Development of an intelligent stretching device for ankle joints with contracture/spasticity

A stretching device with intelligent control was developed to treat spastic/contractured ankles of neurologically impaired patients and evaluate the outcome. The device stretched the ankle joint safely throughout the range of motion (ROM) to extreme positions until a specified peak resistance torque was reached with the stretching velocity controlled based on the resistance torque. The ankle was then held at the extreme position for a period of time to let stress relax before it was rotated back to the other extreme position. The stretching was slow at the joint extreme positions, making it possible to reach a larger ROM safely, and it was fast in the middle ROM so the majority of the treatment was spent in stretching the problematic extreme ROM. The device was evaluated in five healthy subjects and used to treat four stroke patients. Furthermore, it was used to evaluate treatment outcome in multiple aspects, including passive/active joint ROM, stiffness, viscous damping, and reflex excitability. The intelligent control and yet simple design of the device suggest that the device can be made portable at relatively low cost, making it available to patients/therapists for frequent use in clinics/home and allowing more effective treatment and long-term improvement.