Altius Peripheral Nerve Stimulation in Amputees After TMR/RPNI

Inclusion Criteria: * Adults (≥18 years old) * Lower extremity amputees with prior TMR, RPNI at least 9 months prior to enrollment, or similar nerve-targeted surgery who have persistent neuropathic pain * Persistent chronic/intractable neuropathic pain that is moderate to severe (VAS ≥4) * 50% or greater pain reduction after receiving SOC ultrasound-guided lidocaine injection * Able and willing to provide consent Exclusion Criteria: * Non-LE amputees * LE amputees without moderate to significant pain * LE amputees who have not undergone TMR, RPNI, or similar nerve targeted surgeries, amputees who have undergone these surgeries less than 9 months prior to enrollment, or amputees who have undergone these surgeries and do not have persistent pain * Patients with contraindications to implant surgery * Presence of any active implantable device (e.g, pacemaker, implantable cardioverter-defibrillator, other neurostimulator or drug pump) * Anticipated need for MRI or diathermy after implantation * Uncontrolled diabetes, defined as HbA1c \> 8.0 at screening due to increased risk of surgical complications and delayed wound healing * Pregnant, breastfeeding, intending pregnancy during the study period, or unwilling to use effective contraception * Suspected or known allergy to any component of the Altius system or to lidocaine used for the diagnostic lidocaine block. * Severe scarring, skin grafting, or other anatomic constraints over the planned implant site that would prevent safe placement of the cuff electrode(s), lead(s), or IPG * Spasticity of the residual limb preventing comfortable full range of motion, which may interfere with stability or comfort of the implanted leads. * Other significant pain syndromes that, in the investigator's judgment, would likely confound assessment of phantom limb or residual limb neuropathic pain outcomes. * Active substance abuse; severe psychiatric illness that may interfere with study participation (e.g., recent psychiatric hospitalization or other condition that impairs ability to comply with study procedures); or inability to comply with follow up visits or operation of the Altius Direct Electrical Nerve Stimulation System. * Uncontrolled infection at the amputation site or bleeding disorders * Unable to operate the Altius® Direct Electrical Nerve Stimulation System * Unsuitable for the Altius implant surgery * Unable to participate in follow-ups according to study schedule (1 month, 3 months, and 6 months post-op)