Comparison of Intravascular Injection Incidences and Technical Easiness Between Anteroposterior and Oblique Approaches During S1 Transforaminal Epidural Injection

Transforaminal epidural injection (TFEI) is a useful intervention for radicular leg pain. Compared to TFEI in lumbar level, S1 TFEI is reported to have higher incidence rates of intravascular injection as well as technical difficulties. The purpose of this study is to compare the incidence rates of intravascular injection and foramen passage time between anteroposterior (AP) and oblique (OB) approaches. Prospective randomized trial. An interventional pain management practice in South Korea. One hundred forty-seven patients receiving S1 TFEI for radicular leg pain were randomly assigned to one of 2 approach methods (AP view vs OB view). For S1 TFEI in the OB view group, lineup of the L5-S1 endplate was performed by adjusting the cephalad-caudad tilt. Then C-arm was rotated at an ipsilateral oblique angle, approximately 10° to 15°. After final confirmation of intravascular injection with real time fluoroscopy, the foramen passage time and amount of radiation exposure during S1 TFEI were measured. The incidence rate of intravascular injection in the AP view group was 24.2% (24/99), whereas that of intravascular injection in the OB view group was 10.1% (17/99, P = 0.008). The radiation dose required to pass the S1 foramen was significantly higher in the AP view group than in the OB view group (51.3 ± 27.2 cGy/cm2 vs 41.0 ± 17.0 cGy/cm2, P = 0.002). The foramen passage time during S1 TFEI was significantly higher in the AP view group than in the OB view group (103.5 ± 44.1 second vs 84.9 ± 21.0 second, P = 0.001). The failure rate of S1 TFEI was significantly higher in the AP view group than in the OB view group (13% vs 4%, P = 0.022). The physicians involved in the present study were not blinded to the type of approach method (AP view vs OB view) by fluoroscopy. Our study demonstrated reduced incidence rates of intravascular injection and reduced foramen passage time and radiation dosage with the use of OB view method during S1 TFEI.