Pain in the Residual Limb
After amputation, the residual limb may be painful. Causes include
Deep tissue infection (eg, osteomyelitis, vascular graft infection)
Pressure points with or without skin breakdown
Skin infection and breakdown have clear, visible manifestations and should be dealt with. Deep infection may be more difficult to diagnose because focal swelling and erythema may not become apparent until pain has been present for some time; systemic manifestations such as fever or tachycardia may appear first and should not be ignored. Painful neuroma can occur in any severed nerve (from surgery or trauma) and may cause focal pain that can be temporarily blocked (as a diagnostic maneuver) by local anesthetic injection. Patients whose amputation was necessitated by ischemic vascular disease are at risk for further ischemia, which can be difficult to diagnose but may be suggested by a very low transcutaneous O2 tension (< 20 mmHg) on the skin of the distal limb. Phantom limb pain should be considered when more medically urgent causes have been excluded.
If there is no medical disorder causing the pain, massaging the residual limb sometimes relieves the pain. If massaging is ineffective, analgesics can be used. Typically, NSAIDs or acetaminophen is used, but sometimes opioid analgesics are required. If these measures do not relieve the pain or patients require prolonged opioid therapy, consultation with a pain management specialist may be required to supervise treatment, which may include using mechanical devices (eg, a vibrator), ultrasound, and drugs such as antidepressants (eg, nortriptyline, desipramine) and anticonvulsants (eg, gabapentin).
Sometimes pain is felt in other limbs or in the hips, spine, shoulders, or neck. This pain may occur because wearing a prosthesis makes patients change their gait or body alignment or causes them to repeat movements. Regularly doing specific stretching and strengthening exercises may help prevent or relieve this type of pain. A physical therapist can help design an appropriate exercise program.
Many patients experience phantom pain at some time. The phantom aspect is not the pain, which is real, but the location of the pain—in a limb that has been amputated. Phantom pain is more likely if the pain before amputation was severe or lasted a long time. In some cases, the pain can be severe depending on the mechanism of amputation (eg, traumatic amputation vs elective surgical removal).
Phantom pain is often more severe soon after the amputation, then decreases over time. Postsurgical desensitizing therapies are available and recommended to reduce pain during initial weight-bearing in the prosthesis. For many patients, phantom pain is more common when the prosthesis is not being worn (because the limb and interface have no contact), for example, at night. The risk of having this pain is reduced if a spinal anesthetic and a general anesthetic are used during surgery.
There are a number of other, nonpharmacologic therapies that may be added to the treatment plan, among them transcutaneous electrical nerve stimulation (TENS), acupuncture, and spinal cord stimulation.
Most patients experience phantom sensation, which feels as though the amputated limb is still there. Phantom sensation can be painful during the immediate postoperative period. However, the pain tends to disappear for most amputees. Phantom sensation with new amputees can be a problem, especially at night when they have to go to the bathroom, and believing their limb is still there, do not remember to don their prosthesis. Many prosthetists recommend that a protective device be worn while sleeping, to protect the amputee from injury.