Preoperative Venous Circumference-Squared-to-Area Ratio (C2/A) and D-dimer for Deep Vein Thrombosis Prediction After Orthopedic Surgery.

Deep vein thrombosis (DVT) is a common complication after orthopedic surgery. This prospective observational study evaluated whether a single preoperative baseline measurement of the venous circumference-squared-to-area ratio (C2/A), alone and with D-dimer, was associated with DVT detected during the first 7 postoperative days. One hundred fifty adults undergoing orthopedic surgery were enrolled; 37 developed DVT and 113 did not. Preoperative circumference (C) and area (A) were measured separately at end-expiration with the ultrasound system's built-in measurement package during the same acquisition cycle. Investigators calculated C2/A as C2 divided by A. To apply this rule consistently to the retained participant-level dataset, all revision analyses used C2/A recalculated from the retained C and A fields. Postoperative ultrasound was performed at 12-h intervals for 7 days under a prespecified intensified study-surveillance schedule used only for outcome ascertainment. The areas under the receiver operating characteristic curves were 0.893 for common femoral vein C2/A, 0.817 for superficial femoral vein C2/A, 0.906 for popliteal vein C2/A, and 0.834 for D-dimer. The originally specified superficial femoral vein C2/A plus D-dimer model had an apparent area under the curve of 0.887 and a stratified 5-fold cross-validated out-of-fold area under the curve of 0.877. A 5-variable exploratory model had an out-of-fold area under the curve of 0.938. Using cohort-derived thresholds of 16.26 for superficial femoral vein C2/A and 2.15 mg/L FEU for D-dimer, DVT occurred in 0 of 78 patients with neither marker elevated, 15 of 50 with one elevated, and 22 of 22 with both elevated. Preoperative venous C2/A and D-dimer were associated with early postoperative DVT, but the thresholds and models are exploratory and require external validation.