MR imaging of the postoperative lumbar spine.

The greatest costs associated with lower back pain occur in patients who have pain longer than three months and those with recurrent episodes of disabling pain. For these groups, evaluation by MR imaging is critical because it provides evidence for continued pain and functional incapacitation in 19% of cases. The causes of delayed recurrence of lower back and sciatic pain are multiple and include arachnoiditis, epidural fibrosis, facet osteoarthritic degenerative change, instability, new intervertebral disc herniation, spinal stenosis (lateral or central, from postoperative bony overgrowth), and vertebral osteomyelitis.