Useful Points of Geometry and Topography of the Lumbar Triangle for Transversus Abdominis Plane Block

BACKGROUND A new look at the topography of the lumbar triangle becomes a challenge for modern anesthesia. The aim of this study was to redefine the topography of the lumbar triangle for transverse abdominis plane block. MATERIAL AND METHODS We explored 74 lumbar regions in 37 preserved cadavers (17 F and 20 M). RESULTS The lumbar triangle was identified in 66 (89%) out of all explored cadavers' lumbar regions. The predominant triangle was the acute-angled shaped. It was identified in 39 (59%) out of all explored lumbar regions. The second type of dissected triangles had the obtuse-angled shaped. Most triangles of acute-angled shaped and obtuse-angled shaped (36) had medium surface (range from 3 cm2 to 6 cm2), which accounted for 55% of all dissected lumbar triangles. The mean surface of the lumbar triangle was 3.6±2.2 cm2. Based on other measurements, we demonstrated that the majority of the lumbar triangles (62 triangles) were beyond the posterior axillary line. CONCLUSIONS According to the obtained results, the randomized searching for lumbar triangle should be limited to the area situated beyond of the posterior axillary line. The region situated anteriorly to the midaxillary line was defined in the study as the critical area for finding the lumbar triangle. Outcomes from the study revealed that the size and the location of the lumbar triangle as the gate for the transverse abdominal plane block may be responsible for difficulties encountered by anesthetists. Thus, establishing the area with the highest probability of localization of the lumbar triangle can improve both safety and efficiency of transversus abdominis plane block.