Regenerative Peripheral Nerve Interface (RPNI) Surgery for Mitigation of Neuroma and Postamputation Pain.

Ask the patient preoperatively to point at the site of maximal tenderness, as this can serve as a guide for where the symptomatic neuroma may be located. The incision can be made either through the previous site of the amputation or directly over the site of maximal tenderness longitudinally. The pitfall of incising directly over the site is creating another incision with its attendant risk of wound infection.Excise the terminal neuroma with a knife until healthy-appearing axons are visualized.The free nonvascularized skeletal muscle graft can be obtained from local muscle (preferred) or from a separate donor site. A separate donor site can introduce donor-site morbidity and complications, including hematoma and pain.The harvested skeletal muscle graft should ideally be approximately 35 mm long, 20 mm wide, and 5 mm thick in order to ensure survivability and to prevent central necrosis. The harvesting can be performed with curved Mayo scissors.The peripheral nerve should be implanted parallel to the direction of the muscle fibers, and the epineurium should be secured to the free muscle graft at 1 or 2 places. One suture should be utilized to tack the distal end of the epineurium to the middle of the bed of the muscle graft. Another suture should be utilized to start the wrapping of the muscle graft around the nerve using a bite through the muscle, a bite through the epineurium of the proximal end of the nerve, and another bite through the other muscle edge in order to form a cylindrical wrap around the nerve.Wrap the entire muscle graft by taking only bites of muscle graft around the nerve to secure the muscle graft in a cylindrical structure using 2 to 4 more sutures.Avoid locating the RPNI near weight-bearing surfaces of the residual limb when closing. The RPNI should be in the muscular tissue, deep to the subcutaneous tissue and dermis.Do perform intraneural dissection for large-caliber nerves to create several (normally 2 to 4) distinct RPNIs, to avoid too many regenerating axons in a single free muscle graft.