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Failed back syndrome: 10 real causes and 7 evidence-based solutions

  • Failed back syndrome describes pain that persists or returns after one or more spine surgeries.
  • It does not always mean the “surgery was a failure”: mechanical, neurological and chronic pain factors often coexist.
  • Management combines precise diagnosis, active rehabilitation, pain control and, in selected cases, neuromodulation or revision surgery.
  • Recovery times and prognosis depend on the identified cause, the preoperative condition and the team’s experience.

 

What is failed back syndrome?

It refers to the situation in which a person continues to have low back pain, leg pain or neuropathic symptoms after undergoing spine surgery. It can appear immediately or months/years later. It is an umbrella term: it does not indicate a single cause but several possible ones. The goal is not to “label” the patient, but to determine what is causing the pain today and how to address it with the least possible risk.

 

10 common causes (and how they are investigated)

  1. Persistent or recurrent neural compression. Example: a recurrent disc herniation at the same level, stenosis that was not fully decompressed or that progresses. It is evaluated with up-to-date magnetic resonance imaging and clinical correlation.
  2. Pseudoarthrosis (failure of fusion). It usually causes mechanical pain and sometimes a sensation of “instability”. It is confirmed with dynamic X-rays and, if necessary, computed tomography.
  3. Malpositioned implants or screws. They can irritate nerve roots or fail to stabilize properly. CT and clinical assessment guide the decision.
  4. Undiagnosed instability. When the main problem was instability and only decompression was performed, symptoms may persist. It is reassessed with dynamic tests and physical examination.
  5. Adjacent level failure
  6. Coexisting facet or sacroiliac pain. Posterior joints or the sacroiliac joint may become the main pain source after a fusion. Clinical maneuvers and diagnostic injections help confirm it.
  7. Epidural fibrosis/adhesions. It can contribute to persistent radicular pain. MRI and clinical findings guide management; it does not always alone explain the picture.
  8. Centralized neuropathic pain. The nervous system may become “sensitized”, amplifying pain beyond the initial injury. It requires a multimodal approach (pain education, exercise, psychological support, adjuvant drugs).
  9. Progression of deformity (scoliosis/kyphosis) or uncorrected sagittal malalignment.
  10. Low-grade late infection. Uncommon but important to detect. It is suspected with persistent pain and elevated inflammatory markers; sometimes confirmed with specific studies.

 

Diagnosis: useful and dispensable tests

Diagnosis is based on history and neurological examination, correlated with current imaging (MRI of the affected region; flexion/extension X-rays if instability is suspected; CT to review implants or fusion). Tests should be requested if they can change management: repeating studies without a clear clinical question rarely adds value.

 

Non-surgical alternatives with evidence

  • Pain education and active exercise. A structured program of strength, mobility and lumbopelvic motor control reduces disability and supports return to activity.
  • Prudent pharmacological treatment. First-line analgesics (paracetamol/NSAIDs if not contraindicated), adjuvants for neuropathic pain (tricyclic antidepressants or antiepileptics in limited, supervised regimens). Avoid chronic opioids except in very specific situations.
  • Selective injections in chosen cases (transforaminal epidural for radiculopathy, facet or sacroiliac blocks for diagnostic/therapeutic purposes).
  • Biopsychosocial approach (cognitive-behavioral therapy, sleep strategies, fear-of-movement reduction).

 

Neuromodulation (spinal cord stimulation): when to consider it?

Spinal cord stimulation (SCS) can be an option for people with refractory chronic neuropathic pain, especially when radicular leg pain predominates after surgery and there is no correctable mechanical compression. A temporary trial is performed before permanent implantation to assess benefit and tolerance. There are different “waveforms” (tonic, high-frequency such as 10 kHz, or advanced modes); choice is individualized. Evidence is heterogeneous: there are studies and guidelines supporting its use in selected cases, and also reviews questioning its effect for pure axial low back pain. In any case, it should be considered after optimizing conservative management and with clear informed consent about benefits and limitations.

 

When to consider revision surgery?

Reintervention is not “automatic.” It is considered when there is a clinical-radiological correlation that justifies further action: for example, persistent radicular compression or painful pseudoarthrosis. Surgical options include:

  • Targeted decompression (micro-surgery or endoscopy) if radicular pain is due to localized compression.
  • Instrumentation revision (repositioning screws, removing symptomatic hardware).
  • Supplementary fusion if there is instability or pseudoarthrosis.
  • Deformity correction when clinically relevant malalignment exists.

The decision should weigh age, bone density, comorbidities, patient goals and team experience. The goal is to improve function and quality of life, not just “fix the image.”

 

Expected benefits and risks/adverse effects

Benefits

  • Pain reduction when the nerve is decompressed or stability is improved.
  • Improved ability to walk, sit and perform daily tasks.
  • Less bleeding and quicker recovery with minimally invasive techniques compared with traditional open surgeries.

Risks and limitations

  • Infection, bleeding, nerve injury, thrombosis, persistence of pain.
  • Reoperation carries cumulative risks (scarring, adhesions, worse “operative field”).
  • Neuromodulation does not work the same for everyone; it requires realistic expectations and follow-up.

 

Practical referral criteria

  • Significant pain and functional limitation after 6–12 weeks of well-conducted conservative management.
  • Progressive neurological deficit.
  • Imaging that explains symptoms and is correctable (for example, focal compression, pseudoarthrosis).
  • Failure of reasonable non-surgical measures for neuropathic pain with a good indication for neuromodulation.

 

Realistic recovery times

  • After targeted decompression (micro/endoscopic): early ambulation; basic tasks within a few days; office work in 2–6 weeks depending on progress; physical jobs, 6–12 weeks or more.
  • After complex fusion/revision: slower recovery; several months of progressive rehabilitation are commonly planned.
  • Neuromodulation: the trial phase lasts a few days; if beneficial, permanent implantation requires a short adaptation period.

Timelines depend more on preoperative status, job type and adherence to rehabilitation than on the “name” of the technique.

 

When to go to the emergency room

  • Rapid loss of leg strength or foot drop.
  • High fever with severe low back pain or wound drainage.
  • Urinary/bowel changes or saddle anesthesia.
  • Sudden pain with new neurological signs after a fall or trauma.

 

Myths and realities

  • Myth: “If the MRI looks bad, you must reoperate.” Reality: treat the person, not the image.
  • Myth: “Neuromodulation cures pain forever.” Reality: it is a useful tool in selected cases, not a universal “off switch.”
  • Myth: “A fusion prevents movement.” Reality: many people resume activity with good function if fusion consolidates and an exercise program is followed.

 

Frequently asked questions

Is every postoperative pain a “failed back”?

No. Pain in the first weeks is expected. Failed back syndrome is used when pain persists or returns and limits daily life after a reasonable recovery period.

Is neuromodulation useful if pain is only in the low back and does not radiate to the leg?

Results are more consistent when neuropathic leg pain predominates. For pure axial low back pain, evidence is more debated; the decision is case-by-case after optimizing conservative management.

How many people need reoperation?

It depends on the cause. If there is clear compression or painful pseudoarthrosis, a well-indicated revision can help. If the cause is centralized pain, reoperation usually offers little benefit.

Endoscopy or microsurgery for recurrent herniation?

Both can be valid. Choice depends on the level, hernia location, prior surgeries and team experience.

How long does a spinal cord stimulator implant last?

Current generators can last several years. A trial is always performed first to estimate potential benefit.

Can I do sports afterwards?

In many cases, yes, with guided progression. High-impact activities or maximal loads are reintroduced gradually according to recovery and clinical judgment.

 

Glossary

  • Pseudoarthrosis: lack of bone consolidation after a fusion.
  • Decompression: surgery to free compressed nerves.
  • Neuromodulation/spinal cord stimulation: a technique that uses electrical impulses to modulate pain perception.
  • Radiculopathy: pain and/or symptoms from irritation of a nerve root.
  • Epidural fibrosis: scar tissue around the dural sac and nerve roots.

 

References

  1. Dr. Vicenç Gilete – Neurosurgeon. https://complexspineinstitute.com/instituto/#equipo_medico
  2. Dr. Augusto Covaro – Orthopedic and trauma surgeon. https://complexspineinstitute.com/instituto/#equipo_medico
  3. NICE. Differential Target Multiplexed spinal cord stimulation for chronic lower back and leg pain (MIB305). 2022. https://www.nice.org.uk/guidance/mib305/
  4. Cochrane Review. Spinal cord stimulation for low back pain. 2023. https://www.cochrane.org/evidence/CD014789_spinal-cord-stimulation-low-back-pain
  5. Gallego H, et al. Treatment Options for Failed Back Surgery Syndrome. 2023. https://pmc.ncbi.nlm.nih.gov/articles/PMC11007241/
  6. Kallewaard JW, et al. 10 kHz Spinal Cord Stimulation for FBSS. 2020. https://pmc.ncbi.nlm.nih.gov/articles/PMC8247309/

 

Important notice: This content is educational and does not replace individual assessment by a healthcare professional.