Study population

Consecutive patients with hemophilia A undergoing simultaneous TKA at a single center (blind the name) between January 2015 and December 2020 were retrospectively reviewed. The study protocol of this research was authorized by the local ethics committee (NO. 2021 − 450) and each patient signed an informed consent form. The inclusion criteria included: (1) patients diagnosed with severe hemophilia A; (2) patients undergoing bilateral simultaneous TKA successfully; (3) patients without active bleeding event before surgery. We excluded subjects with: (1) a history of VTE in the previous 5 years; (2) any previous anticoagulant treatment use for any indication; (3) severe ipsilateral or contralateral hip or ankle hemophilic arthropathy; (4) a history of other major surgeries within 2 years follow-up.

The following information was collected at enrolment: age, sex, body mass index (BMI), history of VTE, infection by human immunodeficiency virus, severity of hemophilia.

Criteria for classification of the severity of hemophilia followed the recommendations of the Scientific Standardization Committee of the International Society on Thrombosis and Haemostasis: severe hemophilia if factor VIII plasma levels < 1% [18].