LMWH vs Aspirin for VTE Prophylaxis in Orthopaedic Oncology

Overview

Aspirin and low molecular weight heparin (LMWH) are both commonly employed pharmacologic methods of venous thromboembolism (VTE) prophylaxis after orthopaedic surgery. Data comparing these two methods of VTE prophylaxis in patients undergoing pelvic/lower extremity orthopaedic surgery for malignancy are lacking, however, as compared to the data and guidelines present for VTE chemoprophylaxis after joint arthroplasty and hip fracture surgery. In this clinical trial, our specific aim is to compare the post operative incidence of VTE between patients receiving aspirin and LMWH after pelvic/lower extremity orthopaedic oncology procedures.

Lower extremity orthopaedic surgery and malignancy are both known major risk factors for venous thromboembolism (VTE). Guidelines from high quality data exist with regards to VTE prophylaxis in patients undergoing orthopaedic surgery, particularly joint arthroplasty. Far fewer data are available regarding the efficacy of various methods of pharmacologic VTE prophylaxis in patients undergoing surgery for primary or metastatic musculoskeletal malignancies as malignancy itself is known to confer a hypercoagulable state. The existing data, including published data from our institution, are almost exclusively from retrospective studies. Given the limited external validity of existing guidelines and limitations inherent in applying data from retrospective studies, a randomized, prospective study comparing two of the most common methods of pharmacologic VTE prophylaxis would help to guide clinical care of this patient population. In addition, large dead spaces susceptible to hematoma formation are often created from tumor resections in orthopaedic oncology. Our retrospective data suggest that hematoma formation may be an independent predictor of infection. An important risk of chemical VTE prophylaxis is an increased incidence of bleeding into these dead spaces, leading to hematomas. This illustrates the complexity of selecting a method of VTE prophylaxis in patients at both high risk of VTE and hematoma formation and the need for high quality data to guide clinical decision-making in this patient population. The specific aim of this study is to compare the post operative incidence of symptomatic deep vein thrombosis (DVT) and pulmonary embolus (PE) between patients who receive low molecular weight heparin (LMWH) versus aspirin for prophylaxis after having undergone pelvic or lower extremity orthopaedic oncology surgery (primary bone sarcomas, soft tissue sarcomas, and metastatic osseous disease). Our secondary aim is to compare the incidence of hematoma formation and wound complications between these methods of pharmacologic prophylaxis in the aforementioned patient population. Our hypothesis is that there is no significant difference in the incidence rate of symptomatic DVT/PE in patients administered LMWH versus aspirin for prophylaxis; however there may exist a difference in the rate of wound complications between these prophylaxis methods.