Bone Transport Techniques

Bone transport is a technique using distraction osteogenesis to move a bone segment across a defect, generating new bone in its wake. Developed from Ilizarov's principles, it is the definitive treatment for segmental bone defects not amenable to conventional bone grafting.

Indications:

• Segmental bone loss greater than 4cm
• Post-traumatic bone defects
• Post-tumor resection reconstruction
• Infected nonunion with bone loss
• Congenital pseudarthrosis

Advantages over massive bone grafting:

• Uses patient's own regenerative capacity
• No donor site morbidity for large grafts
• Can address defects larger than available graft
• Simultaneous soft tissue regeneration
• Can be combined with infection treatment

Disadvantages:

• Prolonged treatment time (months)
• Pin site complications
• Technical complexity
• Patient compliance required

Biology of Bone Transport

Regenerate formation:

• New bone forms at the corticotomy site during transport
• Same principles as limb lengthening
• Rate 1mm/day preserves biology
• Regenerate consolidates after transport complete

Docking site biology:

• Two bone ends meeting - often avascular
• Variable healing potential
• May have fibrous interposition
• Frequently requires augmentation

Transport Methods

Monofocal:

• Single osteotomy proximal or distal to defect
• Transport segment moves across defect
• Simple technique, longer transport distance
• Docking site at one end

Bifocal:

• Two osteotomies, one at each end of defect
• Two segments transport toward middle
• Each segment moves half the distance
• Docking site in middle of defect

Trifocal:

• Three osteotomies
• Central segment transported, end segments moved in
• For very large defects
• Complex but faster

Bone transport itself is described by the number of osteotomies (focal level), but the defect and host are classified by widely used trauma and reconstruction systems that drive decision-making.

Patient Assessment

History:

• Mechanism of bone loss
• Infection history (critical for planning)
• Previous surgery and implants
• Comorbidities affecting healing

Physical examination:

• Soft tissue envelope quality
• Limb alignment
• Neurovascular status
• Signs of active infection

Preoperative Planning

Imaging:

• Full-length bone radiographs
• CT for defect measurement and bone quality
• MRI if infection suspected

Defect characterization:

• Size in centimeters
• Location (metaphyseal vs diaphyseal)
• Bone quality at proposed osteotomy sites
• Soft tissue condition

Imaging

Plain radiographs:

• Full-length views of affected bone
• Assess defect size and location
• Bone quality evaluation

CT scan:

• Accurate defect measurement
• Plan osteotomy site
• Assess sequestra in infection

MRI:

• Soft tissue evaluation
• Infection extent
• Marrow involvement

Imaging Gallery

Infection Workup

For infected cases:

• ESR and CRP (baseline and monitoring)
• White cell count
• Intraoperative cultures (at least 5 samples)
• Histopathology

Method Selection

Transport Complications

• Poor regenerate: Slow rate, bone graft if persistent
• Premature consolidation: Speed up rate or accordion
• Axial deviation: Adjust frame during transport
• Soft tissue tethering: May limit transport

Docking Site Complications

• Nonunion: 25-50% need bone grafting
• Malalignment: Correct before union
• Infection persistence: Further debridement

General Complications

• Pin site infection: Standard external fixator issue
• Joint contracture: Aggressive physiotherapy
• Refracture: Protect after frame removal (risk rises with defects over 8cm)

The key exam decision is not "how to do transport" but "which technique for this defect, this host, these soft tissues". The four mainstream options are compared below.

• Transport vs induced membrane vs free fibula: No high-quality randomised data establishes superiority. Systematic review evidence shows equivalent bony and functional outcomes between transport and free fibula, with free fibula achieving faster union and fewer complications but requiring microsurgery (Paul 2023). Choice remains expertise- and biology-driven.
• Prophylactic docking-site grafting: Whether to graft the docking site at the time of contact versus waiting to see if it unites spontaneously is unresolved. Acute grafting (as in nail-assisted series) may pre-empt the 25 to 50% nonunion rate but commits every patient to an extra procedure.
• Optimal distraction rate and rhythm: 1mm/day in 4 increments is conventional, but slower rates may be needed for poor regenerate and faster increments tolerated in children; the ideal rhythm for transport (as opposed to lengthening) is extrapolated rather than proven.
• Role of biologics (BMP, PRP, bone-graft substitutes): Used adjunctively at problem docking sites and to augment regenerate, but evidence is largely off-label and low-level; routine use is not established.
• Salvage vs amputation: For very large defects with severe soft-tissue and neurovascular injury, prolonged reconstruction may not outperform early amputation and prosthetic rehabilitation in function or cost - a shared decision, not a technical default.

Distraction and Monitoring Phase

• Start distraction after the 5 to 7 day latency; instruct the patient/carer on 0.25mm four-times-daily adjustments.
• Pin-site care: daily cleaning regimen; pin-site infection is expected and treated early with oral antibiotics, escalating only if deep.
• Weight-bearing: encouraged within tolerance to load the regenerate, which improves bone quality.
• Radiographs: regenerate reviewed approximately every 2 weeks; slow the rate for poor regenerate, speed up or perform an accordion manoeuvre for premature consolidation.
• Range of motion: aggressive physiotherapy for adjacent joints throughout to prevent equinus (tibia) and knee/hip contractures.

Consolidation and Frame Removal

• Continue the frame through consolidation (roughly 1 month per cm transported).
• Confirm union of regenerate and docking site before removal - 3 of 4 cortices visible on orthogonal views.
• After removal, protect the limb (cast/brace) to reduce refracture risk, especially for defects over 8cm.

Pooled data come from systematic reviews and case series rather than registries. Reported figures (verified in the Evidence Base) include:

• Union: achievable in the high 80s to mid 90s percent with appropriate docking-site management; nonunion rates are comparable between transport and free fibula.
• Infection eradication: transport markedly reduces deep infection in infected lesions (risk ratio 0.14 in meta-analysis).
• Docking-site grafting: required in 25 to 50% of cases - the principal predictable hurdle.
• Refracture: about 5% overall, rising roughly 3.7-fold for tibial defects over 8cm.
• Amputation: around 2.9%, including a voluntary amputation rate of about 1.6% reflecting treatment burden.
• External fixation index: roughly 1.5 months/cm with a frame alone, falling to as low as 0.4 months/cm when transport/lengthening is performed over a nail.

Functional outcomes (ASAMI) are good to excellent in most series, but treatment is long and demanding; patient selection and counselling are decisive prognostic factors.

All primary clinical studies below have been verified against PubMed. Society guidance and core textbook principles are flagged as Guideline-level and do not carry a PMID.

Global Epidemiology

Segmental long-bone defects most often follow high-energy open tibial fractures (Gustilo IIIB/IIIC), infected nonunion/osteomyelitis, and tumour resection. Worldwide the tibia is the commonest site because of its subcutaneous position and tenuous blood supply. There is no dedicated international registry for bone transport; the evidence base is dominated by single-centre case series and a small number of systematic reviews, so reported figures vary widely with defect size, infection and host status.

Side-by-Side Guidance

The common thread across all bodies: control infection and achieve healthy soft-tissue cover first, then reconstruct bone with the method best matched to defect length, host biology and local expertise. None mandates a single technique.

Registry and Outcome Notes

No arthroplasty-style registry tracks bone transport. The best pooled outcome data come from systematic reviews (e.g. Papakostidis 2013, Paul 2023) rather than national registries, so quoted union, refracture and amputation rates derive from aggregated case series and carry meaningful heterogeneity.

High- vs Limited-Resource Practice Variation

The induced-membrane (Masquelet) technique is the principal global alternative to transport: a two-stage approach with a PMMA cement spacer to induce a vascular membrane, followed by autologous cancellous grafting (usually at 4 to 8 weeks). Transport better tolerates very large defects and active infection; induced membrane is technically simpler and avoids prolonged external fixation but is graft-volume limited. Vascularised free fibula is favoured for large defects with a good recipient vessel bed.