We thank Dr. Huang for his interesting comments. We agree that frequent control of the correct needle position by the use of fluoroscopy is important during interventional pain procedures.1 

The depth of the needle position on a lateral view is important because antiinflammatory agents must be injected as close as possible to the site of pathology; i.e. , in the anterior plane of the epidural space.2With respect to the presented anteroposterior view (Fig. 2a in our article)1and in accordance with another review,3the insertion of the needle no further medial than the six o’clock position in the anteroposterior view reduces the risk of dural puncture.3Moreover, when our needle had been positioned intradurally at this level, a discogram could not have been explained.

Finally, low back pain and sciatica resulting from migrated disc herniations are an indication for transforaminal epidural infiltrations.4By placing the needle in a correct fluoroscopic position, the needle can accidentally encounter a rostrally displaced disc herniation, which possibly explains this unexpected event. Our finding emphasizes the use of fluoroscopy in interventional pain procedures.

* Multidisciplinary Pain Center, Genk, Belgium. kris.vissers@skynet.be

1.
Haspeslagh S, Van Zundert J, Puylaert M, Heylen R, van Kleef M, Vissers K: Unilateral diagnostic infiltration of lumbar L3 nerve root resulting in an inadvertent discogram: the importance of fluoroscopic guidance in interventional pain therapy. Anesthesiology 2004; 100:1019–21
2.
Derby R, Bogduk N, Kine G: Precision percutaneous blocking procedures for localizing spinal pain: Part 2. The lumbar neuroaxial compartment. Pain Digest 1993; 3:62–75
3.
Noor MG: Selective nerve root blocks for low back pain and radiculopathy. Reg Anesth and Pain Med 2004; 29:234–56
4.
Vad VB, Bhat AL, Lutz GE, Cammisa F: Transforaminal epidural steroid injections in lumbosacral radiculopathy: a prospective randomized study. Spine 2002; 27:11–6