Lumbar Plexus Block

Excerpt

The concept of a regional anesthesia technique that provides neural blockade of the entirety of the lumbar plexus, a lumbar plexus block (LPB), dates back nearly 50 years. The first description of such a block by Winnie et al. in 1973 was an “inguinal perivascular technique” alternatively referred to as a “3 in 1 technique”. Winnie proposed that a large volume of local anesthetic injected in the femoral nerve sheath could spread proximally to produce blockade of the obturator, lateral femoral cutaneous, as well as femoral nerve (and presumably the other nerves of the lumbar plexus). Later work would show that, in fact, this rarely succeeded and typically only blocked the femoral and lateral femoral cutaneous nerves. In 1976 Chayen et al. described a “posterior lumbar plexus block” or “psoas compartment block,” which proved to be a more reliable realization of that goal of blocking the whole of the lumbar plexus with a single injection. Touray et al. were among those who demonstrated that whereas both approaches effectively block femoral and lateral femoral cutaneous nerves, indeed, only the posterior lumbar plexus approach is also able to block the obturator nerve. Thus today, the term “lumbar plexus block” is generally not associated with the inguinal femoral nerve block and is considered synonymous with the posterior approach.

Since the initial description of the posterior lumbar plexus block, a number of variations of the technique have been described. Most of these differ from the original technique of Chayen et al. in only minor detail and are related to the distance of the needle insertion point from midline or the lumbar level at which the block is performed. Perhaps the most significant changes have been in defining the block’s endpoint. The original technique relied on a “loss of resistance,” but this transitioned to the more common use of a nerve stimulator technique (typically looking for motor stimulation of the femoral nerve with quadriceps twitch). More recently, the nerve stimulation method has given way to ultrasound-guided techniques of lumbar plexus block for which several approaches have been described. Thus far, the evidence is lacking to support the superiority of any one of the ultrasound-guided techniques.