Ankle contractures in muscular dystrophy: mechanisms and tissue adaptations

Project Summary/Abstract
Ankle contractures in muscular dystrophy: mechanisms and tissue adaptations
Duchenne muscular dystrophy (DMD) is a genetic disorder that causes progressive muscle degeneration and
weakness leading to difficulties walking, using the arms, and breathing. In addition to muscle weakness,
individuals with muscular dystrophy often lose flexibility in joints such as their ankles, knees, hips, elbows, and
hands. This loss of range of motion, called a contracture, can cause difficulty with function, positioning, and
comfort. The loss of ankle joint range of motion and development of plantarflexion contractures affects nearly all
children with DMD while they are still able to walk, and contracture prevention and management is a major goal
of rehabilitation for ambulatory children with DMD to allow for maximal function and quality of life. However, there
is little convincing evidence to demonstrate that currently prescribed contracture interventions are effective or
improve function, and this is likely due to a gap in knowledge about the pathophysiology of contracture
development in DMD. The goal of this proposal is to prospectively evaluate the potential mechanisms driving
loss of ankle range of motion in DMD and the plantarflexor muscle and/or tendon changes that result. Our central
hypothesis is that progressive proximal muscle weakness and degeneration drives ankle contracture
development in ambulatory children with DMD and that the primary adaptation in the plantarflexor muscle-tendon
unit is shortening of the Achilles tendon. In aim 1, we will quantitatively evaluate lower extremity muscle strength
and muscle replacement by fat using magnetic resonance imaging (MRI) to evaluate the impact of muscle
weakness and degeneration on ankle joint dorsiflexion range of motion in ambulatory individuals with DMD. In
aim 2, we will evaluate the tissue adaptations occurring alongside loss of joint range of motion including changes
in plantarflexor muscle length, Achilles tendon length, Achilles tendon structure, and muscle-tendon passive
stiffness. Data collected from this study will help physical therapists and other rehabilitation professionals better
understand the causes of ankle contractures in muscular dystrophy, which will lead to more evidence-based
decisions about targeted interventions that may help prevent or slow contracture formation.

Grant Number: 1R03HD111034-01A1
NIH Institute/Center: NIH
Principal Investigator: Alison Barnard