Optimal Needle Entry Angle for Cervical Transforaminal Epidural Injections

Abstract

Background: Cervical epidural steroid injections can be performed through either interlaminar or transforaminal approaches, although the interlaminar approach is more frequently used, for cervical radicular pain as a result of cervical disc herniation or spinal stenosis. Cervical selective nerve root block (CSNRB) is an injection that uses a similar approach to that of cervical transforaminal epidural steroid injection (CTFESI) but CSNRB is mainly used for diagnostic injection, often with local anesthetic only. Objective: The aim of this study was to investigate an optimal needle entry angle for cervical transforaminal epidural steroid injection (CTFESI) or cervical selective nerve root block (CSNRB) using the fluoroscopically guided anterior oblique approach. The angle for optimal entry into the neuroforamen was measured at various vertebral levels using cross-sectional cervical spine computed tomography (CT) scans. Study Design: Retrospective case series analysis. Methods: From March 2009 to July 2012, consecutive patients with presumed discogenic neck pain underwent cervical post discography CT scans. The axial images of these CT scans were used to measure the optimal angle for needle entry into the neuroforamen. The angles were taken bilaterally at levels of C3-4, C4-5, C5-6, C6-7, and C7-T1. The average angle between the patient’s left and right side was calculated. A total of 190 patients were analyzed, including 73 men and 117 women, with ages ranging from 21 to 78 years old. Results: In both men and women, the mean optimal angle (in degrees) with standard deviation measured in the 190 patients at C3-4, C4-5, C5-6, C6-7, and C7-T1 were 48 ± 4, 49 ± 4, 49 ± 4, 49 ± 5, 48 ± 6, respectively. The 95% confidence interval for the true value of the parameter is within 39.84 to 57.56 degrees. Limitations: The data for the optimal needle entry angle for CTFESI has yet to be tested or confirmed in clinical studies. Conclusion: This is the first study investigating the optimal needle entry angle for performing CTFESIs or CSNRB. Based on a patient population of 190, the optimal entry angle using the anterior oblique approach appears to be between the range of 33 to 68 degrees with an average of slightly less than 50 degrees. Further research with angle of needle entry and/or initial fluoroscopic alignment of approximately 50 degrees in CTFESI or CSNRB is warranted to confirm the usefulness of these findings. Key words: Pain medicine, transforaminal, cervical, epidural, cervical selective nerve root block, cervical disc herniation, interlaminar, neck pain, vertebral artery, radiculomedullary artery