"Is this injection going to hurt?" Quantifying the pain experience during common lumbosacral spine injections.

Background: "Is this injection going to hurt?" Physicians typically answer this from experience since accurate answers are not available in the literature.

Objective: To quantify pain during common lumbosacral spine injections and compare to baseline pain prior to the injections. Analyze differences based on demographic and procedure variables.

Methods: This is a secondary analysis of prospectively collected data from a multicenter trial of patients undergoing bilateral symmetric transforaminal epidural (TFE), facet joint (FJ), or sacroiliac joint (SIJ) injections. Numeric pain ratings (0-10) were obtained at baseline in preop ("What is your current pain?") and for each injection procedure ("How much did this injection hurt from start to finish?") first on the right side then the left. Between group comparisons used Chi-squared and ANOVA for categorical and continuous variables, respectively. T-tests compared various pain responses, and multivariate regression determined factors associated with higher procedure pain.

Results: From 244 injections (124 TFE, 60 FJ, 60 SIJ) on 122 consecutive patients (mean age 57.2, 50 % female), age and BMI did not differ between injection groups while sex did (p = 0.001) with more FJ males and SIJ females. Mean baseline pain was statistically equivalent between demographic and injection groups. Mean procedure pain was consistently higher than mean baseline pain, however this difference was small and non-significant for TFE (4.0 vs 3.8) and FJ (3.9 vs 3.3), but larger and significant for SIJ (5.3 vs. 3.6; p = 0.0001). In the multivariate regression analysis only 2 variables remained associated with higher procedure pain, older age (p < 0.0001) and SIJ injection group (p = 0.0021).

Conclusion: The majority of patients (79.1 %) report mild or moderate pain during common lumbosacral spine injections. The average procedure pain of 4.3 on the NPRS scale was only 0.7 points higher than baseline pain recorded in pre-op. Procedure pain from TFE and FJ injections is statistically equivalent to baseline pain and to each other, while SIJ injections produce higher procedure pain with a significant +1.7 point mean increase in pain from baseline. Finally, older adults report significantly greater procedure pain compared to those under 65 years old.