Gholamreza Mohseni - Associate Professor MD Department of Anesthesiology ,ShahidBeheshti University of Medical Sciences,Tehran,Iran

Ultrasound guidance currently represents the gold standard for regional anesthesia. In particular for lower extremity blocks, despite the heterogeneity and the lack of large randomized controlled trials, current literature shows a modest improvement in block onset and quality compared with other localization techniques. This review aims to present the most recent findings on the application of ultrasound guidance for each single lower extremity approach.The use of ultrasound applied to peripheral nerve blocks has been the object of several randomized controlled trials (RCTs) and reviews in the last two decades 1– 3. Despite the heterogeneity of RCTs comparing ultrasound guidance to other localization techniques in terms of type of block, anesthetic agents, and control groups, a recent systematic review published by Liu has shown a moderate superiority of ultrasound guidance for the majority of the evaluated block characteristics 2. The effectiveness of ultrasound guidance showed by Liu was previously pointed out by Lewis et al. 4. The authors conducted a meta-analysis showing that ultrasound guidance produces a superior success rate in terms of readiness for surgery after sensory and motor test and fewer blocks requiring analgesic supplementation or conversion to general anesthesia compared to other localization techniques 4. Unfortunately, only six of the 32 studies considered by Lewis et al. were related to lower extremity blocks 4.The interest and the evidence related to the use of ultrasound guidance applied to lower extremity blocks have been growing in the last few years 2. In fact, Liu 2 identified nine new RCTs evaluating lower extremity blocks, beside the eight pre-existing studies included in the first review in 2010 5. Based on the analyzed data, the author shows that ultrasound guidance provides a modest improvement in block onset and quality when applied to lower extremity blocks 2. In particular, three studies reported a faster onset by 5 to 14 minutes if ultrasound was used to perform lower extremity blocks 2.This review aims to present the most recent findings on the application of ultrasound guidance for main lower extremity blocks and approaches. Ultrasound provides the possibility to directly visualize the nerves, vessels, needle, and local anesthetic distribution in the majority of patients 6, but it does not replace the full comprehension of the anatomy that still represents the foundation for safe and successful blocks and for the right management of the anesthetic/analgesic plan.The lumbar plexus is an anastomotic complex formed by the anterior branches from L1 to L4 roots 7. The lumbosacral trunk is formed by the anterior branch of L5 together with an anastomotic branch from L4.