Epidural Steroid Injections For Disc-Related Low Back Pain

Although epidural steroid injections (ESIs) are typically thought of as a treatment for the radicular pain (leg pain), there is significant medical evidence that suggests ESIs can also be used to reduce the low-back pain associated with disc herniation and annular tear. [1-6]

What is an epidural steroid injection? In a nutshell, an ESI, which have been around since the 1950s, is an outpatient medical procedure that involves inserting a thin needle into the epidural space at the level of the disc herniation and then injecting a corticosteroid (a very powerful anti-inflammatory) and anesthetic, which in turn travels from the injection site to the symptomatic disc herniation and reduces the pain-generating inflammatory process.

Who should perform the ESI procedure? Although many doctors of many different specialties are doing these procedures in this day and age of post-Obama care, only a fellowship-trained interventional pain medicine physician—one who has devoted his entire practice to using these injective procedures—would be good enough to treat my patients or me. [3]

Do epidural steroids really work? Unlike the experimental procedures mentioned above, there has been a lot of research performed on epidural steroid injections, and the short answer is yes, they do work in the short term (< 6months) for the relief of back and leg pain associated with disc herniation. [2,7] However, if you have spondylolisthesis or have waited longer than a year to try them, then the chances of success are not as good. [7] It is, however, important to understand that there's no significant evidence that demonstrates ESIs will have any effect on long-term clinical outcomes. [2] In other words, they are not going to affect how you are doing five years after the herniation occurs.

Another very important component of the ESI procedure is fluoroscopic imaging. Specifically, the fluoroscopy procedure uses a special low-radiation x-ray machine (figure 8) that creates a continuous radiographic picture (kind of like the one created when you pass through security screening at the airport) of the low back during the procedure. This way the physician can see exactly where the tip of the razor-sharp needle is at all times, which not only increases the chances of proper placement of the injectate (steroid + anesthetic), [8] but decreases the chances of patient injury. [9] Fluoroscopic guidance should be used during all ESI procedures, no matter which of the three approaches is used. [7]

Although using fluoroscopy during the procedure may sound like a no-brainer, you would be shocked at the number of physicians who don't use it, which results in the steroid being injected into the wrong spot 30-40% of the time! [7,8] Furthermore, by not using fluoroscopic guidance (or CT guidance) the risk of minor and major procedural complications significantly rises. [9] Therefore, I would not allow any of my patients or myself to undergo ESI without it.

The final things to understand about ESIs is that in order to get the desired effect (decrease in back and/or leg pain), you will most likely have to undergo more than one procedure. However, you should not have more than three ESIs per year;[3] although, if the first ESI fails to reduce your pain, then a second ESI will probably fail as well, and really shouldn't be attempted. [10]

As noted above, the ESI procedure can be done via three different approaches. Let's talk about them.

Caudal ESIs involve threading the needle completely through the narrow caudal canal of the sacrum and then releasing the steroid into the posterior epidural space (which of course is behind the thecal sac) only at the level of L5/S1. After its release the injectate (steroid + numbing-agent) must diffuse from the posterior epidural space, around the thecal sac, and (hopefully) enter the anterior epidural space in order to find its target (the disc herniation). Although this technique is still useful for patients who have suffered a lot of scar tissue (perineural fibrosis) in the anterior epidural space from a previous spine surgery, the technique has really fallen out of favor and is not encouraged. [3,7]

Interlaminar ESIs, which are still commonly used today, involve putting the needle between the lamina of the affected motion segment and then through the ligamentum flavum, which results in a "pop" and "loss of resistance" that the injectionist (doctor doing the procedure) can hear and feel. Like the caudal ESI, the injectate is released into the posterior epidural space and has to migrate around the thecal sac to the anterior epidural space in order to find its target. Again, some authors believe it "improbable" that the steroid will actually reach its target in the anterior epidural space and discourage the use of this procedure. [7]

Transforaminal ESIs, which are very popular these days, involve placing the needle within the neural foramen of the affected motion segment, after which the steroid is released into the foramen and distal anterior epidural space. The injectate now must travel only a short distance to reach the disc herniation target. (figure 7.6 & 7.9)

Figure 7.9 is a para-sagittal cartoon through the neural foramina that demonstrates the traditional needle placement for a transforaminal ESI.

Note the good-sized vein that is in close proximity to the needle tip. Now, perhaps you may realize why using fluoroscopic guidance is so important when performing ESIs. Even with the use of fluoroscopy, there is vascular penetration of the needle tip into the vein 7.4% of the time. [9] Luckily, because of the fluoroscopic guidance, the injectionist will soon realize that he has "poked" the vein and will reposition the needle accordingly.

Because of the long distance between the site of injection and the disc herniation target, both interlaminar and caudal ESIs must use a significantly higher volume of steroid (typically ~9mL) in order to be effective. [4,6] Such a high volume of steroid can increase the risk for large spikes in blood glucose and blood pressure, which might not bode well for patients who are diabetic and/or hypertensive. On the other hand, because they are performed within the anterior epidural space, transforaminal ESIs use a much lower volume of steroid (typically ~3mL) yet are just as effective, if not more effective then the posterior epidural procedures. [5]

Personally, I have had both the interlaminar and transforaminal injections and, although they both eliminated back and leg pain, the transforaminal effect lasted much longer (one month) than the interlaminar injection (one week).

References

1) Parr AT, Diwan S, Abdi S. Lumbar interlaminar epidural injections in managing chronic low back pain and lower extremity pain: a systematic review. Pain Physician 2009;12:163-188.

2) Chou R, Atlas SJ, Stanos SP, Rosenquist RW. Nonsurgical interventional therapies for low back pain: a review of the evidence for an American Pain Society clinical practice guideline. Spine 2009;34:1078-1093.

3) Fetzer A, Scott DR. Nonsurgical treatment of herniated nucleus pulposus. In: Phillips FM, Lauryssen C, eds. The lumbar intervertebral disc. New York, NY: Thieme; 2010:86-91.

4) Manchikanti L, Cash KA, McManus CD, et al. A randomized, double-blind, active-controlled trial of fluoroscopic lumbar interlaminar epidural steroid injections in chronic axial or discogenic low back pain: results of two-year follow-up. Pain Physician to 13;16:E491-E504.

5) Rados I, Sakic K, Fingler M, et al. Efficacy of interlaminar versus transforaminal epidural steroid injection for the treatment of chronic unilateral radicular pain: prospective randomized study. Pain Medicine 2011; 12:1316-1321.

6) Parr AT, et al. Caudal epidural injections in the management of chronic low back pain: a systematic appraisal of the literature. Pain Physician 2012;15:E159-198.

7) Vad VB, Bhat AL, Lutz GE, et al. Transforaminal epidural steroid injections in lumbosacral radiculopathy: a prospective randomized study. Spine 2002; 27:11-16.

8) Weinstein SM, Herring SA, Derby R. Contemporary concepts in spine care: epidural steroid injections. Spine 1995; 20:184-186.

9) Karaman H, Kavak GO, Tufek A, et al. The complications of transforaminal lumbar epidural steroid injections. Spine 2011; 36:E819-E824.

10) Arden NK, et al. A multicenter randomized control trial of epidural corticosteroid injections for sciatica. Rheumatology 2005; 44:1399-1406.

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