Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content ++ The lumbar plexus is usually formed by the ventral rami of the L1–L3 and part of the ventral branch of L4The sacral plexus is formed by the lumbosacral trunk (L4, L5), the first sacral ventral ramus, part of the ventral branch of S2, and a small portion of the ventral branch of S3Classically, the ventral branch of L4 is the junction between the two plexi; it gives off a branch to the femoral nerve, one to the obturator nerve, and the lumbosacral trunk that becomes part of the sciatic nerveThere are several varieties of lumbosacral plexus: The most common is a “prefixed” plexus, including all or part of T12A “normal” plexusA “postfixed” plexusOr even a plexus spread in both directions: These anatomical variations can affect regional anesthesia practice because of variations in motor and sensory distributionsThe division into two planes of the lumbosacral plexus is less clear than for the brachial plexusThe two terminal branches of the lumbar plexus are the femoral nerve and obturator nerve, which correspond, respectively, to the dorsal and the ventral layersFor the sacral plexus, the tibial nerve is the ventral layer and the common peroneal nerve the dorsal layerThe layout of the main nerves of the lumbosacral plexus requires the use of combined blocks for anesthesia of the lower limb ++Figure 139-1. Lumbosacral PlexusGraphic Jump LocationView Full Size||Download Slide (.ppt)++Figure 139-2. Lumbosacral Plexus and Muscle InnervationGraphic Jump LocationView Full Size||Download Slide (.ppt) Your Access profile is currently affiliated with '[InstitutionA]' and is in the process of switching affiliations to '[InstitutionB]'. Please click ‘Continue’ to continue the affiliation switch, otherwise click ‘Cancel’ to cancel signing in. Get Free Access Through Your Institution Learn how to see if your library subscribes to McGraw Hill Medical products. Subscribe: Institutional or Individual Sign In Username Error: Please enter User Name Password Error: Please enter Password Forgot Username? Forgot Password? Sign in via OpenAthens Sign in via Shibboleth