Patients who have undergone one or more operations on the lumbar spine, and continue to experience and report pain afterward can be divided into two groups. The first group are those in whom surgery was never indicated, or the surgery performed was never likely to achieve the desired result; and those in whom the surgery was indicated, but which technically did not achieve the intended results

The second group includes patients who had incomplete or inadequate operations. Lumbar spinal stenosis may be overlooked, especially when it is associated with disc protrusion or herniation. Removal of a disc, while not addressing the underlying presence of stenosis can lead to disappointing results.

According to a 2004 study, 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, it is estimated over $2.5 billion was billed for fusion surgery hardware alone. For patients with continued pain after surgery which is not due to the above complications or conditions, doctors attempt to determine what anatomic structure is causing a "pain response".  While not always successful, a surgeon must operate on the structure to correct the source of pain.

Patients with continuing pain are often found to have disc bulges on multiple levels, which imaging studies do not always identify. This according to a 2002 study.  In addition, the 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 vertebrae.