Hospital and Patient Factors Associated With Length of Hospitalization in Patients Who Have Osteoarthritis Undergoing Primary Total Knee Arthroplasty: An Analysis of National Data.

Background: By 2040, an estimated 3.5 million primary total knee arthroplasties (TKAs) are expected to be performed annually in the United States. Osteoarthritis (OA) is the most common indication for primary TKA. We examined the association of hospital, regional, and patient-level factors with extended lengths of hospital stay (eLOS).

Methods: We studied patients who have OA who underwent primary TKA from 2016 to 2019 using a national inpatient database. We used the International Classification of Diseases codes to identify diagnoses and procedures. There were 2,592,469 patients who had OA who underwent primary TKA from 2016 to 2019. We used univariate and multivariable-adjusted logistic regression analyses to assess whether patient, payer, hospital, and geographic factors were associated with an eLOS. Predictive probabilities from multivariable analyses were used to estimate the area under the curve.

Results: Patient race and ethnicity, Medicaid or Medicare payer status, income, age/sex, and nearly all regional and hospital characteristics were independently associated with eLOS (>3 days; receiver-operating characteristic C-statistic = 0.74). Sensitivity analyses that used the most recent years of data from 2020 to 2021 (COVID-19 pandemic years) or adjusted for individual organ system complications reproduced the main results without much attenuation.

Conclusions: Age, sex, race, ethnicity, hospital location and teaching status, elective procedure designation, perioperative complications, and insurance payer status significantly influenced the LOS for primary TKA hospitalizations in the United States. Recognized disparities were linked to longer hospital stays after primary TKA in patients who had OA. Implementing policies and interventions that target these factors could help shorten hospital stays for high-risk patients after primary TKA.