Guides for Pain Clinicians?

which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Although there have been debates and different practice guidelines on the indication of epidural blocks for pain management [1], there remain patients for whom few alternative options are available, including painless delivery and some postoperative patients. Even though the use of fluoroscopy is recommended for the correct localization of the epidural space, this procedure is not always possible in the above mentioned situations. We therefore have to rely solely on the loss of resistance technique using our hands. The problem with this method is that there is always a risk of puncturing the dura mater even with the most experienced hands. Some studies have previously indicated the presence of gaps in the human ligamentum flavum, causing apprehension in pain clinicians [2-4]. In the present issue of the Korean Journal of Pain, Yoon et al. [5] reports anatomic variations of the cervical and high thoracic ligamentum flavum. Having directly examined the ligamentum flavum from C3 to T6 in 15 human cadavers, they report that the incidence of midline gaps in the ligamentum flavum is 87%-100% between C3 and T2. The incidence decreases below this level and is the lowest at T4-T5 (8%). The incidences of midline gaps seem to be higher in this study than in prior studies. Among the levels presenting gaps, the location of a gap in the caudal third of the ligamentum flavum is more frequent than in the middle or cephalic portion of the ligamentum flavum. Therefore, the authors warn that the midline approach for cervical and high thoracic epidural blocks could pose a risk of failure to recognize a loss of resistance. This risk can be further increased when the needle is inserted into the caudal portion of the intervertebral space. Some investigators have tried to solve this problem using ultrasonogram. Lee et al. [6] wrote an article titled, " Sonoanatomy of the lumbar spine in patients with previously unintentional dural punctures during labor epi-durals " , and concluded that abnormal sonoanatomy of the ligamentum flavum may present anatomical variations of this structure, which may be related to an increased incidence of unintentional dural punctures during epidural placements. Another study looked into the sonoanatomy of the lumbar spine in pregnant women at term [7], and identified a grossly incomplete or absent ligamentum flavum. However, other authors have contended …