(From the ACCP guidelines)

Deep venous thrombosis (DVT) is a blood clot in the deep veins of the leg or thigh and occasionally the arm. A pulmonary embolus (PE) is a blood clot that breaks off and goes to the lungs. The latest guidelines from the American College of Chest Physicians (ACCP) recommend medical and mechanical prevention for high-risk orthopedic surgery patients. Total knee replacement (TKR), total hip replacement (THR), and hip fracture surgery (HFS) have the highest incidence of blood clots. The short and long-term risks include lung clot, death, long-term swelling of the legs or arms, heart strain, and recurrent blood clots. Thus, prevention is critical in at-risk patients. Although specific recommendations vary by the type of surgery, injectable heparin medicines or oral Coumadin (warfarin) are effective alone or with compression hose and devices. Goals of treatment are to prevent blood clots and complications of blood clots.

Risk Assessment

Patients going to surgery, particularly lower extremity reconstruction, are at the highest risk for blood clots. The risk may be increased in patients with acquired or familial disorders associated with thrombosis. General risk factors include advanced age, trauma, immobilization, prior blood clots, and varicose veins. Secondary or acquired risk factors include smoking, pregnancy/post partum, malignancy, use of hormonal therapy or contraception in women, prior central vein catheterization, myeloproliferative (blood problems), and inflammatory bowel disease. Other factors, including genetics, can also increase the risk of blood clots. Usually these risk factors are additive, with increasing numbers of concurrent risk factors leading to a heightened risk of blood clots. If you have a family history of clotting or any other risk factors noted, please let us know.

Treatment Options

Injectables: heparin products (LMWH) that are currently available in the United States include dalteparin (Fragmin) and enoxaparin (Lovenox).  Another injectable anticoagulant is fondaparinux (Arixtra). One advantage is that these do not generally require monitoring of coagulation time (lab tests).  A disadvantage is that they are more expensive. The risk of treatment is mainly bleeding complications.

Coumadin: Advantages of Coumadin include that it is inexpensive and it can be given orally. Disadvantages include the need for continuous laboratory monitoring of prothrombin time (often 2 – 3 times a week) with dose adjustments, and drug and food interactions.


The ACCP guidelines regarding the sole use of aspirin in blood clot prevention in joint replacement patients do not recommend that aspirin be used alone as the means of prevention. For hip fracture surgery patients, aspirin is not recommended because it is less effective than other options.

Mechanical Prevention

Mechanical prevention consists of graduated compression stockings (SCDs) and TED hose. The main advantage of these methods is that they do not have clinically significant side effects, such as bleeding. Mechanical methods are effective, but less so than pharmacologic prophylaxis, and thus are recommended by the ACCP only for patients at high risk of bleeding with Coumadin or injectable medications or as a combination therapy. We use the above mechanical devices during surgical procedures and continue them postoperatively until the patient is able to walk.

Specific Surgeries

Knee Surgery

The guidelines suggest Coumadin as an option for knee replacement patients, but they also note that Coumadin may not be as effective as some of the injectable products. Bleeding risk may be lower, however. In contrast to knee replacement, knee arthroscopy does not require routine protection other than early mobilization. The ACCP does recommend the use of prevention for patients who have preexisting blood clots risk and are going to have knee scopes.

Total Hip Replacement

About half of all hip replacement patients who do not receive treatment will develop asymptomatic blood clots, and up to 5% will develop symptomatic blood clots. Mortality from PE occurs in about 1 in 500 hip replacement patients. The ACCP guidelines recommend injectable medicines or Coumadin.

Total Knee Replacement

Without treatment, at least half of knee replacement patients will experience blood clots, up to 10% will develop symptomatic lung clots, and up to 2% will die from lung clots. The ACCP guidelines recommend injectable medicine or Coumadin, with TED hose and SCDs as a possible alternative treatment.

Hip Fracture Surgery

Among orthopedic surgery patients, those undergoing hip fracture surgery (HFS) have the greatest risk of death from lung clots, up to 7.5%. In the absence of prophylaxis, half of HFS patients develop blood clots. The ACCP guidelines recommend prevention with injectable medicines or Coumadin.

Other Surgery

The ACCP guidelines were specific to some of the highest risk surgery. However, patients with a family history of blood clots or multiple risk factors should consider prevention.

Timing and Duration of Treatment

In a review of available evidence on the timing of treatment after major orthopedic surgery, administration at 6 hours following surgery is effective and does not increase bleeding risk. The optimal duration of treatment is unclear. According to the ACCP, it should be continued at least 10 days following surgery for knee or hip replacement, or hip fracture surgery. The guidelines also support extended treatment (28 – 35 days) for patients undergoing hip replacement or fracture surgery. Options recommended for extended treatment are injectable medicines or Coumadin.

Final Thoughts

Routine prevention is the standard of care for patients undergoing knee/hip replacement or hip fracture surgery since they are at particularly high risk for blood clots. The ACCP guidelines provide evidence-based recommendations for preventing blood clots in orthopedic surgery patients, primarily through injectable medicine or Coumadin, alone or with mechanical prophylaxis. Given appropriately, prevention is effective in reducing overall mortality and fatal lung clots in patients undergoing major orthopedic surgery.

Bryan Bomberg