Kinematic modeling of four-point walking patterns in paraplegic subjects

We present a kinematic model of a paraplegic subject walking with crutches where the subject with the crutches is modeled as a parallel kinematic structure. The model is employed to investigate if certain quadrupedal gait patterns can be implemented with functional electrical stimulation. The study is motivated by the fact that the existing crutch-assisted gait realized by the electrical stimulation is slow and energy inefficient. Gait patterns that would improve the walking are identified. The main characteristic of the patterns is that some of their states are not statically stable. During such states, the subject is supported by only a leg and a crutch. It is demonstrated that if the forward motion is provided by the stimulation of the plantar flexors the trajectory of the center of the body can closely follow the trajectory that is observed during walking of healthy subjects. We argue that the resulting gait is smooth and energy efficient. In addition, the unstable states make the walking faster.