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Interfascial Spread of Injectate After Adductor Canal Injection in Fresh Human Cadavers

Goffin, Pierre MD*; Lecoq, Jean-Pierre MD*; Ninane, Vincent MD; Brichant, Jean Francois MD, PhD*; Sala-Blanch, Xavi MD, PhD; Gautier, Philippe E. MD§; Bonnet, Pierre MD, PhD; Carlier, Alain MD; Hadzic, Admir MD, PhD

doi: 10.1213/ANE.0000000000001441
Regional Anesthesia and Acute Pain Medicine
Free

The adductor canal block has become a common analgesic technique in patients undergoing knee arthroplasty. Dispersion of local anesthetic outside the adductor canal through interfascial layers and blockade of smaller nerves that confer innervation to the knee could contribute to the analgesic efficacy of the adductor canal block. We studied the diffusion of local anesthetic mixed with dye after injection into the adductor canal in fresh human cadavers. In all 8 legs, injectate was found in the popliteal fossa in contact with the sciatic nerve and/or popliteal blood vessels. Interfascial spread patterns were identified.

From the *Department of Anesthesia and Intensive Care Medicine, Liege University Hospital, Liege, Belgium; Department of Anesthesia and Intensive Care Medicine, Hospital Saint-Joseph, Liege, Belgium; Department of Anesthesiology, Hospital Clinic, University of Barcelona, Barcelona, Spain; §Department of Anesthesiology, Clinique Ste Anne-St Remi, CHIREC, Brussels, Belgium; Department of Anatomy, Liege University Hospital, Liege, Belgium; and Department of Anesthesiology, Critical Care and Multidisciplinary Pain Center, Ziekenhuis Oost-Limburg, Genk, Belgium.

Admir Hadzic, MD, PhD, is currently affiliated with the New York School of Regional Anesthesia, New York, New York.

Accepted for publication May 6, 2016.

Funding: Department of Anesthesiology, Clinique Ste Anne-St Remi, Brussels, Belgium.

Conflict of Interest: See Disclosures at the end of the article.

Reprints will not be available from the authors.

Address correspondence to Admir Hadzic, MD, PhD, 2753 Broadway, Suite 183, New York, NY 10025. Address e-mail to admir@nysora.com.

Although adductor canal blockade has become a common method to provide analgesia after knee surgery, its mechanism of action is somewhat controversial.1–3 The adductor canal begins at the apex of the femoral triangle and ends at the adductor hiatus, where the femoral artery becomes the popliteal artery. This intermuscular tunnel is triangular in cross section, lies posterior to the sartorius muscle, and may serve as a passageway for the neurovascular bundle from the femoral triangle to the popliteal fossa, being in anatomic continuity with these 2 compartments.4 Depending on level, the canal may contain femoral artery and vein, saphenous nerve and branches to the vastus medialis muscle, and branches of the posterior obturator nerve and of the medial retinacular nerve (a branch of the common peroneal nerve).5 It is possible that the reported analgesic efficacy of the adductor canal block in patients undergoing knee arthroplasty could be contributed, at least in part, by interfascial spread of injectate to smaller nerves outside the adductor canal that innervate the knee. For instance, proximal spread of injectate over the anterior surface of the vastus medialis muscle and unexpected femoral nerve block have been reported.6,7 Local anesthetic injected into the adductor canal may also spread into the popliteal fossa.8 In this report, we describe the diffusion patterns of a dye-containing solution of local anesthetic after injection into the adductor canal in fresh human cadavers.

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METHODS

After local ethics approval by the Comité d’Ethique Hospitalo-Facultaire Université de Liège, 8 limbs of fresh cadavers, kept at 4°C and free of obvious pathology, were studied. To facilitate recognition of the femoral artery, an embolectomy catheter (Edwards Lifesciences Corp, Irvine, CA) was introduced into the lumen of the femoral artery at the groin and advanced to the level of the adductor canal. The adductor canal was imaged on traverse ultrasound view in the distal third of the thigh. After insertion of the needle (in-plane) with a posteromedial to anterolateral direction around the artery into the adductor canal, 20 mL 0.2% ropivacaine with 0.01% methylene blue was injected with the needle tip next to the femoral artery. Injections were made just above the level where the artery changed course deeper and posterior toward the popliteal fossa. The injections were administered with a hand-held syringe, and injection speed was approximately 20 mL/min, as in clinical practice. After all cadavers were injected, they were placed in the prone position, and the popliteal fossa was dissected. Careful dissection of the tissue sheaths, adductor magnus, and hiatus between femoral bone and adductor muscle was performed to explore the interfascial spread of the methylene blue–containing solution. The cadavers were kept at room temperature. Data are presented descriptively.

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RESULTS

Table.

Table.

Figure 1.

Figure 1.

Figure 2.

Figure 2.

Dispersion and anatomical location of dye are shown in the Table. Methylene blue was found in the popliteal fossa in contact with the sciatic nerve in all 8 legs (Figure 1). Dye was found on the anterior and posterior aspects of the adductor magnus muscle, indicating that circumferential fascial spread had occurred underneath the adductor muscle fascia and into the popliteal fossa (Figure 2). In 5 legs, the dye tracked proximally above the level at which the tibial and common peroneal nerves diverged. In 3 legs, the dye traveled through the inferior hiatus containing the popliteal vessels; and in 2 legs, the dye was found passing through the accessory hiatus between the femur and adductor magnus muscle.

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DISCUSSION

Our study in fresh human cadavers demonstrated that an injection into the adductor canal may result in interfascial spread of injectate outside the adductor canal toward the popliteal fossa. Substantial spread of injectate from the adductor canal into the popliteal fossa may affect various nerves that travel in those tissue sheaths and can help to explain the reported analgesic benefits of the adductor canal block in living patients. These observations are consistent with our previous report in which injectate was found on computed tomographic images in the popliteal fossa in the vicinity of the sciatic nerve and resulted in sensory block of the popliteal sciatic nerve.8 Future studies are indicated to determine the extent and patterns of neural blockade in patients undergoing knee surgery with adductor canal block.

In summary, injection of local anesthetic into the adductor canal in fresh human cadavers results in spread into the popliteal fossa through interfascial planes. Dispersion of injectate through these fascial planes may offer additional insight into the mechanism(s) of analgesia for knee surgery.

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DISCLOSURES

Name: Pierre Goffin, MD.

Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.

Conflicts of Interest: Pierre Goffin declares no conflicts of interest.

Name: Jean-Pierre Lecoq, MD.

Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.

Conflicts of Interest: Jean-Pierre Lecoq declares no conflicts of interest.

Name: Vincent Ninane, MD.

Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.

Conflicts of Interest: Vincent Ninane declares no conflicts of interest.

Name: Jean Francois Brichant, MD, PhD.

Contribution: This author helped design the study and write the manuscript.

Conflicts of Interest: Jean Francois Brichant declares no conflicts of interest.

Name: Xavi Sala-Blanch, MD, PhD.

Contribution: This author helped perform the cryodissection and discuss the paper.

Conflicts of Interest: Xavi Sala-Blanch declares no conflicts of interest.

Name: Philippe E. Gautier, MD.

Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.

Conflicts of Interest: Philippe E. Gautier declares no conflicts of interest.

Name: Pierre Bonnet, MD, PhD.

Contribution: This author helped with the dissection procedure.

Conflicts of Interest: Pierre Bonnet declares no conflicts of interest.

Name: Alain Carlier, MD.

Contribution: This author performed the dissections.

Conflicts of Interest: Alain Carlier delcares no conflicts of interest.

Name: Admir Hadzic, MD, PhD.

Contribution: This author helped write the manuscript and interpret the data.

Conflicts of Interest: Admir Hadzic has consulted and advised for Skyepharma, GE, Sonosite, Codman & Shurtleff, Inc (Johnson & Johnson), Cadence, Pacira, Baxter, and B. Braun Medical. His recent industry-sponsored research includes Glaxo Smith-Kline Industries, Pacira, and Baxter. He receives royalty income from B. Braun Medical.

This manuscript was handled by: Richard Brull, MD, FRCPC.

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REFERENCES

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