lumbosacral plexus lumbosacral plexus the anterior divisions of the lumbar nerves, sacral nerves, and coccygeal nerve form the lumbosacral plexus, the first lumbar nerve being frequently joined by a branch from the twelfth thoracic. for descriptive purposes this plexus is usually divided into three parts: lumbar plexus sacral plexus pudendal plexus lumbosacral plexusplan of lumbar plexus.plan of sacral and pudendal plexuses.detailsidentifierslatinplexus lumbosacralismeshd008160ta98a14.2.07.001ta26516fma5907anatomical terms of neuroanatomy injuries to the lumbosacral plexus are predominantly witnessed as bone injuries. lumbosacral trunk and sacral plexus palsies are common injury patterns.