Lower-extremity sclerotomes: clinical applications and the modified mayo block.

A sclerotome is an anatomical concept that defines an area of bone supplied by a single spinal nerve. Similar to the familiar dermatomes, sclerotomes provide an element of depth to the sensory innervation of the lower extremity based on the deep fascia as an embryologic boundary. Anatomical knowledge of sclerotomes can be used clinically in the diagnosis and treatment of pain and in the perioperative setting. Specifically, a modified version of the classic Mayo block is presented to highlight an active anatomical approach to peripheral nerve blockade.