Review Question - QID 211102

A 64-year-old male retired farmer presents to the orthopaedic surgery clinic with chronic left knee pain. Radiographic imaging demonstrates severe tricompartmental osteoarthritis. The patient has a history of diabetes mellitus, chronic kidney disease, hypertension, hyperlipidemia, and congestive heart failure. He undergoes a left knee replacement without complications. A Foley catheter was placed in the operating room and removed in the post-anesthesia care unit. He receives subcutaneous heparin and has sequential compression devices in place to prevent deep venous thromboses. On post-operative day 1, he develops suprapubic pain and dysuria and is subsequently found to have a urinary tract infection. He is discharged on post-operative day 2 with an appropriate antibiotic regimen. However, he presents to the emergency room on post-operative day 6 with severe left leg pain. Venous dopplers demonstrate an occlusive thrombus in the popliteal vein. He is readmitted for anticoagulation and monitoring. A quality improvement team in the hospital estimates that the probability of getting both a urinary tract infection and a deep venous thrombosis is 0.00008 in patients undergoing routine total knee replacement. Furthermore, they estimate that the probability of getting a urinary tract infection in a similar patient population is 0.04. Assuming that the development of urinary tract infections and deep venous thromboses are independent, what is the risk of developing a deep venous thrombosis following total knee replacement?