The gold standard for selecting patients for lumbar radiofrequency ablation (RFA) is medial branch block (MBB). An ideal lumbar MBB would anesthetize the targeted medial branch, with minimal to no spread to surrounding structures. Injectate spread can be affected by numerous factors, including injection volume, and location. Optimizing these factors is important to improve specificity and minimize the number of false positive responders. Capture of unintended structures is relevant as it may impact specificity of the MBB and warrants further investigation. Therefore, the objective of the current study was to perform fluoroscopic guided lumbar MBBs in cadaveric specimens and conduct meticulous dissection to assess dye spread and nerve capture rates. Fluoroscopy-guided contrast and dye injection (n = 20) was performed targeting lumbar MB (L1-L5). Following dye injection (0.25 mL), each specimen was meticulously dissected to expose the course of the lumbar dorsal rami branches relative to dye spread. Photographs were taken to document the extent of dye spread and structures that were stained. The capture rate was quantified and reported as a percentage. A total of 20 fluoroscopy-guided lumbar MBB were performed. Location of contrast flow on fluoroscopy was consistent with the location of dye spread observed in dissected specimens. Dissection post injection consistently found injectate staining all branches of the lumbar dorsal ramus. Injectate was found to spread anteriorly to the lateral aspect of the vertebral body. Fluoroscopy guided lumbar MBB using contrast and dye were performed in anatomical specimens to assess spread and nerve capture rates. Lumbar MBB at small volumes stained all branches of the lumbar dorsal ramus suggesting it is non-selective. Further anatomical and clinical research is required.
Tran et al. (Mon,) studied this question.