Objective: To evaluate accuracy of needle placement and flow patterns of fluoroscopically guided caudal epidural injections.
Design: A prospective observational study of patients with low back pain undergoing caudal epidural injections under fluoroscopy.
Background: Epidural administration of corticosteroids is one of the commonly used interventions in managing chronic low back pain. Sacral or caudal epidural placement of the needle is one of the commonly used means to access the lumbar epidural space for administration of various drugs.
Methods: A total of 100 consecutive patients underwent fluoroscopically guided caudal epidural injections. Needle insertion was performed blindly (without the use of fluoroscopic guidance) based on palpable landmarks, palpation of subcutaneous airflow, subjective impression that the needle was in a satisfactory position, and ease of injection of contrast. These clinical criteria were compared with the position of the needle as seen under fluoroscopy and the spread of radiopaque contrast in the epidural space. The contrast flow patterns, ventral or dorsal epidural filling, nerve root filling, and correlation of filling to the side of pain were evaluated.
Results: Successful injection placement without fluoroscopic visualization was confirmed on subsequent fluoroscopic visualization in 77% of the patients. Various filling and flow patterns showed that with injection of 10 mL of contrast, filling was noted up to S1 in 70% of the patients, followed by L5 nerve root filling in 12% of the patients. Ventral epidural filling was seen in 69% of the patients, in contrast to dorsal filling in 92% of the patients. Nerve root filling correlated with leg pain in only 43% of the patients. Intravenous placement of the needle was noted in 14% of the patients with positive flashback and aspiration in 50% of the patients.
Conclusion: Caudal epidural injections are ideally performed with fluoroscopic guidance as the gold standard for accurate needle placement. However, this does not assure either targeted delivery or accurate placement of the drug.