Hip kinetics during gait are clinically meaningful outcomes in young boys with Duchenne muscular dystrophy

• This was the first natural history study of gait biomechanics in boys with DMD.
• Peak hip moments and powers were inadequate in young boys with DMD at baseline.
• Hip kinetics showed improvement with a corticosteroid intervention.
• This improvement was significant compared to a steroid-naïve group.
• Gait kinetics may prove useful in clinical trials for novel therapeutics.

Duchenne muscular dystrophy (DMD) is an X-linked genetic neuromuscular disorder characterized by progressive proximal to distal muscle weakness. The success of randomized clinical trials for novel therapeutics depends on outcome measurements that are sensitive to change. As the development of motor skills may lead to functional improvements in young boys with DMD, their inclusion may potentially confound clinical trials. Three-dimensional gait analysis is an under-utilized approach that can quantify joint moments and powers, which reflect functional muscle strength. In this study, gait kinetics, kinematics, spatial-temporal parameters, and timed functional tests were quantified over a one-year period for 21 boys between 4 and 8 years old who were enrolled in a multisite natural history study. At baseline, hip moments and powers were inadequate. Between the two visits, 12 boys began a corticosteroid regimen (mean duration 10.8 ± 2.4 months) while 9 boys remained steroid-naïve. Significant between-group differences favoring steroid use were found for primary kinetic outcomes (peak hip extensor moments (p = .007), duration of hip extensor moments (p = .007), peak hip power generation (p = .028)), and spatial-temporal parameters (walking speed (p = .016) and cadence (p = .021)). Significant between-group differences were not found for kinematics or timed functional tests with the exception of the 10 m walk test (p = .03), which improves in typically developing children within this age range. These results indicate that hip joint kinetics can be used to identify weakness in young boys with DMD and are sensitive to corticosteroid intervention. Inclusion of gait analysis may enhance detection of a treatment effect in clinical trials particularly for young boys with more preserved muscle function.