Feasibility of Neural Feedback for Lower Limb Amputees

Inclusion Criteria:

* Adults age 18 or greater
* Chronic, medically stable ( \> 3 months) 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.