Epidural Corticosteroid Injections: Technical Considerations, Part A
The practitioners who commonly perform epidural steroid injections include physicians with specialty training in anesthesiology, physiatry (Physical Medicine & Rehabilitation), and radiology. The majority of these practitioners have completed advanced training in interventional spine and pain management techniques, whether it be in a fellowship setting or in cadaveric or CME coursework with a limited mentorship. These procedures are more commonly performed in a hospital or ambulatory surgery outpatient center because of the availability of imaging equipment and staff for monitoring and assessment, however there are some practitioners who perform a restricted number of "blind" (no imaging) techniques in the office setting. Most practitioners will require that their patients complete a "pain diary", frequently using a VAS (Visual Analogue Scale), spanning up to one week’s duration post injection as a way of more specifically measuring the anesthetic and corticosteroid pain-reducing response to the procedure.
There are no data to support the routine use of a series of three epidural steroid injections in spinal pain syndromes. Unpublished practice audits have found that if there is no response to the first fluoroscopic guided ESI, then a second will be of no benefit. Most practitioners do not routinely order a series of three epidurals, but if there is good partial relief/benefit from the first, with enough residual pain to warrant further treatment, then a second epidural can be repeated in two weeks as the duration of both the suppression of the hypothalamic-pituitary axis and of corticosteroid side-effects is approximately two to three weeks.
Although epidural steroid injections can be attempted without fluoroscopy and contrast medium, numerous convincing arguments exist that mandate their use, including greatly increased accuracy and safety, coupled with improved therapeutic benefit. Studies show that up to 40% of blind (non-fluoroscopic) injections may miss the epidural space. The physician may then erroneously perceive that epidural placement occurred but did not because of inadequate or excessive depth of tissue penetration or because of intravascular placement despite failure to aspirate blood, certainly plausible considering the highly vascular nature of the epidural space. By imaging the spinal anatomy, adequate localization and spread of the corticosteroids can be documented, allowing for the ideal placement of medication at the optimal (symptomatic) level, side, or nerve root (7, 8).
Fig 2. Caudal epidural blocks can be performed using a single-needle technique, typically utilizing a 22-gauge spinal needle, or alternatively employing a catheter technique. The catheter allows the contrast to be placed at higher levels as desired. The epidurogram shows the injection of 10 cc of local anesthetic containing contrast. The contrast reaches the L3-4 level and the L4, L5, and S1 roots are outlined.
Various routes may be utilized for the administration of epidural steroids. The caudal route (Fig. 2) involves introduction of a needle via the sacral hiatus. A larger volume of fluid needs to be injected to act as a "carrier" so that the active agent can reach the lumbar nerve roots, which are at least 10 cm cephalad to the site of injection (3). Caudal and translaminar epidural injections may be affected by scarring or by the arrangement of epidural ligaments which may prevent migration of the posteriorly injected medicine to the targeted ventral or anterior epidural space.