Predictors of Salvage After Re‐Exploration of Compromised Free Anterolateral Thigh Flaps for Post‐Traumatic Extremity Reconstruction
Jannik Hinzmann, Suzan Kalkan, Sonja Verena Schmidt, Yonca Steubing, Marius Drysch, Flemming Puscz, Maxi von Glinski, Marcus Lehnhardt, Christoph WallnerABSTRACT
Introduction
Vascular compromise after free anterolateral thigh (ALT) flap reconstruction is a time‐critical event and may result in total flap loss despite re‐exploration. Although earlier re‐exploration is associated with improved salvage, this relationship is often simplified by arbitrary thresholds, and internally validated prediction models remain scarce. We aimed to quantify this relationship and assess the additional predictive value of systemic factors beyond timing.
Methods
This retrospective single‐center cohort study included all free ALT flaps for post‐traumatic extremity reconstruction between 2005 and 2020 that underwent re‐exploration for suspected vascular compromise on postoperative day (POD) 0–4. The primary endpoint was flap salvage at POD 5. Intraoperative findings were compared between salvaged and failed flaps. Univariable logistic regression examined the association between POD and salvage, followed by a multivariable model with prespecified covariates. Restricted cubic splines assessed nonlinearity, and 1000 bootstrap resamples were used to obtain optimism‐corrected estimates of discrimination and calibration.
Results
Among 222 ALT flaps, 58 (26.1%) required re‐exploration; 33 (56.9%) were salvaged and 25 (43.1%) failed. Salvage rates were 90.0%, 51.7%, 37.5%, 57.1%, and 50.0% for re‐exploration on POD 0–4, respectively. Arterial and venous compromise were more frequent in failed flaps, without significant differences. Salvage probability crossed the 50% threshold between POD 1 and POD 2. Spline modeling demonstrated significant nonlinearity, with a steeper decline during the first two PODs followed by a relative plateau (LRT p = 0.037). Most systemic variables added little predictive information. Apparent discrimination was moderate (AUC 0.714), and optimism‐corrected performance was modest (AUC 0.622; calibration slope 0.69).
Conclusion
Salvage probability declined in a biologically plausible, continuous, and nonlinear manner with increasing POD of re‐exploration, with a steeper decline at earlier time points, although salvage remained possible later. Timing appeared to be the principal determinant of salvage, while systemic variables added limited predictive value.