Deep Vein Thrombosis
Joint replacement surgery, especially in the lower extremities, is becoming more common. Orthopaedic surgeons performed about 520,000 hip replacements and about 581,000 knee replacements in 2006 (Source: National Center for Health Statistics; Centers for Disease Control and Prevention; 2006 National Hospital Discharge Survey.) The vast majority of these surgeries are very successful, and patients go on to live fuller, more active lives without pain.
But no operation is without risks. One of the major risks facing patients who undergo surgery in the lower extremities is a complication called deep vein thrombosis, a form of venous thromboembolic disease.
Cause
Deep vein thrombosis (DVT) refers to the formation of a thrombus (blood clot) within a deep vein, commonly in the thigh or calf.
Contributing Factors
Deep vein thrombosis is the formation of a thrombus (blood clot) within a deep vein, commonly in the thigh or calf.
Although venous thromboembolic disease can develop after any major surgery, people who have surgery on the lower extremities are especially vulnerable.
Three factors contribute to formation of clots in veins:
1. Stasis, or stagnant blood flow through veins
This increases the contact time between blood and vein wall irregularities. It also prevents naturally occurring anticoagulants from mixing in the blood. Prolonged bed rest or immobility promotes stasis.
2. Coagulation
Coagulation is encouraged by the presence of tissue debris, collagen or fats in the veins. Orthopaedic surgery often releases these materials into the blood system. During hip replacement surgery, reaming and preparing the bone to receive the prosthesis can also release chemical substances (antigens) that stimulate clot formation into the blood stream.
3. Damage to the vein walls
This can occur during surgery as the physician retracts soft tissues as part of the procedure. This can also break intercellular bridges and release substances that promote blood clotting.
Other factors that may contribute to the formation of thrombi in the veins include:
Age
Previous history of DVT or PE
Metastatic malignancy
Vein disease (such as varicose veins)
Smoking
Estrogen usage or current pregnancy
Obesity
Genetic factors
