[An X-ray study of catheters abnormally placed in the epidural space]

We investigated the roentgenogram of the epidural catheter in 82 patients in whom the injection of local anesthetics had no effect. Contrast medium 0.5 ml was injected through the epidural catheter and antero-posterior roentgenogram was taken. The roentgenograms were categorized into three patterns, according to the relationship of the catheter to the pedicle of lamina, or to the spread of contrast medium. In 43 cases, the catheter passed through the intervertebral foramen. The tip of the catheter was located outside the foramen, and the contrast medium spread outside the vertebra. In 4 cases, the tip of the catheter was located laterally in the vertebral column, and only the catheter itself was contrasted but no spread of medium was observed. The catheter was thought to be misinserted intravascularly. In other 35 cases, catheter ran laterally on the pedicle of lamina, or the spread of medium 2 mins after the injection was indicated by a dumpling-shape even when the tip was in the vertebral column. In these cases, the catheter was thought not to be outside the epidural space.