The purpose of the clinical trial is to learn whether electrical nerve block via the Altius System is a safe and effective treatment for patients with post-amputation pain.

The Altius System is an implanted device designed to electrically block nerve signals and alleviate pain. Use of this device may be associated with providing an effective, mechanism-based yet non-destructive, treatment for managing intractable limb pain in amputees. In a given patient, the Altius System will be deemed effective if treatment results in 50% reduction of pain score for more than 50% of all pain episodes.

Key Inclusion Criteria:

• Age ≥ 21 years old
• Unilateral amputated leg ≥ 12 months
• Chronic post amputation pain ≥ 6 months
• Pain episodes typically lasting ≥ 60 minutes
• Stable drug regimen ≥ 4 weeks
• No changes to medications or prosthesis for 3-month primary study period

Key Exclusion Criteria:

• Implanted with an active implantable medical device (i.e. pacemaker)
• Confounding source of pain that interferes with reporting of limb pain
• Uncontrolled diabetes
• Spasticity preventing full range of motion of involved side
• Extremely short stump; sits on end
• Untreated psychological condition (i.e. borderline personality)
• Condition requiring MRI studies or diathermy after device implant
• Life expectancy of less than 24 months
• Progressive neurological disease (i.e. multiple sclerosis)
• Subjects with active local or systemic infection or immunocompromised