Evaluation of gait kinematics and kinetics using a powered ankle-foot orthosis for gait assistance in people with multiple sclerosis

Gait impairment is one of the many motor symptoms of multiple sclerosis (MS) but has the largest perceived impact on overall quality of life for people with the disease. Currently, there is no cure for MS and no treatments or therapies can reverse the progression of symptoms. Typically, gait speed becomes slower with disease progression requiring the prescription of assistive devices to maintain or improve movement ability and promote independence. For people with MS who suffer from drop foot (i.e., the diminished or lack of ability to dorsiflex the foot), prescription of a passive ankle-foot orthosis is common. The purpose of these devices is to hold the foot in neutral position and prevent the foot from dropping during forward swing. Although these devices can be beneficial, ankle-foot orthoses generally prevent the ability to plantarflex the ankle, and successful implementation of these devices has been limited. Recently, powered orthotics and exoskeletons have been developed for people with neurological impairments or injuries that impact gait function. These devices can provide active motion control and assistance in both plantarflexion and dorsiflexion of the ankle. The purpose of this thesis was to investigate the utility of a powered ankle-foot orthosis for gait assistance in people with MS. Specifically, the analyses performed in this thesis focused on the kinematic and kinetic changes in gait associated with a powered ankle-foot orthosis compared to a passive ankle-foot orthosis and walking without an assistive device. Results indicate that the vertical ground reaction force during the propulsive phase of gait (i.e., terminal stance) was increased with the powered ankle-foot orthosis, counteracting the diminished behavior typically observed in people with MS. However, peak plantarflexor torque during this same phase of gait was diminished compared to walking without an assistive device, which may have been due to a slower gait speed. The only difference between a powered ankle-foot orthosis or prescribed passive ankle-foot orthosis was an increased mid-stance minima in the vertical ground reaction force, which could also be an indicator of slower gait speed. The findings of this study provide an initial baseline for future studies of powered orthoses in people with MS. Further investigation and tuning of the powered orthosis used in this study is needed