Why Is My Pain Worse After Spinal Fusion? Understanding Failed Back Surgery Syndrome

By Sina Hartung, MMSC-BMI, Harvard Medical SchoolReviewed by Eureka Health Medical Group
Published: June 28, 2025Updated: June 28, 2025

Summary

Pain that is equal to or greater than before surgery six months after a lumbar or cervical fusion is called failed back surgery syndrome (FBSS). Common causes include adjacent-segment breakdown, hardware irritation, non-union of the bone, and nerve scarring. A repeat MRI, CT, and diagnostic nerve blocks pinpoint the problem, and most people improve with a mix of targeted physical therapy, image-guided injections, neuromodulation, or—rarely—revision surgery.

Why can pain feel worse even after the bones are fused?

Fusion stops motion at one spinal level but cannot remove every pain generator. New stresses shift to neighboring joints and nerves, and some fusions never knit solidly. As Sina Hartung, MMSC-BMI, explains, "Up to one in four fusions show a non-union, and that alone can keep pain circuits firing."

  • Adjacent-segment overload adds new painAfter L4-L5 fusion, the L3-L4 disc sees 25 % more bending stress, leading to faster degeneration and renewed back or leg pain.
  • Pseudoarthrosis keeps micro-movements aliveCT scans reveal that 10–24 % of lumbar fusions do not fully fuse; microscopic motion around hardware irritates bone and muscle.
  • Epidural fibrosis can tether nerve rootsScar tissue forms in 20–36 % of cases, gluing the dura to bone and recreating sciatica despite an intact fusion mass.
  • Implant position may irritate soft tissuePedicle screws touching the medial facet or iliac crest spur constant muscle spasm and dull aching.
  • Central sensitisation keeps nerves hyper-reactiveSix months of continuous pain can rewire the spinal cord, so even light pressure is read as severe pain, according to the team at Eureka Health.
  • Sacroiliac joint often becomes the next pain sourceMayo Clinic reports that the SI joint accounts for pain in nearly 50 % of patients who develop new or persistent low-back pain after lumbar fusion. (Mayo)
  • Almost one-third of fusion patients remain dissatisfiedA review from Caring Medical notes that up to 28 % of individuals are dissatisfied and experience recurrent back or leg pain even when imaging shows the fusion has healed. (CaringMed)

References

Which post-fusion symptoms are red flags needing urgent care?

Some warning signs suggest infection, hardware failure, or nerve damage that cannot wait until the next routine visit. "Prompt imaging within 24 hours can save function when new weakness appears," notes the team at Eureka Health.

  • Progressive leg or arm weaknessLosing one muscle grade per day suggests compressive hematoma or screw malposition.
  • Fever above 38.5 °C plus wound drainageDeep surgical site infection occurs in 1–4 % of fusions and can destroy bone graft if untreated within days.
  • Loss of bladder or bowel controlCauda equina syndrome after fusion is rare (<1 %) but needs same-day decompression.
  • Sudden audible crack with sharp painImplant fracture shows on plain X-ray; bending or twisting can break a rod if fusion has not taken yet.
  • Unremitting night pain unrelieved by positionCould signal osteomyelitis or tumor at the fusion level and warrants emergency MRI.
  • Severe neck stiffness with trouble swallowing or breathingA rapidly expanding prevertebral hematoma after cervical fusion can narrow the airway; SpineMD urges immediate emergency assessment if neck becomes rigid and swallowing or breathing difficulties emerge. (SpineMD)
  • Grinding sensation or bulge over instrumentationVisible hardware prominence or a grinding/clicking feeling near the incision often signals loose screws or rod migration—The Advanced Spine Center advises prompt imaging to avert nerve injury. (ASC)

References

How do doctors confirm failed back surgery syndrome after fusion?

FBSS is a diagnosis of cause, not just persistent pain. The work-up layers history, exam, imaging, and targeted anesthetic blocks. "A lidocaine root sleeve injection that cuts pain by 80 % tells us the nerve, not the disc, is the driver," says Sina Hartung, MMSC-BMI.

  • Standing X-rays test hardware integrityDynamic flexion-extension views pick up screw loosening when the halo around a screw widens by more than 1 mm.
  • CT shows pseudoarthrosis better than MRILack of continuous trabecular bridge on thin-slice CT has 90 % sensitivity for non-union.
  • MRI with metal-artifact reduction maps soft tissueSequences like MAVRIC show epidural fibrosis or adjacent-level stenosis without screw glare.
  • SPECT-CT lights up active bone inflammationHigh uptake at the fusion bed suggests mechanical non-union rather than neuropathic pain.
  • Diagnostic blocks isolate the culpritFacet, SI-joint, or transforaminal nerve blocks giving >50 % relief for the anesthetic duration localise pain generators for targeted treatment.
  • FBSS complicates 5–10 % of lumbar spine surgeriesPopulation studies cited by the NIH review estimate that 5–10 % of people continue to have disabling pain that meets the definition of failed back surgery syndrome after lumbosacral operations. (NIH)
  • Gadolinium-enhanced MRI distinguishes scar from recurrent discThe same review notes that contrast-enhanced MRI is the most sensitive and specific imaging test for the postoperative lumbosacral spine, reliably separating enhancing epidural fibrosis from non-enhancing new herniation so revision surgery targets the true lesion. (NIH)

References

What can I do at home today to reduce post-fusion pain?

Self-care focuses on unloading adjacent joints, calming nerve sensitivity, and keeping general fitness. The team at Eureka Health reminds patients, "Small position tweaks often drop mechanical load by double-digit percentages."

  • Limit sitting to 30-minute boutsEvery extra 15 minutes of unsupported sitting increases lumbar disc pressure by 40 % compared with standing.
  • Use a neutral spine log-roll techniqueRolling instead of twisting in bed reduces torsion on fused segments by up to 60 % in biomechanical studies.
  • Start aquatic therapy when the incision is closedWater buoyancy unloads the spine; a 2019 trial showed 35 % pain score reduction after six weeks of pool walking.
  • Practice paced breathing before pain flaresSix cycles per minute of diaphragmatic breathing lowers sympathetic tone and muscle guarding.
  • Track pain triggers in a daily logDocumenting activity and pain peaks helps spot patterns that a clinician can translate into specific restrictions or exercises.
  • Alternate cold and heat packs for 15–30 minutesBegin with cold to curb swelling, then shift to moist heat to relax tight paraspinals; each modality can be used for 15–30 minutes several times a day to blunt post-fusion pain. (AtlasWellness)
  • Add short, surgeon-approved walks during weeks 1–4Healthline’s recovery timeline notes that light, frequent walking is typically introduced in the first month to stimulate circulation, reduce stiffness, and relieve discomfort without overloading the fusion. (Healthline)

References

Which tests, injections, and medications might help and what do their results mean?

Not every patient needs another operation. Results from labs, imaging, and trial therapies guide the next step. "We treat the positive test, not the image that looks abnormal," stresses Sina Hartung, MMSC-BMI.

  • ESR/CRP help rule out infectionCRP above 10 mg/L six weeks post-op raises suspicion; a normal CRP has a 95 % negative predictive value for deep infection.
  • CT-guided hardware blocks predict screw removal benefitAnesthetic around pedicle screws giving >70 % relief signals hardware irritation; many patients decide on screw removal alone.
  • Transforaminal epidural steroid injections calm nerve rootsRandomized studies show a 50 % pain reduction at one month in selected FBSS patients, buying time for rehab.
  • Neuromodulation trials identify respondersHigh-frequency spinal cord stimulation provides durable relief in 60–70 % of FBSS cases that pass the seven-day trial lead period.
  • Medication reassessment prevents polypharmacyCombining two or more sedating drugs doubles fall risk; a pharmacist review often removes redundant agents while keeping pain scores stable.
  • Post-operative MRI pinpoints treatable lesionsIn a 30-patient series, MRI identified recurrent or residual disc herniation in 53 %, epidural scar tissue in 20 %, and combined pathology in 10 %, guiding clinicians toward focused rather than exploratory revision. (NCBI)
  • Each repeat lumbar fusion has falling success oddsReported outcomes show success rates drop from roughly 50 % after the first spine surgery to 30 % for a second, 15 % for a third, and just 5 % by the fourth, highlighting why less-invasive strategies should be exhausted first. (APM)

References

How can Eureka’s AI doctor guide me through persistent pain after fusion?

Eureka’s AI doctor asks targeted questions, triangulates likely causes, and suggests next steps grounded in guideline data. "Our algorithm flags red-flag symptoms in under 30 seconds and drafts an imaging order set a spine surgeon would recognise," reports the team at Eureka Health.

  • Personalised triage in real timeIf you report new numbness, the AI recommends same-day assessment instead of routine follow-up.
  • Evidence-based test suggestionsFor suspected pseudoarthrosis, it proposes a thin-cut CT and serum bone turnover labs, ready for physician sign-off.
  • Medication optimization promptsThe system checks current drugs against Beers criteria and flags risky combos like opioids plus gabapentinoids.
  • Goal-oriented exercise plansIt tailors a 10-minute core-stabilisation routine based on your pain diary and fusion level.

Why do people with post-fusion pain keep using Eureka, and how could it help you?

Users rate the app highly because it listens, tracks, and acts. A recent survey showed patients with chronic spine pain gave Eureka 4.7 out of 5 stars for "feeling taken seriously."

  • Private, secure conversationAll entries are encrypted, and only you and the reviewing clinician can see them.
  • Seamless lab and prescription workflowIf the AI suggests a CRP or a hardware block, a licensed physician reviews and sends the order to your local center.
  • Daily symptom check-ins build a pain graphVisual trends help you and your surgeon spot when pain peaks relate to activity or weather.
  • Community-vetted tips appear in-appYou receive practical ideas—like using a reacher tool—that other FBSS users rated most helpful.
  • Free to use, with no surprise billsYou pay only standard lab or pharmacy fees if those services are used; the AI consultation itself costs nothing.

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Frequently Asked Questions

How long should pain last after a lumbar fusion before I worry about FBSS?

Most surgeons expect steady improvement within 3 months; pain that is unchanged or worse at 6 months deserves full evaluation.

Can physical therapy make adjacent-segment disease worse?

When guided, therapy reduces risk; problems arise when patients do high-impact or excessive rotation exercises too early.

Will removing the hardware fix my pain?

Only if imaging or diagnostic blocks prove the screws or rods are the main pain source; otherwise removal rarely helps.

Is spinal cord stimulation safe if I have metal rods?

Yes. Leads sit in the epidural space and do not interact with titanium implants, but MRI safety must be re-checked.

Could vitamin D deficiency delay fusion healing?

Yes. Levels under 30 ng/mL correlate with higher non-union rates; supplementation is often started once detected.

What is the success rate of revision fusion surgery?

When the exact pain generator is clear, revision success is 50–70 %, but drops below 30 % if the cause is uncertain.

Are muscle relaxants safe to take long term for FBSS?

Chronic use increases fall risk and sedation; most guidelines limit them to short courses during acute spasms.

Can Eureka’s AI doctor refill my medication automatically?

No. It can draft the refill request, but a licensed clinician reviews and approves each prescription.

Do epidural injections harm the fusion mass?

Steroids in standard doses have not been shown to impede bone healing when given after three months post-op.

This content is for informational purposes only and is not intended as medical advice. Always consult with a qualified healthcare provider for diagnosis, treatment, and personalized medical recommendations.

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