Improving intraoperative perfusion reliability in anterolateral thigh free flap reconstruction for diabetic foot ulcers

Figure 1 Improving anterolateral thigh free-flap perfusion reliability in diabetic foot ulcers. This schematic frames anterolateral thigh (ALT) free-flap perfusion in diabetic foot ulcer (DFU) as an integrated continuum linking systemic modifiable physiology - glycemic status [hemoglobin A1c (HbA1c)/perioperative glucose], anemia/iron status, respiration and oxygen delivery (DO₂) [arterial partial pressure of carbon dioxide/oxygen (PaCO₂/PaO₂), ventilation], and nutritional reserve (albumin/prealbumin) - to regional vascular capacity in the setting of diabetes-related medial arterial calcification (MAC), where ankle-brachial index (ABI) may be misleading, and distal perfusion should be characterized using toe pressure/toe-brachial index (TBI), skin perfusion pressure (SPP), and transcutaneous oxygen tension (TcPO₂), with revascularization when indicated. These layers converge with microcirculatory dysfunction and impaired capillary recruitment at the flap and recipient-site level (conceptual note: “Brightness ≠ exchange efficiency”). The central intraoperative quantitative perfusion decision hub integrates systemic status, distal perfusion context, and standardized indocyanine green fluorescence angiography (ICG-FA) acquisition, emphasizing fluorescence-time curve kinetics [wash-in slope, time to maximum intensity, maximum fluorescence intensity, area under the curve (AUC)] rather than single intensity snapshots. Outputs are actionable intraoperative strategies (revise anastomosis, trim hypoperfused margins, supercharging/additional venous outflow, proceed vs delay/optimize) to reduce partial/total necrosis and reoperation and improve limb salvage. ROI: Region of interest.

Figure 2 Quantitative, multimodal pathway for anterolateral thigh flap perfusion in diabetic foot ulcer. This workflow summarizes a stepwise, bundle-based algorithm for diabetic foot ulcer (DFU) candidates undergoing anterolateral thigh (ALT) free-flap reconstruction. Step 1 (preoperative evaluation) integrates distal perfusion testing [toe pressure/toe-brachial index (TBI), skin perfusion pressure (SPP), transcutaneous oxygen tension (TcPO₂)], systemic optimization targets [glucose control, hemoglobin (Hb), oxygenation/ventilation, nutritional reserve], and comorbidity risk flags [peripheral artery disease (PAD), medial arterial calcification (MAC), edema/inflammation]. If perfusion and optimization targets are not met, an optimization/revascularization bundle is initiated and reassessed before proceeding. Step 2 (intraoperative perfusion imaging) applies indocyanine green fluorescence angiography (ICG-FA) under a standardized acquisition protocol and prioritizes fluorescence-time curve quantification [e.g., wash-in slope, time-to-peak, area under the curve (AUC)] to avoid intensity-only snapshots. Step 3 (multimodal validation) cross-checks ICG-FA kinetics against distal perfusion metrics and optional monitoring tools (near-infrared spectroscopy [NIRS]/tissue oximetry and laser Doppler perfusion) to adjudicate marginal perfusion. When quantitative kinetics suggest borderline perfusion, targeted intraoperative corrective actions (trim hypoperfused margins, revise anastomosis, supercharging) are implemented; otherwise, the surgeon proceeds to inset/closure. Step 4 (postoperative monitoring and endpoints) emphasizes structured surveillance (clinical assessment with optional near-infrared spectroscopy/TcPO₂) and links the pathway to clinically meaningful outcomes, including partial/total necrosis, wound healing, and limb salvage. Tmax: Time to maximum fluorescence intensity; StO₂: Tissue oxygen saturation; PU: Perfusion units.