Introduction The human lumbar plexus emanates from the lumbar spine providing sensory and motor innervation to the abdominal wall, suprapubic region, external genitalia, inguinal region, and the thigh.The lumbar plexus or its branches may be injured during open and laparoscopic herniorrhaphy, lateral approaches to spinal fusion surgery, iliac crest bone graft harvesting, and other procedures. Health care providers especially surgeons should be aware of these variations to avoid injuries to the nerves. The natural anatomical variation between individuals greatly contributes to the uncertainty surrounding procedural outcomes. Many publications describing the human lumbar plexus have been reported in the literature; however, these reports are frequently contradictory, owed potentially to the natural variation in the genetic composition of human populations and small sample sizes. The aim of performing a systematic review and meta-analysis of the published literature regarding lumbar plexus morphology is an appropriate step forward in ascertaining a more accurate view of the nerves. Materials and Methods A systematic review and meta-analysis using PRISMA guidelines were designed to access the literature published about the spinal levels of origin contributing to the nerves of the lumbar plexus. A comprehensive search was carried out through PubMed, Google Scholar, and CINAHL with specific search terms. Two independent reviewers evaluated the Title and Abstract of qualifying articles discovered from index searches. Data from qualifying publications were extracted and aggregated. Results We evaluated 1522 studies from the online databases and excluded any publications after January 31, 2020. Thirteen studies of the femoral nerve (773 total nerves) were found to originate from the spinal nerves as follows: L2-L4 82.8%, L1-L4 6.2%, L3-L4 4.4%, L3-L5 2.2%, L1-L3 1.4%, L4 0.6%, L5 0.4%, L2-L5 0.3%, T12-L4 0.3%, L2-L3 0.3%, T12-L3 0.3%, L3 0.1%, and missing or unreported 0.8%. Ten studies of the obturator nerve (477 total nerves) were as follows: L2-L4 82.8%, L4 8.4%, L1-L4 3.4%, L1-L3 1.5%, L3-L4 1.5%, L2-L3 0.8%, L3 0.4%, L5 0.4%, T12-L3 0.4%, L2-L5 0.2%, and L3-L5 0.2%. Ten studies of the ilioinguinal nerve (629 total nerves) were found as follows: L1 80.8%, L1-L2 6.2%, T12-L1 6%, L2-L3 3.5%, L2 0.6%, T12 0.5%, L3, 0.2%, and missing or unreported 2.2%. Nine studies of the iliohypogastric (429 total nerves) were found as follows: L1 83.2%, T12-L1 12.4%, T12 2.6%, and missing or unreported 1.9%. Twelve studies of the lateral femoral cutaneous nerve (580 total nerves) were found as follows: L2-L3 71.6%, L2 10.2%, L1-L2 4.8%, L2-L4 2.9%, L1-L3 1%, L3 1%, L1 0.7%, T12-L1 0.2%, and missing or unreported 7.6%. Nine studies of the genitofemoral nerve (457 total nerves) were as follows: L1-L2 81.4%, L2 9%, L1 2.6%, L2-L3 1.5%, L1-L3 1.1%, T12-L1 0.9%, and missing or unreported 3.5% of cases. Conclusion The result of this study showed the vast number of variations of the different nerves of the lumbar plexus from its spinal levels. Lesions to the lumbar plexus are rare and difficult to treat. The lumbar plexus may be injured during clinical interventions; thus, the knowledge of these variations is important to physicians, surgeons, and anesthesiologists.
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