title: Factors Affecting Readmission Cost After Primary Total Knee Arthroplasty in Michigan.
abstract: The increasing readmission risk of primary total knee arthroplasty (TKA) represents a significant economic burden and public health challenge. Many have investigated the predictors of readmissions after TKA while little work has studied the associated readmission costs. This article investigated the factors affecting readmission cost after primary TKA at the time of initial discharges using clinical and resource-use information and compared the factors between 2 payer groups (Medicare-or-Medicaid and non-Medicare-nor-Medicaid groups).
  
  
  
  We used data from the Michigan State Inpatient Database of the Healthcare Cost and Utilization Project, Agency for Healthcare Research and Quality. We identified readmissions after primary TKA in 2012 using International Classification of Diseases, Ninth Revision, code 81.54. Total readmission cost was modeled using multivariate regression to identify predictors.
  
  
  
  Of 1358 readmissions after primary TKA, 949 were in the Medicare-or-Medicaid group, and 409 were in the non-Medicare-nor-Medicaid group. The overall mean and median total readmission costs were $9335 (standard deviation $10,528) and $6810, respectively. Significant predictors of total readmission cost for the Medicare-or-Medicaid group included length of stay (P < .001), discharge disposition (P < .001), number of chronic conditions (P = .001), and total cost of initial admission (P < .001). Only total cost of initial admission was significant in predicting total readmission cost for the non-Medicare-nor-Medicaid group (P < .001).
  
  
  
  Total cost of initial admission was a significant predictor of total readmission cost in both Medicare-or-Medicaid and non-Medicare-nor-Medicaid groups, independent of length of stay and number of chronic conditions.
authors.affiliation: Department of Industrial and Operations Engineering, University of Michigan, Ann Arbor, Michigan.
authors.forename: Moses Y H
authors.initials: MYH
authors.lastname: Chan
authors.affiliation: Department of Industrial and Operations Engineering, University of Michigan, Ann Arbor, Michigan.
authors.forename: Shair A
authors.initials: SA
authors.lastname: Malik
authors.affiliation: Department of Orthopaedic Surgery, University of Michigan Health System, Ann Arbor, Michigan.
authors.forename: Brian R
authors.initials: BR
authors.lastname: Hallstrom
authors.affiliation: Department of Industrial and Operations Engineering, University of Michigan, Ann Arbor, Michigan; Department of Orthopaedic Surgery, University of Michigan Health System, Ann Arbor, Michigan; Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Hughes
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000191:economics*; D002648:Child; D005260:Female; D006801:Humans; D007902:Length of Stay / Q000191:economics; D008297:Male; D008484:Medicaid; D006278:Medicare; D008824:Michigan; D008875:Middle Aged; D010359:Patient Readmission / Q000191:economics*; D014481:United States; D055815:Young Adult
keywords: Medicaid; Medicare; knee; readmission cost; total knee arthroplasty