Tibial Nonunion

Definition:

• FDA: Fracture not healed at 9 months.
• Clinical: Fracture showing no radiographic progression over 3 consecutive months.
• Tibial Shaft: The most common location for long bone nonunion due to poor blood supply (anteromedial surface subcutaneous) and high energy trauma.

Key Concepts:

• Diamond Concept: Considers the biological and mechanical environment.
• Biology: Cells (osteoblasts), Scaffold (matrix), Signals (BMPs), Vascularity.
• Mechanics: Strain environment. Micro-motion promotes callus; too much motion prevents it; absolute rigid stability promotes primary healing (no callus).

Vascular Anatomy (Critical)

The tibia is subcutaneous anteromedially, making its blood supply vulnerable:

Nutrient Artery:

• Enters via posterior cortex at the proximal third
• Supplied by Posterior Tibial Artery
• Often disrupted in the initial fracture
• Provides 30-40% of blood supply

Periosteal Supply:

• The sole supply after nutrient artery disruption
• Depends on the surrounding soft tissue envelope
• Anterior tibial artery/muscles (lateral)
• Posterior tibial artery/muscles (posterior)
• Provides 60-70% of blood supply

Watershed Zone:

• The distal third of the tibia has the poorest blood supply
• Highest nonunion rate (distal third)
• Limited collateral circulation

Biomechanics

Strain environment:

• Primary healing: Strain less than 2% (absolute stability, no callus)
• Secondary healing: Strain 2-10% (micro-motion, callus formation)
• Nonunion: Strain greater than 10% (excessive motion prevents healing)

Fibula role:

• Acts as a strut
• If healed, prevents compression of the tibia ("holding it open")
• May require fibulectomy to allow compression

Pathophysiology

Hypertrophic nonunion:

• Biology: Good (abundant callus formation)
• Stability: Poor (excessive motion)
• Mechanism: Strain greater than 10% prevents bridging
• Treatment: Increase stability (exchange nailing)

Atrophic nonunion:

• Biology: Poor (no callus, sclerotic bone)
• Stability: Variable
• Mechanism: Biological failure (poor vascularity, dead bone)
• Treatment: Improve biology (bone graft) + stability

Infected nonunion:

• Biology: Poor (biofilm prevents healing)
• Stability: Variable
• Mechanism: Infection prevents biological healing
• Treatment: Eradicate infection first (debridement, antibiotics)

History

Pain:

• Pain upon weight bearing is the hallmark
• Pain at rest suggests infection
• Persistent pain despite adequate time for healing

Constitutional symptoms:

• Fevers/chills (infection)
• Night sweats (infection)
• Weight loss (infection, malignancy)

Risk factors:

• Smoking (most important - 50% reduction in success)
• Diabetes (poor healing)
• NSAID use (inhibits bone healing)
• Steroids (inhibits bone healing)
• Previous open fracture (infection risk)

Physical Examination

Inspection:

• Condition of skin/flaps (previous surgery, open fracture)
• Sinus tracts (infection - pathognomonic)
• Deformity (malalignment, shortening)
• Swelling (infection, chronic inflammation)

Palpation:

• Tenderness at fracture site
• Motion at fracture site (gross instability)
• Warmth (infection)
• Crepitus (motion at nonunion)

Neurovascular:

• Distal pulses (posterior tibial, dorsalis pedis)
• Sensation (saphenous, sural, superficial peroneal)
• Motor function (dorsiflexion, plantarflexion)

Associated Conditions

• Infection: Previous open fracture, sinus tracts
• Metabolic disease: Vitamin D deficiency, hyperparathyroidism
• Smoking: Most important modifiable risk factor
• Diabetes: Poor healing, infection risk

Laboratory:

• Infection: CBC, ESR, CRP. (If elevated, Aspiration/Biopsy).
• Metabolic: Calcium, Phosphate, ALP, Vitamin D (25-OH), PTH, TSH, HbA1c, Albumin.

Imaging:

• X-rays: AP/Lat/Oblique. Assess callus, implant failure, alignment.
• CT Scan: Gold standard for assessing bony bridging (often obscured by metal on X-ray). Look for less than 50% bridging on cuts.
• Nuclear Medicine:
  • Bone Scan: High sensitivity, low specificity.
  • WBC Scan (Indium/Sulfur colloid): Useful to differentiate infection from remodelling.

Infection Recurrence

10-20% incidence:

• Cause: Especially in previously open fractures, biofilm presence
• Prevention: Thorough debridement, antibiotics, staged approach
• Management: Radical debridement, hardware removal, antibiotics, reconstruction

Re-fracture

5-10% incidence:

• Cause: Through graft site or screw holes, premature weight bearing
• Prevention: Protected weight bearing, gradual progression
• Management: Revision fixation if needed

Donor Site Morbidity

10-20% incidence:

• Cause: Iliac crest harvest (cluneal nerve injury), RIA (femur fracture)
• Prevention: Careful technique, consider RIA for large volumes
• Management: Pain management, nerve blocks if needed

Compartment Syndrome

Less than 5% incidence:

• Cause: Bleeding into tight compartments after surgery
• Prevention: Monitor, careful hemostasis
• Management: Fasciotomy if needed (four-compartment)

Immediate Postoperative

• Immobilization: None (early mobilization)
• Weight bearing: Partial weight bearing initially (depends on fixation stability)
• ROM: Early knee and ankle ROM (immediate)
• PT: Ambulation training, strengthening

Rehabilitation Protocol

Weeks 0-2:

• Partial weight bearing (20-50% body weight)
• Knee and ankle ROM exercises
• Quadriceps and calf strengthening
• Ice and elevation

Weeks 2-6:

• Progressive weight bearing (50-75% body weight)
• Continue ROM and strengthening
• Balance and proprioception

Weeks 6-12:

• Progressive to full weight bearing
• Full ROM
• Progressive activity

Weeks 12+:

• Full weight bearing
• Return to activity (when union confirmed)
• Continue monitoring with serial X-rays

Dynamization

If healing slow at 3-4 months:

• Remove static locking screws (proximal or distal)
• Allow localized compression at nonunion site
• Monitor with serial X-rays

Adjunctive Treatments

Low-intensity pulsed ultrasound (LIPUS):

• FDA approval for fresh fracture nonunions
• Evidence debated (TRUST trial showed no benefit)
• May be considered in selected cases

Overall Outcomes

Exchange nailing:

• Success rate: Greater than 90% for hypertrophic nonunions
• Time to union: 6-9 months after revision surgery
• Complications: 10-15% (infection recurrence, re-fracture)

Compression plating:

• Success rate: 85-90%
• Time to union: 6-9 months after revision surgery
• Complications: 10-15% (infection, hardware failure)

Ilizarov bone transport:

• Success rate: Greater than 90% for infected nonunions
• Time to union: 9-12 months (longer for large defects)
• Complications: 20-30% (pin site infection, joint stiffness)

Functional Outcomes

Return to activity:

• Timeline: 6-12 months postoperatively
• Rate: 80-85% return to pre-injury level
• Factors: Nonunion type, treatment method, smoking status, rehabilitation compliance

Functional testing:

• Strength: 90%+ of contralateral
• ROM: Full (if no complications)
• No pain or instability

Long-Term Prognosis

Union rates:

• Hypertrophic: Greater than 90% with exchange nailing
• Atrophic: 85-90% with bone graft + fixation
• Infected: 80-90% with staged reconstruction

Risk factors for failure:

• Smoking: Reduces success rate by 50%
• Infection: Higher failure rate
• Poor bone quality: Osteoporosis, metabolic disease
• Large defects: Greater than 5cm

Factors Affecting Outcomes

Positive factors:

• Hypertrophic nonunion (good biology)
• No infection
• Smoking cessation
• Good bone quality
• Complete rehabilitation

Negative factors:

• Atrophic nonunion (poor biology)
• Infection present
• Continued smoking
• Poor bone quality
• Large defects