Functional and Neuroprotective Effects of Restoring Lower Limb Sensation After Diabetic Peripheral Neuropathy

The purpose of this study is to evaluate the effectiveness of providing sensation of the missing limb to individuals with above and below the knee limb loss. The investigators will implanted stimulating electrodes to send small electrical currents to the remaining nerves. These small electrical currents cause the nerves to generate signals that are then transferred to your brain similar to how the information about your foot and lower limb used to be transferred to the brain prior to your limb loss. Additionally, there is the option to have muscle recording electrodes implanted within the muscles of the lower limb with the goal to develop a motor controller that would allow the user to have intuitive control of a robotic prosthetic leg.

Electrodes are surgically implanted on one to four nerves of the residual limb. Intramuscular recording electrodes can be implanted in the lower limbs and hip muscles in order to obtain electromyography (EMG) signals. The EMG recordings will be used to develop an algorithm which can operate an advanced robotic prosthesis in which the prosthesis joint(s) movements could be controlled. An external wearable stimulation device controls the delivery of electrical pulses to the implanted system. An instrumented prosthesis will be developed such that perceived sensations would correspond to prosthesis interactions with the floor. The instrumented prosthesis 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.

Eligibility Criteria:
Inclusion Criteria:

* Chronic, medically stable lower limb amputation due to diabetes or insensate foot due to Diabetic peripheral neuropathy
* Being ambulatory and ability to stand or walk with prosthesis or orthosis
* Viable target nerves in the lower extremity as determined by standard-of-care clinical tests of nerve conduction, response to stimulation, sensory evoked potentials (SEP) 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:

* Active pressure ulcers or chronic skin ulcerations
* Uncontrolled diabetes with HbA1c greater than or equal to 69 mmol/mol (8.5%)
* Significant vascular disease
* Significant history of poor wound healing
* Significant history of uncontrolled infections
* Active infection
* Significant pain in the foot, residual or phantom limb
* Pregnancy
* Inability to speak English: The study design requires the subject to communicate and describe the elicited sensations in their lower limb
* History of vestibular or movement disorders that would compromise balance or walking
* Class II or III obesity (Body Mass Index \> 35)
* Uncontrolled depression, psychoses or cognitive impairments. Subjects with unstable mental illness or severe cognitive impairments may be unable to comply with a long term study schedule
* Expectation that MRI will be required at any point for the duration of study or while percutaneous leads are in place. At this time MRI is contraindicated, subjects who require regular MRI should not enroll
* Arthritis in the area of implant- Inflammation or stiffness in the area of implant could limit placement of the electrodes