title: System dynamics to model the unintended consequences of denying payment for venous thromboembolism after total knee arthroplasty.
abstract: BACKGROUND
  The Hospital Acquired Condition Strategy (HACS) denies payment for venous thromboembolism (VTE) after total knee arthroplasty (TKA). The intention is to reduce complications and associated costs, while improving the quality of care by mandating VTE prophylaxis. We applied a system dynamics model to estimate the impact of HACS on VTE rates, and potential unintended consequences such as increased rates of bleeding and infection and decreased access for patients who might benefit from TKA.
  
  
  RESULTS
  The system dynamics model uses a series of patient stocks including the number needing TKA, deemed ineligible, receiving TKA, and harmed due to surgical complication. The flow of patients between stocks is determined by a series of causal elements such as rates of exclusion, surgery and complications. The number of patients harmed due to VTE, bleeding or exclusion were modeled by year by comparing patient stocks that results in scenarios with and without HACS. The percentage of TKA patients experiencing VTE decreased approximately 3-fold with HACS. This decrease in VTE was offset by an increased rate of bleeding and infection. Moreover, results from the model suggest HACS could exclude 1.5% or half a million patients who might benefit from knee replacement through 2020.
  
  
  CONCLUSIONS
  System dynamics modeling indicates HACS will have the intended consequence of reducing VTE rates. However, an unintended consequence of the policy might be increased potential harm resulting from over administration of prophylaxis, as well as exclusion of a large population of patients who might benefit from TKA.
authors.affiliation: Research on Research Group, Department of Surgery, Duke University, Durham, North Carolina, United States of America.
authors.forename: Mathias
authors.initials: M
authors.lastname: Worni
authors.forename: Ricardo
authors.initials: R
authors.lastname: Pietrobon
authors.forename: Guilherme Roberto
authors.initials: GR
authors.lastname: Zammar
authors.forename: Jatin
authors.initials: J
authors.lastname: Shah
authors.forename: Bryan
authors.initials: B
authors.lastname: Yoo
authors.forename: Mauro
authors.initials: M
authors.lastname: Maldonato
authors.forename: Steven
authors.initials: S
authors.lastname: Takemoto
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Vail
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000191:economics / Q000331:legislation & jurisprudence*; D035881:Compensation and Redress; D003198:Computer Simulation; D003658:Decision Making, Computer-Assisted; D017048:Health Care Costs; D006291:Health Policy; D006801:Humans; D020370:Osteoarthritis, Knee / Q000601:surgery; D061214:Patient Safety; D011050:Policy Making; D018570:Risk Assessment; D054556:Venous Thromboembolism / Q000191:economics* / Q000209:etiology