Lit Matters 1: Ankle Immobilization and VTE Risk

Ankle fracture immobilization raises venous thromboembolism risk even when the absolute event rate stays low. In ED patients discharged with lower-limb immobilization, VTE risk is several-fold higher than matched upper-extremity injury controls, making risk stratification and prophylaxis conversations clinically relevant.

Ankle Immobilization and VTE Risk

• Ninety-day event rate: The 90-day incidence of venous thromboembolism after ED discharge with an immobilized ankle fracture was 1.3%, a low absolute risk that still matters because a third of DVTs progress to PE.
• Relative risk signal: Lower-extremity fracture plus immobilization carried a 5- to 6-fold higher hazard of VTE than matched controls with finger wounds or wrist fractures, a useful framing point for bedside counseling.
• Highest-risk patient profile: Prior VTE or superficial venous thrombosis was the strongest predictor, with older age, recent hospitalization, recent non-ankle fracture surgery, and later ankle surgery also increasing risk.
• Routine prophylaxis limits: Empiric anticoagulation for every immobilized ankle fracture is hard to justify; a large POT-CAST trial found no significant VTE reduction with prophylactic LMWH during casting.
• Selective chemoprophylaxis strategy: The practical move is targeted prophylaxis discussion for higher-risk patients, balancing bleeding risk against clot risk and reviewing warning symptoms we get into in the episode.