Risk Factors for Increased Hospital Cost for Primary Total Knee Arthroplasty.

INTRODUCTION: Patients who have more complex medical comorbidities increase the cost of primary total knee arthroplasty (TKA). The goal of this study was to evaluate and quantify the impact of medical comorbidities on the cost of primary TKA.

METHODS: Hospital billing data for 3,077 primary total knee arthroplasty patients (Current Procedural Terminology (CPT) code 27447) from January 2017 to March 2020 at a high-volume academic medical center were retrospectively reviewed. Cost data included expenses associated with the index procedure: anesthesia, operating room costs, the orthopaedic surgeon, the recovery room, hospital room and board, physical therapy, and medical supplies. Patient demographics, comorbidities, and admission data were collected. Univariate and multivariate gamma regression analyses were performed to identify associations with increased cost during primary TKA admissions.

RESULTS: The median cost of TKA was $32,129. The highest proportion of cost was attributed to medical supplies, which accounted for $14,966 (46%), followed by room and board at $4,976 (15%) and the operating room at $4,267 ($13%). Body mass index (BMI) ≥ 35, American Society of Anesthesiologists (ASA) score of 3 to 4, diabetes, congestive heart failure (CHF), and mild liver disease were found to be independent risk factors for increased cost. Total cost increased with increasing Charlson Comorbidity Index (CCI) scores, with a median total cost of $31,545 for CCI scores of 0 to 5 and a median total cost of $35,099 for CCI scores of 5 or more.

CONCLUSION: Body mass index ≥ 35, ASA 3 to 4, diabetes, CHF, and mild liver disease were independent risk factors for increased cost during the index hospitalization for a primary TKA. The cost of primary TKA increased as CCI increased.