Incidence and Risk Factors Associated with Venous Thromboembolism After Orthopaedic Below-knee Surgery.

INTRODUCTION: Among patients undergoing below-knee orthopaedic surgery, no consensus exists regarding the need for or type of postoperative prophylaxis to prevent venous thromboembolic (VTE) events. The purpose of this study was to assess the incidence and risk factors associated with symptomatic VTE among orthopaedic patients undergoing below-knee surgery who were subject to different types of pharmacologic thromboprophylactic strategies.

METHODS: A total of 20,043 adult patients who underwent surgery for a below-knee orthopaedic condition between August 2005 and August 2015 were identified. Retrospective chart review recorded patient demographics, comorbid data, and anatomic location of any procedures performed. Multivariable logistic regression analysis was used to determine factors associated with postoperative development of symptomatic VTE among patients receiving various thromboprophylactic regimens.

RESULTS: The incidence of symptomatic VTE in patients who underwent below-knee surgery was 2.5% (492/20,043). For patients who did not receive thromboprophylaxis, the incidence was 1.5% (134/9,127 patients). In this group, risk factors for developing VTE were male sex; nonwhite race; surgery performed below the knee but above the ankle; combination procedures of the forefoot/midfoot, hindfoot/ankle, and/or lower leg; history of VTE; and Charlson Comorbidity Index score greater than 2. Among patients who received an antiplatelet agent, the VTE incidence was 1.7% (33/1,992 patients). The incidence of VTE among patients who received an oral or injectable anticoagulant was 3.6% (325/8,924 patients). In this group, risk factors for developing VTE were male sex; surgery performed below the knee but above the ankle; combination procedures of the forefoot/midfoot, hindfoot/ankle, and/or lower leg; and history of VTE.

CONCLUSION: Allowing for different types of thromboprophylactic strategies, the results of this study demonstrate a higher rate of symptomatic thromboembolic disease compared with previously reported <1% VTE incidence rates among orthopaedic patients undergoing below-knee surgery. Certain patients are at higher risk for thromboembolic disease after below-knee orthopaedic surgery. This risk was not found to be lowered by thromboprophylaxis as performed in patients in this database. Future research should be directed at determining what the best thromboprophylactic strategies are for lowering this risk.

LEVEL OF EVIDENCE: Therapeutic study level III.