Adaptive control of a variable-impedance ankle-foot orthosis to assist drop-foot gait.

Abstract

An active ankle-foot orthoses (AAFO) is presented where the impedance of the orthotic joint is modulated throughout the walking cycle to treat drop-foot gait. During controlled plantar flexion, a biomimetic torsional spring control is applied where orthotic joint stiffness is actively adjusted to minimize forefoot collisions with the ground. Throughout late stance, joint impedance is minimized so as not to impede powered plantar flexion movements, and during the swing phase, a torsional spring-damper control lifts the foot to provide toe clearance. To assess the clinical effects of variable-impedance control, kinetic and kinematic gait data were collected on two drop-foot participants wearing the AAFO. For each participant, zero, constant, and variable impedance control strategies were evaluated and the results were compared to the mechanics of three age, weight, and height matched normals. We find that actively adjusting joint impedance reduces the occurrence of slap foot allows greater powered plantar flexion and provides for less kinematic difference during swing when compared to normals. These results indicate that a variable-impedance orthosis may have certain clinical benefits for the treatment of drop-foot gait compared to conventional ankle-foot orthoses having zero or constant stiffness joint behaviors.

• Authors: Joaquin A Blaya, Hugh Herr
• Journal: IEEE transactions on neural systems and rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society (IEEE Trans Neural Syst Rehabil Eng) Vol. 12 Issue 1 Pg. 24-31 (Mar 2004) ISSN: 1534-4320 [Print] United States
• PMID: 15068184 (Publication Type: Clinical Trial, Controlled Clinical Trial, Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)

Topics

• Aged
• Ankle (physiopathology)
• Elasticity
• Electric Impedance
• Equipment Failure Analysis
• Feedback
• Female
• Foot (physiopathology)
• Gait
• Gait Disorders, Neurologic (physiopathology, rehabilitation)
• Humans
• Male
• Middle Aged
• Orthotic Devices
• Prosthesis Design
• Therapy, Computer-Assisted (instrumentation, methods)
• Treatment Outcome