.

INTERPRETATION

Our findings suggest that patients with Duchenne muscular dystrophy exhibit decline in functional capacity after 2 years from the baseline. Moreover, to cope with disease progression, patients try to maintain an effective gait by changing the balance dynamic strategies (i.e. increase in proximal muscle coactivation) during the course of disease.

Walking and weakness in children: a narrative review of gait and functional ambulation in paediatric neuromuscular disease

Background

Weakness is the primary impairment in paediatric neuromuscular diseases, impacting gait and gait-related functional activities in ambulant children affected by these rare and often degenerative diseases. Gait speed is an indicator of health and disability, yet gait is a complex, multi-faceted activity. Using the International Classification of Function, Health and Disability (ICF) model, assessment of gait and functional ambulation should consider the impairments, activity limitations and participation restrictions due to disease, and factors related to the environment and the individual person.

Methods

This narrative review involved a literature search of databases including Medline, Embase and Pubmed from 1946 to October 2019. Inclusion criteria included assessments of gait, endurance and ambulatory function in paediatric (0–18 years) neuromuscular diseases.

Results

Fifty-two papers were identified reporting assessments of gait speed, timed function, endurance and ambulatory capacity, gait-related balance and qualitative descriptive assessments of gait function and effect of disease on gait and gait-related activities. Gait speed is an indicator of disability and children with neuromuscular disease walk slower than typically developing peers. Increasing disease severity and age were associated with slower walking in children with Duchenne muscular dystrophy and Charcot-Marie-Tooth disease. The six-minute walk test is used widely as a test of endurance and ambulatory capacity; six-minute walk distance was substantially reduced across all paediatric neuromuscular diseases. Endurance and ambulatory capacity was more limited in children with spinal muscular atrophy type 3, congenital muscular dystrophy and older boys with Duchenne muscular dystrophy. Only a few papers considered normalisation of gait parameters accounting for the effect on gait of height in heterogeneous groups of children and linear growth in longitudinal studies. Balance related to gait was considered in five papers, mainly in children with Charcot-Marie-Tooth disease. There was limited investigation of factors including distance requirements and terrain in children’s typical environments and personal factors related to self-perception of disease effect on gait and gait-related function.

Conclusion

Assessments of gait and functional ambulation are important considerations in documenting disease progression and treatment efficacy in the clinical setting; and in clinical trials of disease-modifying agents and physiotherapeutic interventions in paediatric neuromuscular diseases. There is a need for expert consensus on core gait and functional ambulation assessments for use in clinical and research settings.

EMG-based Indicators of Muscular Co-Activation during Gait in Children with Duchenne Muscular Dystrophy

Muscular weakness is one of the main signs associated with the onset and progression of Duchenne Muscular Dystrophy. During motor functions, this disease also determines deviations in muscular activity, especially in terms of coordination and activation between muscles acting on the same joints. In this study, surface EMG activity of the lower limb muscles of 10 children with Duchenne Muscular Dystrophy at different times from disease onset were recorded along with kinematics during unconstrained gait. Muscular co-activation of muscle pairs was then evaluated by extracting different co-activation indicators, and linking them with kinematic markers of motor function. The combination of disease progression and pharmacological treatment resulted in a significant decrease in terms of co-activation indexes for two pairs of agonist-antagonist muscles, and for one of these two pairs the decrease in co-activation was correlated with a decrease in the motor function of gait.

Evaluation of gait in Duchenne Muscular Dystrophy: Relation of 3D gait analysis to clinical assessment

Walking ability in Duchenne Muscular Dystrophy (DMD) deteriorates progressively until complete loss of the function. Interventions aimed at maintaining ambulatory ability relies on accurate clinical-based scores and evaluations of walking. This kind of assessment has intrinsic limitations. A 3D optoelectronic system could provide elements useful for the functional evaluation of patients with DMD. Nineteen boys with DMD were evaluated using the 6-Minutes Walking Test, North Star Ambulatory Assessment and 3D gait analysis. Participants' gait parameters were compared to those of an age-matched control group and correlated with standard clinical scores. Seventeen kinematic variables differed between DMD and control groups. Strong correlations with North Star Ambulatory Assessment were found for stride width, gait velocity and ankle angles on the sagittal plane. The 6-Minutes Walking test did not correlate with investigated kinematic variables but showed a correlation with North Star Ambulatory Assessment. Our data support the reported DMD gait pattern characterized by increased anterior pelvic tilt and ankle plantar flexion. The stride width and ankle kinematics emerged as the main representative gait parameters of DMD global ambulatory status. Although preliminary, our findings suggest that 3D gait analysis may provide useful objective and accurate parameters reflecting the functional ability of individuals with DMD.

Large variation in effects during 10 years of enzyme therapy in adults with Pompe disease

Objective

To determine the effects of 10 years of enzyme replacement therapy (ERT) in adult patients with Pompe disease, focusing on individual variability in treatment response.

Methods

In this prospective, multicenter cohort study, we studied 30 patients from the Netherlands and France who had started ERT during the only randomized placebo-controlled clinical trial with ERT in late-onset Pompe disease (NCT00158600) or its extension (NCT00455195) in 2005 to 2008. Main outcomes were walking ability (6-minute walk test [6MWT]), muscle strength (manual muscle testing using Medical Research Council [MRC] grading), and pulmonary function (forced vital capacity [FVC] in the upright and supine positions), assessed at 3- to 6-month intervals before and after the start of ERT. Data were analyzed with linear mixed-effects models for repeated measurements.

Results

Median follow-up duration on ERT was 9.8 years (interquartile range [IQR] 8.3–10.2 years). At the group level, baseline 6MWT was 49% of predicted (IQR 41%–60%) and had deteriorated by 22.2 percentage points (pp) at the 10-year treatment point (p < 0.001). Baseline FVC upright was 54% of predicted (IQR 47%–68%) and decreased by 11 pp over 10 years (p < 0.001). Effects of ERT on MRC sum score and FVC supine were similar. At the individual level, 93% of patients had initial benefit of ERT. Depending on the outcome measured, 35% to 63% of patients had a secondary decline after ≈3 to 5 years. Still, at 10 years of ERT, 52% had equal or better 6MWT and/or FVC upright compared to baseline.

Conclusions

The majority of patients with Pompe disease benefit from long-term ERT, but many patients experience some secondary decline after ≈3 to 5 years. Individual variation, however, is considerable.

Classification of evidence

This study provides Class IV evidence that for the majority of adults with Pompe disease, long-term ERT positively affects, or slows deterioration in, muscle strength, walking ability, and/or pulmonary function.

Gait deviations in Duchenne muscular dystrophy-Part 2. Statistical non-parametric mapping to analyze gait deviations in children with Duchenne muscular dystrophy

BACKGROUND

Prolonged ambulation is considered important in children with Duchenne muscular dystrophy (DMD). However, previous studies analyzing DMD gait were sensitive to false positive outcomes, caused by uncorrected multiple comparisons, regional focus bias, and inter-component covariance bias. Also, while muscle weakness is often suggested to be the main cause for the altered gait pattern in DMD, this was never verified.

RESEARCH QUESTION

Our research question was twofold: 1) are we able to confirm the sagittal kinematic and kinetic gait alterations described in a previous review with statistical non-parametric mapping (SnPM)? And 2) are these gait deviations related to lower limb weakness?

METHODS

We compared gait kinematics and kinetics of 15 children with DMD and 15 typical developing (TD) children (5-17 years), with a two sample Hotelling's T² test and post-hoc two-tailed, two-sample t-test. We used canonical correlation analyses to study the relationship between weakness and altered gait parameters. For all analyses, α-level was corrected for multiple comparisons, resulting in α = 0.005.

RESULTS

We only found one of the previously reported kinematic deviations: the children with DMD had an increased knee flexion angle during swing (p = 0.0006). Observed gait deviations that were not reported in the review were an increased hip flexion angle during stance (p = 0.0009) and swing (p = 0.0001), altered combined knee and ankle torques (p = 0.0002), and decreased power absorption during stance (p = 0.0001). No relationships between weakness and these gait deviations were found.

SIGNIFICANCE

We were not able to replicate the gait deviations in DMD previously reported in literature, thus DMD gait remains undefined. Further, weakness does not seem to be linearly related to altered gait features. The progressive nature of the disease requires larger study populations and longitudinal analyses to gain more insight into DMD gait and its underlying causes.