LAUSR

phasizing that patient-specific indications for filter placement were not fully captured in our recently published data.1 The trauma surgery guidelines2 for inferior vena cava filter (IVCF) placement advocate that IVCFs be considered in highrisk trauma patients without a deep vein thrombosis or pulmonary embolism or in those with a contraindication for chemoprophylaxis, but the guidelines do not equivocally state when an IVCF should be placed. Therefore, it is not feasible to match based on indications for IVCF insertion, as treating physician discretion plays a significant role in determining the absolute contraindication for thromboprophylaxis and ascertaining who is considered high risk. In addition, mortality— our main outcome—is not necessarily affected by indication for IVCF placement; therefore, we chose to match patients based on criteria that do affect short-term and long-term mortality, such as age and injury severity. Matching for Abbreviated Injury Scale (AIS) for specific anatomic regions was not logistically possible, but we thought it prudent to include the data for brain AIS, as mortality is proportional to severity of brain injury in addition to overall injury severity.3,4 While not an indication for IVCF placement per se, brain injury is associated with increased risk of venous thromboembolism and is often a contraindication for prophylactic or therapeutic anticoagulation.5 Extremity AIS was included on the recommendation of a reviewer. As observed in Table 1,1 and noted by Fitzgerald and Mitra, patients in the IVCF group had more extremity injuries, but this is not a definite indication for filter placement. Although it was not explicitly mentioned in the article, we did account for the imbalance in the extremity AIS and brain AIS in the multivariable analysis. We disagree with the hypothesis that IVCFs mitigated fatal pulmonary emboli in patients with more extremity injuries by improving their survival to that of patients with fewer extremity injuries matched by Injury Severity Score. The fatality rate of pulmonary embolism is impossible to measure, so our hope was to match patients based on inherent characteristics that may affect this risk. The mature follow-up data presented, within the limitations mentioned, support the conclusion that IVCFs do not affect the long-term overall survival of trauma patients.