Lumbosacral Radiculopathy Definition. Lumbosacral radiculopathy is a broad term referring to a range of symptoms associated with the nerves of the lumbosacral plexus in the lower back. The lumbosacral plexus encompasses the nerves that exit the spinal cord at the lumbar, sacral and coccygeal regions of the spine.Radiculopathy occurs when an anatomical abnormality has caused one or more of these nerves to become irritated, pinched or impinged.he lumbosacral plexus encompasses the nerves that exit the spinal cord at the lumbar, sacral and coccygeal regions of the spine. Radiculopathy occurs when an anatomical abnormality has caused one or more of these nerves to become irritated, pinched or impinged.