Failed Back Surgery Syndrome (FBSS): A Clinically Oriented Classification & Treatment Playbook

failed back surgery

Failed Back Surgery Syndrome or FBSS is a misnomer. Many other operations also leave some patients with persistent pain (e.g., post-thoracotomy, post-cholecystectomy), yet we don’t label those “failed” procedures. In spine care, the term persists, but the smarter approach is to recognize FBSS as a syndrome—a cluster of potential mechanisms rather than one disease.

What Failed Back Surgery or FBSS Really Means (Working Definition)

Persistent or new-onset pain after spine surgery—of any type and at any time post-op (weeks to years)—without a single unifying pathophysiology. It is clinical, not purely radiologic.

Key implications

  • There is no time limit: symptoms beginning months or years later still qualify.
  • Imaging alone misleads. Classic data show a high rate of incidental MRI findings in asymptomatic adults (e.g., disc bulges and even extrusions without pain), underscoring the need to correlate history + examination + targeted diagnostic blocks, not pictures alone.

Why a Clinical Classification Helps

Surgeons often stratify by structural findings; pain physicians should stratify by what the patient feels now versus what they felt pre-op. This drives the diagnostic blocks you choose and the interventions that help.

Three Clinical Groups

  1. Group 1 — “Same Pain”
    Character and distribution match pre-op (intensity may differ).
  2. Group 2 — “Modified Pain”
    Character and/or distribution change after surgery (often within weeks–months): some relief of the original pain but new or shifted complaints.
  3. Group 3 — “New Pain”
    Completely new pain phenotype and territory, often emerging later, unrelated to index pathology.

We’ll walk through each group: common causes, how to confirm the pain generator, and what to do.

Group 1 — Same Pain After Surgery

Clue: Post-op pain looks and feels like the pre-op pain in distribution or charachter.

Most likely reason

Target–generator mismatch: the operated level/structure was not the true pain source. Surgery can be “technically perfect” yet miss the generator.

Frequent culprits (often invisible or unreliable on MRI)

  • Facet joint pain
    Imaging–pain concordance only ~25–27%. Normal-looking facets can hurt; abnormal-looking facets may be painless.
  • Sacroiliac (SI) joint pain
    Imaging concordance ~45%—still coin-flip territory.
  • Myofascial pain
    Especially psoas, quadratus lumborum, piriformis.
    • Psoas spasm can entrap elements of the lumbar plexus → anterior-thigh/medial-leg pain (femoral/obturator pattern).
    • Piriformis spasm can compress sciatic/common peroneal fibers → posterior-leg/calf pain; some variants traverse the muscle belly.
  • Fibromyalgia (FM)
    Prevalence ≈ 4% in the general population, ~20% in pain clinics. FM mimics radiculopathy: widespread tenderness, positive SLR, paresthesias, marked post-exertional flare, poor sleep, fatigue, cognitive fog, multiple somatic symptoms. Without formal FM scoring, over/under-diagnosis is common.
  • Multilevel disc disease with single-level surgery
    The operated level wasn’t the dominant generator.

How to confirm (don’t guess; block it)

  • History & exam focused on character (neuropathic vs nociceptive) and distribution (e.g., buttock–PSIS point → SIJ; paraspinal focal tenderness → facet; deep gluteal/greater trochanteric pain with seated intolerance → piriformis/QL).
  • Targeted diagnostic blocks (small-volume local anesthetic):
    • Facet: medial branch blocks.
    • SI joint: intra-articular block.
    • Myofascial: trigger point/local anesthetic into suspected muscle (psoas, QL, piriformis).
    • If discogenic vs SI/facet unclear or multilevel disease: do staged blocks to identify the dominant generator.
  • Only after positive, reproducible diagnostic response should you escalate to therapeutic procedures.

Treatment roadmap

  • Facet: confirm with dual MBBs → radiofrequency ablation (RFA) if sustained relief on blocks.
  • SI joint: intra-articular steroid; lateral branch RFA; physical therapy focused on pelvic stabilization.
  • Myofascial: manual therapy, dry needling/TPIs, stretching (hip external rotators/hip flexors), address secondary myofascial pain after healed disc herniations.
  • Fibromyalgia: manage first (education, sleep restoration, graded activity, SNRIs/pregabalin where appropriate). Re-assess spine pain after FM control.

Prevention lesson: when clinical picture ≠ MRI, do diagnostic blocks before surgery.

Group 2 — Modified Pain After Surgery

Clue: Initial radicular pain improves, but new back-dominant pain emerges (difficulty sitting, turning in bed), or a different radicular pattern appears.

A. Side effects (sequelae) of otherwise appropriate surgery

  1. Epidural fibrosis (EF)
    • Posterior EF rarely hurts by itself (few pain fibers posteriorly).
    • Anterior/anterolateral EF can tether dura/roots → diffuse axial back pain (anterior dura is pain-sensitive) ± traction-type radicular pain.
    • EF also narrows central/lateral recesses → can mimic/produce stenosis and claudication.
    Endoscopic grading (conceptual)
    • Grade 1: flimsy, filmy strands; often post-inflammation, non-surgical; usually painless unless anterior.
    • Grade 2: angry pink, recent scar (≤ ~6 months); easier to break this adhesion.
    • Grade 3: paler, contracted scar; difficult to break this adhesion..
    • Grade 4: dense, pan-segmental scar; scope/catheter passage may be impossible; surgery rarely considered.
  2. Load redistribution/adjacent segment overload
    After rigid fixation, the rotation/translation capacity of fused segments transfers to adjacent levels → facet arthropathy is common (≈ 1/3 of cases).
  3. Post-operative myofascial pain
    Paraspinals, QL, gluteals, piriformis—especially after prolonged guarding.
  4. CRPS (Type 1 or 2) after surgical trauma in a genetically susceptible subset.
    Treat with early neuropathic meds, desensitization/graded motor imagery, consider sympathetic blocks; SCS for refractory cases.

B. Complications (usually avoidable and must be ruled out early)

  • Infection, pseudoarthrosis, pedicle fracture, implant reactions/malposition, canal/foraminal compromise. These require surgical re-evaluation.

How to confirm EF vs other causes

  • Epiduroscopy (via caudal access): filling defects suggest adhesions; correlate with symptoms.
  • Diagnostic blocks again for adjacent facet or SI sources; myofascial exam.
  • Keep a low threshold to image for complications if red flags or systemic features are present.

Management options for EF

  1. Volumetric epidural adhesiolysis (caudal)
    • Steps:
      a) Caudal access → epidurography (map defects).
      b) Hyaluronidase (e.g., 1,500 IU diluted) to soften scar.
      c) Normal saline to distend/break filmy bands (total procedural volume up to ~40 mL, including dye + meds).
      d) Finish with local anesthetic + steroid.
    • Safety pearl: Avoid rapid large-volume epidural injection (especially in stenosis) → can spike CSF pressure and has been associated with retinal/intracranial hemorrhage. Use short rapid pulses with pauses, not a continuous forceful push.
    • Expected benefit: often months (≈ 3–12 mo on average).
  2. Targeted catheter adhesiolysis (Racz technique)
    • Steerable, reinforced catheter navigated to anterior epidural space at the symptomatic level (confirm in lateral view).
    • Two-and-fro mechanical disruption across scar planes, then 10% hypertonic saline (perineural decongestion + partial C-fiber neurolysis), followed by steroid + LA.
    • Costly but more precise than volumetric distension.
    • Typical relief: ~6–18 months.
  3. Epiduroscopic adhesiolysis
    • For old, dense (Grade 3–4) scars or failed catheter lysis.
    • Direct visualization; mechanical instruments ± laser for hemostasis.
    • Consumables can be expensive; benefit can last ~1-3 years, but recurrence is common.
  4. Spinal cord stimulation (SCS) — increasingly preferred for durable relief without disturbing scar
    • Place leads above the surgical field (often mid-thoracic for L4–S1 territories; many target ~T8 lower border, adjust by paresthesia/coverage testing; modern systems may be paresthesia-free).
    • Best-supported indication: FBSS. Also useful for CRPS and painful diabetic neuropathy; more conditional for phantom limb and post-herpetic neuralgia.
    • Particularly valuable when EF recurs after lysis or when pain is mixed axial/radicular.
  5. Adjacent segment facet pain
    • Confirm with medial branch blocks adjacent to the construct; treat with RFA if blocks are positive.
  6. Myofascial / CRPS
    • As above (Group 1 and CRPS note), with early interdisciplinary rehab.

Group 3 — New Pain, New Pathology

Clue: A different pain syndrome arises later with no logical link to the operated site.

Examples: de novo SIJ dysfunction after altered biomechanics, hip OA, vertebral osteoporosis fracture, peripheral neuropathy, or entirely non-spinal sources. Treat on first principles: fresh clinical work-up, targeted blocks, manage the actual generator.

A Practical Bedside Algorithm

  1. Sort into a Group
    • Same vs Modified vs New pain (compare character + distribution with pre-op).
  2. Screen for red flags/complications
    Fever/wound issues, new neurologic deficits, severe nocturnal pain → urgent surgical review ± imaging.
  3. Map likely generators
    • Buttock/PSIS point, sitting intolerance, Fortin finger → SIJ.
    • Paraspinal focal tenderness, pain with extension/rotation, sit→stand pain → facet.
    • Deep gluteal tenderness, seated pain, FAIR test → piriformis.
    • Anterior hip flexor tenderness, pain on resisted hip flexion → psoas.
    • Widespread tenderness, sleep/fatigue, multiple somatic symptoms → fibromyalgia.
  4. Confirm with blocks (small volume, image-guided)
    • Positive, reproducible relief (≥ 70–80% short-term) → proceed to definitive therapy for that structure.
  5. If Modified Pain after surgery
    • Consider EF, adjacent segment facet, myofascial, CRPS. Use epidurography to assess adhesions; treat per EF pathway or facet/CRPS pathways.
  6. If EF dominates and recurs
    • Move earlier to SCS instead of repeated lysis cycles.
  7. Rehab & secondary prevention
    • Core stabilization, hip abductor/extensor strength, hamstring/hip flexor flexibility, graded activity, sleep restoration (especially in FM), and patient education to reduce fear-avoidance.

Procedural Pearls & Pitfalls

  • Match the map: Character (neuropathic vs nociceptive) and dermatomal/myotomal map steer you; MRI is confirmatory at best.
  • Don’t shotgun levels: With multilevel disease, identify the dominant generator with diagnostic blocks before any revision surgery or ablation.
  • Anterior vs posterior dura matters: Anterior dura is pain-sensitive; posterior fibrosis alone seldom explains pain.
  • Epidural injections: Avoid continuous forceful large-volume injections; use incremental boluses with pauses.
  • Adhesiolysis expectations: Relief is time-limited; counsel patients on recurrence and the role of SCS.
  • CRPS vigilance: Disproportionate pain with color/temp changes, edema, allodynia—treat early and consider neuromodulation if refractory.
  • Adjacent segment disease: Expect and screen for facet pain above/below rigid fusions.

Putting It All Together (Example Pathways)

  • Same L5-pattern sciatica post-laminectomy → Check SI/facet/piriformis; staged blocks. If negative and epidurography shows anterior filling defect → targeted adhesiolysis; consider SCS if recurrence.
  • Radicular leg pain improved; now disabling axial back pain → Think anterior dura tethering or adjacent facet: epidurography ± medial branch blocks → volumetric/targeted lysis or facet RFA as indicated; rehab.
  • Late new buttock pain pointing to PSIS → SI joint block → lateral branch RFA if validated.
  • Widespread pain, sleep dysfunction → Fibromyalgia program first; re-assess spine-specific pain thereafter.

Take-Home Messages

  • FBSS ≠ “failed surgeon.” It’s a pattern-based problem requiring generator-specific diagnosis.
  • Three groups (Same / Modified / New) keep you honest and guide testing.
  • Diagnostic blocks are the backbone—they de-bias decisions when imaging is noisy.
  • Epidural fibrosis is common but anterior EF is the pain-maker; adhesiolysis helps but recurs—SCS is the modern, evidence-strong option for durable relief in suitable patients.
  • Always consider adjacent segment facet pain, myofascial contributors, and CRPS, and treat FM first when present.

Watch the lecture by Gautam Das