extruded or sequestered disc fragment. Inadequate or inappropriate surgical exposure can lead to other problems in not getting to the underlying pathology. Hakelius reported a 3% incidence of serious nerve root damage. In 1992, Turner et al. published a survey of 74 journal articles which reported the results after decompression for spinal stenosis. Good to excellent results were on average reported by 64% of the patients. There was, however, a wide variation in outcomes reported. There was a better result in patients who had a degenerative spondylolisthesis. A similarly designed study by Mardjekto et al. found that a concomitant spinal arthrodesis (fusion) had a greater success rate. Herron and Trippi evaluated 24 patients, all with degenerative spondylolisthesis treated with laminectomy alone. At follow-up varying between 18 and 71 months after surgery, 20 out of the 24 patients reported a good result. Epstein reported on 290 patients treated over a 25-year period. Excellent results were obtained in 69% and good results in 13%. These optimistic reports do not correlate with "return to competitive employment" rates, which for the most part are dismal in most spinal surgery series. 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 22% increase from 1990 in fusions per 100,000 population, increasing to an estimate of 250,000 in 2003, and 500,000 in 2006. In 2003, the national bill for the hardware for fusion alone was estimated to have soared to $2.5 billion a year. 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. To be effective, the surgeon must operate on the correct anatomic structure, but is often not possible to determine the source of the pain. 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. In addition, spinal fusion itself, particularly if more than one spinal level is operated on, may result in "adjacent segment degeneration". 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