A method to evaluate contractures effects during the gait of children with Duchenne dystrophy

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.

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.

Knee Strength and Ankle Range of Motion Impacts on Timed Function Tests in Duchenne Muscular Dystrophy: In the Era of Glucocorticoids

BACKGROUND

Duchenne Muscular Dystrophy (DMD) is a neuromuscular disorder that presents in childhood and is characterized by slowly progressive proximal weakness and lower extremity contractures that limit ambulatory ability [1, 2]. Contractures develop in the ankles, knees, and hips due to muscle imbalances, fibrotic changes, loss of strength, and static positioning [2, 5]. Currently, standards of care guidelines emphasize the importance of maintaining good musculoskeletal alignment through stretching, bracing, and glucocorticoid (GC) therapy to preserve strength and function.

METHODS

This is a retrospective analysis of prospectively collected data through the CINRG Duchenne Natural history study (DNHS). The objectives of this analysis are to understand the progression of ankle contractures for individuals with DMD and to investigate the relationship between progressive lower limb contractures, knee strength, and Timed Function Tests.A collection of TFTs including supine to stand (STS), 10 meter walk test (10MWT), and timed stair climbing (4SC) have been used to monitor disease progression and are predictive of loss of ambulation in these patients [4]. Multiple factors contribute to loss of ambulation, including progressive loss of strength and contracture development that leads to changing biomechanical demands for ambulation. A better understanding of the changes in strength and range of motion (ROM) that contribute to loss of function is important in a more individualized rehabilitation management plan. In this longitudinal study, we measured strength using quantitative muscle testing (QMT) with the CINRG Quantitative Measurement System (CQMS)), ROM was measuresed with a goniometer and TFTs were measured using a standard stopwatch and methodology.

RESULTS

We enrolled 440 participants; mean baseline age was 8.9 (2.1, 28.0) years with 1321 observations used for analysis. GC use was stratified based on duration on drug with 18.7%at <  6 months or naïve; 4.3%<1 year; 58.0%1 <  10 years; and 19.3%between 10-25 years of GC use. Ankle ROM was better for those on GC compared to GC naive but did not significantly influence long-term progression rates. QMT, ROM, age and GCs contribute to speed of TFTs. Knee extension (KE) strength and Dorsiflexion (DF) ROM are significant predictors of speed for all TFTs (p <  0.001). Of the variables used in this analysis, KE strength is the primary predictor of walking speed, estimating that every pound increase in KE results in a 0.042 m/s improvement in 10MWT, and a smaller similar increase of 0.009 m/s with every degree of ankle DF ROM.

CONCLUSION

GC use provides an improvement in strength and ROM but does not affect rate of change. Knee strength has a greater influence on speed of TFTs than DF ROM, although both are statistically significant predictors of speed. Results show that retaining knee strength [1, 2], along with joint flexibility, may be important factors in the ability to perform walking, climbing and supine to stand activities.

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.

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.

Responsiveness of the Gait Domain of the Functional Evaluation Scale for Children with Duchenne Muscular Dystrophy

AIM

To determine the responsiveness of functional gait assessment of children with Duchenne muscular dystrophy (DMD).

METHOD

A total of 160 films of 32 children (mean age: 9.5 ± 2.7) with DMD were scored by the gait domain of the Functional Evaluation Scale - DMD. Children were recorded every 3 months for 1 year (0, 3, 6, 9, and 12 months). Responsiveness was analyzed by the effect sizes (ES) and standardized response means (SRM).

RESULTS

Responsiveness was low to moderate at the 3-month interval (ES 0.12 to 0.34; SRM 0.27 to 0.80); low to high at the 6-month interval (ES 0.36 to 0.72; SRM 0.37 to 1.10); moderate to high at the 9-month interval (ES 0.70 to 1.0; SRM 0.50 to 1.43), and it was high at the 12-month interval (ES 0.74 to 1.34; SRM 0.88 to 1.53).

CONCLUSION

Functional gait assessment of children with DMD was responsive since 3-month intervals. Responsiveness increased as reassessment intervals got longer. The highest responsiveness was observed when children were reevaluated after 12 months. The use of the gait domain of the Functional Evaluation Scale - DMD is recommended in 6- to 12-month intervals, which showed moderate to high responsiveness.

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.

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

BACKGROUND

Although prolonged ambulation is considered important in children with Duchenne muscular dystrophy (DMD), articles describing gait deviations in DMD are scarce.

RESEARCH QUESTION

Therefore, our research questions were the following: 1) what are the most consistently reported spatiotemporal-, kinematic-, kinetic-, and muscle activity deviations in children with DMD in literature, 2) what is the quality of the studies describing these deviations, and 3) is there need for further research?

METHODS

We conducted a systematic literature search for studies published before the end of June 2017 in six online databases. We created a data extraction form to define information on materials and methods and on the analyzed gait parameters for each paper included in the review. If enough information was available, we calculated standardized mean differences (SMDs).

RESULTS

The search yielded nine articles, but generalizability was poor. Seventy-nine parameters were analyzed by seven research groups, but they only agreed on a decrease in walking speed (minimal SMD: 1.26), stride length (1.83), step length (1.80), dorsiflexion during swing (1.43), maximal power generation at the hip (0.92), maximal knee extension torque (0.99), maximal dorsiflexion torque (-1.30), and maximal power generation at the ankle (0.92), and an increased knee range of motion (-0.82) in DMD.

SIGNIFICANCE

In order to keep children with DMD ambulant as long as possible, a clear understanding of their pathological gait pattern is necessary. However, gait deviations in DMD appear not well defined. Previous studies appear to be of an exploratory nature while using predefined gait parameters to assess an undirected null hypothesis. This made them prone to regional focus bias, thereby increasing the chance of a type I error. Therefore, further research is required to define the altered gait pattern in children with DMD.

Development and Reliability of the Functional Evaluation Scale for Duchenne Muscular Dystrophy, Gait Domain: A Pilot Study

BACKGROUND AND PURPOSE

The progression of Duchenne muscular dystrophy (DMD) results in the emergence of multiple and varied synergies to compensate muscle weakness and to deal with the demands of the functional tasks (e.g. gait). No functional evaluation instrument for individuals with DMD allows the detailed description (subjective qualitative evaluation) and compensatory movement scoring (objective quantitative evaluation) exclusively of gait. For this reason, clinicians and therapists face difficulties in assessment and decision-making of this functional activity. This study aimed to elaborate the gait domain of the Functional Evaluation Scale for DMD (FES-DMD-GD) and test its intra-rater and inter-rater reliabilities and its relationship with age and timed motor performance.

METHOD

We listed all the compensatory movements observed in 102 10-m gait videos of 51 children with DMD. Based on this report, the FES-DMD-GD was created and submitted to the review of 10 experts. After incorporating the experts suggestions, three examiners scored the videos using the FES-DMD-GD. The intra-rater and inter-rater reliabilities was calculated. Spearman correlation tests investigated the relationships between FES-DMD-GD and age and timed motor performance (p < 0.05).

RESULTS

The FES-DMD-GD was composed of three phases and had 14 items to quantify compensatory movements on gait. Intra-class correlation coefficients ranged from acceptable (0.74) to excellent (0.99). FES-DMD-GD correlated to age and timed motor performance.

CONCLUSION

This pilot version of FES-DMD-GD showed reliability and correlated to age and timed motor performance.

Physical therapy evaluation and management in neuromuscular diseases

Neuromuscular disorders (NMDs) are a group of myopathic or neuropathic diseases that directly or indirectly affect the functioning of muscle. Physical therapists (PTs) have extensive specialized training in musculoskeletal evaluation and assessment that gives them the tools to meet the significant needs of this population. This article reviews the role of PTs in treating the NMD population with a discussion of available evaluation techniques and interventions and with an effort to differentiate between treatments known to apply to this population and conventional practice of PTs. The status of currently available outcome measures used for research and their applicability to clinics are presented.