Editor’s note: The following content was published in the AAOS Now Special Edition and distributed in June 2020. The content was originally scheduled for the AAOS Now Daily Edition, which publishes each year onsite at the AAOS Annual Meeting but this year’s meeting in March was canceled due to COVID-19. Despite the cancellation, members can access virtual content from the Annual Meeting by visiting the Academy’s Annual Meeting Virtual Experience webpage.

Following Medicare’s removal of total knee arthroplasty (TKA) from the inpatient-only (IPO) list, it has become increasingly important to appropriately select patients who would be viable candidates for same-day discharge (SDD). A new study explored factors associated with SDD among TKA patients; the researchers hope the information will help hospitals, professionals, families, and others plan for TKA. Kevin J. Bozic, MD, MBA, FAAOS, of the Department of Surgery and Perioperative Care at the Dell Medical School in Austin, Texas, presented the study as part of the Annual Meeting Virtual Experience.

Dr. Bozic told AAOS Now that he and his colleagues chose to undertake the study because they were interested in furthering their understanding of “preoperatively available clinical, demographic, and procedural data that can be used to identify TKA patients who are most likely to be discharged on the day of surgery, and those who are at risk for staying in the hospital more than two midnights, which is particularly relevant now that TKA has been removed from the Medicare IPO list.”

The retrospective study included 325 consecutive unilateral primary TKAs performed within a single hospital system. Patients who completed the Perioperative Surgical Home preoperative optimization pathway were included. The study authors employed stepwise logistic regression modeling to determine preoperatively determined factors correlated with SDD and inpatient TKA; the predictive ability of those models was compared to that of the length of stay (LOS) Risk Assessment and Prediction Tool (RAPT) score alone.

Final analysis included 32 SDD patients, 189 next-day discharges, and 104 inpatients. Patients with a lower body mass index (BMI) (odds ratio [OR], 0.92; 95 percent confidence interval [CI], 0.85–1.00; P = 0.04) and those who self-reported fewer allergies (OR, 0.66; 95 percent CI, 0.46–0.95; P = 0.03) were more likely to have SDD. The researchers’ SDD model was superior to the RAPT alone (C-statistics, 0.73 versus 0.52; P < 0.01). Predictors of inpatient discharge were older age (OR, 0.96; P = 0.04), higher BMI (OR, 0.93; P = 0.01), lower RAPT score (OR, 1.2; P = 0.035), and later surgery start time (OR, 0.80; P < 0.01). The inpatient model was also superior to RAPT alone (C-statistic, 0.74 versus 0.62; P < 0.01).

Principal author David Brigati, MD, recommended institutions use the RAPT because it is well-known and easy to use: “The [RAPT] is a short, familiar survey that can serve as a baseline questionnaire for institutions seeking to start predicting [greater than two] midnight LOS after TKA. Institution-specific, data-driven questions can be added to the RAPT to improve its predictive accuracy.”

Dr. Bozic said, “It will be important to validate our results by applying these predictive algorithms to cohorts of TKA patients who receive care in different settings, as we acknowledge that the predictive variables may vary over time and based on practice setting. It is important for each practice and healthcare system to identify and understand the variables that predict LOS in their own practice environment.”

Dr. Bozic’s coauthors of Paper 235, “Enhanced Selection of Candidates for Same-Day and Outpatient Total Knee Arthroplasty,” are Meredith G. Moore, BS; David P. Brigati, MD; Tom J. Crijns, MD; Thomas R. Vetter, MD, MPH; and William R. Schultz, MD.

Kaitlyn D’Onofrio is the associate editor for AAOS Now.