Thirteen RCTs were included in the review with 722 participants (357 received active treatment; 353 received control group treatment; and 20 participants not stated which arm they were assigned to).
Methodological quality scores ranged from 12 to 84 and were unrelated to the results of epidural steroid therapy. The number of studies with more than 20 patients per treatment group was higher in the two studies that found no evidence of efficacy.
Five trials demonstrated greater pain relief within the first month in the steroid group as compared to the control group. They did not assess pain relief after 1 month. In one study that evaluated the effect of the therapy on resumption of work, 91% of patients had returned to work after three months in the epidural steroid group versus 60% in the control group. No differences between the two treatment groups were noted in this study regarding subsequent surgical therapy.
Eight trials found no measurable benefits. Of these, four studies followed patients for > 3 months and three studies followed patients for 6-12 months. In one study that evaluated the effect of the therapy on return to work, after 3 months 33% of patients in the steroid group versus 44% in the control group had returned to work, however this result was not statistically significant. In two studies, no differences between the two treatment groups were noted regarding subsequent surgical therapy.
Obstacles to meaningful comparisons across studies included differences in the patient populations, steroid used, volume injected, and number of injections.
The differences across studies regarding the volume injected (2 to 50 ml) and injection route (sacral hiatus or lumbar approach) apparently had no influence on the results of epidural steroid therapy.