The role of disc replacement must come from new indications not defined in todays literature or a relaxation of current contraindications.A study by Regan     found the result of replacement was the same at L4-5 and L5-S1 with the CHARITE disc. However, the ProDisc II had more favorable results at L4-5 compared with L5-S1.A younger age was predictive of a better outcome in several studies. In others it has been found to be a negative predictor or of no predictive value. Older patients may have more complications.Prior spinal surgery has mixed effects on disc replacement. It has been reported to be negative in several studies. It has been reported to have  no effect in other studies. Many studies are simply inconclusive. Existing evidence does not allow drawing definite conclusions about the status of disc replacement at present. Electrical stimulation
Many failed back patients are significantly impaired by chronic pain in the back and legs. Many of these will be treated with some form of electrical stimulation. This can be either a transcutaneous electrical nerve stimulation device placed on the skin over the back or a nerve stimulator implanted into the back  with electrical probes which directly touch the spinal cord. Also, some chronic pain patients utilize fentanyl or narcotic patches. These patients are generally severely impaired and it is unrealistic to conclude that application of neurostimulation will reduce that impairment. For example, it is doubtful that neurostimulation will improve the patient enough to return to competitive employment. Neurostimulation is palliative.
Neoplasia also includes direct seeding of the cerebrospinal fluid (CSF) from primary central nervous system (CNS) tumors such as glioblastoma multiforme, medulloblastoma, ependymoma, and choroid plexus carcinoma. Strictly speaking, the most common cause of arachnoiditis in failed back syndrome is not infectious or from cancer. It is due to non-specific scarring secondary to the surgery or the underlying pathology. Nerve injury
Laceration of a nerve root, or damage from cautery or traction can lead to chronic pain, however this can be difficult to determine. Chronic compression of the nerve root by a persistent agent such as disc, bone (osteophyte) or scarring can also permanently damage the nerve root. Epidural scarring caused by the initial pathology or occurring after the surgery can also contribute to nerve damage. In one study of failed back patients, the presence of pathology was noted to be at the same site as the level of  surgery performed in 57% of cases. The remaining cases developed pathology at a different level, or on the opposite side, but at the same level as the surgery was performed. In theory, all failed back patients have some sort of nerve injury or damage which leads to a persistence of symptoms after a reasonable healing time. Diagnosis
Avoiding post-laminectomy/laminotomy syndrome
Smaller procedures that do not remove bone (such as Endoscopic Transforaminal Lumbar Discectomy and Reconfiguration) do not cause post laminectomy/laminotomy syndrome. Management
Failed back syndrome (FBS) is a well-recognized complication of surgery of the lumbar spine.