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.

Biology of Bone Transport

Transport Methods

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.

When bone transport follows an infected nonunion, the Cierny-Mader classification named above determines how much bone must be resected and whether the host can heal a reconstruction at all. It combines an anatomic type with a physiological host class.

Patient Assessment

Preoperative Planning

Imaging

Imaging Atlas

Infection Workup

For infected cases:

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

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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.

The induced-membrane technique is the principal alternative to transport for a segmental defect, and the examiner expects you to know its two stages and why the membrane matters.

Why the induced membrane works: the foreign-body reaction to the cement creates a vascularised pseudosynovial membrane that secretes growth factors (VEGF, BMP-2, TGF-beta), prevents graft resorption, and provides a contained, well-vascularised bed; its bioactivity peaks at around one month, which is why grafting is timed to roughly 6 to 8 weeks.

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.

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.

• 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.