The effect of severity of illness on total joint arthroplasty costs across New York state hospitals: an analysis of 172,738 cases.

We explored the average cost of 94,197 total knee and 78,541 total hip arthroplasties (TKA and THA) using the New York State Hospital Inpatient Cost Transparency database to evaluate the effect of beneficiary health status on hospital reported cost for the two operations. Using the 3M APR-DRG severity of illness index as a measure of patient's health status, we found a significant increase in cost for both TKA and THA for patients with higher severity of illness index. This study confirms the greater cost and variability of TKA and THA for patients with increased severity of illness and illustrates the inherent unpredictability in cost forecasting and budgeting for these same patients.