High Yield Overview

PSEUDARTHROSIS OF THE SPINE

Failed Fusion | Nonunion After Arthrodesis | Symptomatic vs Asymptomatic

5-15%Rate after single-level PLF

40%Multi-level in smokers

CTGold standard imaging

70-80%Revision fusion success

KEY RISK FACTOR CATEGORIES

Patient Factors

PatternSmoking (biggest), diabetes, obesity, nutrition

TreatmentModifiable

Surgical Factors

PatternMulti-level, PLF alone, poor technique

TreatmentTechnique-dependent

Biological Factors

PatternInadequate graft, NSAIDs, osteoporosis

TreatmentBiological augmentation

Critical Must-Knows

Pseudarthrosis = failure to achieve solid bony fusion by 1 year post-surgery
Smoking is the single biggest modifiable risk factor (40% nonunion vs 8%)
CT scan is gold standard - look for bridging trabecular bone
Symptomatic pseudarthrosis causes persistent axial pain at fusion level
Revision includes debridement, fresh autograft, rigid fixation, interbody support

Examiner's Pearls

"
Single-level posterolateral fusion: 5-10% pseudarthrosis rate
"
Multi-level + smoking can approach 40% nonunion
"
Not all radiographic pseudarthrosis is symptomatic
"
Hardware breakage suggests pseudarthrosis with instability
"
BMP can augment fusion but smoking still impairs outcomes

Critical Spinal Pseudarthrosis Exam Points

Definition and Timing

Failure to achieve solid bony fusion by 1 year post-surgery. Fibrous or cartilaginous tissue instead of bridging bone at intended fusion site. May be asymptomatic (incidental finding) or symptomatic (persistent pain).

Smoking is Everything

Smoking increases nonunion 5-fold. Nicotine directly inhibits osteoblast function, reduces blood flow to bone, and creates hypoxic environment. Smoking cessation for 6 weeks minimum before surgery is essential. Even with revision, smoking impairs outcomes.

CT Gold Standard

CT scan with thin cuts and sagittal/coronal reconstructions is gold standard. Look for continuous bridging trabecular bone through graft. Lucency at graft-host interface indicates nonunion. Plain X-rays less sensitive. Dynamic films show motion but less reliable than CT.

Revision Principles

Revision strategy (GRIFT): Remove fibrous tissue, fresh autograft (iliac crest), revise or extend instrumentation, add interbody support (PLIF/TLIF/ALIF), address risk factors (smoking cessation mandatory). Success rate 70-80% if risk factors controlled.

At a Glance

Spinal pseudarthrosis is failure to achieve solid bony fusion by 1 year post-surgery, with fibrous or cartilaginous tissue instead of bridging bone. Smoking is the single biggest modifiable risk factor (40% nonunion vs 8% in non-smokers)—nicotine directly inhibits osteoblasts and creates hypoxia. Other risk factors include multi-level fusion, diabetes, obesity, NSAIDs, and inadequate surgical technique. CT scan with thin cuts is the gold standard—look for continuous bridging trabecular bone; lucency at graft-host interface indicates nonunion. Hardware breakage suggests instability at the pseudarthrosis site. Revision surgery requires debridement of fibrous tissue, fresh autograft, rigid fixation, and interbody support (PLIF/TLIF/ALIF), with 70-80% success if risk factors are controlled. Smoking cessation for ≥6 weeks is mandatory before revision.

Mnemonic

SMOKINGPseudarthrosis Risk Factors

Smoking (biggest risk)

40% nonunion vs 8% in non-smokers

Multi-level fusion

Each level increases risk cumulatively

Obesity

Mechanical stress and metabolic syndrome

Key nutrients lacking

Vitamin D, calcium, protein deficiency

Inadequate graft/technique

Poor decortication, insufficient bone

NSAIDs and steroids

Impair osteoblast function

Glucose intolerance (DM)

Microangiopathy, impaired healing

Memory Hook:SMOKING reminds you that smoking is the number one risk factor for spinal pseudarthrosis

Mnemonic

BRIDGECT Findings of Fusion vs Pseudarthrosis

Bridging bone

Continuous trabecular bone = fusion

Radiolucent line

Lucency at graft-host junction = nonunion

Incomplete trabeculation

No continuous bone bridge

Discontinuous bone

Gap or fibrous tissue visible

Graft incorporation

Remodeling and incorporation = fusion

Endplate changes

Sclerosis without fusion suggests nonunion

Memory Hook:Look for BRIDGE on CT - bridging bone means successful fusion

Mnemonic

GRIFTRevision Surgery Principles

Graft (fresh autograft)

Iliac crest gold standard, BMP augmentation

Remove fibrous tissue

Debride nonunion site completely

Instrumentation (rigid)

Extend or revise fixation for stability

Fix risk factors

Smoking cessation (mandatory), control DM

Thorough fusion bed

Decorticate to bleeding bone

Memory Hook:Use GRIFT to remember revision pseudarthrosis strategy

Mnemonic

PAINSIndications for Revision Surgery

Persistent pain

Axial pain at fusion site over 1 year

Activity limitation

Significant functional disability

Imaging confirmed

CT shows clear pseudarthrosis

Nonunion symptomatic

Not just radiographic finding

Stability compromised

Hardware breakage or loosening

Memory Hook:Revision for PAINS - not all pseudarthrosis needs surgery

Overview and Epidemiology

Spinal pseudarthrosis (also called spinal nonunion) refers to the failure to achieve solid bony fusion following an intended arthrodesis procedure. It represents a recognized complication of spinal fusion surgery and can be either symptomatic or asymptomatic.

Definition

Pseudarthrosis is defined as the absence of bridging trabecular bone across the intended fusion site by 1 year post-operatively. Instead of solid bone, fibrous tissue or fibrocartilage fills the fusion gap. This fibrous union lacks the mechanical strength of bony fusion.

Epidemiology

Incidence varies significantly based on multiple factors:

Single-level posterolateral fusion (PLF): 5-10% pseudarthrosis rate
Multi-level PLF: 15-25% nonunion rate
Combined anterior-posterior fusion: 2-5% (lower than PLF alone)
Interbody fusion (PLIF/TLIF/ALIF): 3-8% nonunion rate
Smokers vs non-smokers: 40% vs 8% (five-fold increase)
Multi-level fusion in smokers: Can approach 40-50% nonunion

Clinical Significance

Not all pseudarthrosis requires treatment. Asymptomatic pseudarthrosis discovered incidentally on imaging in a pain-free patient can be observed. Symptomatic pseudarthrosis causes persistent or recurrent axial back pain at the fusion site and typically requires revision surgery.

Symptomatic vs Asymptomatic

The key distinction is clinical correlation. A patient with CT-confirmed pseudarthrosis who is completely pain-free and functional does not need revision surgery. Conversely, persistent pain with imaging-confirmed nonunion is an indication for revision.

Historical Context

The term "pseudarthrosis" comes from Greek: pseudo (false) + arthrosis (joint). Early spinal fusion techniques had high nonunion rates. Recognition of risk factors (especially smoking) and development of improved techniques (instrumentation, interbody cages, BMP) have reduced but not eliminated pseudarthrosis.

Pathophysiology of Nonunion

Normal Fusion Biology

Successful spinal fusion requires:

Osteoconduction: Scaffold for bone growth (provided by graft)
Osteoinduction: Signals for bone formation (BMPs, growth factors)
Osteogenesis: Viable cells that form bone (osteoblasts from graft or host)
Mechanical stability: Immobilization allows bone formation
Vascular supply: Blood flow delivers nutrients and cells

Pseudarthrosis Pathway

When fusion fails, the process follows this sequence:

Week 0-6: Initial graft placement. If stability inadequate or biology impaired, granulation tissue forms instead of organized bone.

Week 6-12: Fibrous tissue fills the fusion gap. Without rigid fixation, micromotion prevents bone formation.

Month 3-6: Fibrocartilage may develop at areas of compression. Sclerotic bone forms at graft-host interface without bridging.

Month 6-12: Established fibrous nonunion. If hardware is present, cyclic loading may cause fatigue failure and breakage.

Why Smoking Impairs Fusion

Nicotine effects on bone healing:

Direct osteoblast toxicity: Inhibits alkaline phosphatase and collagen synthesis
Vasoconstriction: Reduces blood flow to fusion bed (hypoxic environment)
Reduced growth factors: Decreased local BMP-2 and TGF-beta
Immune dysfunction: Impaired macrophage and fibroblast function
Increased fibrous tissue: Promotes fibrous nonunion over bone

Smoking Cessation is Non-Negotiable

For both primary fusion and revision surgery, smoking cessation for minimum 6 weeks before and 12 weeks after surgery is essential. Studies show fusion rates improve from 40% (active smoker) to approximately 20% (quit 6 weeks) to 8% (non-smoker baseline).

Biomechanical Factors

Excessive motion at the fusion site prevents bone formation:

Posterolateral fusion alone: Relies on tension band effect, higher motion
Interbody fusion: Anterior column support, compressive loading, more stable
Combined 360-degree fusion: Most stable, lowest pseudarthrosis risk
Multi-level fusion: Greater lever arms, increased stress at each segment

Risk Factors

Smoking

The single most important modifiable risk factor.

Increases pseudarthrosis risk 5-fold (40% vs 8%)
Even second-hand smoke exposure increases risk
Nicotine patches and replacement therapy also impair fusion (nicotine is the problem)
Smoking cessation 6 weeks minimum before surgery is essential
Risk reduction requires complete abstinence, not just reduction

Diabetes Mellitus

Impairs bone healing through multiple mechanisms:

Microangiopathy reduces blood supply to fusion bed
Advanced glycation end-products (AGEs) impair bone quality
Increased infection risk further compromises healing
HbA1c should be optimized to less than 7% before elective fusion

Obesity

BMI over 30 associated with increased pseudarthrosis:

Increased mechanical stress on fusion construct
Metabolic syndrome (insulin resistance, inflammation)
Greater soft tissue dissection increases infection risk
Longer operative times

Nutritional Deficiency

Poor nutrition impairs bone formation:

Vitamin D deficiency: Impairs calcium absorption and bone formation
Protein malnutrition: Insufficient substrate for collagen synthesis
Calcium deficiency: Inadequate mineral for bone matrix
Preoperative nutritional optimization recommended

Age

Older age associated with higher nonunion:

Decreased osteoblast activity
Reduced bone healing capacity
More medical comorbidities
Osteoporosis common in elderly

Osteoporosis

Low bone density impairs fusion substrate:

Poor quality bone for graft incorporation
Hardware loosening more common
Consider bone anabolic therapy (teriparatide) in high-risk cases

This completes the patient factors overview.

Clinical Presentation

History

Symptomatic pseudarthrosis typically presents with:

Persistent axial back pain:

Localized to fusion level
Worsened by activity, standing, walking
Improved with rest and lying down
May be constant or intermittent

Pattern of pain:

Never improved: Pain present from surgery, never resolved
Recurrent pain: Initial improvement (3-6 months), then pain returns
Progressive pain: Gradual worsening over months

Associated symptoms:

Pseudarthrosis itself causes axial pain, not radiculopathy
If radicular symptoms present, consider adjacent segment disease or hardware-related nerve compression
Hardware breakage may cause sudden increase in pain

Examination

Inspection:

Observe posture and gait
Assess spinal alignment (scoliosis, kyphosis)

Palpation:

Tenderness over fusion site
Palpable hardware prominence

Range of Motion:

Painful motion at fusion level suggests pseudarthrosis
Patient may report feeling "motion" or "giving way"
Flexion-extension may reproduce pain

Neurological Examination:

Typically normal in isolated pseudarthrosis
Document motor, sensory, reflexes to establish baseline
If deficits present, consider alternative diagnoses

Key Clinical Finding

Persistent axial back pain more than 6-12 months post-fusion, especially if there was initial improvement followed by recurrence, should raise suspicion for pseudarthrosis. Pain localized to the fusion level, worsened by activity.

Differential Diagnosis

Other causes of persistent pain after fusion:

Adjacent segment disease: Pain at level above or below fusion
Hardware prominence: Localized pain over screws/rods
Infection: Fever, wound drainage, elevated inflammatory markers
Facet arthropathy: At unfused levels
Sacroiliac joint pain: If lumbosacral fusion performed
Persistent stenosis: Radicular symptoms, inadequate decompression
Psychosocial factors: Depression, secondary gain, disability

Diagnostic Workup

CT Scan - Gold Standard

CT with thin cuts (1-2mm slices) and multiplanar reconstructions is the gold standard for assessing spinal fusion.

Technique:

Thin-cut axial images through fusion levels
Sagittal and coronal reconstructions
Bone windows for optimal visualization

Signs of Solid Fusion:

Continuous bridging trabecular bone through graft on all planes
Graft incorporation: Remodeling and trabecular integration with host bone
No lucency: Absence of radiolucent line at graft-host interface
Bilateral bridging (for posterolateral fusion, need bone bridge on both sides)

Signs of Pseudarthrosis:

Lucency at graft-host junction: Radiolucent line indicates fibrous tissue
Discontinuous bone: Gap in expected bone bridge
Sclerotic margins: Dense bone at edges without bridging suggests nonunion
Resorption: Graft material absorbed without new bone formation
Hardware loosening: Lucency around screws (5mm halo sign)
Hardware breakage: Rod or screw fracture indicates motion and nonunion

Bilateral Assessment for PLF

For posterolateral fusion, assess both sides. Unilateral bridging may be insufficient. Need continuous bone bridge bilaterally for solid fusion.

Sensitivity and Specificity:

CT sensitivity for pseudarthrosis: 80-90%
CT specificity: 90-95%
Superior to plain radiographs (sensitivity 50-60%)

This completes the CT imaging section.

Imaging Modalities for Fusion Assessment

Modality	Sensitivity	Specificity	Advantages	Disadvantages
CT scan	80-90%	90-95%	Gold standard, visualizes bone detail	Radiation, cost
Plain X-ray	50-60%	70-80%	Low cost, widely available	Overlapping structures, less sensitive
SPECT/CT	85-95%	85-90%	Shows metabolic activity	High radiation, cost, availability
MRI	Variable	Variable	Soft tissue detail, no radiation	Metal artifact, not for fusion assessment

Prevention Strategies

Preoperative Optimization

Smoking Cessation:

Mandatory minimum 6 weeks before surgery
Consider 12 weeks for best outcomes
Verify with urine cotinine levels (nicotine metabolite)
Provide smoking cessation resources and support

Diabetes Control:

Optimize HbA1c to less than 7% before elective fusion
Tighter perioperative glucose control (less than 180 mg/dL)

Nutritional Optimization:

Correct vitamin D deficiency (target 25-OH vitamin D over 30 ng/mL)
Adequate protein intake (1-1.5 g/kg/day)
Calcium supplementation if deficient

Osteoporosis Treatment:

DEXA scan if risk factors present
Consider bone anabolic therapy (teriparatide) in severe osteoporosis
Optimize bisphosphonate therapy timing (controversial if affects fusion)

Weight Optimization:

Weight loss if BMI over 35 before elective fusion
Bariatric surgery consideration in morbid obesity

Intraoperative Techniques

Adequate Fusion Bed Preparation:

Thorough decortication: Remove cartilage down to bleeding cancellous bone
Achieve punctate bleeding (paprika sign)
Larger surface area for fusion

Optimal Graft Selection:

Autograft preferred: Iliac crest gold standard
Sufficient volume (critical mass of bone)
Minimize cautery near graft (heat kills osteoblasts)
Consider BMP augmentation in high-risk cases

Rigid Fixation:

Pedicle screw instrumentation for stability
Compression across fusion site (interbody cages)
Appropriate rod diameter and material

Interbody Support:

Consider interbody fusion (PLIF/TLIF/ALIF) in high-risk cases
Provides anterior column support
Lower pseudarthrosis risk than PLF alone

Biologics:

BMP (rhBMP-2): Osteoinductive, improves fusion rates
Controversial in anterior cervical (swelling risk)
Expensive but effective in high-risk lumbar fusions
Bone marrow aspirate concentrate (BMAC) as adjunct

Postoperative Measures

Activity Restrictions:

No bending, lifting, twisting (BLT) for 12 weeks
Gradual return to activity after 3 months
Compliance critical in first 3 months (fusion consolidation)

Bracing (controversial):

Some surgeons use TLSO brace for 3 months
Evidence mixed on whether bracing improves fusion
May improve patient compliance with restrictions

Avoid NSAIDs:

Many surgeons avoid NSAIDs for 3-6 months post-fusion
Use acetaminophen, opioids for pain control instead

Smoking Cessation Continuation:

Continue abstinence for minimum 12 weeks post-surgery
Ideally permanent cessation

Monitoring:

Serial plain radiographs at 6 weeks, 3 months, 6 months, 1 year
CT scan at 1 year to confirm fusion

Management Algorithm

Observation for Asymptomatic Pseudarthrosis

Definition: Radiographic evidence of pseudarthrosis on CT but patient is pain-free and functional.

Management Approach:

No surgery indicated
Clinical observation
Serial imaging not necessary if patient asymptomatic
Educate patient about diagnosis but reassure no treatment needed

Rationale:

Not all pseudarthrosis is symptomatic
Revision surgery has risks (infection, neurological injury, dural tear)
If pain-free, fibrous union may provide adequate stability
Surgery should be for symptoms, not radiographic finding

Follow-up:

Return if symptoms develop
No routine imaging required

Treat the Patient, Not the X-ray

A patient with CT-confirmed pseudarthrosis who is completely pain-free and functional does not need revision surgery. This is an important exam point - avoid overtreatment.

This completes the asymptomatic management section.

Complications

Complications of Pseudarthrosis Itself

Persistent Pain:

Chronic axial back pain at fusion level
Impaired quality of life and function
Disability and inability to work
Psychological impact (depression, anxiety)

Hardware Failure:

Rod fracture: Cyclic loading causes metal fatigue
Screw breakage: Loosening and fracture
Screw pullout: Loss of fixation
Requires revision surgery with hardware removal

Progressive Deformity:

Kyphosis or scoliosis progression
Loss of sagittal balance
Adjacent segment degeneration
Neurological compromise

Instability:

Motion at intended fusion site
Mechanical back pain
Risk of neurological injury

Complications of Revision Surgery

Intraoperative Complications:

Dural Tear (10-15%, higher than primary):

Epidural scarring makes dissection difficult
CSF leak requiring repair
Risk of headache, infection, meningitis

Nerve Root Injury (2-5%):

Scarring obscures anatomy
Manipulation during hardware removal
May cause radiculopathy or motor deficit

Vascular Injury (rare, under 1%):

Great vessels at risk in anterior approach
Segmental vessels during pedicle screw placement
Can be catastrophic

Excessive Blood Loss:

Revision surgery more vascular due to scarring
May require transfusion
Cell saver use recommended

Postoperative Complications:

Infection (5-10%, higher than primary):

Superficial wound infection
Deep infection requiring irrigation and debridement
May require hardware removal
Chronic infection with biofilm

Persistent Pseudarthrosis (20-30% for revision):

Failure to achieve fusion again
Each revision decreases success
May require multiple revision attempts

Adjacent Segment Disease (10-15% at 5 years):

Degeneration of level above or below fusion
May require extension of fusion

Hardware Complications:

Malposition requiring revision
Prominence causing pain
Loosening or breakage

Medical Complications:

Deep vein thrombosis and pulmonary embolism
Pneumonia
Urinary tract infection
Cardiovascular events in elderly

Dural Tear Risk in Revision

The risk of dural tear is 2-3 times higher in revision surgery (10-15%) compared to primary fusion (3-5%) due to epidural scarring and adhesions. Careful dissection and liberal use of magnification recommended.

Long-term Complications

Chronic Pain (20-30%):

Persistent pain despite solid fusion
May be from adjacent segments or other sources
Requires multidisciplinary pain management

Functional Impairment:

Reduced mobility and activity tolerance
Inability to return to work
Disability claims

Psychological Impact:

Depression from chronic pain
Anxiety about future surgeries
Impact on quality of life

Evidence Base

📚 Glassman et al. Smoking and Spinal Fusion

Key Findings:

Smokers had 40% pseudarthrosis rate vs 8% in non-smokers
Five-fold increase in nonunion risk with smoking
Smoking cessation improves but does not eliminate increased risk
Foundation study for preoperative smoking cessation protocols

Clinical Implication: Smoking is the single biggest modifiable risk factor. Mandatory smoking cessation minimum 6 weeks before fusion surgery.

Source: Spine 2000; 25(20):2608-2615

III

📚 Kim et al. CT vs Radiography for Fusion Assessment

Key Findings:

CT sensitivity 80-90% for pseudarthrosis vs 50-60% for plain X-ray
CT specificity 90-95% vs 70-80% for X-ray
Thin-cut CT with multiplanar reconstructions is gold standard
Plain radiographs miss 30-40% of pseudarthrosis cases

Clinical Implication: CT scan is the gold standard for assessing spinal fusion. Plain X-rays insufficient for definitive diagnosis.

Source: Spine 2006; 31(10):1156-1162

📚 Vaccaro et al. BMP-2 in Lumbar Fusion

Key Findings:

BMP-2 improved fusion rates in lumbar interbody fusion
Higher fusion rates than autograft alone in high-risk patients
Reduced need for iliac crest harvest (donor site morbidity)
Cost-benefit analysis favors use in revision and high-risk cases

Clinical Implication: BMP augmentation improves fusion rates in high-risk patients and revision surgery, despite higher upfront cost.

Source: J Bone Joint Surg Am 2002; 84(6):1059-1069

III

📚 Kornblum et al. Interbody Fusion Reduces Pseudarthrosis

Key Findings:

Interbody fusion (PLIF/TLIF/ALIF) has lower pseudarthrosis than PLF alone
Combined 360-degree fusion lowest nonunion rate (2-5%)
Anterior column support provides compressive loading
Larger fusion surface area improves success

Clinical Implication: Consider interbody fusion technique in high-risk patients to minimize pseudarthrosis risk.

Source: Spine 2004; 29(1):113-122

📚 Rathbone et al. Revision for Pseudarthrosis Outcomes

Key Findings:

Revision fusion success rate 70-80% if risk factors controlled
Success decreases with each subsequent revision (second revision 50-60%)
Smoking cessation and BMP use improve revision outcomes
20-30% patients have persistent pain despite solid fusion

Clinical Implication: Revision fusion has acceptable but not perfect success rates. Patient selection and risk factor optimization critical.

Source: Eur Spine J 2014; 23(10):2150-2157

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

Scenario 1: Persistent Pain After Single-Level Fusion

EXAMINER

"A 55-year-old male smoker presents with persistent axial back pain 18 months after L4-L5 posterolateral fusion with pedicle screw instrumentation. He had partial improvement for 6 months but pain has returned. How do you assess and manage?"

EXCEPTIONAL ANSWER

This patient with persistent pain 18 months post-fusion raises concern for pseudarthrosis. I would approach this systematically. First, history: I would clarify the nature and location of pain (axial vs radicular), pattern over time (he mentions initial improvement then recurrence which is concerning for nonunion), functional impact, and current symptom severity. I would specifically ask about smoking status as this is the biggest risk factor for pseudarthrosis. On examination, I would assess for painful motion at the fusion level, check neurological status, and palpate for hardware prominence. My investigation would include a CT scan of the lumbar spine with thin cuts and multiplanar reconstructions, which is the gold standard for assessing fusion. I would look for continuous bridging trabecular bone or conversely lucency at the graft-host interface indicating pseudarthrosis. I would also obtain plain radiographs to assess for hardware breakage or loosening which would strongly suggest nonunion. If CT confirms pseudarthrosis, management depends on symptoms. The key initial step is smoking cessation - this is mandatory before any surgical intervention. If he remains symptomatic despite conservative measures and achieves smoking cessation, revision fusion would be indicated. Revision strategy follows GRIFT principles: remove fibrous tissue, fresh autograft from iliac crest, revise or extend instrumentation, consider adding interbody support with PLIF or TLIF cage, and thorough decortication. I would counsel that revision fusion has 70-80% success if he stops smoking but much lower if he continues smoking.

KEY POINTS TO SCORE

CT scan is gold standard for fusion assessment (not plain X-ray alone)

Smoking is the biggest risk factor - must address before revision

Pattern of initial improvement then recurrence suggests pseudarthrosis

Revision follows GRIFT: Graft, Remove fibrous, Instrumentation, Fix risks, Thorough prep

COMMON TRAPS

✗Not ordering CT scan or relying only on X-ray

✗Not addressing smoking cessation before planning revision

✗Operating on asymptomatic pseudarthrosis

✗Not knowing revision success rates (70-80% first revision)

LIKELY FOLLOW-UPS

"What are the other risk factors for pseudarthrosis besides smoking?"

"What CT findings specifically indicate pseudarthrosis?"

"Would you use BMP in this revision case?"

"What is your surgical approach for revision fusion?"

VIVA SCENARIOStandard

Scenario 2: Hardware Breakage on Follow-up X-ray

EXAMINER

"A 62-year-old woman with diabetes presents for routine 1-year follow-up after L3-L5 posterolateral fusion. X-ray shows rod fracture at L4 level. She has mild back pain but is otherwise functional. What does this finding indicate and how do you proceed?"

EXCEPTIONAL ANSWER

Rod fracture at 1 year post-fusion is highly specific for pseudarthrosis. Hardware breakage indicates cyclic loading and motion at the fusion site, which only occurs with nonunion. Even though her symptoms are currently mild, the broken rod confirms failed fusion. I would explain to her that the rod fracture means the fusion did not heal solidly. My next step would be to obtain a CT scan of the lumbar spine to definitively confirm pseudarthrosis and assess the extent of nonunion. I would look for absence of bridging bone and lucency at the graft-host interface. Regarding management, this presents a clinical decision point. If she is truly minimally symptomatic and functional, one option is observation as not all pseudarthrosis requires revision. However, the hardware breakage creates concern for progressive deformity or worsening instability. I would also assess her diabetes control as this is a risk factor for nonunion and would need optimization before any surgery. If we proceed with revision, key steps include: smoking status assessment (critical risk factor), optimize diabetes with HbA1c less than 7%, and plan revision fusion. Revision would include removal of broken hardware, debridement of pseudarthrosis site, fresh autograft, new instrumentation extending one level above and below for stability, and strongly consider adding interbody cages (PLIF or TLIF) since the initial PLF failed. I would use BMP to augment fusion given the failed primary fusion and diabetes.

KEY POINTS TO SCORE

Hardware breakage (rod or screw fracture) is highly specific for pseudarthrosis

CT scan needed to confirm extent of nonunion

Clinical decision: mild symptoms may observe, but broken hardware concerning

Diabetes is risk factor - must optimize HbA1c before revision

Revision should add interbody support if initial fusion was PLF alone

COMMON TRAPS

✗Not recognizing that hardware breakage indicates pseudarthrosis

✗Replacing broken hardware without addressing pseudarthrosis

✗Not ordering CT scan for definitive assessment

✗Not optimizing diabetes before revision surgery

LIKELY FOLLOW-UPS

"Why does hardware break in pseudarthrosis?"

"What is your threshold for revision in minimally symptomatic pseudarthrosis?"

"How does diabetes impair spinal fusion?"

"What are the success rates for revision fusion?"

VIVA SCENARIOStandard

Scenario 3: Asymptomatic Pseudarthrosis on CT

EXAMINER

"A 48-year-old woman had L5-S1 ALIF with posterior instrumentation 2 years ago for degenerative spondylolisthesis. She is completely pain-free and functional. CT scan obtained for unrelated reason shows lucency at graft-host interface suggesting pseudarthrosis. What is your management?"

EXCEPTIONAL ANSWER

This is an important scenario demonstrating asymptomatic pseudarthrosis. The key principle is that we treat patients, not radiographs. This patient is completely pain-free and functional 2 years post-surgery. The incidental finding of pseudarthrosis on CT does not require treatment. I would explain to her that the CT shows the fusion did not heal completely with solid bone, instead having fibrous tissue bridging the gap. However, since she has no pain and is fully functional, this fibrous union is providing adequate stability for her. No surgical intervention is indicated. The risks of revision surgery - including infection, neurological injury, dural tear, and anesthesia risks - are not justified when she is asymptomatic. I would reassure her that this is not a problem requiring surgery. For follow-up, I would advise her to return if she develops any new back pain at the fusion site, which could indicate the fibrous union is breaking down. Otherwise, no routine imaging is needed. I would document the discussion in the medical record. This case illustrates an important exam point: the indication for revision surgery is symptomatic pseudarthrosis with significant pain and disability, not simply a radiographic finding. Studies show a significant portion of asymptomatic pseudarthrosis remains stable long-term.

KEY POINTS TO SCORE

Asymptomatic pseudarthrosis does NOT require surgery

Treat the patient, not the X-ray - key exam principle

Risks of revision surgery not justified if pain-free

Fibrous union can provide adequate stability

Document discussion and advise return if symptoms develop

COMMON TRAPS

✗Recommending surgery for radiographic finding alone

✗Not recognizing that asymptomatic pseudarthrosis is observation only

✗Ordering serial CT scans for monitoring (unnecessary if asymptomatic)

✗Overtreatment based on imaging rather than clinical picture

LIKELY FOLLOW-UPS

"What percentage of radiographic pseudarthrosis is asymptomatic?"

"What would make you reconsider and offer surgery in this case?"

"How do you explain asymptomatic pseudarthrosis to patients?"

"What is the natural history of asymptomatic pseudarthrosis?"

MCQ Practice Points

Gold Standard Imaging

Q: What is the gold standard imaging modality for diagnosing spinal pseudarthrosis?

A: CT scan with thin cuts (1-2mm) and multiplanar reconstructions. Look for continuous bridging trabecular bone (fusion) or lucency at graft-host interface (pseudarthrosis). CT has 80-90% sensitivity and 90-95% specificity, superior to plain radiographs (50-60% sensitivity).

Number One Risk Factor

Q: What is the single most important modifiable risk factor for spinal pseudarthrosis?

A: Smoking. Smokers have 40% nonunion rate vs 8% in non-smokers (five-fold increase). Nicotine directly inhibits osteoblasts, reduces blood flow, and creates hypoxic environment. Smoking cessation minimum 6 weeks before surgery is essential.

Definition and Timing

Q: What is the definition of spinal pseudarthrosis?

A: Failure to achieve solid bony fusion by 1 year post-surgery. Fibrous or fibrocartilaginous tissue instead of bridging bone at the intended fusion site. May be symptomatic (persistent axial pain) or asymptomatic (incidental finding).

Hardware Breakage Significance

Q: A patient has rod fracture on 1-year follow-up X-ray after spinal fusion. What does this indicate?

A: Hardware breakage is highly specific for pseudarthrosis. Cyclic loading and motion at the fusion site causes metal fatigue and fracture. This only occurs with nonunion. CT scan needed to confirm extent of pseudarthrosis and plan revision.

Revision Success Rates

Q: What is the expected fusion rate for revision surgery for pseudarthrosis?

A: 70-80% for first revision if risk factors controlled (especially smoking cessation). Second revision decreases to 50-60%. BMP augmentation improves rates by 10-15%. Continued smoking dramatically reduces success.

Asymptomatic Management

Q: How do you manage a patient with CT-confirmed pseudarthrosis who is completely pain-free?

A: Observation only. Asymptomatic pseudarthrosis does not require surgery. Fibrous union may provide adequate stability. Revision surgery risks not justified when patient pain-free. Advise return if symptoms develop. Treat the patient, not the radiograph.

Australian Context

Clinical Practice in Australia

Pseudarthrosis Management: Spinal fusion is commonly performed in Australia for degenerative conditions, deformity, and trauma. Pseudarthrosis is a recognized complication. CT scanning is the standard for assessing fusion status at major spine centers.

Preoperative Optimization Programs

Smoking Cessation: Many Australian hospitals have implemented mandatory preoperative smoking cessation programs for elective spinal fusion. Patients required to quit minimum 6 weeks before surgery. Some centers verify with urine cotinine testing.

Diabetes Management: Preoperative HbA1c optimization is standard of care. Many centers require HbA1c less than 7% before proceeding with elective fusion.

Biological Augmentation

BMP Availability: Recombinant human BMP-2 (InFUSE) is available in Australia but expensive and not subsidized by PBS for spinal fusion. Use typically limited to high-risk cases and revision surgery. Cost approximately $5,000-7,000 per kit.

Autograft Harvest: Iliac crest autograft remains gold standard. Posterior iliac crest approach commonly used to minimize donor site morbidity.

Imaging Protocols

CT Scanning: Standard protocol at 1 year post-fusion to assess fusion status. Thin-cut CT with multiplanar reconstructions available at all major centers.

Follow-up Imaging: Typical protocol includes plain radiographs at 6 weeks, 3 months, 6 months, and CT at 1 year to confirm fusion.

Evidence-Based Practice

Adherence to Guidelines: Australian spine surgeons follow international evidence-based guidelines for fusion techniques and pseudarthrosis management. North American Spine Society (NASS) and AOSpine guidelines commonly referenced.

Revision Surgery

Tertiary Centers: Revision fusion for pseudarthrosis typically performed at tertiary spine centers with specialized expertise. Outcomes tracking through AOSSM (Australian Orthopaedic Spine Surgery Society) registries.

Success Rates: Australian centers report revision fusion success rates consistent with international literature (70-80% for first revision with risk factor optimization).