Optimizing Warfighter Performance with Neurally Integrated Robotic Lower Limb Prostheses
Abstract
Despite noteworthy advances in robotic prostheses for lower-limb amputees, natural sensory feedback from the lost limb has not yet been incorporated into current prosthetic technologies. Neither has direct, intuitive volitional control of sophisticated wearable robotic limbs. To compensate for the lack of sensation and intuitive control, amputees increase the loads applied to their intact limb, putting them at risk for long-term damage from over use. Amputees are also extremely slow to adapt to the loss of their limbs, resulting in life-long fear of falling. Except for the mechanical loads transferred to the residual limb or conscious visual attention, no lower limb prosthesis offers a permanent and reliable method to restore a natural sense of the status of the missing limb and its interactions with the ground or surrounding environment. Externally applied loads are also the only way to communicate user intent to advanced motorized prostheses, which act on them stereotypically in preprogrammed manners appropriate only for walking on level surfaces. Although there have been numerous attempts to provide feedback by substituting vibrations on other areas of the skin unassociated with leg-ground interactions, nothing to date has successfully restored useful sensations that are perceived immediately and directly as coming from the missing limb. Similarly, no device offers direct, intuitive control of the advanced wearable robotic joints currently on the market. The objective of this 4-year project is to devise a fully bidirectional interface between advanced robotic prostheses and the intact elements of the nervous system. Exciting the peripheral sensory nerves that remain intact after amputation will activate existing areas in the brain associated with plantar pressure or skin contact in the missing limb, thus making the evoked sensations seem natural and as if they arise from the phantom limb. The effects of these electrically elicited sensations on standing balance, gait mechanics, and symmetry, and the user’s ability to negotiate unstructured terrain and uneven surfaces will be quantified. Positive effects on the cognitive burden of walking in unfamiliar or distracted environments, body image, balance confidence, and frequency and severity of phantom pain are anticipated. Recordings of the electromyographic (EMG) activity of the muscles in the residual limb formerly associated with movements of the missing joints, as well as more proximal muscles about the hip, will be exploited to provide users with a direct, volitional, and intuitive means to adjust the actions of advanced commercially available powered knee and ankle prostheses. Three individuals with trans-femoral and three with trans-tibial limb loss will each have two new 16-contact Composite-Flat Interface Electrodes (C-FINEs) implanted on the femoral nerves in the back of the thigh of their residual limbs, and two sets of four bipolar intramuscular (IM) electrodes will be inserted into the remaining musculature to record EMG. Each electrode will be connected to temporary lead wires that exit the skin. After fully characterizing the stimulus-evoked sensation and devising efficient control algorithms, subjects will be fit with an advanced microprocessor-controlled prosthetic joints with a rich set of embedded sensors that monitor limb loading, knee angle, and other important information about how the limb interacts with the environment. Data from the sensors will be mapped to stimulation to the appropriate electrode contact to generate the corresponding sensation, and the activities of the contacting muscles will drive the onboard motors in the prostheses. After determining the relative benefits of the bidirectional neuroprosthesis on posture, balance, walking, stair climbing, and negotiating ramps or obstacles in the laboratory, two users will have their temporary percutaneous leads removed and replaced with a new, completely implanted stimulation a
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 10, 2021
- Source ID
- W81XWH2010802
Entities
People
- Ronald J Triolo
Organizations
- Case Western Reserve University
- United States Army