RT Journal Article SR Electronic T1 Comparing two posterior quadratus lumborum block approaches with low thoracic erector spinae plane block: an anatomic study JF Regional Anesthesia & Pain Medicine JO Reg Anesth Pain Med FD BMJ Publishing Group Ltd SP 549 OP 555 DO 10.1136/rapm-2018-100147 VO 44 IS 5 A1 Hesham Elsharkawy A1 Gausan Ratna Bajracharya A1 Kariem El-Boghdadly A1 Richard L. Drake A1 Edward R. Mariano YR 2019 UL http://rapm.bmj.com/content/44/5/549.abstract AB Background and objectives Both posterior quadratus lumborum (QL) and erector spinae plane (ESP) blocks have been described as new truncal interfascial plane blocks. Distribution of injectate is influenced by fascial anatomy; therefore, different injection sites may produce similar spread. This anatomic study was designed to test the hypothesis that a posteromedial QL block at L2 level will more closely resemble a low thoracic ESP block when compared with the posterolateral approach at L2 level.Methods Left-sided ESP blocks were performed in six cadavers at T10–11. Three of these cadavers received right-sided posteromedial QL block at L2, while the other three received right-sided posterolateral QL block at L2. All injections were composed of 20 mL methylcellulose 0.5 % mixed with India ink and 10 mL of Omnipaque (Iohexol) 240 mg/mL. CT 24 hours after injection and cadaver dissection were used to evaluate injectate spread.Results Cephalocaudal spread of injectate by CT and cadaveric dissection was highly correlated (r=0.85 [95% CI 0.51 to 0.95]). Cadaver dissection showed ESP injectate spread deep to the muscle (mean [SD]) 11.7 (2.3) levels compared with 7.3 (1.2) levels for posterolateral QL and 9.7 (1.5) for posteromedial QL (p=0.04 overall, with a statistically significant pairwise difference between ESP and posterolateral QL only). The subcostal nerve and dorsal rami were commonly involved in most blocks, but the paravertebral space and ventral rami had inconsistent involvement. The lumbocostal ligament limited cranial spread from the posterlateral QL block approach.Conclusions The posteromedial QL block at L2 produces more cranial spread beyond the lumbocostal ligament than the posterolateral QL block, and this spread is comparable with a low thoracic ESP block. Both posterior QL and ESP blocks show unreliable spread of injectate to the paravertebral space and ventral rami, but the dorsal rami were frequently covered.