Failed Back Surgery Syndrome

Failed back surgery syndrome refers specifically to persistent or recurrent, chronic debilitating low back pain after one or more surgical procedures on the lumbosacral spine, such as a discectomy, laminectomy, and lumbosacral fusion.

A spine surgery in the lumbar region  is mainly done for two causes

• To decompress a nerve root
• To stabilize a painful joint.

All over the world, nowadays, the number of surgeries for back pain has increased.

New invasive procedures such as percutaneous discectomy and chemonucleolysis, while reducing some morbidities, have broadened the indications for treatment and thus added new categories of treatment failures.

Failed back surgery syndrome is a group of disorders with persistent or recurrent symptoms following spinal surgery with hallmarks of back pain, sciatica, and functional impairment. The severity of failed back surgery is often sufficiently great to cause a change in the job.

The procedures frequently associated with failed back surgery syndrome are

• Laminotomy
• Discectomy
• Spinal Fusion

Terms failed back syndrome is used interchangeably with failed back surgery syndrome, though in a stricter sense may bean the failed treatment, not necessarily surgical treatment.

The term failed back is also used vaguely for this condition but in a more broader sense implies functional failure of the back, as opposed to the failure of treatment or surgery.

Causes of Failed Back Surgery Syndrome

• Inappropriate or premature selection of patients for surgery [Most common
  cause]
• Irreversible neural injury
  • Second most common cause
  • Loss of primary afferent neurons has been shown to be a risk factor for chronic neuropathic pain
• Incomplete decompression
  • Unrecognized lateral recess stenosis
  • Lateral disc herniation
  • Missed sequestered free disc fragment
• Extensive fusion or extensive instrumentation leading to loss of normal lumbar lordosis (flat-back syndrome)
• Infections

Persistent or Recurrent Disc Herniation

Removal of a disc at one level can lead to disc herniation at the same level or a different level at a later time. Even the most complete surgical excision of the disc still leaves 30-40% of the disc, which cannot be safely removed. This retained disc can re-herniate sometime after surgery. Most common cause of a failed back syndrome is caused by recurrent disc herniation at the same level originally operated. A rapid removal in a second surgery can be curative.

Spinal stenosis

Spinal stenosis can be a late complication and is thought to be a significant cause of failed back.

Postoperative Infection

A small minority of lumbar surgical patients will develop a post-operative infection. In most cases, this is a bad complication with incidence from 0-12%. The incidence of infection tends to increase as the complexity of the procedure and operating time increase. Use of metal implants tends to increase the risk of infection.

Factors associated with an increased infection include diabetes mellitus, obesity, malnutrition, smoking, previous infection, rheumatoid arthritis, and immunodeficiency. Previous wound infection should be considered as a contraindication to any further spinal surgery

Epidural Scar

Epidural scarring may occur following repeated surgeries.

Arachnoiditis

Arachnoiditis is a means inflammation of the meninges and subarachnoid space. The most common cause of arachnoiditis in failed back syndrome 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

Clinical Presentation of Failed Back Surgery Syndrome

The diagnosis of a failed back is often a clinical challenge. There is a history of one or more back surgeries. Common symptoms associated with failed back surgery syndrome include diffuse, dull and aching pain involving the back and/or legs. Abnormal sensibility may include sharp, pricking, and stabbing pain in the extremities.

Details of previous procedure should be sought.

The patient should be examined for the musculoskeletal and neurologic signs.

The patient should also be examined for functional signs or psychosomatic issue should also signs, and also functional signs.

It is essential to detect physical findings predictive of poor outcome, of a repeat surgical procedure.

Abnormalities such as weakness or sensory loss that appear and disappear at various times, change location, are suggestive of secondary gain or psychological problems and argue against repeat surgery.

Imaging

Xray, contrast-enhanced CT, MRI, aid in diagnosis. Out of these MRI has got the best sensitivity and accuracy.

Gadolinium-enhanced MRI is the imaging of choice.  MRI has limitations, however, in defining bony anatomy which often can be better visualized by plain- X-Ray and CT.

Electromyography

In FBSS patients, EMG is useful in differentiating acute and chronic muscle denervation. .

Psychological Testing

The standardized psychological testing has been helpful in identifying comorbidities requiring treatment,

Diagnostic Blocks

A series of nerve root blocks can be useful in the evaluation of FBSS patients with multilevel anatomic abnormalities. By knowing which abnormalities are contributing to a patient’s pain syndrome, surgery can be limited to those levels.

Limited predictive value of nerve root blocks has been reported before rhizotomy.

Provocative Discography

The basic idea of performing discography is to determine whether mechanical loading of individual disks reproduces an individual patient’s characteristic pain. Negative results of discography are helpful in avoiding further unnecessary surgery in FBSS patients.

Lab Investigations

There are no specific lab tests. Routine tests for general well being and factors like diabetes and other co-morbidities may be done.

Treatment of Failed Back Surgery Syndrome

There is no definitive treatment for this problem. Therefore failed back surgery syndrome can be a challenging, difficult and frustrating syndrome to treat. Most of these patients have had pain for a longer duration, have had multiple interventions, and often have financial and psychosocial difficulties.

Non-Operative Treatment

Options include

The treatments  used are

• Physical therapy
• Nerve blocks
• Transcutaneous electrical nerve stimulation (TENS)
• Behavioral medicine
• Non-steroidal anti-inflammatory (NSAID) medications
• Opioids
• Membrane stabilizing drugs
• Antidepressants
• Spinal cord stimulation
• Intrathecal morphine pump
• Epidural steroid injections

Treatment also includes addressing the contributing medical factors, such as obesity or depression. Patients who already had one unsuccessful surgery should be even more strongly considered for a detailed trial of medical management. This may take months, on even several years, because there are many drugs that help some of these patients, but no one medication or class of medications has universal efficacy.

These patients are very likely to be using pain medications including opioids. Physical tolerance can develop. Use of chronic opioid analgesics is not a contraindication for reoperation.

Facet (or Zygapophyseal) joint block

The facet joints form an articulation between the inferior articular process of the vertebra above and the superior articular process of the vertebra below. The joint is enclosed by a capsule, and it is an underappreciated cause of low back pain and of pain radiating to the buttocks or upper legs. Patients with the pain of facet origin usually present with axial and proximal radicular-type pain, worsened by lumbar extension, and not associated with sciatic tension signs.

The facet block determines that whether facet arthropathy is contributing to their low back pain.

Epidural Steroids in FBSS

Response to epidural steroids is achieved when the drug is placed in closest proximity to the pain source. Following epidural steroids, improvement in cognitive functions and pain relief occur but only 3-9 months.

Other Therapies

• Physical therapy
• Acupuncture
• Relaxation
• Biofeedback

But unequivocal evidence is still lacking.

Surgery

Following are considered indications for surgery in failed back surgery syndrome.:

• Failure of an extended program of conservative therapy.
• An abnormal myelogram, CT, MRI showing nerve root or cauda equina compression and/or signs of segmental instability consistent with the patient’s presenting symptoms and physical findings.
• In patients with radicular pain, conformity to physiologic dermatomal patterns and one or more of the following:
• Corresponding segmental sensory loss
• The motor loss in the appropriate segments
• Abnormal deep tendon reflexes in the appropriate segment.

The reported success rate of surgeries is 12-100% in different studies.

Ablative Procedures

Ablative procedures have had a relatively poor outcome and significant morbidity in FBSS patients. Dorsal Rhizotomy does not interrupt all afferent input

Removal of the entire dorsal root ganglion may thus be more effective than rhizotomy.

Ablative procedures can compromise the result of other neurosurgical procedures.

Spinal cord stimulation

In SCS, low-voltage electrical stimulation is applied to the spinal cord to create a current field which activates neurons in the dorsal column. This produces paresthesia, which interferes with or blocks pain signals to the brain. The power supply of the system is either a fully implanted pulse generator containing a battery and electronic circulatory or an external battery source that transmits radio frequency signals to an implanted receiver. The power supply produces electrical impulses which are carried along a conducting wire, or extension, to the lead. The lead typically.

Implantable, Programmable Drug Infusion system :

The use of implanted pumps for subarachnoid infusion to deliver opiates intrathecally (and to minimize systemic complications.