How soon after an epidural steroid injection can you predict the patient's response?

Background

Epidural steroid injections (ESI) are utilized for the management of radicular pain, but there are no previous published studies that detail the specific timeline of patient response to an ESI.

Purpose

To describe patients’ temporal response in pain relief following an ESI.

Study design/setting

Prospective in vivo study of consecutive patients at an outpatient physical medicine and rehabilitation clinic at a single academic spine center.

Patient sample

134 consecutive patients who received an ESI between January 2020 through June 2020.

Methods

Patients were contacted every 3 days ± 1 day for 21 days post ESI to assess pain as measured via 11-point numeric pain score and subjective percentage pain relief question.

Results

134 consecutive patients were enrolled, with 108 (80.6 %) having follow-up data through 3 weeks post ESI. At 3 weeks, 51/108 patients (47.2 %) had reported a successful response as defined by at least 50 % reduction of their pain index. Of these 51 patients, 37 (72.5 %) reported >50 % relief on day 1, a further 11 (21.6 %) first reported >50 % relief on day 4, and the remaining 3 (5.9 %) successes first reported >50 % relief on days 13, 16, and 22. 57/108 patients (52.8 %) were non-responders, most of whom never reached the 50 % threshold at any time point. Of these non-responders, 19/57 (33.3 %) did report >50 % relief on day 1. Those patient's pain relief fell below 50 % on day 4 (12/19 patients, 63.2 %), day 7 (5/19 patients, 26.3 %), day 13 (1 patient, 5.3 %), and day 16 (1 patient, 5.3 %). A positive response or negative response at each follow up point was looked at as a predictor of a concordant three-week outcome for the population. The positive likelihood ratio at follow-up day 1, day 4, day 7, and day 10, was 2.14, 6.12, 7.97, and 40 respectively. The negative likelihood ratio at follow-up day 1, day 4, day 7, and day 10 was 0.42, 0.15, 0.16, and 0.24 respectively.

Discussion/conclusion

This is the first study to meticulously follow up patients every 72 h after ESI. A patient's response on day 4, either positive or negative, is predictive of their 3-week outcome. Sustained relief at day 7 or 10 further increases the likelihood of a positive 3-week outcome.