Comparison of the caudal and lumbar approaches to the epidural space. (Southampton Genera Hospital, Southampton, United Kingdom) Ann Rheum Dis 2000;59:879–882.
Authors: Price C. M. , Rogers P. D. , Prosser A. S. J. , Arden: N. K. 
Published: March 2003

This study investigated the accuracy of placement of epidural injections using the lumbar and caudal approaches and to identify which factors, if any, predicted successful placement. Two‐hundred consecutive patients referred to a pain clinic for an epidural injection of steroid were randomly allocated to one of two groups. Group L had a lumbar approach to the epidural space and Group C, a caudal approach to the epidural space. Both groups then had epidurography preformed using Omnipaque and an image intensifier to determine the position of the needle. Body mass index (BMI), grade of operator, and route of injection were predictors of a successful placement. Ninety‐three percent of lumbar and 64% of caudal epidural injections were correctly placed. Ninety‐sevent percent of lumbar and 85% of caudal epidural injections clinically thought to be correctly placed were confirmed radiographically. For epidural injections where the clinical impression was “maybe,” 91% of lumbar injections, but only 45% of caudal injections were correctly placed. Obesity was associated with a reduced chance of successful placement. A more senior grade of operator was associated with a reduced chance of successful placement. However, small numbers may have accounted for the latter result. Conclude that the weight of the patient and intended approach need to be considered when deciding the method used to enter the epidural space. In the nonobese patient, lumbar epidural injections can be accurately placed without x‐ray screening, but caudal epidural injections, to be placed accurately, require x‐ray screening no matter what the weight of the patient.

Comment by Gabor B. Racz, M.D. The study compared lumbar epidural versus caudal epidural injections by 14 experienced anesthesiologists. The success rate for the lumbar epidural were higher so long as the patient was not obese and was significantly lower for the caudal placement. A reflection of the British system, the more senior consultants had a lower success rate than the registrar grade practitioners, reflecting the bulk of the pain work being done by the less experienced practitioner. The overall problem with the assessment is the fact that they did not standardize the injections deeming, individual experience to be the best for that individual which may or may not be so. The recommendations, however, are appropriate in recommending fluoroscopy in the caudal approach as well as the more difficult obese patient. Nevertheless, the paper reflects the lack of understanding of the current trend that the target site is not necessarily just epidural space but the ventral and lateral epidural space where most of the pathology is occurring and simple access to the spinal canal does not assure appropriate delivery of medication to the site where the most benefit can be obtained. There was no attempt by the authors to evaluate the outcome of the injections. Rather they discussed the nonstandardized delivery of steroids as verified by fluoroscopy and occasionally fluoroscopy in a nonstandardized manner.