Correlation between venous thromboembolism risk and venous congestion in microvascular reconstruction of the lower extremity

Background: Risk for venous thromboembolism formation and the relationship to postoperative free flap venous congestion and flap failure have not been adequately evaluated in a trauma population. The authors aim to use the Caprini Risk Assessment Model to evaluate the association between venous thromboembolism risk and postoperative flap venous congestion following lower extremity free tissue transfer. Methods: A retrospective analysis was conducted of all patients who underwent lower extremity free flap reconstruction of traumatic defects at a single institution between 2007 and 2016. A Wilcoxon rank sum test was used for nonparametric analysis of aggregate Caprini Risk Assessment Model scores and flap outcomes. Flap venous congestion and failure rates as associated with the categorical variables underlying the Caprini Risk Assessment Model were further studied. Logistic regression was used to evaluate each of these outcomes and other flap-related covariates relative to the Caprini Risk Assessment Model categorical variables that had the greatest effect on our patient sample. Results: One hundred twelve patients underwent lower extremity free flap reconstruction. One hundred eight free flaps were analyzed. Eight patients were excluded. The majority of patients were male (75.9 percent) and required reconstruction because of acute trauma (68.1 percent versus 31.9 percent for chronic wounds). There was no statistically significant association found between age, body mass index, or timing of trauma versus venous congestion, flap failure, or other flap-related covariates. Conclusion: In patients with significantly elevated Caprini Risk Assessment Model scores, there was no significant association between venous thromboembolism risk and flap failure following free tissue reconstruction of lower extremities. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, III.