Chapter 37

Victor Pauchet first described the sciatic nerve block in L'Anesthésie Régionale in 1920: “the site of needle insertion for blocking the sciatic nerve at the level of hip: 3 cm along the perpendicular that bisects a line drawn between the greater trochanter and the posterior superior iliac spine.”1 Although this technique is referred to as “The classic approach of Labat,” it was in fact first described by Labat's teacher, Pauchet. Perhaps the reason for the name designation comes from the fact that the sciatic nerve block was first described in anesthesia literature in 1923 by Gaston Labat in his book, Regional Anesthesia: Its Technic and Clinical Application.2 Of note, Labat in the same year founded the American Society of Regional Anesthesia (ASRA). Anecdotally, Labat intended to name the new group “the Labat Society” in his honor, but the name ASRA remains today as we know it. Labat's book went through several reprintings of the first edition and was one of the first English language anesthesia textbooks of regional anesthesia in the United States. Curiously, this book was similar to L'Anesthésie Régionale, written by Labat's tutor, Pauchet, from 1918 to 1920 in the University of Paris.

Alon Winnie eventually modified the Labat approach in 1975.3 In 1963, Beck4 described an anterior approach, and, in 1975, Raj proposed a lithotomy approach.4,5 These alternative approaches were devised to allow the sciatic nerve to be blocked in the supine patient. Since its original description, a number of new approaches to sciatic nerve blocks were proposed, most of which include minor modifications of questionable clinical significance. Based on the clinical studies of various approaches, the most useful of these newer techniques appear to be the subgluteal and parasacral approaches introduced by di Benedetto and Mansour, respectively.6–8 Discussion of all described techniques and approaches is beyond the scope of this chapter. Instead, this chapter focuses on the classic approach to sciatic nerve block, parasacral and subgluteal modifications, and the anterior approach.

### Indications & Contraindications

Indications for sciatic nerve block include lower-limb surgery, often combined with a femoral or psoas compartment block.8 For distal surgery of the lower extremity, however, more distal approaches such as ankle block or popliteal sciatic nerve block are preferable when feasible. Note that the sciatic nerve block almost always needs to be combined with supplemental block, which involves components of the lumbar plexus (femoral nerve).

Contraindications to sciatic nerve block are few, and may include local infection and bed sores at the site of insertion, coagulopathy, preexisting central or peripheral nervous systems disorders, and allergy to local anesthetics.

### Functional Anatomy

The union of the lumbosacral trunk with the first three sacral nerves forms the sacral plexus (Figure 37–1). The lumbosacral trunk originates from the anastomosis of the last two lumbar nerves with the anterior branch of the first ...

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