Regenerative Peripheral Nerve Interface: Surgical Protocol for a Randomized Controlled Trial in Postamputation Pain

We're investigating surgical procedures to treat pain after limb amputation, that is residual limb pain and phantom limb pain. In particular, we aim to produce high-quality scientific evidence on the efficacy of surgical procedures in which nerves are given new muscular targets to avoid the formation of neuromas and pain. The reasons for limb amputation are diverse and these often happen unplanned, as in the case of traumatic injuries.

These result in a wide difference in the anatomy of residual limbs. Such variability poses challenges to the standardization of surgical procedures. Nevertheless, in this research, we have achieved a common surgical technique in consensus with experienced surgeons worldwide.

This protocol provides a standardized method to perform the Regenerative Peripheral Nerve Interface Technique, which was agreed upon by a large consortium of experienced surgeons. This standardization will minimize bias in our randomized control trial and will allow the procedure to be used and implemented in other clinics conducting amputational care. To begin, position the subject arm, depending on the side of the painful neuroma and plan for the skin incisions.

Make a skin incision on the painful neuroma site. Using blunt dissection, identify the nerve with the painful neuroma. Gently isolate the nerve and the neuroma with fine instruments.

Using a commercial nerve cutting preparation set or a sharp scaffold, mobilize the nerve and transect the neuroma up to the healthy neural fascicles. Now, with straight micro scissors, perform longitudinal intraneural dissections from the distal end of the nerve, for approximately two to three centimeters. Prepare the neural fascicles, depending on the amputation level and the size of the nerve.

After identifying a healthy native donor muscle, make a skin incision over the muscle and use dissecting scissors to dissect the muscle graft along the main axis of the muscle fibers. Gently excise adipose tissue and the muscle fascia from the muscle graft. Keep the harvested muscle in a moist gauze, soaked in a sterile 0.9%sodium chloride solution until use.

Expose the nerve previously isolated and divided into fascicles. Position the fascicle on the muscle graft, ensuring the distal stump is in the central or proximal third of the graft and parallel to the muscle fibers. Using 60 non-resorbable monofilament sutures, secure the nerve stump in the center of the longitudinal axis of the muscle graft.

Place an additional stitch at the proximal edge of the muscle graft. Fold the muscle graft around the fascicle and secure it with a 60 interrupted or continuous non-resorbable monofilament suture. Similarly, suture the other muscle grafts around the nerve.

Perform blunt dissection in the residual limb to provide a protected area where each RPNI can lie comfortably in out of the way bearing surfaces of the limb. Then offset the location of each RPNI in series. Finally, close the surgical wounds in layers.