Development of a robotic device to improve chronic ankle instability through controlled perturbation

We have created a lightweight compliant robotic ankle orthotic designed to rehabilitate patients with chronic ankle instability (CAI) through controlled perturbations during gait. This patient population has deficits in ankle sensorimotor control, making it difficult for them to sense and move the ankle and foot properly. This usually leads to recurrent ankle sprains, a factor that has been linked to an increased risk of osteoarthritis and articular degeneration. Current rehabilitation methods are often static, as clinicians cannot provide perturbation in a dynamic condition such as walking. Our device was developed in response to this issue. It can provide controlled force perturbations to the ankle joint in the sagittal and frontal planes during the swing phase of gait using pneumatic artificial muscles. These artificial muscles are back-drivable and extremely light compared to other types of actuation. These features along with the device being a soft orthotic allow patients to correct the error caused by the perturbations in a proactive or reactive manner. The only rigid component is a foot plate that supports the foot and provides attachments to the pneumatic muscles. The entire device weighs approximately 1.1 kg, this lightweight feature allows patients to walk with their natural gait while wearing the device. The device uses rotary encoders to measure the ankle angles as well as force sensors to determine when the foot is in contact with the ground. Initial results show that while wearing the device, plantarflexion and dorsiflexion were virtually unaffected while eversion was slightly increased during swing phase.