Development of Pneumatic-based Continuous Passive Motion System for Ankle Dorsiflexion and Plantarflexion

Ankle rehabilitation is essential for enhancing patient outcomes, reducing the recurrence of ankle injuries, and restoring functional activities. This study aimed to develop a low-cost, pneumatic-based continuous passive motion device for ankle dorsiflexion and plantarflexion, driven by a Pneumatic Muscle Actuator (PMA) system and integrated with an Inertial Measurement Unit (IMU) and Force Sensing Resistor (FSR). Static validation of the IMU was performed using a protractor and smartphone IMUs, while dynamic validation was conducted with a 3D full-body motion tracker (Sony ™ Mocopi). A moderate-to-high percentage error was observed in the IMU during dorsiflexion and an acceptable error during plantarflexion, while the FSR showed reasonable moderate error due to the inconsistency of point load. A total of 5 subjects of similar age, with varying weights, heights, and genders, were recruited to test the device's ability in active stretching. Data from the IMU revealed the range of motion (ROM) in dorsiflexion and plantarflexion, while the FSR measured the force exerted by the subject's foot during exercise. The analysis revealed that the maximum ROM of the device was inversely related to the weight of the subjects. In conclusion, this study successfully developed a low-cost pneumatic-based continuous passive motion device for ankle rehabilitation, capable of measuring range of motion and exerted force during dorsiflexion and plantarflexion. While the device demonstrated acceptable accuracy for plantarflexion, moderate errors in dorsiflexion and force measurements suggest the need for further refinement. Overall, the device shows promise for effective ankle rehabilitation with potential for improved precision.