Pseudarthrosis of the Spine

Smoking

The single most important modifiable risk factor.

• Roughly doubles pseudarthrosis risk (meta-analysis RR 2.2; Glassman 26.5% vs 14.2%)
• 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.

Number of Levels Fused

Multi-level fusion increases pseudarthrosis risk cumulatively:

• Single level: 5-10% baseline
• Two levels: 15-20%
• Three or more levels: 20-30%
• Long constructs (more than 5 levels): 30-40%

Each additional level increases mechanical stress and healing demand.

Fusion Technique

Posterolateral fusion (PLF) alone has highest nonunion rate:

• PLF only: 10-15% pseudarthrosis
• Interbody fusion (PLIF/TLIF): 5-8%
• ALIF: 3-5%
• Combined anterior-posterior (360): 2-5%

Why interbody fusion is more successful:

• Anterior column load-bearing support
• Compressive forces across graft promote fusion
• Larger surface area for fusion
• Better blood supply from vertebral body endplates

Instrumentation

Non-instrumented fusion has higher nonunion:

• Non-instrumented: 20-30% pseudarthrosis
• Instrumented: 5-15%
• Pedicle screws provide rigid fixation reducing micromotion

Graft Type

Autograft vs allograft vs bone substitutes:

• Autograft (iliac crest): Gold standard, osteogenic + osteoconductive + osteoinductive
• Local bone from laminectomy: Good if sufficient volume
• Allograft alone: Higher nonunion (15-20%), no viable cells
• BMP (rhBMP-2): Improves fusion but expensive, side effects
• Bone marrow aspirate: Augments fusion when combined with scaffold

Surgical Technique Factors

Poor technique increases pseudarthrosis risk:

• Inadequate decortication: Fusion bed must be bleeding bone
• Insufficient graft volume: Need critical mass of bone
• Damage to graft: Excessive cautery kills osteoblasts
• Excessive distraction: Increases tension, impairs fusion
• Hardware malposition: Eccentric loading, instability

Revision Surgery

Previous fusion attempt increases difficulty:

• Scarring and poor biology
• Avascular fusion bed from prior surgery
• Each revision decreases success rate
• Primary fusion 90-95% success, first revision 70-80%, second revision 50-60%

This completes the surgical factors section.

Medications

NSAIDs (controversial):

• Animal studies suggest impaired fusion
• Human studies show mixed results
• Many surgeons avoid NSAIDs for 3-6 months post-fusion
• COX-2 inhibitors may have less effect than traditional NSAIDs

Corticosteroids:

• Chronic steroid use impairs bone formation
• Delays fracture healing and fusion
• If possible, minimize dose perioperatively

Chemotherapy and Radiation:

• Cytotoxic agents impair cell division and healing
• Radiation damages local vascularity
• History of radiation to fusion site increases nonunion risk

Systemic Disease

Rheumatoid arthritis and autoimmune disease:

• Disease itself and immunosuppressive medications impair healing
• Higher infection risk

Chronic kidney disease:

• Renal osteodystrophy affects bone quality
• Parathyroid dysfunction

Hypothyroidism:

• Impaired bone turnover
• Should be corrected before surgery

Infection

Postoperative infection dramatically increases pseudarthrosis:

• Infection prevents bone formation
• May require hardware removal (loss of stability)
• Biofilm on hardware prevents fusion
• Requires eradication before revision fusion attempt

This completes the medical factors section.

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

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.

Plain X-rays

Less sensitive than CT but useful for initial assessment and follow-up.

Standard Views:

• AP and lateral lumbar spine
• Oblique views if posterolateral fusion assessed
• Dynamic flexion-extension views to assess motion

Signs Suggesting Fusion:

• Continuous bony trabeculae across fusion site
• Incorporation of graft with host bone
• Stable hardware position over time

Signs Suggesting Pseudarthrosis:

• Hardware breakage: Rod or screw fracture (highly specific for nonunion)
• Hardware loosening: Progressive lucency around screws over serial films
• Motion on dynamic films: Greater than 3-4 degrees angulation or 3mm translation
• Persistent radiolucent line: At graft-host interface
• Halo sign: Lucency around pedicle screws (more than 2mm suggests loosening)

Limitations:

• Overlapping structures obscure fusion mass
• Cannot assess anteriorly located bone (interbody fusion)
• Less sensitive than CT (misses 30-40% of pseudarthrosis)

Role:

• Initial screening
• Serial follow-up if CT already confirmed fusion
• Identifying hardware complications

This completes the plain radiograph section.

SPECT/CT

Single-photon emission computed tomography combined with CT.

Advantages:

• Metabolic activity: Identifies biologically active pseudarthrosis
• Distinguishes active vs quiescent: Bright uptake suggests symptomatic nonunion
• Guides treatment: Active uptake may predict who benefits from revision

Limitations:

• More expensive than CT alone
• Radiation exposure higher
• Not always available
• Uptake can be positive for other reasons (infection, hardware reaction)

Indications:

• Equivocal CT findings
• Clinical-radiographic discordance (pain but CT shows fusion)
• Planning revision surgery (identify active site)

MRI

Not gold standard for fusion assessment but has role.

Limitations for Fusion Assessment:

• Metal artifact from hardware degrades images
• Difficult to visualize trabecular bone detail
• Less accurate than CT for bridging bone

Useful for:

• Infection: Abscess, discitis, osteomyelitis
• Adjacent segment disease: Disc degeneration, stenosis
• Nerve compression: Hardware-related radiculopathy
• Soft tissue: Hematoma, seroma

Laboratory Tests

Inflammatory markers if infection suspected:

• ESR and CRP: Elevated in infection
• White blood cell count: May be elevated
• Blood cultures: If systemic sepsis

Bone turnover markers (research setting):

• P1NP (bone formation marker)
• CTX (bone resorption marker)
• May predict fusion but not used clinically

This completes the advanced imaging section.

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

This completes the asymptomatic management section.

Conservative Management

Initial approach for symptomatic pseudarthrosis:

Indications for Trial of Non-operative Treatment:

• Mild to moderate symptoms
• Patient wishes to avoid surgery
• Medical comorbidities make surgery high-risk
• Recent diagnosis (within 12-18 months, may stabilize)

Treatment Options:

Activity Modification:

• Avoid aggravating activities
• Weight management
• Ergonomic adjustments

Bracing (controversial):

• TLSO brace may reduce motion and pain
• Limited evidence for efficacy
• Some patients report symptomatic improvement

Physical Therapy:

• Core strengthening to support spine
• Not curative but may reduce pain
• Avoid aggressive manipulation

Pharmacological:

• Acetaminophen for pain control
• Avoid NSAIDs (may impair fusion)
• Neuropathic pain medications if nerve component
• Minimize opioid use (chronic pain, addiction risk)

Interventional Pain Management:

• Epidural steroid injections (not curative, temporary relief)
• Facet injections for adjacent segment pain
• Radiofrequency ablation (palliative)

Risk Factor Modification:

• Smoking cessation: Even if established pseudarthrosis, cessation may allow late fusion
• Diabetes control
• Nutritional optimization
• Bone health (vitamin D, calcium)

Expected Outcomes:

• Most symptomatic pseudarthrosis does not resolve without surgery
• Conservative measures provide temporary relief
• Definitive treatment requires revision fusion if symptoms persist

This completes the symptomatic non-operative section.

Operative Management - Revision Fusion

Indications:

• Symptomatic pseudarthrosis causing significant pain and disability
• Failed conservative management (minimum 3-6 months trial)
• CT-confirmed nonunion
• Patient medically fit and willing
• Smoking cessation achieved (mandatory, minimum 6 weeks)

Contraindications:

• Active smoking (relative contraindication, very high failure risk)
• Active infection (must eradicate first)
• Medical comorbidities precluding surgery
• Asymptomatic pseudarthrosis

Revision Strategy - GRIFT Principles

1. Debridement (Remove fibrous tissue):

• Expose pseudarthrosis site
• Remove all fibrous tissue and scar
• Excise sclerotic bone margins
• Create fresh bleeding bone surfaces

2. Decortication (Thorough fusion bed):

• Decorticate transverse processes (PLF)
• Prepare vertebral endplates (if interbody fusion)
• Achieve punctate bleeding (paprika sign)
• Maximum surface area for fusion

3. Graft (Fresh autograft):

• Iliac crest autograft - gold standard
• Posterior iliac crest if available (less morbidity than anterior)
• Local bone from revision laminectomy if sufficient volume
• Morselized graft packed into fusion bed
• Structural graft for interbody (cage with autograft)

4. Instrumentation (Rigid fixation):

• Revise existing hardware if loose or malpositioned
• Extend construct proximally and/or distally for stability
• Consider larger diameter rods for greater stiffness
• Ensure solid purchase in bone (rescue screws if needed)

5. Interbody Support (Add anterior column):

• PLIF (Posterior Lumbar Interbody Fusion)
• TLIF (Transforaminar Lumbar Interbody Fusion)
• ALIF (Anterior Lumbar Interbody Fusion)
• Interbody cage provides compressive loading and larger fusion surface
• Consider if initial fusion was PLF alone

6. Biological Augmentation:

• BMP (rhBMP-2): Osteoinductive, improves fusion in revision setting
• Expensive but effective in high-risk revisions
• Bone marrow aspirate concentrate (BMAC) as adjunct
• Demineralized bone matrix (DBM) as extender

Approach Selection

Posterior approach:

• Re-explore original posterior fusion site
• Access to posterolateral fusion bed
• Can perform PLIF or TLIF
• Scar tissue and epidural fibrosis make dissection challenging

Anterior approach (if adding ALIF):

• Fresh tissue planes
• Excellent visualization of disc space
• Can place large structural graft
• Separate incision, longer total surgery
• Consider if posterior anatomy too scarred

Combined anterior-posterior (360-degree fusion):

• Most stable construct
• Highest fusion rates in revision setting
• Morbidity of two approaches
• Consider in high-risk or multiply failed fusions

Expected Outcomes

Success rates for revision fusion:

• First revision: 70-80% fusion if risk factors controlled
• Second revision: 50-60% fusion
• Smoking cessation: Essential for acceptable success rates
• BMP use: May improve rates by 10-15%

Complications:

• Dural tear: 10-15% (higher than primary due to scarring)
• Infection: 5-10%
• Nerve injury: 2-5%
• Persistent pain: 20-30% even with solid fusion
• Adjacent segment disease: 10-15% at 5 years

This completes the revision surgery section.

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

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