Matthew L. Magruder

Introduction: Total knee arthroplasty (TKA) is among the most common and cost-effective orthopaedic procedures in the United States. Policy changes, including removal from Medicare's inpatient-only (IPO) list, and advances in surgical and perioperative care have accelerated its shift to outpatient and same-day settings. The aim of this study was to model national TKA volume trends and forecast growth through 2040. Methods: We conducted a retrospective analysis using data from the National Inpatient Sample and Nationwide Ambulatory Surgery Sample from 2016 to 2022. Procedures were stratified by setting: inpatient with overnight stay, inpatient same-day discharge, and outpatient in ambulatory surgical centers (ASCs). Survey-weighted regression models were used to evaluate trends, and future volumes were projected using negative binomial and autoregressive integrated moving average modeling. Regional cost trends and payer composition were also analyzed. Results: Between 2016 and 2022, inpatient TKA volumes with length of stay ≥1 day declined by 85.0%, while same-day discharge volumes decreased by 46.7%. Outpatient TKA performed in ASCs rose from 104,971 cases in 2018 to 539,175 in 2022, representing a 413.6% increase after Medicare's removal of TKA from the IPO list. Forecasting models project that by 2040, annual ASC TKA volumes will exceed 2.1 million cases, while inpatient volumes will continue to decline substantially. Regionally, the South is expected to lead in ASC volume, reaching 881,000 cases annually by 2040. In 2022, ASC charges were highest in the West ($74,123) and lowest in the Midwest ($50,200). Medicare's share of ASC TKA cases increased from 42.5% in 2016 to 59.2% in 2022, reflecting a payer shift toward outpatient care. Conclusion: TKA has undergone a dramatic shift toward outpatient delivery, with ASC procedures poised to dominate the national landscape by 2040. These findings highlight the need for policy and infrastructure planning to support the continued growth of outpatient arthroplasty.

Background: Robotic-assisted (RA) and computer-navigated (CN) total hip arthroplasty (THA) are increasingly performed, but prior studies comparing the two techniques and their outcomes were limited. This study aimed to compare clinical outcomes and costs of receiving THA using RA and CN technology. Methods: We conducted a retrospective cohort study using a nationwide administrative database from January 1, 2010, to October 31, 2022. The study included patients undergoing THA either via RA (n = 4,473) or CN (n = 4,473) technology. Subjects were matched for age and pertinent comorbidities. Clinical outcomes evaluated included emergency department visits and readmissions within 90 days of surgery, lengths of stay, and implant-related complications within 90 days and 2 years of surgery. Costs were analyzed on the day of surgery and within a 90-day global period. Statistical analysis was performed using multivariate logistic regression analysis with a P < 0.01 considered statistically significant. Results: There were no significant differences between the RA and CN cohort in ED visits or readmission within 90 days of surgery or in lengths of stay. Similarly, no differences were found in any of the implant-related complications at 90 days or 2 years following surgery. Same-day mean reimbursement for RA-THA was higher than for CN-THA ($4,472.23 vs. $3,890.61; P < 0.01). 90-day reimbursement did not differ significantly. Conclusion: We demonstrated that readmission, ED visits, lengths of stay, and short-term implant-related outcomes did not differ between RA and CN-THA cohorts. Further studies are needed to explore the long-term benefits and cost implications of RA-THA.

➢ Orthopaedic surgeon pay structures are diverse, but most commonly are productivity-based. ➢ Physician ownership of ambulatory surgery centers is a growing phenomenon and may have effects on clinical decision-making. ➢ Hospital systems are paid by multiple mechanisms, including case-based reimbursement (based on Diagnosis-Related Groups). Incentives are substantially different between the types of payers (Medicare and Medicaid compared with private insurance). ➢ Payer revenues stem from risk-adjusted premiums and investments in income-generating assets; a growing focus on cost-effective care and outcome-focused data by payers has led to changes in pay structures.

Antoinette R. Portnoy, BS, Shirley Chen, BS, MS, Ameer Tabbaa, MD, Matthew L. Magruder, MD, Kevin Kang, MD, Afshin E. Razi, MD. Hip Pelvis 2024;36:204-10. https://doi.org/10.5371/hp.2024.36.3.204