Surgery is a risk factor for VTE. As with any surgical procedure, the blood clotting system can be activated as a result of the surgical intervention, and certain surgeries, such as orthopaedic surgery, activate the coagulation system. Coupled with reduced blood flow or ‘stasis’ as a result of being immobile, surgery fulfils the triad of categories that increase the risk of thrombosis.

The risk of thrombosis can be increased even in the absence of other risk factors, depending on the type of surgery. A risk assessment will be carried out in hospital in order to establish the level of risk and to determine if measures should be taken to reduce the likelihood of a VTE. For some operations, the increased risk of VTE is still present even after hospital discharge. For example, as many as six in ten patients may suffer a DVT after hip fracture surgery in the absence of preventative treatment (known as prophylaxis) [5].