Is Routine Use of VTED Chemical Prophylaxis Ever Warranted in Foot and Ankle Surgery? Results of a Cost-Effectiveness Analysis

Abstract

INTRODUCTION AND OBJECTIVES: The purpose of this study was to determine whether some foot/ankle surgeries would benefit from routine use of low molecular weight heparin (LMWH) as postoperative DVT prophylaxis. METHODS: We conducted a formal cost-effectiveness analysis using a decision analytic tree to represent the risk of complications under a scenario of no prophylaxis and a scenario of routine LMWH prophylaxis for 4 weeks. The two scenarios were compared for five procedures: 1) Achilles tendon repair (ATR), 2) total ankle replacement (TAR), 3) hallux valgus surgery (HVS), 4) hindfoot arthrodesis (HA), and 5) ankle fracture surgery (AFS). Outcomes assessed included short and long-term costs, quality-adjusted life-years (QALYs), and incremental cost per QALY gained. Costs were evaluated from the health care system perspective and expressed in US dollars at a 2015 price base. In the short-term, routine prophylaxis was always associated with greater costs compared to no prophylaxis. RESULTS: For ATR, TAR, HA and AFS prophylaxis was associated with slightly better health outcomes; however, the gain in QALYs was minimal compared to the cost of prophylaxis (ICER was well above $50,000/QALY threshold). For HVS, prophylaxis was associated with both worse health outcomes and greater costs. In the long-term, routine prophylaxis was always associated with worse health outcomes. CONCLUSIONS: We conclude that the decision to use LMWH prophylaxis should not be based solely on the type of foot/ankle surgery planned. Patient factors also need to be carefully weighed.

Introduction

• Venous thromboembolism disease (VTED) is a well-known complication of surgery and includes the occurrence of deep vein thrombosis (DVT) and pulmonary embolism (PE). There is considerable interest among foot and ankle surgeons for further guidance regarding the appropriateness of pharmacologic DVT prophylaxis after foot and ankle surgery.[1]
• The Clinical Consensus Statement committee for DVT prophylaxis has identified the following three general areas of VTED risk for patients undergoing foot/ankle surgery:[2]

1)personal factors (e.g., age, obesity, etc.)

2) procedure-specific risks (e.g., procedure type [Achilles repair], general anesthesia, etc.) and

3) unique conditions surrounding surgery(e.g., immobilization, nonweight bearing bed rest, etc.).

• There is now growing concern within the medical community over asymptomatic, symptomatic and distal DVTs which can result in post-thrombotic syndrome (PTS), recurrent DVT, proximal progression, and other negative health effects. Low molecular weight heparin (LMWH) is a commonly prescribed prophylactic anticoagulant following orthopedic surgery, often taken for a minimum of 2-4 weeks, to prevent DVT and its potential complications. When LMWH is given for the duration of lower limb immobilization, it has been shown to decrease the risk of VTED with a low side effect profile in postoperative patients and those with lower limb jniuries[3]

Objectives

• This study aims to evaluate the cost effectiveness of using prophylactic therapy with LMWH to prevent VTED during the postoperative period during five commonly encountered clinical scenarios: 1) Achilles tendon repair, 2) total ankle replacement (TAR) surgery, 3) hallux valgus surgery, and 4) midfoot/rearfoot arthrodesis, and 5) ankle fracture surgery
• The purpose is to assess whether there are certain types of surgeries or postoperative conditions, that would warrant routine prophylaxis with LMWH regardless of patient factors.

Methods

We analyzed the health effects and costs associated with our two competing treatment strategies, administering prophylactic low molecular weight heparin (enoxaparin) and no prophylactic treatment. Health effects, both in natural unit of outcome (eg, number of deaths) and QALYs (Quality Adjusted Life Years), and the costs associated with these strategies were calculated using a decision analytic tree for each of the five surgical scenarios (Achilles tendon repair, total ankle replacement, hallux valgus surgery, rearfoot arthrodesis, and primary ankle fracture repair). The rates and probability of each health effect were retrieved from the available literature. Associated costs were also derived from available literature, drug manuals, and the Centers for Medicare and Medicaid.

Configuration of the Tree 

• Using TreeAge Pro Healthcare 2014 a decision tree was created for each of the five surgical scenarios and all possible outcomes.
• Each endpoint in the decision tree has associated costs.

Costs associated with each health effect may include diagnostic costs and treatment costs (eg, outpatient and inpatient costs, pharmacological treatment, and disease management).

Results

• In the short-term, routine prophylaxis was always associated with greater costs compared to no prophylaxis. For ATR, TAR, HA and AFS prophylaxis was associated with slightly better health outcomes; however, the gain in QALYs was minimal compared to the cost of prophylaxis (ICER well above $50k threshold). For HVS, prophylaxis was associated with both worse health outcomes and greater costs.
• In the long-term, routine prophylaxis was always associated with worse health outcomes. For ATR and TAR, prophylaxis resulted in slightly lower costs (about $200 less per patient over lifetime). Prophylaxis was associated with greater long-term costs for HVS, HA and AFS.

Discussion/Conclusion

Although the use of chemical prophylaxis has shown to decrease risk of VTED, the associated short term and long term costs and overall effectiveness do not warrant routine prophylaxis.

The decision to use LMWH prophylaxis should not be based solely on the type of foot/ankle surgery planned. Patient risk factors also need to be carefully weighed prior to prophylaxis.