 Investigators used the numerical rating scale NRS as well as the Korean version of the Oswestry Disability Index ODI to evaluate clinical efficacy in terms of reducing pain and functional improvement at pretreatment and 2 weeks after the ESI series. ESI was performed twice with a 2 weeks interval before the final treatment outcome evaluation with the NRS and ODI. All patients reported average severity of their symptoms over the previous 1 week. A score of 0 on the NRS represents no pain, and a score of 10 represents the worst pain imaginable. The Korean version of the ODI 0-50 was used to assess functional improvement. 