Accuracy of blind versus fluoroscopically guided caudal epidural injection

A prospective observational study of a case series of patients with low back pain referred for epidural injection of corticosteroid.

To evaluate the accuracy of caudal epidural injections performed without the use of fluoroscopic guidance and to determine the value of specific clinical tests performed during the procedure in predicting successful epidural needle placement.

Epidural injection of corticosteroid is one of many treatments currently used in the nonsurgical management of low back pain. The face validity of many studies evaluating the efficacy of epidural corticosteroid injections has been criticized for use of a blind technique. Although there currently is no consensus in the spine literature as to whether epidural injection of corticosteroid (by any technique) is effective, it is imperative first to establish the accuracy of the technique being used.

A total of 54 consecutive patients underwent fluoroscopically guided caudal epidural injections. Needle insertion was performed blindly (without the use of fluoroscopic guidance), and the success of needle placement was predicted according to the presence of palpable landmarks, palpation of subcutaneous airflow, and the subjective impression that the needle was in a satisfactory position. These clinical criteria then were compared with the position of the needle as seen under fluoroscopy and the spread of radio-opaque contrast in the epidural space after the procedure.

Successful injection placement on the first attempt occurred in 74.1% of the patients. Results were improved when anatomic landmarks were identified easily (87.5%) and no air was palpable subcutaneously over the sacrum when injected through the needle (82.9%). The combination of these two signs predicted a successful injection in 91.3% of attempts.

Caudal epidural injection is performed ideally with fluoroscopic guidance as the gold standard for accurate drug placement. If fluoroscopic guidance is unavailable, impractical, or contraindicated, the presence of readily palpable anatomic landmarks at the sacral hiatus and the absence of palpable subcutaneous airflow over the sacrum significantly increase the operator's confidence in the likelihood of an accurate injection even before any products are administered into the epidural space.