Injectate Volumes Needed to Reach Specific Landmarks and Contrast Pattern in Kambin's Triangle Approach with Spinal Stenosis

OBJECTIVE To identify the volumes of contrast material needed to reach the specific landmarks and contrast pattern during Kambin's triangle approach (KB-A) in lumbar spinal stenosis. METHOD Sixty patients undergoing KB-A were investigated. Fifty-six patients were included in this study. KB-A were performed with the use of contrast-enhanced fluoroscopic visualization. After confirming the appropriate spinal needle position, a slow injection of up to 5.0 ml of nonionic contrast material was carried out. Under intermittent fluoroscopic guidance, contrast volumes were recorded as flow reached specific anatomic landmarks: ipsilateral inferior or superior neural foramen. RESULTS After 2.0 ml of contrast was injected, 93.2% of KB-A cases spread to the medial aspect of the inferior pedicle of the corresponding level of injection and 86.3% of KB-A spread to the medial aspect of the superior pedicle of the corresponding level of injection. After 3 ml of contrast was injected, 95.3% of KB-A spread to cover both the medial aspect of the inferior pedicle and the superior pedicle of the corresponding level of injection. A volume of 2 ml of injectate reaches the anterior epidural space 100% of the time. CONCLUSION This study demonstrates injectate volumes needed to reach the specific anatomic landmarks in KB-A. A volume of 3.0 ml of injectate reaches both the medial aspect of theinferior pedicle and the superior pedicle 94.6% of the time. Therefore, Interventionalists may consider a 1-level instead of a 2-level injection for patients with a bleeding risk or for 2 level central pathology.