How Important Is Evidence-Based Medicine in Epidural Injection for Low Back Pain?
There are several evidence-based (EB) guidelines that address the use of epidural injections for the treatment of low back pain. But how influential are these guidelines to the everyday decision-making of physicians? To study this question, the Accreditation Association for Ambulatory Health Care (AAAHC) Institute for Quality Improvement, a subsidiary of AAAHC, conducted a study of epidural low back injections (LBI) in the ambulatory setting to see how guidelines influence day-to-day practices.
The study results suggest that while most of the practices fall within the parameters of one or more guidelines, a significant proportion do not. Areas in which day-to-day practice differs from EB guidelines included the indications/contraindications for the procedure, use and duration of conservative therapy, and number and frequency of injections.1 This article will summarize the AAAHC study results, as well as give context to the findings.
Why Evidence-Based Guidelines
Imperfect adherence to guidelines is not unique to pain management. Many guidelines are equivocal or contradictory, there often is not enough evidence to reach definitive conclusions, and there is evidence that physicians, in general, often do not follow guidelines. Moreover, in rapidly evolving technologies such as interventional pain management, the “latest” guidelines may not reflect the latest research.
Despite these concerns, guidelines play an increasing role in patient care and reimbursement decisions. This is primarily because federal and state agencies and third-party payers look to EB recommendations to guide efforts to improve quality of care and halt the precipitous increase in health care costs.
This trend has important implications for the treatment of chronic back pain. From 1997 through 2006, there was a 49% increase in the number of patients seeking spine-related treatment for back and neck pain problems, and a 65% increase in health care expenditures related to these conditions.2 A dramatic increase in interventional techniques for treating low back pain has been a major driver of these increases in costs. A recent analysis of the Medicare population documents an increase in interventional procedures for low back pain from 1,460,495 in 2000 to 4,815,673 in 2011, an increase of more than 200%. The vast majority of these interventions included epidural injections, facet joint injections, or other nerve blocks. For example, the number of epidural injections grew from 832,000 to 2.3 million over the last decade (Figure 1).3
Day-to-Day Practice for Epidural LBI
The AAAHC Institute study offers a snapshot of the practice of LBI for pain, as performed in the ambulatory setting. In 2006, 60% of LBIs were performed in an ambulatory setting.4,5 The performance measures were reported from a sampling of 623 patients treated in 31 ambulatory organizations, which performed a total of 65,000 LBI procedures per year. These organizations included freestanding ambulatory surgery centers (ASCs) and office-based practices. Multi- and single-specialty organizations were represented as well as those owned and operated by physicians or joint ventures.
The results of the survey were compared to guideline recommendations for:
- Types of injections
- Indications/symptoms for which LBI is appropriate
- Duration of conservative therapy prior to LBI
- The number and frequency of injections per patient
Types of Injections
There are 3 common methods for delivering steroid into the epidural space: the interlaminar, caudal, and transforaminal approaches (Table 1). According to the North American Spine Society, an interlaminar epidural spinal injection (ESI), involves placing the needle into the posterior epidural space and delivering the steroid over a wider area. Similarly, the caudal approach uses the sacral hiatus to allow for needle placement into the very bottom of the epidural space.6 With both approaches, the steroid spreads over several segments and can cover both sides of the spinal canal. With a transforaminal ESI, often referred to as a “selective nerve root block,” the needle is placed alongside the nerve as it exits the spine and medication is placed into the “nerve sleeve.” The medication then travels up the sleeve and into the epidural space from the side, allowing for more concentrated delivery of medications into the affected area.6
The type of procedures reflected in the survey included 49% lumbar/sacral caudal epidural injections, 38% lumbar/sacral transforaminal injections, and 17% paravertebral facet joint injections. Of note, several patients received multiple types of LBIs. Of all of the injections, 75% were considered therapeutic, 7% diagnostic, and 18% both therapeutic and diagnostic.
There is significant dispute regarding the use of LBI, including what conditions and symptoms are considered appropriate indications. In fact, even when investigators have used the same criteria, there have been conflicting conclusions.7-10
Symptoms that often are considered indicative of LBI include nonspecific back pain, limited range of motion or function, radiating pain, disc herniation (possible positive straight leg raise), post-lumbar surgery or laminectomy syndrome, and spinal stenosis. “Red flags,” such as cauda equina and suspicion of cancer, should be distinguished from other low back-related pain and treated accordingly.
Additionally, there is conflicting evidence regarding the long-term efficacy of LBIs.8-15 The most recent EB review of these procedures, the 2013 update of the Interventional Pain Management (IPM) guidelines of the American Society of Interventional Pain Physicians,16 concluded that, overall, the evidence was fair to good for 62% of diagnostic and 52% of therapeutic interventions that were assessed. The relative efficacy of the various types of epidural injections and the rated evidence were considered to be good for patients with a herniated disk or sciatica, but less so for other patient symptoms/history. Table 2 reviews the IPM Guidelines for different indications/symptoms.
The vast majority of patients in the survey, 80%, were diagnosed with radiculitis and/or disc herniation, and had a variety of presenting symptoms including: radiating pain, 65% (n=403); localized pain, 61% (n=378); herniated disc, 57% (n=354); limited range of motion, 46% (n=287); weakness, 26% (n=165); spinal tenderness, 22% (n=139); and positive straight leg test, 12% (n=77).
Furthermore, 78% of patients rated the severity of their symptoms as greater than 5 on a scale of 0 to 10 on the visual analog scale (0= no pain, 10 = most severe pain).