PURPOSE: Venous thromboembolism (VTE) represents a frequent complication of major orthopedic surgery (MOS). Extending post-discharge prophylaxis is recommended but infrequently given. Differences in outcomes based on the form of extended prophylaxis (oral vs. injectible) remain poorly described.
METHODS: We examined differences in clinical and economic outcomes in patients undergoing MOS in a large administrative dataset covering March 2002 to September 2005. We included persons who underwent total hip or knee arthroplasty or hip fracture surgery and who received post-discharge VTE prophylaxis with either injectible agents (dalteparin, enoxaparin, or fondaparinux) or warfarin. Subjects were matched 1:1 based on demographics (gender, age) and clinical characteristics (prior thrombotic event, Charlson comorbidity score). The primary endpoints included rates of VTE and major bleeding during the 30 and 90 day periods following discharge. These were identified by ICD-9 codes. Average total 6-month healthcare costs from the payer perspective served as a secondary endpoint.
RESULTS: The cohort included 12,724 patients (injectible=6,362; oral=6,362). The mean age was 55.6±8.6 years. By day 30, patients treated with warfarin were approximately 30% more likely to experience a VTE than those treated with an injectible anticoagulant (6.3% vs. 4.9%; OR=1.3; 95% CI: 1.1-1.5). This difference in VTE rates persisted to day 90 (VTE with warfarin 7.4% vs. 6.3% with injectibles; OR: 1.2, 95% CI: 1.0-1.4). We observed no differences in bleeding events (<0.4%) based on the type of anticoagulation. Reflecting differences in VTE rates, average adjusted total 6-month costs were significantly higher for the oral cohort ($18,039 vs. $16,429; p<0.0001), although the pharmacy component of costs was nearly $400 higher in the injectible group ($1,614 vs. $1,994).
CONCLUSION: VTE is common following MOS, even in persons receiving extended prophylaxis. Reliance on injectible agents may result in fewer clinical VTEs without increasing the risk for major bleeding. Despite higher pharmacy acquisition costs for injectible anticoagulants, these agents may result in significant per patient savings.
CLINICAL IMPLICATIONS: Clinicians should consider broader use of injectible anticoagulants in persons needing extended VTE prophylaxis following MOS.
DISCLOSURE: Andrew Shorr, No Product/Research Disclosure Information; Grant monies (from industry related sources) GSK; Employee GSK; Consultant fee, speaker bureau, advisory committee, etc. GSK