Feasibility of Neural Feedback for Lower Limb Amputees

The purpose of this study is to evaluate the effectiveness of providing sensation of the missing limb to individuals with lower limb loss, including above and below knee amputees. The approach involves delivering small electrical currents directly to remaining nerves via implanted stimulating electrodes. These small electrical currents cause the nerves to generate signals that are then transferred to your brain similar to how information about the foot and lower limb used to be transferred to your brain prior to the amputation.

Individuals also have the option to have recording electrodes implanted within muscles of the lower limb(s) in an attempt to develop a motor controller that would enable the user to have intuitive control of a robotic prosthetic leg.

Electrodes are surgically implanted on one to four nerves of the residual limb. An external wearable device controls the delivery of electrical pulses to the implanted system. The participant will be asked to verbally describe the perceived sensations and highlight their locations on a drawing of a foot presented to them on an electronic screen. An instrumented prosthesis will be developed such that perceived sensations would correspond to prosthesis interactions with the floor. This instrumented prosthesis, also known as a sensory neuroprosthesis, will be worn while the participant is engaging in various functional tasks, such as standing, walking, or climbing stairs, or with visual or mental distractions.

Intramuscular recording electrodes can be implanted in the lower limb(s) and/or hip muscles in order to obtain electromyography (EMG) signals. The EMG recordings from the residual muscles will be used to develop an algorithm which can operate an advanced robotic prosthesis in which the movement of the joint(s) could be controlled.

Eligibility Criteria:
Inclusion Criteria:

* Adults age 18 or greater
* Chronic, medically stable ( \> 3 months) unilateral trans-tibial or trans-femoral amputation at the time of implant surgery.
* Potential user of trans-tibial or trans-femoral prostheses for standing or walking
* Viable target nerves in the lower extremity as determined by standard-of-care clinical tests of nerve conduction, response to stimulation, sensory evoked potentials and the like
* Good skin integrity and personal hygiene
* Absence of autoimmune deficiencies, seizure disorders or cardiac abnormalities contraindicating stimulation
* Sufficient social support and personal ability to tolerate study procedures and comply with follow-up schedule

Exclusion Criteria:

* Uncontrolled diabetes to a degree that would preclude surgery
* Significant vascular disease
* Chronic skin ulcerations
* Significant history of poor wound healing
* Significant history of uncontrolled infections
* Active infection
* Significant pain in the residual or phantom limb
* Pregnancy
* Inability to speak English
* Expectation that MRI will be required at any point for the duration of study or while percutaneous leads are in place
* Severe neurological conditions that significantly impair balance or mobility to an extent that independent ambulation is impossible without assistance ( as determined by a healthcare provider)
* Appropriate body habitus (height and weight within acceptable limits as determined by study physician)
* Poor surgical candidate
* Psychiatric or cognitive conditions that could affect cooperation or understanding of instructions and willingness to undergo psychological evaluation, if recommended by study surgeons or investigators.