Background: Interlaminar epidural steroid injection is a well-established intervention for the treatment of radicular pain. Pain is commonly reported during the injection into the epidural space; this provocation is typically either concordant or discordant with the patient's baseline pain. It is not well known how this provocation pain relates to treatment outcomes.
Objective: To determine the relationship between concordant versus discordant provocation during interlaminar epidural steroid injection and its effects on pain reduction at follow-up.
Study design: Secondary analysis of a single center, prospective randomized double-blind study.
Methods: Interlaminar epidural steroid injections under fluoroscopic guidance were performed on 48 patients with radicular lumbosacral pain. After injection with 80 mg methylprednisolone and 2 mL of normal saline at a single level, patients were asked to report if pain was provoked, and whether the pain was concordant or discordant with their baseline pain. The primary outcome measure was self-rated percentage of pain reduction from baseline at 2-week follow-up. Secondary outcomes included improvement in activity level and decreased analgesic consumption.
Results: Provocation was observed in 37 out of 48 patients (77%). This was further classified as concordant (22/37, 60%) or discordant (15/37, 40%) pain. The concordant group achieved a significant decrease in self-reported pain as compared to the discordant group at 2-week follow-up (61%, t = 2.45, P < 0.01). There were also significantly more patients in the concordant group who reported 75% pain reduction as compared to the discordant group (X = 6.44, df(1), P < 0.05). There were no significant differences between concordant and discordant groups in regard to improvements in activity level (X = 2.56) and decreased analgesic use (X = 3.28).
Limitations: The secondary analysis did not examine long-term outcomes.
Conclusions: The concordant group demonstrated significantly higher pain reduction as compared to the discordant group. There were no significant differences between the 2 groups in terms of improved function or reduced analgesic requirements. Concordant provocation during interlaminar epidural injection may be a predictor of outcome.