“…However, a lumbar epidural block, such as a trigger point injection performed in an outpatient department, cannot be easily performed due to complications [ 2 , 3 ]. Needle guidance using fluoroscopy, computed tomography (CT), sonography [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ], and special devices to increase the sensitivity of the LOR method have been used to minimize these complications. Since the epidural fat layer varies in thickness from patient to patient, the placement of the needle tip in the same area cannot completely avoid the risk of complications.…”