flexion have been recorded [70]. The combination of all compensations seems particularly effective as tor- ques were largely decreased at every joints. Step length was increased by pelvic motions [70]. In type III SMA in adults, large pelvic tilt, knee hyperextension during stance and larger hip adduction are observed [82]. A higher hip adduction torque allows an increase in foot clearance while reducing torque on hip and knee flex- ion/extension[82]. The plantar flexion at the ankle is only slightly impaired as demonstrated by torque am- plitudes similar to the one measured in the control group [82].
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Neuromuscular diseases include heterogeneous group of disease marked by progressive muscle wasting on variable locations. The research in this field is recent and no cure have been discovered yet. Exercising can help maintain a moderate strength of the muscle, but persons with NMD need to be cautious not to overload their muscle as it can lead to the destruction of remaining fibers. The full body, including some parts of the lower and the upper body, is usually affected. Ambulation disorders are one of the main consequences of neuromuscular diseases. However, there is a lack of solutions to support these disorders, canes are rarely used and ankle-foot orthosis significantly improve gait, but it is limited to person with mostly ankle weakness. The most reimbursed solutions in Switzerland are motorized and non-motorized wheelchairs. There is thus a great need for new type of assistive systems for the mobility and promotion of exercising in neuromuscular diseases. The biggest challenge of neuromuscular diseases is the large variability in the symptoms that would either require a multitude of solutions or only a few solutions that would be modular and adaptable.
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Over a literature review of 53 papers that reported observations on ambulation in neuromuscular diseases, 31 studies focused on the kinematics of compensating pattern. Duchenne and Charcot-Marie-Tooth muscular dystrophies account both for about one third of the studies. The rest consist mostly of isolated studies on one neuromuscular disease or heterogeneous studies. The following gait patterns have been reported in the studies:
x Toe walk, where the “heel strike” event that occurs at the beginning of the stance phase is replaced by a first contact with the ground with the toes. The gait is denoted by large plantarflexion during the full gait cycle due to a constant tension on Achilles tendon.
x Foot drop or steppage, where the dorsiflexors are very weak and the foot tends to plantarflex during the swing phase under the effect of the gravity.
x Hyperlordosis, which is denoted by an abnormal anterior tilt of the pelvis and a large curving of the lower back.
x Hyperextension of the knee, where the knee is slightly bended inwards during stance in order to avoid to load the quadriceps group.
x Waddling gait, where the upper body swings largely laterally during double stance in an inverted pendulum-like manner. This motion allows to help and compensate for hip drop in persons with hip abduction weakness.
x Co-contration or stiff gait, which is a common tendency in people with neuromuscular diseases in order to increase their stability.
Each of these compensating patterns are caused by a dysfunction from the musculoskeletal system. Their study allows to address the specific need for people with neuromuscular diseases. In a general manner, all the studies that observed the gait parameters denoted a lower walking velocity, a shorter stride length and a larger stride width in people with neuromuscular diseases compared to the control groups. The large ma- jority of studies were performed on a small group of people, usually between 5 and 15 people. Moreover, apart from Duchenne and Charcot-Marie-Tooth muscular dystrophies, there exist very few studies on the other types of neuromuscular diseases. While the existing studies are non-representative as the number of participants are very limited.
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Following the literature review on gait compensations presented in section 2.4, an investigation was per- formed on a heterogeneous group of people with neuromuscular diseases. This study provided better under- standing of different symptoms of NMD and its various paths of development, while also illustrating the im- plication of NMD-related impairments on various aspects of subjects’ daily lives. In order to investigate the ambulation in a varied population of people with NMD, a group of NMD-impaired people were collected. These subjects all had a residual capacity to walk, whether it be with or without some type of assistive aid. Due to the severe symptoms and complex conditions that arise when a child with NMD is growing, only adults were included in the study. Subjects were found through advertisements in the neuromuscular disease unit of the CHUV (Centre Hospitalier Universitaire Vaudois) and through the ASRIMM (Association Suisse Ro- mande Intervenant contre les Maladies neuroMusculaires).
The study consisted of two parts: an interview and a measurement of muscular strength and gait kinematics. The interview section addressed subjects’ history of symptoms and collected information on how these symptoms impacted activities of daily living (ADL). Then, measurements of muscular strength and recordings of the gait kinematics were taken. The primary goal of the study was to observe the different compensation patterns in NMD, to understand what kind of needs each joint level had that an assistive device would need to provide, and to build up the full specifications for an assistive ambulation device. The work presented here is partially based on the publication “From gait measurements to design of assistive orthoses for people with neuromuscular diseases” by A. Ortlieb, J. Olivier, M. Bouri, H. Bleuler and T. Kuntzer [69]. The experiment was approved by the local Ethics Committee (CER-VD 174/14).
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Two groups of participants took part in the study: a group of people with NMD with a residual ability to walk at least 100m and a control group composed of healthy people without any walking disorder. Fourteen adult subjects with a genetically or histologically confirmed NMD condition volunteered in the study (8 males and