Contrary to what was previously thought, muscle contractures may contribute significantly to walking (gait) abnormalities in patients with Duchenne muscular dystrophy (DMD), according to a recently published study in the Journal of NeuroEngineering and Rehabilitation.
Deciphering gait abnormalities in DMD
Over the course of the disease, patients with DMD develop gait abnormalities such as shorter steps, increased step width, slower movements and increased knee flexion during walking.
Read more about the prognosis of DMD
Muscle weakness has long been considered the primary driver of gait abnormalities in patients with DMD, but some experts have suggested that contractures also play a significant role. Muscle contractures are a result of muscle being replaced by fat and scar tissue. These are less flexible than muscle fibers, and lead to stiffness and limited movement.
Analyzing contracture separately from muscle weakness poses a challenge, as both occur at the same time. The “co-occurrence and simultaneous decline of multiple impairments hamper disentangling the causal contribution of weakness from that of contractures to gait pathology in DMD based on experimental data alone,” the study’s authors noted.
Computer simulations to assess causal relationships
Researchers aimed to use physics-based predictive simulations of gait to determine the specific contributions of muscle weakness and muscle contractures to gait abnormalities. These computer-based simulations apply the fundamental laws of physics to predict how real-world systems respond to specific conditions.
Similar models have previously been used to assess the effects of plantar flexor weakness on gait abnormalities. In this study, the model was built using data from over 30 patients with DMD.
The simulation showed that although muscle weakness remains the principal driver of gait abnormalities in patients with DMD, muscle contractures also contribute — particularly to delayed and increased knee flexion during walking.
However, the authors acknowledged that the simulation did not replicate DMD gait with full accuracy and emphasized the need for further research to validate the findings.
“These results highlight the potential of predictive simulations to improve our understanding of the causal relationships between progressive impairments and pathological gait patterns in boys with DMD,” the authors wrote. “An increased understanding of the differential effects of weakness and stiffness might guide treatment selection.”
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