Using a Vibrotactile Stimulation Device to Improve Knee Extension During Stance Phase in Children with Spastic Cerebral Palsy

Spastic Cerebral Palsy (CP) is the most common motor disability among children, characterized by four inter-related neuromuscular deficits: muscle weakness, spasticity, short muscle-tendon length, and impaired selective motor control. These neuromuscular deficits contribute to debilitating walking disorders, the most common of which is flexed-knee gait. If left untreated, flexed-knee gait can result in progressive loss of walking ability as children age. Studies have shown muscle-focused vibrotactile stimulation can target the aforementioned neuromuscular deficits: increasing muscle strength, reducing spasticity, and improving selective motor control. We developed a novel portable device to administer muscle-targeted vibrotactile stimulation to help improve flexed-knee gait among children with spastic CP.
Our device triggers vibrotactile stimulation at mid-terminal stance. We have implemented two methods for mid-terminal stance identification. The first uses footswitch data (heel-strike and toe-off) to estimate midstance. The second method is a novel neural-network-based approach that uses data collected by an inertial measurement unit (IMU) to make real time gait phase inferences encoded in two scalar outputs: the estimated sine and cosine of the true gait phase. Once the device has identified midstance, an array of vibration motors (tactors) on the patient's soleus muscle located in the lower leg.
Testing of the device has revealed that both gait identification algorithms are successful at identifying mid-terminal stance in users with typical gaits. However, the neural network approach shows more promising results in terms of estimating gait cycle progression in users demonstrating flexed-knee gait. Additionally, through reaction-time tests, we confirmed vibrotactile stimulation elicits comparable reaction times to auditory prompting. Comparable reaction times, combined with the neuromuslcar benefits of vibrotactile stimulation, position our device to help improve flexed-knee gait in children with spastic CP over current gait treatment strategies.