This is a single-center, prospective, within-subject study. This study seeks to enroll a total of 32 prospective subjects who will undergo surgical implantation of the FDA-approved Altius® system. Subjects will be followed longitudinally and will complete a series of patient-reported outcome measure questionnaires, a study intake questionnaire which assesses demographics, amputation and prosthesis history, and medical/medication history.

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)