Analysis of the Risk Factors for Free Flap Necrosis in Soft Tissue Reconstruction of the Lower Limbs.

[OBJECTIVE] Free flaps are widely used for the repair of soft tissue defects in the lower limbs, but there is still a specific rate of necrosis. Few clinical retrospective studies have analyzed the nontechnical risk factors for lower limb free flap necrosis. This study aimed to analyze the nontechnical causes of flap necrosis in lower limb soft tissue reconstruction in order to identify risk factors and improve the survival rate of free flaps.

[METHODS] Clinical data from 244 cases of soft tissue defects of the leg or foot that were repaired with a free flap from January 2011 to June 2020 were retrospectively analyzed. The flap results were divided into complete survival and necrosis groups. The patients' general information, smoking history, soft tissue defect site, Gustilo-Anderson classification, shock after injury, type and size of the flap, and time from injury to flap coverage were recorded. A logistic regression model was used to analyze the correlations between flap necrosis and possible risk factors.

[RESULTS] Of the 244 flaps, 32 suffered from partial or total necrosis, and 212 completely survived. Univariate analysis showed that age, smoking history, soft tissue defect site, and time from injury to flap coverage were significantly correlated with flap necrosis (p ≤ 0.2). Multivariate logistic regression analysis showed that moderate-to-severe smoking history (p < 0.001, odds ratio [OR] = 10.259, 95% confidence interval [CI] = 2.886-36.468), proximal leg defect (p = 0.006, OR = 7.095, 95% CI = 1.731-29.089), and time from injury to flap coverage >7 days (p = 0.003, OR = 12.351, 95% CI = 2.343-65.099) were statistically significant risk factors for flap necrosis (p < 0.05), and age was excluded (p = 0.666; p = 0.924).

[CONCLUSION] The risk of flap necrosis was significantly increased when the soft tissue defect was located in the proximal leg, the time from injury to flap coverage was >7 days, and the patient had a moderate-to-severe smoking history. These three risk factors have an increased influence on flap necrosis and have guiding significance in predicting flap prognosis.