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The use of lumbar or sacral plexus blockade for lower extremity surgeries has not been commonplace until recently. This is because these techniques were thought to be difficult to perform and resulted in frequent failure to accomplish surgical anesthesia.1–3 Dogliotti4 pointed out, “the nerve trunks of the lumbar plexus which run into the inferior extremity are at a great distance from each other, so much so that in order to produce anesthesia, multiple procedures are necessary with separate injections, for each nerve trunk.” Hence, anesthesiologists preferred the quicker and more effective techniques of spinal or epidural anesthesia for most patients. Several variations of the original technique have been proposed, with the main differences being in the level of blockade and the distance from the midline for the needle insertion.4–6 However, given the deep location of the lumbar plexus, various approaches often represent minuscule technical variations rather than clinically relevant modifications. For instance, Chayen's approach is thought to result in too high of an incidence of epidural blockade.7 However, newly proposed techniques have also resulted in a 15% incidence of epidural blockade.8 More recently, ultrasound-guided lumbar plexus block technique has been suggested; unfortunately this requires substantial ultrasonographic skill, and adequate images are difficult to obtain in many patients.9 Regardless of which technique is followed, safety precautions must be used for successful and safe use of this technique.

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Indications

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Lumbar plexus block has been used for a number of lower extremity procedures. It has been shown to be particularly useful for femoral shaft and neck fractures, knee procedures, and procedures involving the anterior thigh.1,10–12 Lumbar plexus block alone cannot provide adequate anesthesia for major surgery of the lower extremity because of the contributing innervation by the sciatic nerve. Even when combined lumbar plexus–sciatic blocks are used for anesthesia in patients undergoing total knee arthroplasty, conversion to general anesthesia may be required in up to 22% of the time.13

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Regional Anesthesia Anatomy & Management

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The lumbar plexus consists of six nerves on each side, the first of which emerges between the first and second lumbar vertebrae and the last between the last lumbar vertebra and the base of the sacrum. As soon as the L2, L3, and L4 roots of the lumbar plexus depart from their spinal nerves and emerge from the intervertebral foramina, they become embedded in the psoas major muscle14 (Figure 33–1). This is because the psoas is attached to the lateral surfaces and transverse processes of the lumbar vertebrae. Within the muscle, these roots then split into anterior and posterior divisions, which reunite to form the individual branches (nerves) of the plexus.15 The major branches of the lumbar plexus are the genitofemoral nerve, lateral femoral cutaneous nerve, femoral, and obturator nerves (Figure 33–2). Within the psoas major muscle, the lateral femoral cutaneous and femoral nerves are separated ...

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