Single-Vessel Lower Limb after Open Tibial Fracture: Free Flap Decisions
A 34-year-old man, a 20-pack-year smoker with type 1 diabetes (HbA1c 9.4%), sustained a Gustilo–Anderson IIIB open fracture of the left tibia 10 days ago. He has an external fixator, a 12 × 8 cm anterior soft-tissue defect, 6 cm of exposed, desiccated cortical bone, and an absent dorsalis pedis pulse. Angiography shows occlusion of the anterior tibial artery and single-vessel runoff through a diseased posterior tibial artery; the peroneal artery is not visualized. Wound cultures grow Pseudomonas aeruginosa and Enterococcus, but he is afebrile with a CRP of 48 mg/L and a WBC of 11.2. He is on an insulin infusion, the wound is managed with vacuum-assisted closure, and the plastic surgery team is asked for definitive coverage. The orthopaedic team wants coverage within 72 hours to allow bone grafting. The patient asks for the fastest option and is unwilling to stop smoking.
1. Which coverage option would you choose, and how would you manage the recipient vessels? Justify your choice against local and pedicled alternatives.
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Choice. A free muscle flap - latissimus dorsi or rectus abdominis - is the most reliable option. The defect is large, bone is exposed, and the wound is colonized, so the flap must fill dead space, improve vascularity, and tolerate bacterial contamination. Muscle flaps do this better than fasciocutaneous flaps and can be skin-grafted secondarily. A local soleus or gastrocnemius flap cannot reliably reach a distal-third tibial defect and would depend on the same compromised angiosome. A pedicled perforator flap is unavailable because the anterior tibial and peroneal vessels are occluded, and a cross-leg flap is obsolete for this indication.
Recipient vessels. The posterior tibial artery is the only runoff vessel, so it must be preserved: perform an end-to-side anastomosis, never end-to-end. Preoperative CT angiography and intraoperative Doppler mapping are essential. If the posterior tibial artery is diseased at the chosen anastomotic site, use a vein graft to a more proximal healthy segment. Anastomose the flap vein to a superficial vein or a venae comitans with good outflow.
Timing. Debride the wound again before coverage, excising desiccated bone and necrotic tissue. Coverage can proceed once the wound is clean and the patient is optimized; waiting for sterile cultures is unnecessary and increases fibrosis and bone loss. The orthopaedic 72-hour target is reasonable if resuscitation and debridement are complete.
2. What preoperative and intraoperative measures would you use to reduce the risk of flap failure in this patient?
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Preoperative. Smoking is the strongest modifiable risk factor. I would require at least 4 weeks of cessation, offer nicotine replacement and counseling, and document that the 72-hour target may need to be adjusted if he continues to smoke. Glycaemic control should be optimized toward an HbA1c below 8% with the insulin infusion, and nutrition should be assessed (albumin, prealbumin, lymphocyte count). Targeted antibiotics should follow deep cultures, but surgery should not be delayed until cultures are sterile. Continue vacuum-assisted closure, perform serial debridement, and treat the wound as contaminated rather than overtly infected. Screen for anemia and correct it; arrange VTE prophylaxis.
Intraoperative. Use meticulous technique with wide exposure of healthy vessels, gentle handling, and a tension-free inset. Avoid vasopressors when possible; maintain normothermia, adequate perfusion pressure, and hydration. Consider a vein graft rather than a compromised anastomosis. Place an implantable Doppler or use hourly clinical monitoring for the first 24 hours.
Postoperative. Keep the limb elevated without pressure on the pedicle, avoid nicotine, monitor hourly, and maintain hemoglobin and temperature. Routine systemic heparin is not supported; use LMWH prophylaxis and reserve therapeutic anticoagulation for documented thrombosis or a hypercoagulable state.
3. At 6 hours the flap is dusky, capillary refill is under 1 second, and the implantable Doppler signal has dropped. How would you assess and manage this?
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This is a threatened flap and requires urgent bedside assessment followed by re-exploration, not observation. First check the dressing, limb position, and any constricting suture or external fixator; release tight closures and ensure the pedicle is not kinked. Distinguish arterial from venous compromise: a cool, pale flap with sluggish or absent bleeding suggests arterial thrombosis; a congested, blue flap with rapid dark bleeding suggests venous thrombosis. Handheld Doppler and, if available, near-infrared spectroscopy or fluorescein help but should not delay surgery.
Take the patient back to theatre immediately. Explore the anastomosis, resect the thrombosed segment, perform thrombectomy with a Fogarty catheter, and use local urokinase or tissue plasminogen activator if distal thrombus persists. If the vessel is damaged or shortened, interpose a vein graft. Ensure adequate inflow and outflow before inset. If re-exploration is not feasible and venous congestion predominates, medicinal leeches can temporize, but they are not a substitute for re-exploration. Document the ischaemia time and monitor for reperfusion injury, compartment syndrome, and rhabdomyolysis with urine output and creatine kinase.