Risk Factors for Partial Flap Loss in a Free Flap: A 12-Year Retrospective Study of Anterolateral Thigh Free Flaps in 303 Lower Extremity Cases.

[BACKGROUND] Despite remarkable improvements in free flap procedures, partial flap losses in perforator flaps still occur. This study aimed to analyze partial necrosis cases that underwent reconstruction of the lower extremities using anterolateral thigh free flaps and to identify risk factors causing the occurrence of partial necrosis.

[METHODS] From January of 2005 to February of 2017, 303 anterolateral thigh free flaps were analyzed retrospectively. After collecting patient data, receiver operating characteristic curve analysis was conducted to find the critical distance between the perforator and the flap margin that distinguishes partial necrosis. Also, the rate of partial losses was calculated for each section after dividing the distance from the perforator to the flap margin into 1-cm sections. Lastly, logistic regression analyses were performed to identify the risk factors.

[RESULTS] Forty-three cases had partial flap loss (14.19 percent). Flaps with supradeep fat layer elevation showed the highest rate of partial necrosis (25.53 percent), with statistical significance ( p = 0.0001). In receiver operating characteristic curve analysis, the cutoff distance was 10.25 cm. In addition, flap tissues 8 cm away from the perforator have a 10.3 percent chance of necrosis, whereas those 12 cm away from the perforator have a 22.9 percent chance. Lastly, supradeep fat layer elevation (OR, 3.952) and large flap size (OR, 1.041) were risk factors for partial flap necrosis on multivariate analysis.

[CONCLUSIONS] The distance from the perforator to the flap margin, the flap elevation layer, and the flap size affected the occurrence of partial necrosis. Taking these into consideration, anterolateral thigh free flaps of appropriate size and thickness should be harvested.

[CLINICAL QUESTION/LEVEL OF EVIDENCE] Risk, III.