Tibial Transverse Bone Transport

Courtesy: Dr Gustavo Lucar MD, Barcelona, Spain

 

Tibial Transverse Bone Transport (TTBT) for Diabetic & Ischemic Foot Salvage

1. Background & Biomechanical/Biological Basis

• Historical Origins: Derived from Ilizarov distraction osteogenesis principles (originally described in the 1950s). Distraction tension across an osteotomy gap induces angiogenesis alongside osteogenesis.

• Biological Rationale:

  • Translating a vascularized cortical bone fragment creates controlled intramedullary and subperiosteal hematoma formation.

  • Upregulates angiogenic growth factors, stimulating systemic and local microvascular regeneration.

  • Restores microvascular distal runoff, increases transcutaneous oxygen pressure, improves regional blood flow on Doppler and angiography, and accelerates chronic ulcer healing.

• Morbidity of Major Amputation: Major limb loss (transtibial/transfemoral) carries a 1-year mortality rate between 30% and 60%, alongside substantial loss of functional independence and socio-economic burden. TTBT functions as a biological limb-salvage strategy to convert non-salvageable limbs into functional weight-bearing feet or lower-level partial amputations.

2. Multidisciplinary Assessment & Indications

• Core Team Composition: Orthopaedic and podiatric surgeons (biomechanics and osseous reconstruction), vascular surgery (perfusion), endocrinology (glycemic control), infectious disease (targeted antimicrobial regimens), wound care nursing, and plastic surgery (soft-tissue coverage).

• Primary Indications (Salvage Strategy):

  • Advanced peripheral arterial disease (PAD) and chronic critical limb ischemia (CLI) with recalcitrant neuroischemic ulcers.

  • Severe microvascular disease with long-segment arterial occlusions where standard endovascular revascularization or open bypass is anatomically, technically, or medically infeasible (“no-option” ischemic limb).

  • Chronic osteomyelitis combined with poor distal perfusion, requiring revascularization to deliver systemic antibiotics and support local debridement.

  • Chronic, refractory ischemic rest pain.

  • Adjunct to complex foot reconstruction (e.g., Charcot neuroarthropathy realignment).

• Contraindications:

  • Active, deep, systemic sepsis or unstable septic shock (avoids a “second hit”).

  • Irreversible, extensive dry or wet gangrene/necrosis extending across the hindfoot/midfoot (established dead tissue cannot be revitalized).

  • Severe uncompensated end-stage cardiac or renal failure.

  • Completely uncontrolled diabetes mellitus.

3. Surgical Technique & Distraction Protocol

• Approach & Flap Management:

  • Located over the proximal to middle anteromedial subcutaneous surface of the tibia.

  • A wide, full-thickness curvilinear or eccentric skin flap is raised with meticulous handling of the soft-tissue envelope to avoid wound breakdown over the hardware.

  • Can be performed open (recommended during the learning curve) or percutaneously in experienced hands.

• Corticotomy:

  • An isolated, rectangular cortical bone window (approx. 8 to 10 cm in length and ~2 cm in width) is outlined on the anteromedial tibial cortex using multiple drill holes and connected with osteotomes.

  • The medullary canal is not completely breached circumferentially; the lateral and posterior tibial cortices remain fully intact, maintaining primary structural load-bearing capacity.

• Fixator Frame & Pin Configuration:

  • Specialized transverse external fixator constructs or modified small-joint distraction frames.

  • Total of 4 pins:

    • 2 outer/peripheral pins placed into the stable, fixed tibial cortical framework.

    • 2 inner/central pins anchored into the mobile, osteotomized cortical bone block.

• Distraction-Compression Protocol:

  • Latency Period: Approximately 5 to 7 days postoperatively.

  • Distraction Phase: Outward lateral/transverse translation at a rate of 1 mm/day (often split into 0.25 mm four times daily) for approximately 20 to 21 days (achieving up to 1.5–2 cm total displacement).

  • Compression/Return Phase: The displaced cortical window is translated back inward toward the tibia at 1 mm/day until it interfaces with the parent cortex.

  • Rehabilitation: Immediate, early postoperative weight-bearing is permitted as tolerated, utilizing the intact posterior and lateral tibial cortices.

4. Clinical Evidence & Global Perspective

• Evidence Base: High-volume clinical trials originate primarily from Asian centers (particularly China), reporting reduced major amputation rates and accelerated healing of recalcitrant ulcers.

• Western Adoption: Western and European literature currently consists largely of small case series, preliminary cohorts, and recent systematic reviews; multicenter randomized controlled trials (RCTs) are underway to evaluate long-term outcomes relative to modern endovascular procedures.

• Procedural Role: Not a replacement for viable endovascular stenting, balloon angioplasty, or open arterial bypass; it serves as a rescue intervention when direct vascular revascularization has failed or is technically impossible.

Master Revision Summary

• Surgical Classification: Tibial Transverse Bone Transport (TTBT/TBT) via controlled cortical distraction osteogenesis.

• Mechanism: Mobilization of an anteromedial cortical window creates tension-stress hematoma, releasing angiogenic cytokines and restoring distal microvascular perfusion

• Primary Target: “No-option” diabetic/neuroischemic critical limb ischemia unsuitable for standard surgical bypass or catheter angioplasty.

• Absolute Exclusions: Systemic sepsis, uncompensated cardiopulmonary failure, and extensive foot gangrene.

• Surgical Construct: Rectangular anteromedial tibial corticotomy (approx. 8–10 cm long) maintained by a 4-pin unilateral transverse frame (2 fixed parent cortex pins, 2 mobile window pins).

• Kinematics: 7-day latency > 1 mm/day outward distraction for 21 days (2cm) > 1 mm/day inward translation to dock against the host tibia >  immediate protected weight-bearing.

• Clinical Goal: Major amputation prevention, converting unsalvageable limbs into functional, plantigrade weight-bearing extremities.