Post-operative Deep Vein Thrombosis (DVT) primarily results from venous stasis, a key component of Virchow's triad. After surgery, especially major or orthopedic procedures, patients often experience immobilization and reduced limb movement, leading to decreased venous return. This stagnant blood flow increases the risk of clot formation in deep veins. While endothelial injury and hypercoagulability are important, the most significant factor post-operatively is the inability to maintain normal venous circulation due to prolonged bed rest and immobility. Arterial spasm is not a part of Virchow’s triad nor relevant here. Preventing venous stasis through early mobilization and mechanical prophylaxis is thus crucial after surgery.
Reference: Harrison's Principles of Internal Medicine, 20th Edition.