Background: Selective diagnostic blocks of the medial branches of the dorsal primary ramus are usually performed under the guidance of fluoroscopic or computed tomography. Recently, however, ultrasound guidance has been suggested as an alternative method. In this study, the distances between the vertebral structures were measured and compared with the values measured using magnetic resonance imaging (MRI) to assess the clinical feasibility of using ultrasound-guided block in Korean patients. Methods: Five male and 15 female patients were enrolled in this study. The target point of the medial branch block in our study was the groove at the base of the superior articular process. We measured the depth from the skin to the target point at the transverse process (d-TP) and to the most superficial point of the superior articular process (d-AP). Results: The d-TP and d-AP values measured under ultrasound guidance were concordant with the values measured using MRI. Conclusions: The images of the bony landmarks obtained under ultrasound examination could be useful for ultrasound-guided lumbar medial branch block. (Korean J Pain 2007; 20: 111-115)

Keywords: facet joint, low back pain, medial branch block, ultrasound.