Presentation Abstract

Session: P111-P205-Adult Reconstruction Knee Posters
Date/Time: Tuesday, Mar 11, 2014, 8:00 AM - 3:00 PM
Presentation Number: P204
Posterboard Number: P204
Title: Impact of Statins on Postoperative Venous Thromboembolic Events Following Total Knee and Hip Replacements
Classification: +Other (Knee)
Keywords: Total Knee Arthroplasty Complications; Total Hip Arthroplasty; Thromboembolic
Author(s): Katharine T. Criner, MD, New York, New York
Arianna Trionfo, MD, Philadelphia, Pennsylvania
Abstract: INTRODUCTION: Statins not only have lipid lowering effects, but pleiotropic anti-inflammatory effects that may account for their ability to decrease the development of thrombotic complications such as venous thromboembolism (VTE). Statins have been reported to decrease the incidence of VTE in healthy, non-surgical patients. However, no data exists that evaluates the effect of statins on VTE in orthopaedic surgical patients. VTE following orthopedic procedures, especially joint replacement, is a unique clinical scenario compared to other medical conditions associated with VTE. Increased systemic inflammatory mediators, endothelial injury and decreased mobility are unique to post-operative lower limb joint replacement and markedly increase VTE development and refractoriness to conventional VTE prophylactic therapy. The purpose of this study was to examine whether statins, in addition to conventional VTE chemoprophylactic interventions, have a protective effect against venous thromboembolic events in the post-operative period of elective total knee and total hip replacement patients.
METHODS: The current procedural terminology (CPT) codes for total knee and total hip replacements at our institution over a seven-year period (January 2, 2005 - May 31, 2012) were queried for a total of 2,009 patients. From this population, 546 patients were randomly selected for the study. Inclusion criteria were patients that had total knee or hip replacements. All patients received the standard chemoprophylactic therapy for VTE in the post-operative period based on American Academy of Orthopaedic Surgeons guidelines. Exclusion criteria included if the procedure was a revision arthroplasty or performed for a diagnosis of fracture. Patients were also excluded if they had a history of coagulopathy disease or hormone replacement therapy. Subjects were divided into groups based on if they were on a statin peri-operatively. The non-statin group was the control group. The statin group was defined as patients that took the medication chronically before their arthroplasty procedure for hypercholesterolemia and the statin was continued at the same dosage during the post-operative period. After exclusion criteria, the remaining study population for statistical analysis was 417 subjects. The statin (N=196) and non-statin groups (N=221) were comparable in regards to VTE risk factors (age, BMI, current smokers, diabetes mellitus, malignancy, past history of VTE). The mean age of subjects was 65.5 years old. A total of 61% of patients were obese with a mean BMI of 33 kg/m2. The statin cohort utilized a variety of different statin agents and doses. The primary outcome was symptomatic VTE (pulmonary embolus and/or deep vein thrombosis); which was determined based on venous duplex and CT angiogram of the thorax studies. Statistical analysis was performed using t-tests and Chi-squared analysis. P-value < 0.05 was considered statistically significant.
RESULTS: All subjects had a minimum of 11 months follow-up (range, 11 months - 8 years). In the total patient population studied, symptomatic VTE occurred in 47/417 patients with an incidence of 11.3% at a mean post-operative day of 26.7 days. The statin group had a significantly lower amount of VTE events [15/196, 7.7% ] compared to the control group [32/221, 14.5%]; p-value < 0.027. The relative risk of VTE with use of statin was reduced by 48%; p-value < 0.041. The number needed to treat (NNT) was 14:1; i.e., 14 joint replacement patients treated with statins to avoid one VTE event.
CONCLUSIONS: Statins in addition to conventional VTE prophylactic therapy significantly reduced the events of VTE in post-operative elective total knee and hip replacements.

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