Treatment for Low Back Pain: Does Lack of Evidence Mean It Doesn't Work?

Some new and important discoveries are being made about low back pain. For example, it used to be said over and over that eight out of 10 people would suffer a bout of back pain at least once in their lifetime. That's still true. But the next part of the story may not be so true.

Based on the best evidence available at the time, doctors told their patients that with a short period of rest followed by as much activity as tolerated, the pain would go away in one to two weeks. That's still true, too -- but not for everyone. In fact, some recent studies have reported that three out of every four back pain patients still have back pain three to 12 months later.

A closer look helps explain some of these statistics. Advanced imaging and neurophysiologic and precision diagnostic techniques have shown scientists that spine pain can come from more than one place. Pain could be from the muscles, ligaments, discs, joints, or a combination of two or more of those places.

Since each one of these areas requires a slightly different approach, one treatment method may not be effective. In fact, that probably explains why there are so many different ways to treat chronic low back pain. Some are nonoperative while others involve complex and challenging surgeries. Somewhere in between is a technique called interventional procedures.

Interventional procedures involve a minimally invasive operation. The surgeon inserts a long needle through a tiny incision in the skin and advances it to the spine in order to carry out the procedure. This method is called percutaneous. A special real-time X-ray called fluoroscopy is used to guide the surgeon.

Or the surgeon can make a slightly larger incision and insert a tube through which an endoscope is placed. The scope has a tiny TV camera on the end that also shows the surgeon the spine and surrounding anatomy. With the guidance offered by fluoroscopy or endoscope, the surgeon can be much more precise and accurate without making a large incision and opening the patient up.

The evidence for interventional procedures is the topic of this report from the American Society of Interventional Pain Physicians (ASIPP). The past president of this organization (Dr. A. Trescot) has put together an evidence-based summary on interventional approaches to chronic low back pain. Epidural steroids, epidural adhesiolysis, nerve blocks, radiofrequency ablation, and sacroiliac joint injections are just a few of the treatments discussed. Treatment for disc problems called intradiscal therapies is also presented.

So what does the literature have to say so far about interventional pain techniques? First, it might be best NOT to measure results based on pain relief. Pain is just too subjective from person to person. It's best to evaluate the patients' function as a better measure of treatment effectiveness.

Specific ASIPP treatment guidelines for epidural injections remind researchers that image-guided injections can be delivered to several different anatomical locations. When studying epidural injections, it's best not to lump all injection sites together in one study. Right now, results from studies that have separated treatment based on site of medication delivery are limited in number. Most studies combined all-site epidural injections into one group of patients.

Epidural injections provide short-term pain relief. If at least 50 per cent of the pain is gone and stays gone for six to eight weeks, then it's okay to repeat the injection at the end of eight weeks -- but only if it's really needed. If more than one area is being targeted, then the injections should be given at the same time. The total number of epidural injections at each site should not be more than four to six times per year.

A second interventional procedure under investigation is adhesiolysis. This particular method uses radiofrequency or extremely cold temperatures (cryoneuroablation) to destroy tiny adhesions. These scars form around the nerve root and inside the epidural space (space around the spinal cord inside the spinal canal formed by the vertebrae). Breaking up the adhesions once again allows normal motion of the nerves as they leave the spinal cord and travel down the limbs.

Adhesiolysis is used most often for patients with disc-related back pain or for those who develop scarring and pain after back surgery. ASIPP treatment guidelines recommend limits to these procedures based on whether they are done percutaneously (needle through the skin) or endoscopically (larger scope down to the surgical site).

Spinal joints called facet or zygapophysial (z-joint) can also generate back pain. When the discs degenerate and lose height, ligaments around the joints become lax. The end result is increased movement at the joint and joint degeneration. Pain from the joints can be relieved with nerve blocks. These nerve blocks can be done first to diagnose and then treat to the problem.

ASIPP guidelines suggest facet joint injections can obtain short- and long-term pain relief. Diagnostic injections should be separated by at least a week (two weeks is better). Therapeutic injections should be separated by two to three months (or longer). Second or third injections are only given when the patient has had at least 50 per cent reduction in pain that lasted at least six weeks.

Nerve blocks don't always last forever. The pain often comes back. But at least the surgeon knows it's coming from the joint. Other methods of dealing with facet joint pain involve not just blocking the nerve pathway but actually destroying it. This is called facet neurotomy. Radiofrequency and cryoneuroablation therapy can be used for this treatment. This is similar to performing a root canal on a tooth. Neurotomy may have to be repeated more than once but should not be done more than three times per year at the same site.

There are several more interventional procedures discussed in this very comprehensive article: sacroiliac joint injections, intradiscal therapies, and spinal cord stimulation. Sacroiliac injections may help with low back pain that is really coming from the sacroiliac joint (SI). At first, diagnostic injections of the SI joint seemed like proof positive that the sacroiliac joint was the source of the problem.

It turns out that these injections don't always give patients pain relief even when the SI joint is the problem. So there are a fair number of false negative responses. False negative means when the joint was injected, the pain didn't go away. The conclusion was that the SI joint wasn't the cause of the problem after all. But in fact, later tests confirmed the sacroiliac joint as the true source of pain. It has been suggested that missing the target with the injection might account for these false negative responses. With the use of fluoroscopy, false negative responses should decrease.

ASIPP guidelines for managing sacroiliac joint pain with steroid injections or radiofrequency neurotomy (destroying nerve tissue) are based on limited evidence. SI injections for diagnostic purposes can be done twice. The same recommendations apply as for other types of injections: repeated only if at least 50 per cent pain relief is reported and no sooner than a week apart. Both sacroiliac joints should be injected at the same time. A maximum of four to six injections per year are suggested for treatment. Radiofrequency neurotomy has a longer separation time (at least three months) and a maximum of three total treatments per year.

What about intradiscal therapies? Surgeons are looking for ways to avoid surgery. Instead of removing the damaged disc, there are ways use heat to destroy (vaporize) the disc. Two examples of interventional procedures of this type for discs include intradiscal electrothermal therapy and radiofrequency posterior annuloplasty. The evidence around both of these procedures is too limited to even make specific guidelines or suggestions at this time.

And finally, implantable therapies such as spinal cord stimulators (SCSs) and intrathecal pumps (ITPs) are discussed. These devices are placed first with electrodes on the outside of the spine. If they provide good relief from pain during a one- to two-week trial, they can be implanted (placed) inside the body.

Like other pain relief mechanisms, the spinal cord implants deliver an alternate stimulus to the spinal cord to override the pain messages. The intrathecal pumps provide a constant stream of pain relieving medications into the spinal fluid.

There has been some good short- and long-term success with implantable therapies. Patients with back pain associated with failed back syndrome and nerve pain from complex regional pain syndrome seem to have the best results with implantable therapy.

The author concludes by saying that current best evidence is always welcomed when making decisions about the most effective way to treat someone's back pain. But studies are limited and sometimes it's not possible to compare one treatment to others or to a placebo (pretend or fake treatment). That makes gathering real evidence a challenge.

A final quote seems to sum up the state of affairs around evidence for or against interventional procedures. Lack of evidence in the literature is not evidence of lack of effectiveness. In other words, just because a treatment hasn't been studied enough or can't be adequately compared to other treatments doesn't mean it doesn't work or isn't effective.

Evaluating these procedures will continue as an ongoing research theme. In the meantime, don't throw the baby out with the bath water while looking for objective measures of success. Any modality that helps control or eliminate pain should be used until conclusively proven ineffective.

Andrea Trescot, MD. Interventional Approaches to the Management of Spinal Pain. In Pain Medicine News. June 2009. Vol. 7. No. 6. Pp. Insert 1-11.

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