Failed back syndrome

Failed Back Syndrome or Post-laminectomy Syndrome is a condition characterized by persistent pain following back surgeries.

Failed back syndrome (FBS), more commonly referred to as "failed back surgery syndrome" (FBSS), refers to chronic back and/or leg pain that occurs after back (spinal) surgery.^[1][2] Multiple factors can contribute to the onset or development of FBS. Contributing factors include but are not limited to residual or recurrent disc herniation, persistent post-operative pressure on a spinal nerve, altered joint mobility, joint hypermobility with instability, scar tissue (fibrosis), depression, anxiety, sleeplessness and spinal muscular deconditioning. An individual may be predisposed to the development of FBS due to systemic disorders such as diabetes, autoimmune disease and peripheral blood vessels (vascular) disease. Smoking is a risk for poor recovery from such an operation as is anything that constricts the blood vessels.

Common symptoms associated with FBS include diffuse, dull and aching pain involving the back and/or legs. Abnormal sensibility may include sharp, pricking, and stabbing pain in the extremities. The term “post-laminectomy syndrome” is used by some doctors to indicate the same condition as failed back syndrome.

The treatments of post-laminectomy syndrome include physical therapy, minor nerve blocks, transcutaneous electrical nerve stimulation, behavioral medicine, non-steroidal anti-inflammatory medications, membrane stabilizers, antidepressants, spinal cord stimulation, and intracathecal morphine pump. Use of epidural steroid injections has been shown to decrease the frequency and intensity of the pain. The targeted anatomic use of a potent anti-inflammatory anti-TNF therapeutic is an emerging treatment option for patients with severe back or neck disc-related pain associated with FBSS (see below).

In the past two decades there has been a dramatic increase in fusion surgery in the U.S.: in 2001 over 122,000 lumbar fusions were performed, a 220% increase from 1990 in fusions per 100,000 population, increasing to an estimate of 250,000 in 2003, and 500,000 in 2006.^[3][4][5] In 2003, the national bill for the hardware for fusion alone was estimated to have soared to $2.5 billion a year.^[4] A single screw that goes into the spine may sell for $1,000.^[5] In 2004, the average hospital bill, excluding professional fees was $34,000 for fusion surgery; if one adds the fee of the surgeon, the assistant surgeon, and the anesthesiologist, one can easily see how fusion surgery alone generates billions of dollars per year in fees for hospitals and surgeons.^[6]

With these increasing numbers of operations, one would expect the incidence of FBSS to also have increased. In contrast to the representation that “spine surgery is no more than 95% predictive of a successful result”,^[7] other sources document a success rate as low as 49%, depending upon the evaluation criteria used.^[8] Other forms of spinal surgery are less invasive than spinal fusion; one such operation is laminectomy, performed more than 250,000 times per year in the U.S.^[9] But even this less invasive form of surgery is not uniformly successful; approximately 30,000-40,000 laminectomy patients obtain either no relief of symptomatology or a recurrence of symptoms.^[10] Another less invasive form of spinal surgery, percutaneous disc surgery, has reported revision rates as high as 65%.^[11] It is no surprise, therefore, that FBSS is a significant medical concern which merits further research and attention by the medical and surgical communities.

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Etiology of the Failed Back Surgery Syndrome

For patients with continued severe pain following spinal surgery the surgeon's first responsibility is to rule out a serious treatable cause of pain: infection, tumor, fracture, spinal instability, or abscess. If present, these causes are usually ferreted out early-on. Surgeons will argue that the etiology of FBSS "can be poor patient selection, incorrect diagnosis, suboptimal selection of surgery, poor technique ...and/or recurrent pathology", as well as including "failure to achieve surgical goals".^[12] Commonly, however, causes of continued pain are difficult to unequivocally identify, and the patient suffers from chronic pain, not readily amenable to surgical intervention.^[13][14] For those contemplating more surgery additional complications must be considered. Complications of spinal fusion surgery may include instrument failure, bone-donor site infection or chronic pain; neural injuries, pulmonary embolus, infections, vascular complications (rare but potentially catastrophic), failure to achieve a solid fusion, and blindness.^[6]

For patients with continued pain after surgery which is not due to the above complications or conditions, interventional pain physicians speak of the need to identify the "pain generator" i.e. the anatomical structure responsible for the patient's pain. Obviously, to be effective, the surgeon must operate on the correct anatomic structure; however it is often not possible to determine the source of the pain.^[13][14] The reason for this is that many patients with chronic pain often have disc bulges at multiple spinal levels and the physical examination and imaging studies are unable to pinpoint the source of pain.^[13] In addition, spinal fusion itself, particularly if more than one spinal level is operated on, may result in “adjacent segment degeneration”.^[15] This is thought to occur because the fused segments may result in increased torsional and stress forces being transmitted to the intervertebral discs located above and below the fused vertebrae.^[15] This pathology is one reason behind the development of artificial discs as a possible alternative to fusion surgery. But the fusion surgeons would argue that spinal fusion is more time-tested, and artificial discs contain metal hardware that is unlikely to last as long as biological material without shattering and leaving metal fragments in the spinal canal.

Another highly relevant consideration is the increasing recognition of the importance of “chemical radiculitis” in the generation of back pain.^[16] A primary focus of surgery is to remove “pressure” or reduce mechanical compression on a neural element: either the spinal cord, or a nerve root. But it is increasingly recognized that back pain, rather than being solely due to compression, may instead entirely be due to chemical inflammation.^{[17][18] [19][16]} In the past five years increasing evidence has pointed to a specific inflammatory mediator of this pain.^[20][21] This inflammatory molecule, called tumor necrosis factor-alpha (TNF), is released not only by the herniated or protruding disc, but also in cases of disc tear (annular tear), by facet joints, and in spinal stenosis.^{[16][22][23][24]} In addition to causing pain and inflammation, TNF may also contribute to disc degeneration.^[25] If the cause of the pain is not compression, but rather is inflammation mediated by TNF, then this may well explain why surgery might not relieve the pain, and might even exacerbate it, resulting in FBSS.

Treatment

If chronic pain in FBSS has a chemical component producing inflammatory pain, then prior to additional surgery it may make sense to use an anti-inflammatory approach. Often this is first attempted with non-steroidal anti-inflammatory medications, but the long-term use of NSAIDS for patients with persistent back pain is complicated by their possible cardiovascular and gastrointestinal toxicity; and NSAIDs have limited value to intervene in TNF-mediated processes.^[14] An alternative often employed is the injection of cortisone into the spine adjacent to the suspected pain generator, a technique known as “epidural steroid injection”.^[26] Although this technique began more than a decade ago for FBSS, the efficacy of epidural steroid injections is now generally thought to be limited to short term pain relief in selected patients only.^[27] In addition, epidural steroid injections, in certain settings, may result in serious complications.^[28] Fortunately there are now emerging new methods that directly target TNF.^[29] These TNF-targeted methods represent a highly promising new approach for patients with chronic severe spinal pain, such as those with FBSS.^[29] Ancillary approaches, such as rehabilitation, physical therapy, anti-depressants, and, in particular, graduated exercise programs, may all be useful adjuncts to anti-inflammatory approaches.^[14] In addition, more invasive modalities, such as spinal cord stimulation, may offer relief for certain patients with FBSS, but these modalities, although often referred to as “minimally invasive", require additional surgery, and have complications of their own.^[30][31]

Emerging Treatment Options

The identification of tumor necrosis factor-alpha (TNF) as a central cause of inflammatory spinal pain now suggests the possibility of an entirely new approach to selected patients with FBSS. Specific and potent inhibitors of TNF became available in the U.S. in 1998, and were demonstrated to be potentially effective for treating sciatica in experimental models beginning in 2001.^[32][33][34] Targeted anatomic administration of one of these anti-TNF agents, etanercept, a patented treatment method,^[35] has been suggested in published pilot studies to be effective for treating selected patients with chronic disc-related pain and FBSS.^[29][36] The scientific basis for pain relief in these patients is supported by the most current review articles.^[37][38] In the future new imaging methods may allow non-invasive identification of sites of neuronal inflammation, thereby enabling more accurate localization of the "pain generators" responsible for symptom production.

References

External links

General Interest

• New York Times Back Pain