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.