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  • Indications: ankle and foot surgery
  • Landmarks for intertendinous approach: popliteal fossa crease, tendons of the semitendinosus and semimembranosus muscles
  • Landmarks for lateral approach: popliteal fossa crease, vastus lateralis, and biceps femoris muscles
  • Nerve stimulation: twitch of the foot or toes at 0.2–0.5 mA
  • Local anesthetic: 30–40 mL

Figure 20.1-1.

(A) Needle insertion for the popliteal intertendinous approach. (B) Needle insertion for lateral approach to popliteal block.

General Considerations

The popliteal block is a block of the sciatic nerve at the level of the popliteal fossa. This block is one of the most useful blocks in our practice. Common indications include corrective foot surgery, foot debridement, and Achilles tendon repair. A sound knowledge of the principles of nerve stimulation and the anatomic characteristics of the connective tissue sheaths of the sciatic nerve in the popliteal fossa are essential for its successful implementation.

Functional Anatomy

The sciatic nerve is a nerve bundle consisting of two separate nerve trunks, the tibial and the common peroneal nerves (Figure 20.1-2). A common epineural sheath envelops these two nerves at their outset in pelvis. As the sciatic nerve descends toward the knee, the two components eventually diverge in the popliteal fossa to continue their paths separately as the tibial and the common peroneal nerves. This division of the sciatic nerve usually occurs between 4 and 10 cm proximal to the popliteal fossa crease. From its divergence from the sciatic nerve, the common peroneal nerve continues its path downward and laterally, descending along the head and neck of the fibula, Figure 20.1-2. Its major branches in this region are branches to the knee joint and cutaneous branches to the sural nerve. Its terminal branches are the superficial and deep peroneal nerves. The tibial nerve is the larger of the two divisions of the sciatic nerve. It continues its path vertically through the popliteal fossa, and its terminal branches are the medial and lateral plantar nerves, Figure 20.1-2. Its collateral branches give rise to the medial cutaneous sural nerve, muscular branches to the muscles of the calf, and articular branches to the ankle joint. It is important to note that the sciatic nerve in the popliteal fossa is lateral and superficial to the popliteal artery and vein, and it is contained in its own tissue (epineural) sheath rather than in a common neurovascular tissue sheath. This anatomic characteristic explains the relatively low risk of systemic toxicity and vascular punctures with a popliteal block (Figure 20.1-3). However, the proximity of the large vessels, popliteal artery, and vein still makes it imperative to carefully rule out an intravascular needle placement by careful aspiration and meticulously slow injection (e.g., ≤20 mL/min).

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