To begin, extend the incision on the back of the neck of an anesthetized mouse with a head plate implantation. With a blunt bone scraper, separate the skin under the neck incision from the underlying tissue. Work the scraper under the skin and behind the neck incision to clear a path for the electrodes.
Insert the tip of a large needle driver through the triceps incision and out of the neck incision. Clamp the needle driver around the electrode needle lengthwise, then pull it through to the triceps incision. Next, bend a 27 gauge needle to give it a slight curve.
Hold the needle with the needle driver. Then press it against the handle of a pair of forceps to result in an additional bend of five to 10 degrees. Add three total bends at different positions along the length of the needle.
Next, identify the entry and exit points on the muscle. With a pair of fine forceps, remove any fat in fascia, obscuring the entry and exit site. After submerging three to five millimeters of wire parallel to the muscle fibers, use the needle driver to insert the needle into the proximal end of the muscle.
Now push the needle through the muscle to the exit site. Once the needle exits the muscle, grab the tip with blunt forceps and pull the needle through. With a pair of forceps, tie a loose distal knot at the exit site.
Tighten the knot down to a one centimeter loop. Push the loop with the forceps and position it over the exit site. After identifying the location over which the distal knot is to be closed, gently grasp the loop with a pair of fine bent forceps and pull the loop tight over the forceps.
Remove the fine forceps from the knot. Push the knot toward the exit site with the fine bent forceps, and pull the needle end with fingers to finish tightening it. Use the straight fine forceps to grasp the exit knot, then tightly curl the distal wire around the forceps to bend the wire around the knot and toward the muscle.
Finally, cut the wire off about 0.5 millimeters distal to the distal knot, leaving a small nub curled around the knot. All the implanted electrodes produced a clean electromyographic signal 36 days after implantation. However, after 72 days, the wrist extensor electrode failed.
