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training guests publications what's new links forum nysora.com disclaimer New York School of Regional Anesthesia     Introduction Anatomy
 Review Indications Contra-
 indications Equipment Reference
 Points Block Performance Protocols Complications Control By Dr. Philippe Macaire
Lyon, France Anatomy review

Lumbar plexus is composed of paravertebral branches of the roots of L1 to L4. These branches have multiple anastomoses and may receive contributory input from the roots of T12 and L5. Lumbar plexus is situated in a cleavable space within the psoas muscle. This space is limited superiorly by the insertion of the muscle psoas on the body of the vertebra (corporeal chief) and behind by its insertion on the apophysis costiforme of the vertebrae (chief costiforme). Posteriorly, this compartment is bordered by the lumbar rachis and peridural space. This compartment is further limited anteriorly by the aponeurosal continuation of the fascia iliaca, thus producing a true sheath which allows diffusion of local anesthetics within the sheath.

The lumbar plexus forms the following nerves:
     •Iliohypogastric (IH)
     •Ilioinguinal (II)
     •Lateral femoral cutaneous nerve of the thigh (CLC)
     •Genito-femoral nerve (GF)
     •Femoral nerve (F)
     •Obturator nerve (Obt)

Lumbar plexus block is a deep block and it is accomplished at depth of between 60 mm to 100 mm. The depth at which the lumbar plexus is encountered depends on many variables such as:
     •gender
     •body build
     •musculature
     •age of the patient

On its path toward the lumbar plexus, the needle transverses the following structures : skin, fat panicle, muscular masses of sacro lumbar (or erectores spinae), lumbar quadratus muscles. Once the needle enters the psoas muscle, it will quickly reach the lumbar plexus. Processus transversus, when encountered, represents an excellent reference mark. The surrounding fascia iliaca allows an excellent diffusion of local anesthetic within this space.     

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Lumbar Plexus Block
   (Posterior Approach)