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| Ultrasound Innovation Award |
| Online Abstract Submission |
| (Author: Jens Krombach ) |
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| Abstract |
| Type: New block technique |
| Title: Sonograhpy for the Saphenous Nerve Block Into the Adductor Canal |
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| Disclosure Statements |
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My research & development of my invention is not supported by a commercial company |
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| Abstract |
| Combined popliteal and saphenous nerve blocks (CPSNB) can provide excellent surgical anesthesia for almost any procedure below the knee without impairing disposition of ambulatory surgery patients.
Ultrasound guiding techniques have had mixed impact on improving facilitation and anesthetic reliability of CPSNB. In contrast to the easy identifiable popliteal nerves, the saphenous nerve is very small and often not clearly distinguishable. However, the saphenous nerve block is essential for complete anesthesia of the foot and ankle. We want to present our 2-year experience with an innovative approach of the ultrasound guided saphenous block (USSB).
With or without ultrasound guidance, the saphenous nerve block is commonly performed within the subcutaneous tissue on the medial side of the lower leg. The saphenous vein can be identified at the level of the tibial tuberosity for paravenous injection.1,2 However, there are several limitations to this approach. First, at this level the saphenous nerve is usually not visible with ultrasound imaging and therefore the block procedure relies on other landmarks. Second, in many patients multiple veins are present to make identification of the saphenous vein difficult. Third, at the level of the tibial tuberosity the saphenous nerve often branched, making incomplete block likely.
The course of the saphenous nerve in the thigh is more consistent. The nerve travels through the adductor (aka Hunter’s) canal, to finally pierce the fascia to join the saphenous vein within the subcutaneous tissue.3
To scan the medial thigh for this approach, the probe is placed perpendicular to the long axis of the extremity, starting 5-7 cm proximal to the popliteal crease. The probe is slid proximally until the typical “T” shaped image of the adductor canal is obtained, with the intersection forming a small triangle. The horizontal line forming the “T” corresponds to the vastoadductor membrane and the investing fascia of the vastus medialis. The vertical line represents the Hunter’s canal. In some subjects, the saphenous nerve can be imaged as it ascends within the adductor canal, ultimately piercing the vastoadductor membrane.
A 22 gauge, 5 cm needle is used for in-plane approach from the anterior aspect of the thigh. Ideally, the needle targets the small triangle of the “T” as described. A total of 10 mL of injected local anesthetic is seen to track vertically down the Hunter’s canal, usually expanding the canal in a “football” shape (Video). Because of the relatively thick fascias of the Hunter’s canal, the local anesthetic spreads usually 12-15 cm within the canal in a proximal and distal fashion and does not redistribute quickly within the surrounding tissue. We believe that both of these consistent observations are responsible for a high success rate despite the saphenous nerve usually not being visible.
Jens Krombach, MD
Andrew T. Gray, MD, PhD
Holger Bauman, MD
Video. The video initially demonstrates the changing anatomy of the Hunter’s canal of the left thigh, moving from distally from about 5 cm above the patella to the mid-thigh. Following the anatomical scan, a needle is inserted in an in-plane approach from the anterior side. It targets the small triangle of the “T” shape as described in the abstract and injects 2 ml of local anesthetics. Re-directing the needle towards the base of the small triangle, the remaining 8ml of local anesthetic spread down the Hunter’s canal.
The last sequence demonstrates the approximately 14cm proximal-distal spread of the local anesthetic within the Hunter’s canal.
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| Clinical Significance |
| We used this approach in more than 200 patients successfully and have significant higher success rates in blocking the saphenous nerve as a surgical and postoperative nerve block, compared to the standard approach. We believe the higher success rate is based on the following:
1.Consistent anatomy on the level of the Hunter’s Canal
2.Anatomic landmarks easy to identify
3.Spread of the local anesthetic within the Hunter’s canal ensures local anesthetic exposure of the saphenous nerve
4.While the branching of the saphenous nerve below the knee might impare the quality of the block, our approach within the Hunter’s canal appears to consistently block the entire sensory area of the saphenous nerve.
Controlled trials will be needed to compare this approach to other methods for saphenous nerve block.
5.The block distributions have included the infrapatellar nerve territory, which is expected because of the proximity of the two nerves at this level. Therefor our new approach was highly successful for perioperative pain managment of below knee amputations of the proximal lower leg
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| Ultrasound Equipment |
| Manufacturer: Philips |
| Model: IU 22 |
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| Probe Used |
| Type: Linear |
| Size: 50 mm |
| Frequency: 12-5 MHz |
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| Files |
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1. Filename: hc01_12_Lg_Prog_TOTAL.mov
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