Use of this content is subject to the Terms and Conditions of the MD Consult web site.
Brown: Atlas of Regional Anesthesia, 3rd ed., Copyright © 2006 Saunders, An Imprint of Elsevier
< Previous Next >

PLACEMENT

Anatomy.

As illustrated in Figure 16-1 , the cephalad popliteal fossa is defined by the semimembranosus and semitendinosus muscles medially and the biceps femoris muscle laterally. Its caudad extent is defined by the gastrocnemius muscles both medially and laterally. If this quadrilateral area is bisected, as shown in Figure 16-1 , the area of interest to the anesthesiologist is the cephalolateral quadrant. Here, both tibial and common peroneal nerve block is possible. The tibial nerve is the larger of these two nerves; it separates from the common peroneal nerve at the upper limit of the popliteal fossa and sometimes higher. The tibial nerve continues the straight course of the sciatic nerve and runs lengthwise through the popliteal fossa immediately under the popliteal fascia. Inferiorly, it passes between the heads of the gastrocnemius muscles. The common peroneal nerve follows the tendon of the biceps femoris muscle along the cephalad lateral margin of the popliteal fossa, as illustrated in Figure 16-2 . After the common peroneal nerve leaves the popliteal fossa, it travels around the head of the fibula and divides into the superficial peroneal and deep peroneal nerves.

Click to view full size figure

Figure 16-1  Popliteal fossa: surface anatomy and technique of the popliteal block.


Click to view full size figure

Figure 16-2  Popliteal fossa: neural anatomy.


Position.

The patient is placed in a prone position, and the anesthesiologist stands at the patient’s side to allow palpation of the borders of the popliteal fossa.

Needle Puncture.

With the patient in the prone position, the patient is asked to flex the leg at the knee, which allows more accurate identification of the popliteal fossa. Once the popliteal fossa has been defined, it is divided into equal medial and lateral triangles, as shown in Figure 16-1 . An X is placed 5 to 7 cm superior to the skin crease of the popliteal fossa and 1 cm lateral to the midline of the triangles, as shown in Figure 16-1 . Through this site, a 22-gauge, 4- to 6-cm needle is advanced at an angle of 45 to 60 degrees to the skin while the needle is directed anterosuperiorly ( Fig. 16-3 ). A paresthesia or motor response is sought; when it is obtained, 30 to 40 mL of local anesthetic is injected.

Click to view full size figure

Figure 16-3  Popliteal fossa: technique of the popliteal block.


When adding a saphenous block to the technique for foot and ankle surgery, the patient’s knee is bent at an approximately 45-degree angle, and the medial aspect of the leg is exposed. Two primary techniques are used for saphenous block. A superficial ring of local anesthetic may be injected just distal to the medial surface of the tibial condyle, often requiring 5 to 10 mL of local anesthetic. Conversely, a more proximal technique (at the cross-sectional level of the superior border of the patella) is possible ( Fig. 16-4 ). In this case, a 22- to 25-gauge, 3- to 4-cm needle is inserted immediately deep to the sartorius muscle in the plane between the vastus medialis and the sartorius muscles, and 10 mL of local anesthetic is injected.

Click to view full size figure

Figure 16-4  Saphenous nerve block: anatomy and proximal technique.


Potential Problems.

Although vascular structures also occupy the popliteal fossa, intravascular injection should be an infrequent occurrence if the usual precautions are carried out. Hematoma formation is possible.

< Previous Next >

About MD Consult Contact Us Terms and Conditions Privacy Policy Registered User Agreement
Copyright © 2007 Elsevier Inc. All rights reserved. www.mdconsult.com 
Bookmark URL: /das/book/0/view/1353/47.html/top