Résumé
BACKGROUND: A volumetric caudal epidural steroid injection has been advocated to facilitate the delivery of medications to a lesion site. This study was aimed to examine the actual spreading patterns of this technique, using an epidurogram. METHODS: A total of 32 patients with chronic low back pain with a radiculopathy of various causes (degenerative spondylosis, herniated nucleus pulposus, spondylolisthesis, and spinal stenosis) were included. A volumetric caudal epidural injection of a 10 ml mixture of contrast medium 5 ml, 0.5% bupivacaine 1 ml, triamcinolone 1.5 ml (60 mg) and normal saline 2.5 ml was performed. Immediately after the cessation of the first spread, the subsequent solution of another 10 ml of contrast medium 5 ml, 0.5% bupivacaine 1 ml and normal saline 4 ml was injected. This procedure was repeated serially until the total volume equaled 50 ml. Continuous fluoroscopic imaging was obtained after each injection. RESULTS: Average time taken to complete the study was 37 seconds per every 10 ml. The spreading levels of the mixture were distributed mainly at the mid to lower lumbar area in the majority of the investigated patients. During the subsequent injections, these levels did not increase significantly. CONCLUSIONS: We concluded that the multiple small volume caudal epidural injections retraced their own tract repeatedly. This was thought to be due to the minimal resistance in the cephalad direction, anatomic variations and the Starling effect of epidural space.