From gait measurements to design of assistive orthoses for people with neuromuscular diseases

Neuromuscular diseases (NMD) such as myopathies are characterized by symptomatic patterns of degenerative muscle weakness leading to severe walking disability. Due to low prevalence and great variability of symptoms, very little effort has been spent on assistive devices as compared e.g. to spinal cord injury (SCI) or stroke rehabilitation. The needs for assistance for persons with NMD are specific and existing solutions for SCI or stroke patients are not adapted to them. This study investigates design specifications of assistive orthoses with the goal of adding months or years of near normal mobility for patients with muscle weakness. Data on strength affection and gait kinematics of 14 subjects (5 Facioscapulohumeral muscular dystrophy, 3 Charcot-Marie-Tooth neuropathy, 2 Becker muscular dystrophy, 2 Myotonic dystrophy and 2 Inclusion body myositis) has been collected. The results highlight the effect of muscle weakness on gait pattern and walking velocity. Design specifications of walk assist exoskeletons for such patients are then proposed and discussed. A novel architecture of a lower limb orthosis is proposed based on these observations.