Regenerative Peripheral Nerve Interfaces for the Treatment of Postamputation Neuroma Pain: A Pilot Study

Abstract

Background:Originally designed for prosthetic control, regenerative peripheral nerve interfaces (RPNIs) prevent neuroma formation by providing free muscle grafts as physiological targets for peripheral nerve ingrowth. We report the first series of patients undergoing RPNI implantation for treatment of symptomatic postamputation neuromas.Methods:A retrospective case series of all amputees undergoing RPNI implantation for treatment of symptomatic neuromas between November 2013 and June 2015 is presented. Data were obtained via chart review and phone interviews using questions derived from the Patient Reported Outcomes Measurement Information System instruments. Statistical analyses were performed using dependent sample t tests with a significance threshold of P < 0.01.Results:Forty-six RPNIs were implanted into 16 amputees for neuroma relief (3 upper extremities and 14 lower extremities). Mean age was 53.5 years (6 females and 10 males). All patients participated in postoperative phone interviews at 7.5 ± 3.4 (range: 3–15) months. Patients reported a 71% reduction in neuroma pain and a 53% reduction in phantom pain. Most patients felt satisfied or highly satisfied with RPNI surgery (75%), reporting decreased (56%) or stable (44%) levels of analgesic use. Most patients would strongly recommend RPNI surgery to a friend (88%) and would do it again if given the option (94%). Complications included delayed wound healing (n = 4) and neuroma pain at a different site (n = 2).Conclusions:RPNI implantation carries a reasonable complication profile while offering a simple, effective treatment for symptomatic neuromas. Most patients report a significant reduction in neuroma and phantom pain with a high level of satisfaction. The physiological basis for preventing neuroma recurrence is an intriguing benefit to this approach.

The Role of the Peripheral Nerve Surgeon in the Treatment of Pain

“…Proponents of these techniques suggest that giving the nerve end an active target will improve neuroma outcomes. To date, published literature of the effectiveness of these techniques consists of only very small studies whose outcomes do not differ significantly from other published techniques [5,98,99]. However, we suspect that TMR, which involves an end-to-end coaptation of the cut nerve to a motor branch into muscle on the deep surface of that muscle, essentially transposing the cut nerve end under a muscle, will likely produce better results in amputees than traditional methods of nerve management in amputation stumps (traction neurectomy or suture ligation, both techniques used elsewhere to produce pain in rat pain models [100,101]).…”

Interfaces with the peripheral nervous system for the control of a neuroprosthetic limb: a review

“…In another animal study, RPNIs were combined with intramuscular electrodes and demonstrated the chronic recording capability of this method for up to twenty months [43]. RPNIs have also shown promising results in the treatment of neuroma pain [37]. An important point to consider when RPNIs are going to be utilized with implanted muscle electrodes is the time of electrode placement.…”

“…2 Myoelectric systems. a Surgical plan for the TMR for high amputations [36] b Illustration of RPNI construction [37] electrodes are the least invasive ones. There are four major types of extraneural electrodes: the epineural electrode, the helical electrode, the book electrode, and the cuff electrode.…”

“…After the implantation procedure, fibrous tissue grows around the electrode as part of a foreign body reaction and this is profitable since it stabilizes the electrode. Following this stabilization process, signals from the nerves are both accurate and reproducible [37,45]. These electrodes also affect muscle fiber distribution.…”

Novel Uses of Nerve Transfers

“…Most strategies, until recently, have been associated with mixed results, but generally poor. More recent strategies including Bnerve to nowhere,^regenerative peripheral nerve interfaces, and targeted muscle reinnervation have had more dramatic success in relieving pain and preventing recurrence [57][58][59][60]. Falling into the alternate target reinnervation category is a nerve transfer strategy referred to as targeted muscle reinnervation.…”