Below the knee muscle weakness, defined by weak dorsiflexor (shin) or plantarflexor (calf) muscle groups, can result from a variety of physical impairments or congenital abnormalities. Stroke, spinal cord injuries, polio and multiple sclerosis are among some of the physical injuries and congenital defects responsible for the condition. The largest complication from below the knee muscle weakness is abnormal gait, which when compensated for can lead to further complications in other muscles and joints.
Ankle-foot-orthoses (AFOs) have been designed to assist afflicted individuals in walking and rehabilitation of the weakened muscle groups. Unfortunately, many commercially available AFOs are passive devices that cannot provide assistance during the propulsive phase of gait. Furthermore, these instruments are not capable of adapting to changes in walking conditions. Powered AFOs have been engineered to overcome these limitations but lack practicality in that they are commonly tethered to off-board power sources.
This technology provides a non-tethered, portable pneumatic powered AFO that controls and assists propulsion of the foot as well as ankle motion using plantarflexor and dorsiflexor torque at the ankle joint.
A custom-built pneumatic rotary actuator is located at the ankle joint. Torque generated by the actuator is used for both motion control of the foot and to provide supplemental torque for the individual during gait. Pressure regulators are used to manage the force produced by the rotary actuator and valves are used to direct the flow of fluid power to the actuator. Control and sensing of the actuator is accomplished through use of pressure and angle sensors and onboard electronics.
Applications
This device can be used to aid individuals afflicted with below the knee muscle weakness or impaired gait resulting from any number of physical injuries or congenital disabilities. Portability of the device permits the device to be used in a variety of locations. Applications include:
- Assistance in walking (including flexibility to walk outside)
- Relief from pain and discomfort during walking
- Rehabilitation of dorsiflexors and plantarflexors (possible from the patients personal residence)
Benefits
The portable pneumatic AFO is beneficial compared to passive AFOs in that it:
- Controls velocity of foot during initial contact to prevent foot-slap
- Provides torque at end of the stance for propulsion
- Supports the foot in the neutral, 90 degree position during swing to prevent foot-drop and allow free range of motion throughout the walking cycle
- Enables full customization of timing and magnitude of assistance through electronic and mechanical means
Benefits over other powered AFOs include:
- Portable, non-tethered power