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Thromboembolic Event After Below-Knee Orthopedic Surgery Quadruples the Risk of Death

Key findings

  • The incidence of symptomatic venous thromboembolism (VTE) in patients who underwent below-knee orthopedic surgery was 2.5%
  • In subgroups at high-risk, thromboprophylaxis did not lower the risk of VTE
  • Nearly 6% of patients diagnosed with VTE died within 90 days
  • VTE quadrupled the risk of death within 90 days

Unlike patients undergoing hip or knee replacement, patients who have below-knee orthopedic surgery do not routinely receive pharmacologic prophylaxis against venous thromboembolism (VTE). No guidelines have been published about which patients are candidates, and VTE increasingly seems to be regarded as a never event.

But in a review in The Journal of the American Academy of Orthopaedic Surgeons, Massachusetts General Hospital researchers including Daniel Guss, MD, MBA, orthopaedic surgeon in the Foot and Ankle Center, Christopher W. DiGiovanni, MD, chief of the Foot and Ankle Center, report rates of symptomatic VTE were higher than the previously reported at <1%. Moreover, this is the first large retrospective study to determine the incidence and risk factors of VTE according to the different types of pharmacologic thromboprophylaxis.

The team examined the records of 23,206 adults who had below-knee surgery between August 2005 and August 2015. They excluded patients if they had postoperative follow-up less than 90 days, a history of thromboembolism, polytrauma or another below-knee surgery within 90 days after surgery.

Of the 20,043 patients remaining:

  • 28% had forefoot/midfoot surgery
  • 27% had lower leg surgery
  • 11% had hindfoot/ankle surgery
  • 34% had some combination of forefoot/midfoot, hindfoot/ankle and/or lower leg surgery during a single intervention

Within 90 days after surgery, symptomatic deep vein thrombosis developed in 1.5% of patients and symptomatic pulmonary embolism developed in 0.6%, for a total VTE rate of 2.5%. Twenty-nine patients (5.9%) with VTE died within 90 days after surgery, compared with 285 patients (1.5%) without VTE. The relative risk of death after developing VTE was 3.9 (95% CI, 3.5–6.7; < .001).

The incidence of VTE was 1.5% in patients who did not receive pharmacologic thromboprophylaxis, 1.7% in those who received antiplatelet agents and 3.6% in those who received anticoagulants. The researchers suspect anticoagulants were used preferentially in patients considered high-risk for VTE.

Overall, the factors significantly associated with developing VTE were male sex, age over 65, lower leg surgery, combination surgery, history of VTE, family history of cardiovascular disease and a Charlson Comorbidity Index (CCI) >2. The VTE risk in these subgroups was not lowered by thromboprophylaxis, and in fact, the risk was substantially increased in some subgroups receiving thromboprophylaxis.

The researchers also studied risk factors according to whether patients received an anticoagulant agent:

  • Among patients who had no pharmacologic prophylaxis (45.5%), significant risk factors for VTE were male sex (odds of VTE increased by 60%), nonwhite race (odds increased 60%), lower leg surgery (odds tripled), combination surgery (odds doubled), history of VTE (odds increased 7-fold) and CCI >2 (odds increased 80%).
  • Among patients who received an anticoagulant (44.5%), significant risk factors for VTE were male sex (odds increased 80%), lower leg surgery (odds tripled), combination surgery (odds increased 70%) and history of VTE (odds quadrupled).

Orthopedic surgeons can use these data to guide patients through shared decision-making about thromboprophylaxis, the authors say. But they caution that prospective studies are needed to more fully understand who needs prophylaxis and which strategies are most effective.

rates of symptomatic VTE among orthopaedic patients undergoing below-knee surgery, higher than previously reported

of patients diagnosed with VTE died within 90 days

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