Microvascular free tissue transfer for reconstruction of complex lower extremity trauma: Predictors of complications and flap failure.

[BACKGROUND] Despite advanced wound care techniques, open fractures in the setting of lower extremity trauma remain a challenging pathology, particularly when free tissue transfer is required for coverage. We aimed to evaluate factors associated with flap failure in this setting using a large, heterogeneous patient population.

[METHODS] Retrospective review of patients who underwent traumatic lower extremity free flap reconstruction (2002-2019). Demographics wound/vessel injury characteristics, pre and perioperative factors, and flap outcomes were analyzed.

[RESULTS] One hundred eighty-eight free flaps met inclusion criteria, with 23 partial (12.2%) and 13 total (6.9%) flap failures. Angiography was performed in 87 patients, with arterial injury suffered in 43.1% of those evaluated. Time to flap coverage varied within 3 days (4.5%), 10 days (17.3%), or 30 days of injury (42.7%). In all, 41 (21.8%) subjects suffered from major flap complications, including failure and takebacks. Multivariate regression demonstrated the presence of posterior tibial (PT) artery injury predictive of both flap-failure (Odds ratio [OR] = 11.4, p < .015) and major flap complications (OR = 12.1, p < .012). Immunocompromised status was also predictive of flap failure (OR = 12.6, p < .004) and major complications (OR = 11.6, p < .007), while achieving flap coverage within 30 days was protective against flap complications (OR = 0.413, p < .049). Defect size, infection, and injury location were not associated with failure.

[CONCLUSIONS] When examining a large, heterogeneous patient cohort, free flap outcomes in the setting of lower extremity open fractures can be influenced by multiple factors. This presence of PT artery injury, flap coverage beyond 30 days of injury, and immunocompromised status appear predictive of flap complications in this context.