Bone Transport: A Comprehensive Guide

1. BIOLOGICAL MECHANISM - The Foundation

The Tension-Stress Effect (Ilizarov's Principle)

2. WHAT IS BONE TRANSPORT?

3. INDICATIONS

Primary Indications

1. Posttraumatic bone defects - Critical-sized defects (generally >2-3 cm) after open fractures, traumatic bone loss, or following debridement of infected bone. Tibia is the most common site.
2. Chronic osteomyelitis with bone loss - After debridement of infected/necrotic bone leaves a defect. Bone transport is uniquely suited here because the transport process itself stimulates vascular ingrowth, reducing risk of re-infection.
3. Infected nonunion - Failed fracture healing complicated by infection where bone resection is necessary.
4. Tumor resection defects - Following en-bloc resection of bone tumors (especially low-grade), particularly in pediatric patients where prosthetic options are less ideal.
5. Congenital bone deficiencies - Congenital pseudarthrosis of the tibia and other congenital bone defects.
6. Limb-length discrepancy - Combined with deformity correction.

Minimum Defect Size Requiring Transport

Contraindications

• Active systemic infection or sepsis
• Severely compromised vascularity (relative - vascular reconstruction may be needed first)
• Non-compliant patient (transport requires daily adjustments for months)
• Severe osteoporosis precluding stable wire/pin fixation

4. PROCEDURE - STEP BY STEP

Frame Options

• Ring (Ilizarov) fixators - most versatile, allow multiplanar correction
• Monolateral fixators with intercalary sliding mechanism
• Taylor Spatial Frame (TSF) / hexapod - computerized 6-axis correction
• Hybrid - external fixation followed by intramedullary nail ("fix and nail" / "rail" technique)
• Intramedullary transport nails - newer generation allowing transport without external frame

Radiograph of Ilizarov ring fixator applied for tibial bone transport

Surgical Steps

• Radical debridement of all infected and necrotic bone/soft tissue
• Obtain margins of healthy, bleeding bone
• Send deep cultures

• Apply proximal and distal rings/blocks to stable bone segments
• Rings must be parallel to adjacent joints and perpendicular to the bone's mechanical axis
• Hexapod frames allow rings in any orientation with computer-assisted correction

• Low-energy, periosteum-preserving bone cut, typically at the metaphysis (better biology than diaphysis)
• Technique: multiple drill holes + osteotome, or Gigli saw
• The periosteum, medullary vessels, and endosteum are preserved - this is why it differs from osteotomy
• The transport segment is cut to create the intercalary piece that will move

• Frame locked, no distraction
• Allows hematoma organization and early callus formation
• Longer latency (7-10 days) in elderly, diabetics, smokers, or irradiated bone

• Rate: 1 mm/day divided into 4 increments of 0.25 mm, 4× daily
• Rhythm: four times daily (more increments = smoother regenerate)
• Patient or family performs adjustments at home
• Radiographs every 2-4 weeks to monitor regenerate quality and transport direction

• When the transport segment reaches the opposite bone end
• Bone grafting at the docking site is often performed (the docking site is a compressed, scarred junction with poor healing potential)
• Compression across the docking site aids union

• Frame maintained until regenerate bone consolidates (corticalization visible on X-ray)
• Consolidation index: approximately 1-2 months per centimeter transported
• Dynamization (partial unlocking of frame) may be used to stimulate consolidation

• When radiographs show solid cortical bridging in at least 3 of 4 cortices
• Protected weight-bearing, then progressive loading

Tibial bone transport series: pre-op deformity (a,b), fixator application (c), active transport on X-rays (d,e), regenerate formation (f,g), final consolidation (h,i)

"Fix and Nail" Hybrid Technique

5. TIMING AND INDICES

6. COMPLICATIONS - PALEY'S CLASSIFICATION

Complete case series: (a) wound with bone loss, (b-c) CT showing defect, (d-e) Ilizarov frame, (f-g) Ilizarov frame on X-ray after transport, (h-i) final healed X-rays, (j) clinical result

A. Pin/Wire Site Complications

B. Regenerate Bone Problems

• Most often an incomplete corticotomy rather than true premature healing
• Commonly in tibia: failure to completely osteotomize the posterolateral cortex
• Prevention: manually distract 1-2 mm under fluoroscopy at time of corticotomy
• Treatment: redo corticotomy, accelerated distraction rate, manipulation

• Causes: too rapid distraction, poor vascularity, infection, smoking, malnutrition
• Regenerate appears lucent, fractures under load
• Management: slow distraction rate, dynamization, bone stimulators, BMP-2

• Frame removal too early before adequate consolidation
• Treat with reapplication of frame or cast

C. Docking Site Problems

• The docking site is a compressed, often scarred/fibrotic junction
• In infected cases, dead or fibrous tissue prevents healing
• Treatment: debridement of docking site + bone graft + bone marrow aspirate concentrate
• Additional compression, possibly exchange nailing

D. Deformity (Axial Deviation) During Transport

• The transport segment drifts off-axis (varus, valgus, procurvatum, recurvatum)
• Incidence: up to 20-30% requiring correction
• Prevention: careful frame alignment, rings perpendicular to bone axis
• Treatment: frame adjustment, strut changes (TSF allows computer-guided correction)

E. Joint Complications

• Common with adjacent joint immobility during prolonged transport
• Prevention: active physiotherapy throughout treatment
• Most common joints affected: knee (during femoral transport), ankle (tibial transport)
• Major complication: may require Achilles tendon lengthening or arthrolysis

• Particularly around the knee during femoral transport
• Prevention: supplemental soft tissue lengthening if needed

F. Neurovascular Complications

• Peroneal nerve palsy is most common with tibial transport (lateral fibular head pin)
• Vascular injury during pin insertion
• Treatment: physiotherapy, nerve decompression if needed

G. Infection-Related

• After transport through previously infected zone
• Caused by inadequate initial debridement
• Requires repeat debridement, culture-directed antibiotics, reassessment

H. Hardware Failure

• Wire/pin breakage from fatigue
• Ring cracking
• Strut failure

7. TREATMENT FAILURES

Classification of Failure

• Occurs when all reconstruction attempts are exhausted
• Indications: recurrent deep infection, soft tissue failure, patient preference
• Incidence: 5-15% in severe cases (Gustilo IIIB/C)

1. Docking site non-union - bone graft + compression ± exchange nail
2. Delayed consolidation - dynamization, bone stimulator (LIPUS, electromagnetic)
3. Regenerate insufficiency - slow distraction, BMP, PRP injection
4. Infection recurrence - repeat debridement, long-term suppressive antibiotics, hyperbaric O2

Predictors of Failure

ASAMI Score (Association for the Study and Application of Ilizarov Methods)

• Excellent: union, no infection, deformity <7°, limb-length discrepancy (LLD) <2.5 cm
• Good: union + 1 of above criteria
• Fair: union + 2 of above criteria
• Poor: non-union, re-fracture, or >3 criteria

• Excellent: active, no limp, no pain, full ROM
• Good: 1 criterion not met
• Fair: 2 criteria not met
• Poor: 3 criteria not met

8. MODERN ADVANCES

Intramedullary Transport Nail

• Fully internal devices (e.g., FITBONE, PRECICE) that allow bone transport without external fixation
• Eliminates pin-tract infections and frame cumbersomeness
• Activated via external magnetic remote controller
• Currently gaining wider adoption for select cases

Bone Transport Over an Intramedullary Nail ("BON")

• External fixator performs transport while a nail maintains alignment
• Reduces axial deviation
• Shorter external fixation time

Masquelet (Induced Membrane) Technique - Comparison

• Stage 1: cement spacer placed in defect to induce biological membrane
• Stage 2 (6-8 weeks): spacer removed, defect packed with bone graft inside the membrane
• Advantages over bone transport: shorter treatment time, no external frame
• Disadvantages: needs large quantities of graft for big defects (>6 cm), soft tissue still required

3D Printing + Ilizarov

• 3D-printed antibiotic bone cement prosthetics combined with Ilizarov frame
• Controls local infection while maintaining length

Summary Table

• Rockwood and Green's Fractures in Adults, 10th ed. 2025 - "Biology of Distraction Osteogenesis" and "Bone Transport" sections
• Campbell's Operative Orthopaedics, 15th ed. 2026 - Distraction osteogenesis technique and complications
• Advances in Bone Transport Techniques - PMC - Ilizarov vs. Masquelet comparison
• Ilizarov Bone Transport for Distal Tibial Defects - Dove Press

Bridge Plating: Principle, Usage, Indications, Methodology, Rules, and Failures

1. THE CORE PRINCIPLE

"Bridge plating is most commonly utilized to span comminuted metaphyseal and diaphyseal fractures. Rather than striving for anatomic reduction and compression of individual fracture fragments, the comminuted region is simply bridged. The resultant construct provides relative rather than absolute stability."

• Rockwood and Green's Fractures in Adults, 10th ed. 2025

Why Relative Stability Promotes Healing in Comminuted Fractures

2. INDICATIONS

Strong Indications

1. Comminuted diaphyseal fractures (3+ fragments) - tibia, femur, humerus, forearm
2. Multifragmentary metaphyseal fractures - distal femur, proximal tibia, proximal humerus
3. Segmental fractures - two fracture lines with an intermediate bone segment
4. Highly comminuted periarticular fractures - where the meta-diaphyseal zone is shattered even when the articular block is reconstructed with absolute stability
5. Open fractures with bone comminution where soft tissue coverage is difficult (especially with MIPO technique)
6. Periprosthetic fractures around hip or knee arthroplasty with comminution (Vancouver B and C)
7. Pathological fractures with comminution around tumor/metastatic lesions
8. Situations where the overlying soft tissues preclude direct access to the fracture zone

Hybrid Fixation - The Combined Approach

• Absolute stability (lag screws / direct reduction) for the articular block - because joint surfaces require anatomic reduction
• Bridge plating (relative stability) for the meta-diaphyseal comminution - preserving biology in the shattered shaft region

Bridge plating: a long plate spans the comminuted zone (shown in red). Screws are placed proximally and distally in the intact bone segments, leaving the fracture zone undisturbed.

Contraindications

• Simple (2-part) transverse or oblique fractures where anatomic reduction and compression are achievable - bridge plating here would leave a biomechanically unfavorable gap
• Active deep infection at the site (relative)
• When intramedullary nailing is clearly superior and safer (most femoral and tibial shaft fractures)

3. BIOMECHANICAL MECHANISM

How the Plate Works as an Internal Splint

• The plate absorbs and distributes bending, torsional, and axial loads across the fracture zone
• It maintains length (prevents telescoping), alignment (prevents angulation), and rotation (prevents malrotation)
• It allows controlled micromotion at the comminuted zone - this is not a flaw but a design feature that drives callus formation

The Working Length Concept (Critical)

The working length (WL) of a bridge plate construct - measured between the two screws closest to the fracture on each side. This ballistic femur fracture was treated with bridge plating.

• Longer WL = more flexibility = more micromotion = more callus stimulus (good for biology, but risks mechanical failure)
• Shorter WL = stiffer construct = less micromotion = may inhibit callus (too stiff) but stronger mechanically

"Working length is determined both by the fracture pattern and by the surgeon and the way a surgical implant is applied." - Rockwood and Green's, 10th ed.

Fixation Span vs. Working Length (Distinction)

Left: Long fixation span with good bridge span - small stress riser at end screw. Right: Short fixation span - large stress riser and risk of construct failure. The proximal femur generates a powerful bending force that must be countered by adequate fixation span.

4. PLATE SELECTION FOR BRIDGE PLATING

Plate Types Used

• Combination holes accept both cortical (conventional) and locking screws
• Locking screws thread into the plate head - the plate does NOT need to contact bone (no periosteal compression)
• Behaves as a fixed-angle device - all locking screws fail simultaneously (not sequentially like conventional screws)
• Ideal for bridge mode especially in osteoporotic bone and short metaphyseal segments

• Early generation of purpose-built bridge plate
• Unicortical self-drilling locking screws
• Percutaneous insertion jig
• First designed specifically for minimally invasive bridge plating of distal femur and proximal tibia

• Can be used in bridge mode but require bone contact (compresses periosteum)
• Less ideal biologically for long bridge spans
• Used when locking plates unavailable or in good bone stock

Locking vs. Conventional Screw Failure Modes

Left: Conventional screws fail sequentially by individual pullout. Right: Locking screws act as a fixed-angle device - all screws fail simultaneously, providing far superior resistance in osteoporotic bone.

5. METHODOLOGY - SURGICAL TECHNIQUE

Pre-operative Planning

1. Study X-rays: identify the fracture pattern, length of comminuted zone, bone quality
2. Template the plate: plate should be at least 2-3x the length of the fracture zone
3. Plan screw positions: minimum 3 screws (6 cortices) on each side of the fracture
4. Plan the approach: direct open vs. MIPO (minimally invasive plate osteosynthesis)
5. Obtain contralateral limb X-rays for length and rotational reference

The MIPO Approach (Preferred for Biologic Reasons)

MIPO technique: the plate is inserted submuscularly through small stab incisions. The fracture site is never directly visualized - reduction is achieved indirectly.

• Zero periosteal stripping at the fracture zone
• Preserves soft tissue attachments to all fragments
• Dramatically reduces infection risk in open fractures
• Faster union due to preserved biology

Step-by-Step Surgical Procedure

• For femur: fracture table with traction allows indirect reduction by ligamentotaxis
• For tibia: supine with leg free
• Image intensifier available throughout

• Apply traction to restore length
• Use femoral distractors, external fixators temporarily, or reduction forceps on proximal/distal segments only
• Check length on image intensifier - compare to contralateral side
• Check alignment (varus/valgus/procurvatum/recurvatum) in both planes
• Check rotation clinically (foot profile, lesser trochanter symmetry, cortical step sign)
• Never directly handle or strip the fracture fragments

• Pre-bend the plate to match the expected bone surface (especially important at metaphysis)
• Slight over-contouring for diaphyseal application (to prevent a gap on the opposite cortex when the plate is tightened)
• If using anatomically pre-contoured plates (LCP distal femur, proximal tibia), contouring may be minimal

• Make a limited incision proximally (5-8 cm) and distally (3-5 cm)
• Create a submuscular tunnel by blunt dissection along the bone surface using fingers or a soft tissue protector
• Slide the plate through the tunnel
• Check position under image intensifier in both planes: plate must be centered, not too anterior or posterior

• Use K-wires through plate holes to temporarily hold the plate to bone at each end
• Confirm alignment, length, and rotation before permanent screws
• Rotational check: compare lesser trochanter appearance bilaterally (femur), ankle position (tibia)

• First screw: most proximal hole
• Second screw: most distal hole
• Re-check alignment and length
• Add additional screws: minimum 3 bicortical screws (6 cortices) on each side
• Leave the fracture zone holes empty - this is mandatory for bridge plating
• For locking screws: drill guide must be perpendicular to the plate (angulation of even 5-10° reduces locking stability by 37-69%)

• Intraoperative fluoroscopy: AP and lateral of both ends and the fracture zone
• Confirm no screw in the wrong fragment or blocking the fracture
• Check plate is flush (not proud) to the bone surface

Bridge plating of a distal tibial metaphyseal fracture - the plate bridges the comminuted zone (pink area), with secure fixation both proximally and distally.

6. THE RULES OF BRIDGE PLATING

Rule 1: Use a LONG Plate

"Many surgeons emphasize the importance of a long plate with judiciously placed screws." - Rockwood and Green's

• Increases the fixation span (more mechanical advantage)
• Reduces stress concentration at the end screws
• Allows wider screw spacing for better biomechanics

Rule 2: Do NOT Fill Every Hole

• They create working length (micromotion for callus)
• Plate strain data shows that holes 5 or more positions away from the fracture gap have negligible strain regardless of screw placement
• Filling every hole creates a construct that is too stiff for secondary bone healing

Rule 3: Minimum 3 Screws (6 Cortices) on Each Side

• Minimum 3 bicortical screws (= 6 cortical purchase points) on each side of the fracture
• Beyond 4 screws per side, additional screws add marginal benefit in normal bone
• In osteoporotic bone: more screws + locking screws required
• The outermost and innermost screws have the greatest biomechanical contribution; middle screws add marginally less

Rule 4: Spread the Screws - Maximize Fixation Span

• Maximizes fixation span
• Reduces stress concentration at the end screw (stress riser)
• One screw near the fracture edge + one screw at the far end of the plate = maximum mechanical advantage

Rule 5: NEVER Directly Reduce or Strip the Comminuted Zone

• No elevating periosteum off the individual fragments
• No clearing hematoma from between fragments
• Indirect reduction only - traction, ligamentotaxis, distractor
• Violation of this rule converts a biologically favorable bridge construct into a devascularized zone prone to non-union

Rule 6: Restore Length, Alignment, and Rotation

• Length: Compare to contralateral limb or preoperative templating
• Alignment: AP and lateral fluoroscopy - no varus/valgus/recurvatum/procurvatum
• Rotation: Clinical assessment (foot profile, lesser trochanter, cortical step sign)

Rule 7: Correct Plate Contouring

• Plate must match the bone surface contour
• A flat plate applied to a curved bone and tightened will cause a gap on the opposite cortex - creating a fulcrum for plate bending failure
• Over-contouring in the mid-diaphysis creates an initial gap between the plate and bone, which closes when the plate is tightened - resulting in compression on the opposite cortex

Rule 8: Screw Density Rule (Plate-Screw Ratio)

• Optimal ratio: 0.4-0.5 (fill only 40-50% of holes)
• Too high (>0.7): construct too stiff, inhibits callus
• Too low (<0.3): inadequate purchase, risk of failure
• This ratio concept is specific to locking plates in bridge mode

7. PLATE FAILURE - Mechanisms and Prevention

The Core Mechanism of Bridge Plate Failure

Left: A gap on the cortex opposite the plate creates a fulcrum. Under offset compression, the plate bends rapidly at the fracture site and fails. Right: When fracture surfaces are compressed, bone cortices resist both compression and torsion - the plate shares load with the bone.

Failure Through a Screw Hole (Stress Riser Failure)

Stress trajectories in bone: (A) uniform tension without a hole - even stress distribution; (B) with a hole - stress lines converge around the hole creating a zone of stress concentration (shown in red). This is why plates and drill holes are stress risers.

Causes of Bridge Plate Failure

The Most Critical Point: Non-union = Inevitable Plate Failure

"Plates are most susceptible to bending failure... If a gap is left on the side opposite the plate, as when a bridge plating technique is used... the fracture site can become a fulcrum around which the plate bends under combined compressive and bending loads." - Rockwood and Green's, 10th ed.

Plate Failure Through a Screw Hole

1. The fracture has not healed (non-union) - most common cause
2. Excessive working length (screws placed too far from fracture edge with large comminuted gap)
3. The construct has been under cyclic fatigue loading without bone healing sharing the load

"Plate strains are highest at the two holes adjacent to the fracture gap... For large zones of comminution, screws should be placed near the fracture gap and spread over a long plate length to reduce strains in the plate." - Rockwood and Green's

8. COMPLICATIONS

Construct-Level

Technique Errors

9. COMPARISON WITH OTHER FIXATION MODES

Summary of Key Rules (Quick Reference)

1. Long plate: ≥ 2-3× the fracture zone length
2. Relative stability: do not compress, do not strip - preserve biology
3. Indirect reduction only: traction, ligamentotaxis, no touching fragments
4. Empty holes at fracture zone: intentional working length
5. 3 screws minimum / 6 cortices each side: secure purchase on intact bone
6. Spread screws far apart: maximize fixation span, minimize stress riser
7. Plate-screw ratio 0.4-0.5: optimal for locking bridge constructs
8. Contour the plate properly: prevent opposite-cortex gap
9. Secondary healing expected: callus = success; no callus + plate fatigue = failure
10. Protect weight-bearing until callus: the plate is temporary - the callus is the real fixation

• Rockwood and Green's Fractures in Adults, 10th ed. 2025 - "Bridge Plating," "Working Length," "Plate Failure," "Fixation Span," "Stress Risers," "Locked Plating" sections
• Campbell's Operative Orthopaedics, 15th ed. 2026 - Submuscular bridge plating techniques
• AO Foundation - Basic Principles of Plating - Bridge plate function and MIPO technique
• OTA Resident Slide Project - Internal Fixation Principles