LAUSR

, The sacral erector spinae block (S-ESPB) is a recently described technique, used mostly for analgesia of the posterior perianal area. 1,2 Albeit the similarity in the name, sacral erector spinae plane (ESP) is anatomically different from the thoracic ESP. The thoracic ESP is bounded anteriorly by the intertransverse ligaments, costotransverse ligaments, and the short rotator muscles which prevent ventral spread of local anaesthetic (LA). The sacral ESP on the other hand is bound anteriorly by the sacral plate which contains the sacral foramina which might be a potential conduit between the dorsal and the ventral aspects of the sacrum. It has recently been termed as a sacral multifidus block (SMFB) as the sacral multifidus (SMF) is the only erector spinae group muscle present in the sacral area unlike the thoracic or lumbar ESP. 3 The mechanism of SMFB is still unclear. Through cadaveric dissections we attempted to understand the spread of injectate