- Moderate to severe CLBP (i.e. pain that occurs in an area with boundaries between the lowest rib and the crease of the buttocks) that 1) must have been present for at least several hours a day for a minimum of 3 months, 2) is not due to a known malignancy, and 3) must be classified as non-neuropathic, neuropathic, or symptomatic for more than 6 months after LBP surgery based on the Quebec Task Force Classification of Spinal Disorders.