ERC Researchers to Test Orthosis on People with Parkinson’s Disease

Achievement date: 

Researchers affiliated with the Center for Compact and Efficient Fluid Power (CCEFP), an NSF-funded Engineering Research Center (ERC) headquartered at the University of Minnesota, have developed an ankle-foot orthosis (AFO) that holds promise of enabling people with mobility impairments to walk with greater stability, confidence, and independence. In a recent collaboration between researchers at the Universities of Minnesota, Maryland, and Illinois, a device known as the pneumatic Portable Powered AFO (PPAFO) is being explored to determine if it can provide an appropriate sequence of joint torques to compensate for deficits in torque generation experienced by people with Parkinson's disease (PD).


Recent studies have demonstrated that mild mechanical perturbations, which elicit postural responses, can significantly improve gait initiation in people with PD, but to date no wearable device has been tested. The PPAFO research collaboration will assess the extent to which the device can aid those suffering from PD. More broadly, AFO development, along with the continuing research behind it, has the obvious benefit of creating novel powered exoskeletons that can assist persons with disabilities. In addition, addressing the complex engineering issues associated with AFOs has facilitated development of miniature fluid-power systems by pushing the practical limits of weight, power, and duration for compact, untethered, wearable fluid-power devices. New market opportunities for the fluid-power industry will likely result from this research.


The use of cues (audio, visual, touch) can improve the ability to start and continue walking in people with severe PD. However, the success of cuing interventions is limited by low reliability and a reduced capacity of patients to produce the forces necessary to generate the anticipatory postural adjustments (APAs) for gait initiation. APAs involve a well-orchestrated sequence of shifts in body weight to prepare the swing limb for smooth forward progression. The first study is assessing whether the presentation of a mechanical cue, such as modest torque at the ankle via the PPAFO, will significantly improve the generation of appropriate APAs required to initiate gait. (See PPAFO in accompanying figure.)

Portable AFOs use pneumatic power, provided by compressed CO2, to move the ankle. Test results have demonstrated that an AFO is capable of providing untethered functional assistance for people with lower-leg weakness. One past test participant had plantar-flexor weakness due to a spinal injury and could no longer generate torque at the ankle to push his toes down. This impairment affected his ability to propel himself forward while walking, making extended walking exhausting. Another past participant had muscular dystrophy, a disorder that caused weakness in both her calf and shin muscles. The CCEFP AFO provided functional assistance to both users.