Effect of injectate viscosity on epidural distribution in lumbar transforaminal epidural steroid injection

Introduction. There is no report on the effect of injectate viscosity on epidural distribution for lumbar transforaminal epidural steroid injections (L-TFESIs). The aim of this study was to evaluate the influence of injectate viscosity on the volume needed to reach specific landmarks in L-TFESIs. Methods. A prospective, randomized, comparative human study involving 118 patients undergoing L-TFESIs was conducted. The study subjects were divided into two groups by a random selection method: raw viscosity group (RV, n=58) and low viscosity group (LV, n=60). Contrast volumes were recorded as the contrast flow reached specific anatomical landmarks under fluoroscopic guidance. Results and Discussion. The possibility of delivering the injectate to each landmark showed a positive correlation with the amount and a negative correlation with the viscosity of the injectate. However, for landmarks at the medial aspect of the superior pedicle of the corresponding level of injection and for those beyond the spinous process over the contralateral spinal segment, the influence of viscosity was not statistically significant. Conclusion. The epidural distribution of the contrast agent through the transforaminal approach was most affected by the injectate volume and was also partly affected by the viscosity.