Prior to administration, the data regarding the demographic characteristics, such as, pain duration, pain severity, and involved nerve root were extracted. Two radiologists retrospectively analyzed and recorded the IDP on postintervention CT scanning images. The injection spread patterns in the cross-sectional CT images included the following: Zone I: extra-foraminal; Zone II: the foraminal spaces; Zone III: intra-foraminal (Figure 3).

The injection distribution area in the cross section of CT image: Line A is from anterolateral vertebral body to the lateral margin of the facet. Line B is from posterior-lateral vertebral body to the interior margin of the facet. Line C is the axial centerline of the epidural space. Zone I The out space of line A is extra-foraminal; Zone II: Between line A and B is the foraminal spaces; Zone III: Between line B and C is intra-foraminal/epidural spaces.

An investigator blinded to the patient assignments/treatments performed patient follow-ups, and recorded pain scores, particularly, NRS during hospital visits at 2 hours, 1 week, and 4 weeks after injection.
Safety was assessed as follows: ① Bleeding situation: Prior to drug injection, we recorded whether there was blood upon withdrawal, and verified the presence or absence of hematoma via CT scan. ② Other adverse reactions, including, puncture point pain, shortness of breath, paresthesias, motor deficit, hematoma, dizziness, headache, vomiting, general spinal anesthesia, and so on.