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.