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TRANSGLUTEAL (POSTERIOR) APPROACH

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  • Indications: surgery on the knee, tibia, ankle, and foot
  • Landmarks: greater trochanter, superior posterior iliac spine, and the midline between the two
  • Nerve stimulation: twitch of the hamstring, calf, foot, or toes at 0.2–0.5 mA current
  • Local anesthetic: 15–20 mL

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ANTERIOR APPROACH

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  • Indications: surgery on the knee, tibia, fibula, ankle, and foot
  • Landmarks: femoral crease, femoral artery
  • Nerve stimulation: twitch of the foot or toes at 0.2–0.5 mA
  • Local anesthetic: 15–20 mL

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Figure 19.1-1.
Graphic Jump LocationGraphic Jump Location

(A) Needle insertion for the transgluteal (posterior) approach to sciatic nerve block. (B) Needle insertion for anterior sciatic block.

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General Considerations

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The posterior approach to sciatic nerve block has wide clinical applicability for surgery and pain management of the lower extremity. Consequently, a sciatic block is one of the more commonly used techniques in our practice. In contrast to a common belief, this block is relatively easy to perform and associated with a high success rate. It is particularly well-suited for surgery on the knee, calf, Achilles tendon, ankle, and foot. It provides complete anesthesia of the leg below the knee with the exception of the medial strip of skin, which is innervated by the saphenous nerve. When combined with a femoral nerve or lumbar plexus block, anesthesia of the entire lower extremity can be achieved.

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Functional Anatomy

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The sciatic nerve is formed from the L4 through S3 roots. These roots form the sacral plexus on the anterior surface of the lateral sacrum and converge to become the sciatic nerve on the anterior surface of the piriformis muscle. The sciatic nerve is the largest nerve in the body and measures nearly 2 cm in breadth at its origin. The course of the nerve can be estimated by drawing a line on the back of the thigh beginning from the apex of the popliteal fossa to the midpoint of the line joining the ischial tuberosity to the apex of the greater trochanter. The sciatic nerve also gives off numerous articular (hip, knee) and muscular branches.

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The sciatic nerve exits the pelvis through the greater sciatic foramen below the piriformis and descends between the greater trochanter of the femur and the ischial tuberosity, superficial to the external rotators of the hip (obturator internus, the gemelli muscles, and quadratus femoris) (Figures 19.1-2 and 19.1-3). On its medial side, the sciatic nerve is accompanied by the posterior cutaneous nerve of the thigh and the inferior gluteal artery. The articular branches of the sciatic nerve arise from the upper part of the nerve and supply the hip joint by perforating the posterior part of its capsule. Occasionally, these branches are derived directly from the sacral plexus. The ...

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