The Impact of Body Mass Index on Radiation Exposure During Lumbar Transforaminal Epidural Steroid Injections for the Management of Lumbar Radiculopathy

Background and/or Objectives: To evaluate the relationship between body mass index and radiation exposure during lumbar transforaminal epidural steroid injections.

Design: This was a retrospective cohort study of subjects who underwent lumbar transforaminal epidural steroid injections under fluoroscopic guidance between 08/01/2022 and 08/31/2024. Linear regression modeling was utilized to formulate the relationship between body mass index (BMI) and radiation exposure during lumbar transforaminal epidural steroid injections. After fitting the model, the initial diagnostics revealed that the radiation exposure variable was right-skewed, violating normality and homoscedasticity assumptions. To address this, we applied log transformation for the radiation exposure variable which stabilized the variance and enhanced fitting. We detected 21 influential data points using Cook’s distance and leverage diagnostics. We fitted the model excluding these points and the reduced model exhibited improved performance: the residual standard error decreased from 0.3743 to 0.3327, the adjusted R² increased from 0.4598 to 0.5020. These metrics indicate a more reliable model given by log (radiation exposure) = beta0 + betaBMI(BMI)+ϵ , ϵ~N(0, sigmaϵ)

Setting : Single community-based physical medicine and rehabilitation clinic.

Participants : 496 patients who underwent their first lumbar transforaminal epidural steroid injection under fluoroscopic guidance for the management of radicular leg pain between 08/01/2022 and 08/31/2024.

Interventions: not applicable

Main Outcome Measures: not applicable

Results: The final model showed that BMI is a statistically significant predictor of log transformed radiation exposure (BMI=0.0473, p-value < 0.001). The fitted model is given by log radiation exposure =2.49+0.0473 BMI. This indicates there is about a 4.7% increase in radiation exposure on the log scale for every unit rise in BMI.

Conclusions: Due to weakening of the fluoroscopic signal, patients with greater BMIs will require more radiation during image-guided procedures. Therefore, greater importance needs to be placed on radiation minimizing strategies in this population.