In-hospital outcomes and hospital charges after robotic-assisted versus conventional total knee arthroplasty: A 2016–2022 Nationwide Inpatient Sample study

BACKGROUND: Robotic-assisted total knee arthroplasty has been adopted to enhance surgical precision, yet contemporary national evidence on clinical and economic outcomes remains limited. OBJECTIVE: To compare in-hospital complications, length of stay, and hospital charges between robotic-assisted and conventional total knee arthroplasty using recent nationwide data. METHODS: We conducted a retrospective cohort study using the Nationwide Inpatient Sample from 2016-2022. Adult elective primary knee arthroplasty admissions were identified; cases with revision procedures or documented coronavirus disease were excluded. Robotic-assisted and conventional procedures were compared after 1:1 propensity score matching on demographics, hospital factors, and comorbidities and year of admission (two cohorts of 173,565 patients each). Outcomes included length of stay, total hospital charges, and major in-hospital complications. Two-sided tests were used with a significance threshold of 0.05. RESULTS: The proportion of robotic-assisted procedures increased from 0.7% in 2016 to 14.9% in 2022. After matching, robotic-assisted surgery was associated with a shorter mean length of stay (1.9 vs 2.7 days; p < 0.001) and lower rates of several complications. When expressed as relative risks (RR) (risk in conventional TKA divided by risk in robotic-assisted TKA), transfusion (RR 3.7), pneumonia (RR 3.0), pulmonary embolism (RR 2.6), prolonged ventilation (RR 2.1), and deep vein thrombosis (RR 1.8) were all higher in the conventional group (all p < 0.01). Acute kidney injury was marginally more frequent with robotic assistance (relative risk 0.9; p = 0.03). Mean hospital charges were higher for robotic-assisted procedures (US$70,758 vs US$62,618; p < 0.001). CONCLUSIONS: In a large, contemporary national cohort, robotic-assisted total knee arthroplasty was associated with fewer in-hospital complications and shorter hospital stays than conventional surgery, while incurring higher hospital charges. These findings support a potential safety advantage for robotic assistance during the index admission and motivate further study of longer-term clinical and economic outcomes. Levels of Evidence: LEVEL III.