Intravascular incidence during S1 transforaminal injection is known to be higher than lumbar injection. Its incidence is reported to be 15~25%.

This study was aimed to see if there is any benefit of reducing the intravasuclar injection rate when S1 transforaminal injection was performed by different fluorosopic approach.

Fluorosocpically guided transforaminal epidural steroid injection is a popular interventional procedure that is effective in radicular pain conditions such as herniated interverebral disc, spinal stenosis and failed back surgery syndrome.

The incidence of inadvertent intravascular needle injection during lumbar transforaminal injection is reported as from 9.9% to 30.8%. In particular, S1 intravascular injection rate is more frequent than at the lumbar level.

Previous study reported that guiding the needle toward the S1 foramen using the S1 scotty dog image as a bony landmark, not in the classic way, but in an oblique fluoroscopic view, during L5 and S1 transforaminal epidural steroid injection, can save procedure time and reduce the risk of radiation exposure.

In this stidy, the investigators aimed to compare the incidence of intravascular injection rate by anteroposterior and oblique view approaches for S1 transforaminal epidural steroid injection. In addition, the investigators also compared the procedure time and radiation exposure between two approach method.

Inclusion Criteria:

• spinal stenosis
• herniated intervertebral disc
• failed back surgery syndrome

Exclusion Criteria:

• coagulopathy
• infection