Patients with neuromuscular disorders display different type of symptoms depending on the type of pathology. Diseases like facioscapulohumeral dystrophy (FSHD), limb-girdle muscular dystrophy (LGMD2b), sporadic inclusion body myositis (SIBM) or Pompe disease (PD) are characterized by severe muscle weakness leading to reduced functional capacities. This leads to a dramatic decrease of quality of life (e.g. reduced autonomy/participation, social isolation, depression) associated with increased fall risk and complications (e.g. trauma, cardio-vascular issues, trauma, chronic pain, loss of bone mass, and weight gain).
However, a residual of level of strength and residual function may be maintained over years, even at severe disease stages allowing transfers and ambulation. However, the maintenance of this type of activity is often associated with substantial compensatory movements, leading to high load on joints, orthopedic complications, and high fall-risk.
In contrast to traditional passive assistive devices such as orthoses, powered assistive devices, frequently termed dermo- or exoskeletons, have a very high potential for compensating muscle weakness and regain mobility and independence. Devices such as the ReWalk or the Indego use rigid structures, in parallel to the user's legs, and electric motors to stabilize the human against gravity during standing and walking. Thus far, these systems have been used mostly in clinical environments for gait rehabilitation in neurological conditions (e.g. spinal cord injury, post-stroke syndrome). Their weight, which can range from 13 to 48 kg , can make them difficult to use and transport, thus limiting their applicability beyond clinical environments. However, for assistive devices to be used in everyday life, they must provide assistance across activities of daily living (ADLs) in an unobtrusive manner.
Wearable motion assistance systems, especially those dedicated to lower limbs are highly promising for ambulant patients with neuromuscular disorders (e.g. FSHD, LGMD, SIBM or PD). In these conditions, the prevalence of lower-limb muscle weakness, in particular in proximal muscle groups (i.e. providing strength/torque to hips and knees) is very high. Schmidt et al. recently introduced a powered knee-hip soft exoskeleton (the Myosuit), a soft, wearable device designed to provide continuous assistance at the hip and knee joint when working with and against gravity in ADLs. This robotic device combines active and passive elements with a closed-loop force controller designed to behave like an external muscle (exomuscle) and deliver gravity compensation to the user. With 5.6 kg including batteries, the Myosuit is one of the lightest untethered devices capable of delivering gravity support to the user's knee and hip joints. In healthy subject, the Myosuit has been shown to effectively assist its users in gravity-intensive ADLs, such as sitting transfers. However, the effect of the device on movement parameters and user perception must be clarified. We believe that ambulant patients with neuromuscular disorders can highly benefit from a system that provides mobility assistance like the Myosuit. The use of such a device has the potential to shift the loss of ambulation/transfer abilities to a higher age and might mitigate disease progression and occurrence of complications. Whether the Myosuit may be safe, usable, and efficient in ambulant patients with neuromuscular disorders, remain to be specifically investigated.
