pain. If a specific disc herniation causing pressure on a nerve root cannot be identified, the results of surgery are likely to be disappointing. Patients involved in worker's compensation, tort litigation or other compensation systems tend to fare more poorly after surgery. Surgery for spinal stenosis usually has a good outcome, if the surgery is done in an extensive manner, and done within the first year or so of the appearance of symptoms. Oaklander and North define the Failed Back Syndrome as a chronic pain patient after one or more surgical procedure to the spine. They delineated these characteristics of the relation between the patient and the surgeon: The patient makes increasing demands on the surgeon for pain relief. The surgeon may feel a strong responsibility to provide a remedy when the surgery has not achieved the desired goals. The patient grows increasingly angry at the failure and may become litigious. There is an escalation of narcotic pain medication which can be habituating or addictive. In the face of expensive conservative treatments which are likely to fail, the surgeon is persuaded to attempt further surgery, even though this is likely to fail as well. The probability of returning to gainful employment decreases with increasing length of disability. The financial incentives to remain disabled may be perceived as outweighing the incentive to recover. In the absence of a financial source for disability or worker's compensation, other psychological features may limit the ability of the patient to recover from surgery. Some patients are simply unfortunate, and fall into the category of "chronic pain" despite their desire to recover and the best efforts of the physicians involved in their care. Even less invasive forms of surgery are not uniformly successful; approximately 30,000–40,000 laminectomy patients obtain either no relief of symptomatology or a recurrence of symptoms. Another less invasive form of spinal surgery, percutaneous disc surgery, has reported revision rates as high as 65%. It is no surprise, therefore, that FBSS is a significant medical concern which merits further research and attention by the medical and surgical communities. Total disc replacement Lumbar total disc replacement was originally designed to be an alternative to lumbar arthrodesis (fusion). The procedure was met with great excitement and heightened expectations both in the United States and Europe. In late 2004, the first lumbar total disc replacement received approval from the U.S. Food and Drug Administration (FDA). More experience