Patient Health International – health information for patients and carers

Causes

Venous thromboembolism (VTE) is a disease that includes deep vein thrombosis (DVT) and pulmonary embolism (PE).

Venous thromboebolism (VTE), deep vain thrombosis (DVT) and/or pulmonary embolism (PE)

Decreased blood flow in the veins, injury to the veins, and an increased clotting ability of the blood can all cause an unwanted blood clot to form in the deep veins of the leg (a DVT). PE is a life-threatening complication of DVT that may occur as a result of the clot breaking away, travelling through the bloodstream and lodging within the blood vessels that supply blood to the lungs.

Conditions that cause poor blood circulation or thickening of the blood contribute to the development of VTE or place people at an increased risk.

The formation of a blood clot within a vein

Figure 1: The formation of a blood clot within a vein

Orthopaedic surgery

Orthopaedics is a medical speciality that looks at how your bones, muscles and joints work together. Surgery aims to repair or replace joints, such as the knee or hip, that have cartilage damage or that are injured.
VTE is a serious complication of orthopaedic surgery that can occur after the operation.
The surgery can cause injury to the blood vessels as well as changes to the flow and composition of the blood.
Most patients requiring orthopaedic surgery are of an older age, and because they are less mobile after the operation, this further increases the risk of VTE.
Blood has an increased ability to clot for some time following orthopaedic surgery.

Known risk factors for VTE place patients who are undergoing orthopaedic surgery at an even greater risk. They include:

History of VTE
High blood pressure (hypertension)
Overweight and obesity*
Age: VTE is more common in people over the age of 40 years.
Varicose veins
Inherited disorders that are associated with thrombosis (e.g. thrombophilia
Diabetes
Oestrogen treatment (including hormone replacement therapy and oestrogen-containing oral contraceptives)
Pregnancy
Smoking

*the World Health Organisation defines overweight as a Body Mass Index (BMI) of at least 25 and obesity as a BMI of at least 30.