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Risk Calculator

The risk calculator is an electronic tool that was developed for orthopaedic surgeons. Surgeons may use this tool to counsel their Medicare-eligible patients (65 years or older) on their individual risk of poor outcomes for total hip and knee replacement surgery.  To use this tool, a surgeon will enter a patient's demographics and comorbidities into to the risk calculator. The tool will calculate a patient's risk of periprosthetic joint infection (PJI) within 2 years and patient mortality within 90 days. 

  • AJRR owns all rights to the risk calculator.
  • The risk calculator was developed by Ortho Apps, a collaborative of Massachusetts General Hospital, Mayo Clinic, University of California, San Francisco, and Exponent, Inc.
  • Ortho Apps used the Medicare 5% sample claims database to calculate PJI within 2 years and mortality within 90 days after primary total hip arthroplasty (THA) and primary total knee arthroplasty (TKA) as a function of demographic and clinical characteristics in 65,499 Medicare patients who underwent primary THAs and 137,546 Medicare patients who underwent primary TKAs between 1998 and 2011.   


AJRR does not recommend patients to use the risk calculator on their own.  This tool was developed for surgeons to provide guidance to patients regarding their prospective total joint replacement surgery.

Instructions on how to use the risk calculator:

  1. Orthopaedics surgeons will need to agree to the Terms and Conditions to access the risk calculator. To agree to the Terms and Conditions, surgeons will click the "Agree" box at the bottom of the page.
  2. Surgeons will enter the patient information by clicking on all appropriate fields of the risk calculator.

    Please note:
    • Height and weight  fields do not need to be entered if obesity is checked in the comorbidity section
    • Definition for the "Buy-In Status" field:
      • "No Buy-In" response means patient does not have Medicaid secondary insurance
      • "State Buy-In" response means patient has Medicaid secondary insurance
  3. Once all appropriate fields have been entered, surgeons will click the "Calculate Risk" box at the bottom of page and the result page will appear. 
  4. At the top of the result page will be a list of the patient's information (i.e., demographics and comorbidities) selected for the patient.
  5. Further instructions to update the patient information are located at the bottom of the results page.