Tibial Nonunion

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 modifiable factor - slower union, more secondary surgery)
• 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

The topic repeatedly asks you to "assess bony bridging", judge whether there has been "no radiographic progression over 3 months", and reach for CT when plain films are equivocal — yet the "is it united?" judgment on plain films is notoriously subjective and disagrees between observers. That matters here, because both the diagnosis of nonunion and the decision to reoperate hinge on that read. The Radiographic Union Score for Tibia (RUST) turns it into a reproducible number.

How RUST is scored

• Use orthogonal radiographs (AP and lateral); each view shows two cortices, so four cortices are scored in total.
• Each cortex scores: 1 = fracture line visible, no callus; 2 = callus present but fracture line still visible; 3 = bridging callus with the fracture line no longer visible.
• Sum the four cortices: RUST ranges from 4 (no healing at any cortex) to 12 (complete union at all four).
• mRUST (modified RUST) scores each cortex out of 4 — adding a top tier for a bridged cortex that has remodelled with no visible line — giving a range of 4 to 16 and finer discrimination, particularly around metaphyseal or plated fractures where callus is subtle.

Why it matters in nonunion

RUST is not just a fresh-fracture tool. In operatively treated tibial nonunions, a low preoperative RUST predicts failure of nonunion surgery and both pre- and post-operative RUST correlate with time to union — so scoring the cortices at presentation risk-stratifies the nonunion itself and calibrates how aggressive (biology plus stability, not stability alone) the reconstruction must be. Track RUST on serial films: a score that plateaus and fails to climb over 3 months supports the nonunion diagnosis and the case for intervention, while CT remains the arbiter when metal obscures cortices or the plain-film score is borderline.

The clinical picture (persistent pain, failure to heal) overlaps with several entities. The single most important fork is infected vs aseptic, because it changes the whole reconstructive plan.

The intact fibula recurs throughout this topic — in the one-pager pearls, the "Intact Fibula" warning, the biomechanics, exchange nailing, the vivas and the cheat sheet — yet the technique and logic of dividing it are never developed. This is a uniquely tibial (two-bone-segment) problem worth owning here.

The mechanical problem

In the leg the tibia and fibula share length. When the fibula has healed (or was never broken) it behaves as a rigid lateral strut. As the tibia tries to compress across its nonunion — under weight-bearing, dynamization, or a compression device — the fibula "holds it open", distracting the tibial bone ends and defeating the very axial compression and callus-generating micromotion the treatment relies on. A persistent tibial gap alongside a united fibula on radiographs is the classic clue.

When to release it

• A hypertrophic (or oligotrophic) tibial nonunion with an intact/healed fibula where compression is the goal.
• Before dynamizing a nailed tibia (removing locking screws will not compress a fracture the fibula is strutting).
• When planning acute shortening of a segmental defect, where the fibula would otherwise resist limb-length adjustment.

Technique and pitfalls

• Perform a segmental fibular osteotomy/ostectomy — remove a short segment (about 1 cm, enough that the fibula cannot simply re-strut by bridging) through a small direct-lateral incision.
• Site the resection at a level offset from the tibial nonunion so the two do not consolidate into a single mass and so the exposure is safe.
• Stay away from the common peroneal nerve at the fibular neck proximally, and preserve the distal syndesmosis and lateral malleolus — a resection too distal destabilises the ankle mortise.
• It is an adjunct, not a stand-alone: fibular release enables the mechanical solution (compression plating/nailing, dynamization, or frame compression) but does not substitute for biology in an atrophic nonunion, and it is unnecessary when the fibula is itself un-united or already absent.

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: Prolongs union and increases need for secondary surgery
• 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

Global Epidemiology

• Tibial shaft fracture is the most common long-bone fracture; nonunion complicates roughly 5-15% of shaft fractures and is higher (up to ~30-50%) after high-energy open (especially Gustilo IIIB/IIIC) injuries.
• The distal third is the highest-risk segment due to a precarious blood supply and thin soft-tissue envelope.
• Modifiable drivers (smoking, diabetes, malnutrition, NSAIDs) and injury factors (open wound, segmental loss, infection) dominate risk across all populations.

Guideline & Registry Landscape (Side by Side)

• Registry evidence: trauma and limb-reconstruction registries (e.g. UK BOA open-fracture audits, national fracture databases) consistently link delayed soft-tissue cover, higher Gustilo grade and smoking to nonunion and deep infection.

High- vs Limited-Resource Practice Variation