Failed back syndrome (FBS) is a well-recognized complication of surgery of the lumbar spine. It can result in chronic pain and disability, often with disastrous emotional and financial consequences to the patient. Many patients have traditionally been classified as "spinal cripples" and are consigned to a life of long-term narcotic treatment with little chance of recovery.

The reported rates of success and failure of lower back surgery vary widely, largely depending on the selection criteria of the patient. In other words, if the diagnosis is very clear the chance of surgical success appears to be around 80% in the short term. In reality, for many possible reasons including patients who have exhausted all other available options, surgery is performed on patients who do not strictly meet the criteria.

Conservatively, over 40% of patients who have undergone lumbar surgery continue to suffer significant pain, and a substantial portion of these (15%) will result in FBS.

Patients with FBS can be divided into one of two groups: 1. Patients in whom surgery was never indicated, or carried a low chance of achieving success, and, 2. patients in whom the surgery was indicated but the surgery was inadequately or incompletely performed.

Several studies have found that up to 95% of FBS patients fit into the first group, in which inappropriate surgery was performed on patients who actually have severe muscle pain which often mimics the pain of a herniated disc. The second group of patients make up the remaining 5%. Causes include the operation being done at the incorrect level, too little or too much bony removal, failure to remove the targeted fragment of disk, scarring and over fusion of joints.