Lumbar epidural steroid injection: Is the success rate predictable?

Objectives: The aim of this study was to determine the relation between the percent of canal compromise and success rate of epidural steroid injection (ESI) in patients with symptomatic lumbar herniated intervertebral discs. Methods: Patients with lumbar herniated intervertebral disc suffering from leg pain and treated with ESI were selected. The axial magnetic resonance (MR) image showing the largest canal compromise by the herniated disc was selected for measurements. The canal area and disc herniation area measurements were calculated from the total number of pixels per cross-sectional area, multiplied by a scan correction factor, mm2/pixel. The percent canal compromise was obtained by the disc herniation area divided by the canal cross-section area, multiplied by 100. For pain assessment, visual analog scale (VAS) was used before (pre-injection VAS) and a month after ESI (post-injection VAS). Demographic data, duration of symptoms, and location and type of herniation were also noted. Results: 39 patients (14 male, 25 female) were included in this study. The mean age was 50.2 +/- 11.6 years (27-76). Twenty-one cases (51%) also had back pain. The mean percent canal compromise ratio was 36.1 +/- 2.4%. The mean duration of symptoms was 19.4 +/- 6.6 months. The post-injection VAS was significantly decreased when compared with pre-injection VAS (p<0.0001), and this significance was related with the duration of symptoms being <3 months (p= 0.021). There was also a significant negative correlation between percent canal compromise and post-injection VAS (p=0.042). However, there was no correlation between post-injection VAS and age, sex, or location or type of herniation (p>0.05). Conclusion: It has been demonstrated that higher benefits of ESI were achieved in patients with short duration of symptoms and high percent of canal compromise.