Powered Prosthetic Advancements Offer Enhanced Mobility
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Even using state-of-the-art passive prostheses, persons with leg amputations use more energy during walking than able-bodied individuals, which limits community mobility. Increased effort is also required for daily activities. A recent wave of technological advances has enabled the development of powered knee and ankle joints that can be controlled together in a coordinated fashion across a broad range of activities. These movements are enhanced by the inclusion of pattern recognition technology. Electrical signals are emitted by all contracting muscles, even those that are partially amputated. By training a computer algorithm to recognize the signal patterns specific to a particular intended movement, electromyography (EMG) sensors decipher user intent and relay that information to safely create prosthetic movement in real time.
Challenges of External Sockets in Leg Prostheses
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While these technological advancements are promising, attaching a prosthetic device to the body presents physical challenges. Leg prostheses are typically connected through an external socket fitted to the individual. However, external sockets can limit the impact of new prosthesis developments. The motor and battery of powered prosthetic devices enable power generation but are heavier than non-powered devices. Providing reliable and comfortable suspension of these devices using traditional sockets can be difficult. Additionally, it is challenging to collect robust EMG data from within a lower-limb socket due to the up and down movement of the leg within the prosthetic socket, sweating, and misalignment of sensors after putting on the socket.
Osseointegration and Targeted Muscle Reinnervation
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In this study, we are utilizing two innovative surgical techniques, osseointegration (OI) and targeted muscle reinnervation (TMR). OI allows for the direct attachment of a prosthesis to remaining bone, eliminating the need for an external socket. OI enables direct transfer of weight from the artificial limb to the skeleton. Benefits include reduced energy expenditure and improvements in walking ability, range of motion, awareness of the prosthetic limb, and comfort while sitting. Additionally, following OI, EMG signal quality will be better than signals measured from within a lower-limb socket due to improved sensor placement and maintenance.
TMR surgery will be paired with OI to enhance utilization of EMG signals. After an amputation, motor commands for the missing limb continue to travel down remaining nerves. During TMR surgery, these residual nerves are transplanted into new target muscle tissue. Once reinnervation is complete, the target muscle tissue contracts in response to activation of the transplanted nerves, producing EMG signals that can be used to control a prosthesis directly.
Our Goals:
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The objective of this study is to evaluate the movement of individuals with leg amputation who have received OI and TMR and are using a fully powered prosthesis. We are studying functional mobility, the effects of non-weight-bearing neural control, and user satisfaction. Our hypothesis is that OI will show benefits for participants including lowerperceived weight of the prosthesis and decreased energy expenditure during movement. Further, we anticipate EMG signals will be higher quality and more robust, potentially allowing for improved pattern recognition in future prosthetic devices.
Participants in this study will:
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- Undergo osseointegration surgery, if they have not already
- Undergo targeted muscle reinnervation surgery, if they have not already
- Attend multiple study visits at the Shirley Ryan AbilityLab
- Be fit for use with a powered prosthesis
- Train with a powered prosthesis
- Perform functional testing wearing a powered prosthesis
Who can participate:
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- 18-70 years old
- Individual with unilateral lower limb amputation at the transfemoral level
- Existing prosthesis wearer with K2/K3/K4 level ambulation
- Able to ascend and descend stairs with current clinically prescribed prosthesis
- Minimum build height of current prosthesis of 47 cm
- Mini-Mental State Exam score greater than 17
- Ability to demonstrate proper safety with passive prosthesis
- Candidate for a myoelectric prosthesis
- Candidate for osseointegration surgery as verified by surgical team or has previously received osseointegration
- Candidate for targeted muscle reinnervation surgery as verified by surgical team or has previously received targeted muscle reinnervation
Compensation:
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Participants will receive compensation for each study visit.
Funding Source:
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Congressionally Directed Medical Research Program (CDMRP)
