An evaluation of contrast medium spread on caudal epidurography with the needle positioned toward the affected side in patients with unilateral lumbosacral radiculopathy

We used caudal epidurography to compare the spread of contrast medium when the needle was inserted toward the affected side in patients with unilateral radiculopathy undergoing caudal steroid injection.We enrolled 24 patients with unilateral radiculopathy. A block needle was positioned toward the affected side in the sacral epidural space. After 5 mL of iodinated contrast medium was injected, a standardized anteroposterior view was imaged. Using Adobe Photoshop software, contrast medium spread was assessed by counting pixels within the areas spread on the affected side and on the opposite side, and the pixel counts of the two sides were compared. Spinal nerve root filling was also assessed.The pixel count within the area of contrast medium spread on the side with the needle was significantly greater than that of the opposite side (mean [SD] 41,368.6 [13,143.1] vs 15,165.3 (10,698.1), P 0.001]. However, 13.6% of the study patients had greater spread on the opposite side. The rates of L5 and S1 nerve root filling in the affected side were 18.2% and 36.4% respectively.When a needle was intentionally inserted toward the side with radiculopathy, the spread of contrast medium and number of delineated roots tended to be greater on the side with the needle, compared with those on the opposite side. However, the pattern of contrast medium spread in the sacral epidural space varied and some patients even had greater spread on the opposite side.