Risk assessment in delayed free flap reconstruction for severe lower extremity trauma.

[PURPOSE] This study aims to identify serum biomarkers that contribute to vascular thrombosis and complete flap failure in delayed reconstruction with free flaps, as well as to develop a scoring system of risk assessment including these biomarkers.

[METHODS] A retrospective review of the database was conducted for lower extremity open fractures reconstructed between 7 and 90 days from injury, from March 2014 to February 2022. We investigated changes in platelet count (PLT), D-dimer, creatine phosphokinase (CPK), and C-reactive protein (CRP) and then, developed a risk assessment system including these biomarkers as risk factors.

[RESULTS] A total of 62 free flaps were enrolled, and vascular thrombosis occurred in 14 flaps (22.6%), 9 of which (14.5%) developed complete flap failure. The risk assessment score was set to a maximum of 6 points for 6 items: age ≤ 40 years, time from injury to coverage ≥ 14 days, zone of injury from middle to distal leg, D-dimer on the day of injury ≥ 60 µg/mL, maximum value of CPK ≥ 10,000 U/L, and maximum value of CRP ≥ 25 mg/dL. The best cutoff score was 3 in the vascular thrombosis model (sensitivity: 0.79, specificity: 0.77) and 4 in the complete flap failure model (sensitivity: 0.78, specificity: 0.92).

[CONCLUSIONS] Our risk assessment system showed that the risk of vascular thrombosis was high at ≥ 3 points and that of complete flap failure was high at ≥ 4 points. Significantly, elevated levels of D-dimer, CPK, and CRP require more caution during reconstruction using free flaps.