The Purpose is to compare the safety and efficacy of the use of aspirin(ASA) with medical compression devices versus aspirin alone for venous thromboprophylaxis following knee and hip arthroplasty.

Venous thromboembolism (VTE), which includes deep vein thrombosis (DVT) and pulmonary embolism (PE), is the most common complication occurring in association with knee and hip arthroplasty procedures due to an activation of the clotting cascade during bone and intramedullary canal preparation.DVT rates ranging from 4% to 15 % and PE rates ranging from 0.83% to 3% have been reported, with fatal PE rates reduced with the use of postoperative anticoagulation. The high risk of thromboembolic disease has led to recommendations that pharmacoprophylaxis be considered routinely. • The combination of short duration outpatient anticoagulation, early mobilization, and mechanical prophylaxis has recently been studied at our institution (Barnes-Jewish Hospital) and has been effective in prophylaxis against VTE. Current American College of Chest Physician (ACCP) guidelines recommend that a longer duration of outpatient anticoagulation following TKA / THA surgery may further reduce the risk of VTE.

Shorter patient hospitalizations and earlier discharge require an outpatient VTE prophylaxis regimen that is simple, effective, easy to monitor, predictable, and has a high patient compliance. Currently, "routine" risk patients receive a combination of ASA 325mg BID (twice daily) for a period of 6 weeks, and portable, mobile pneumatic compression devices (MCDs) for a period of 10 days post- surgery.The study is testing to see whether the use of ASA alone can be equally effective versus the use of ASA with MCDs in "routine" risk patients following total joint arthroplasty.Patients are enrolled fpr 6 months following surgery, and data collection occurs pre-surgery, 14 days after surgery, at the 4-8 wk visit and finally, at 6 months post surgery. We are evaluating the stated outcomes over this 6 month period.

Inclusion Criteria:

• All total knee arthroplasty (TKA), unicompartmental knee arthroplasty (UKA), total hip arthroplasty (THA), and surface replacement arthroplasty (SRA) patients age 18 or older and undergoing an elective primary or revision procedure will be eligible to participate in this study.

Exclusion Criteria:

Patients will be excluded if they are on chronic Coumadin therapy, require prolonged immobilization (i.e. cast/knee immobilizer; inability to be full weight-bearing and out of bed on postoperative day 1), and are scheduled to have multiple surgeries in close proximity to one another. Based on our institution's risk stratification protocol, all patients deemed "high risk" and meeting one of the following criteria will also be excluded as they would receive Coumadin for VTE prophylaxis:

1. Patients will be excluded if they are on chronic Coumadin therapy
2. History of DVT/PE
3. Active Cancer
4. Hypercoaguable States (Protein C, Protein S, Factor V Leiden, etc.)
5. Family history of thrombosis -note: we may remove this criteria after further discussion
6. Patients requiring prolonged immobilization (i.e. cast/knee immobilizer),
7. Patients having multiple surgeries in close proximity to one another.
8. Patients with known allergy or hypersensitivity to Aspirin or Platelet count < 60, 000
9. Patients receiving bilateral joint replacement

Patients who consent to the study and cancel/do not have a surgery scheduled within six months of signing the consent form will not be included. immobilization (i.e. cast/knee immobilizer; inability to be full weight-bearing and out of bed on postoperative day 1), and are scheduled to have multiple surgeries in close proximity to one another. Based on our institution's risk stratification protocol, all patients deemed "high risk" and meeting one of the following criteria will also be excluded as they would receive Coumadin for VTE prophylaxis:

1. Patients will be excluded if they are on chronic Coumadin therapy
2. History of DVT/PE
3. Active Cancer
4. Hypercoaguable States (Protein C, Protein S, Factor V Leiden, etc.)
5. Family history of thrombosis -note: we may remove this criteria after further discussion
6. Patients requiring prolonged immobilization (i.e. cast/knee immobilizer),
7. Patients having multiple surgeries in close proximity to one another.
8. Patients with known allergy or hypersensitivity to Aspirin or Platelet count < 60, 000
9. Patients receiving bilateral joint replacement

Patients who consent to the study and cancel/do not have a surgery scheduled within six months of signing the consent form will not be included. (Note: The surgery does not have to occur within six months of signing the consent form but must be scheduled/re-scheduled within six months of signing the consent form.) If these patients decide to schedule surgery after the six months has passed, they will be re-consented at the time they schedule surgery.

Patients who are not willing to participate will also be excluded from the study.

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