Phantom Limb clinical trials at UCSD

When a limb is amputated, pain perceived in the part of the body that no longer exists often develops, called "phantom limb" pain. The exact reason that phantom limb pain occurs is unclear, but when a nerve is cut-as happens with an amputation-changes occur in the brain and spinal cord that are associated with persistent pain. The negative feedback-loop between the injured limb and the brain can be stopped by putting local anesthetic-called a "nerve block"-on the injured nerve, effectively keeping any "bad signals" from reaching the brain. A "continuous peripheral nerve block" (CPNB) is a technique providing pain relief that involves inserting a tiny tube-smaller than a piece of spaghetti-through the skin and next to the target nerve. Local anesthetic is then introduced through the tiny tube, which bathes the nerve in the numbing medicine. This provides a multiple-day block that provides opioid-free pain control with no systemic side effects, and may prevent the destructive feedback loop that results in phantom limb pain following an amputation. We propose a multicenter, randomized, triple-masked (investigators, subjects, statisticians), placebo-controlled, parallel arm, human-subjects clinical trial to determine if a prolonged, high-concentration (dense), perioperative CPNB improves post-amputation physical and emotional functioning while decreasing opioid consumption, primarily by preventing chronic phantom limb pain.

Pulsed electromagnetic field therapy is a possible method of pain control involving the application of electromagnetic energy (also termed nonthermal, pulsed, shortwave radiofrequency therapy). Food and Drug Administration-cleared devices have been in clinical use for over 70 years. For decades, available devices consisted of a large signal generator and bulky coil applicator that were not portable and produced significant electromagnetic interference, making them impractical for common use. However, small, lightweight, relatively inexpensive, noninvasive, Food and Drug Administration-cleared devices that function for 30 days are now available to treat acute and chronic pain, decrease inflammation and edema, and hasten wound healing and bone regeneration. Therefore, it has the potential to concurrently improve analgesia and decrease or even negate opioid requirements, only without the limitations of opioids and peripheral nerve blocks. The purpose of this pilot study is to explore the possibility of treating chronic post-amputation pain with nonthermal, pulsed shortwave (radiofrequency) therapy, optimize the study protocol, and estimate the treatment effect in preparation for developing subsequent definitive clinical trials.