Effect of Needle Tip Position on Contrast Media Dispersion Pattern in Transforaminal Epidural Injection Using Kambin’s Triangle Approach

PURPOSE: Dispersion of contrast media into the anterior epidural space is correlated with better outcomes after transforaminal epidural injection (TFEI). Needle tip position is an important factor affecting the pattern of contrast media dispersion. It is difficult to advance the needle medially to the interpedicle line with a conventional approach, especially in a severe spinal stenosis. But, with Kambin’s triangle approach, the needle can be advanced more medially even in the severe stenosis. We aimed to compare contrast media dispersion patterns according to the needle tip position in TFEI with Kambin’s triangle approach. PATIENTS AND METHODS: This single-center retrospective study analyzed fluoroscopic data of patients who underwent TFEI from March 2019 to July 2019. Data on the history of lumbar spinal fusion surgery and MRI findings were collected. The needle tip position was evaluated in three positions on fluoroscopic images (final anteroposterior [AP] view): extraforaminal (EF), lateral foramen (LF), and medial foramen (MF). Contrast media dispersion into the epidural space (epidural pattern) in the AP view was evaluated as a dependent variable. The relationship between the contrast media dispersion pattern and needle tip position was analyzed, and other factors affecting the contrast media dispersion pattern were identified. RESULTS: Ninety-eight TFEI cases were analyzed (51 LF, 35 MF, and 12 EF). An epidural pattern of dispersion was observed more frequently in the LF and MF groups than in the EF group. The LF and MF groups showed no significant difference in epidural pattern frequency. On logistic regression analysis, needle tip position emerged as a major factor influencing epidural pattern, while other factors including spine conditions had no significant effect. CONCLUSION: Positioning the needle tip medial to the pedicle helps in the spread of the contrast media into the epidural space during TFEI with Kambin’s approach. Factors other than the needle tip position did not significantly affect the contrast media dispersion pattern.