- Surgery on the knee, calf, achilles tendon, foot, ankle.
- Post operatively for posterior knee pain following surgery
Medial: Semitendinosus and Semimembranosus muscles
Lateral: Long/Short head of Biceps Femoris
There are many approaches to block the sciatic nerve. Using ultrasound, both the popliteal and subgluteal approach are common. Using nerve stimulator, lateral and lithotomy approaches can be used. For now, only the popliteal approach will be described.
- Benefits to this particular approach:
- Able to identify the sciatic nerve at it’s most shallow position
- 1. Place the probe in the popliteal crease in the back of the knee and you should first see three circular structures lined up vertically. The first structure, more echogenic in appearance should be the tibial component to the sciatic nerve. The second structure is the popliteal vein and the third is the popliteal artery.
- 2. Move the probe more cephalad. The common peroneal component will come into view more laterally and the tibial component will move more medially. The popliteal vein and artery should remain in between these two structures. The medial side should reveal the semitendinosus/semimembranosus muscles and the lateral side should reveal the long and short head of the biceps femoris
- 3. Move up even more cephalad until these two nerves come together and form the sciatic nerve.
- 4. Measure the depth that the sciatic nerve is located from the surface of the ultrasound. Then make your skin wheal approximately at a similar distance from the top of the ultrasound probe. This should allow you to insert your needle in a plane which is relatively horizontal to the structure of interest and allow you to maintain great visualization of your needle.
Usual amount of local anesthetic used for this type of block is 20-30cc’s
Typical onset of a sciatic nerve block with ropivicaine/bupivicaine can at times, take up to 30 minutes.
Optimal Ultrasound Probe
The linear Probe allows you to see structures well in a shallow plane but also has a wide field of view so that needle can be viewed.