To cut and ligate a common peroneal and sural nerves with intact tibial nerve, defined as SNIt, has much less motor deficit with a shorter learning curve. The modified mouse SNIt surgery procedure was developed to ligate the common peroneal and sural nerves together with only one nerve ligation and one nerve cutting, which results in shortened procedure time. To begin, place the mouse in a right lateral position.
Keep the left leg up with knee flexion, and secure it with adhesive tape. Remove the hair around the thigh and knee area with an electric shaver and hair removal cream. After placing the mouse on a new sterile surgery towel, disinfect the skin with 2%chlorhexidine and 70%alcohol.
Secure it with adhesive tape. Cut a one centimeter incision starting at one third of the horizontal line, crossing the knee with an approximately 30 degree angle from the vertical line with a scalpel. Two white lines can be visualized under the biceps femoris muscle after separating skin incision with the medial cephalad thick line above the femur and lateral caudal thin line above sciatic nerve.
Blunt dissect the biceps femoris muscle along the caudal white line using curved micro forceps and micro scissors to expose the sciatic nerve. Differentiate the three branches from the sciatic nerve at the superior edge of the gastrocnemius muscle. The tibial nerve has the biggest diameter passing under the gastrocnemius muscle, whereas the sural nerves are lateral and smallest in diameter.
The common peroneal nerve runs above the gastrocnemius muscle. Depending on how the biceps femoris muscle is dissected and opened, visualize the common peroneal nerve as lateral or medial to the tibial nerve. Then separate the common peroneal and the sural nerves from the neighboring tissues using curved micro forceps.
Ligate the common peroneal and sural nerves together with a 6/0 suture. Both nerves run above the gastrocnemius muscle, but the tibial nerve passes under the gastrocnemius muscle. Observe the limb for contraction following the tight ligature.
Cut nerve at a distal part within two to four millimeters of the ligation with a pair of micro scissors. Ensure that the tibial nerve remains untouched during the whole procedure. Close the muscular layer with a 6/0 silk suture and close the skin incision with wound clips.
The results show that the modified approach took almost half the amount of procedure time to perform SNlt compared with the control of the traditional approach. No difference in Von Frey assessment was observed in the two groups at baseline. The traditional method and the modified method induced similar mechanical hypersensitivity on the ipsilateral side from postoperative day one to postoperative day 14.
The percentage response between traditional and modified methods showed similar mechanical hypersensitivity on the ipsilateral side from baseline. Easy and rapid exposure of the sciatic nerve, accurate identification of the common peroneal, tibial, and sural nerves, cutting and ligation of the common peroneal and sural nerves are the three critical steps in this protocol. The method was successfully developed to mimic peripheral nerve injury cardio symptoms and randomized to study the molecular and cellular mechanism of neuropathic pain.
