To determine the effect of needle tip positions on short-term effect of transforaminal epidural steroid injection (TFESI) using nerve stimulator (NS) for lumbar radiculopathy.

Forty-five patients who received TFESI using NS were retrospectively reviewed. The TFESI was conducted under fluoroscopic guide. The goal of positioning was to allow a needle tract toward injection site such as “safe triangle”. We used the NS to optimize the position of needle tip. The needle tip was repositioned to achieve minimal current output (0.2mV) when the patients had paresthesias within dermatomal areas. The needle tip positions were assessed by dividing the intervertebral foramen into 4 quadrants in the anterior-posterior view. The grade of nerve root compression on MRI in 45 patients was evaluated. The outcome measurement (OM) was evaluated before pre-injection and after 2 weeks.

Ninety-one TFESIs were conducted in the 45 patients. The position of needle tip was 68, 19 and 4 cases in the quadrant 1, 2 and 3, respectively. The mean score of OM reduced significantly in the quadrant 1 and 2, but not in the quadrant 3 after 2 weeks. There were no significant differences in the mean score of OM according to the grade of nerve root compression.

As the neural structures lie medially in the foramen, it is believed that a medially placed needle such as quadrant 2 has a higher likelihood of causing neurological complication. Bogduk proposed the ideal needle tip position by defining a “safe triangle” like quadrant 1. Our study showed that there was a similar effect in the quadrant 2 just the same in the quadrant 1. We conclude that the NS to guide TFESI in addition to fluoroscopy can be a useful therapeutic tool in the patient with radicular symptoms.