Unicompartmental knee arthroplasty (UKA) volume has increased with advances in implant design, perioperative protocols, and patient selection. This study analyzed national trends of UKA from 2013 to 2018 and the relationship between patient demographics and postoperative outcomes. Data on UKA (CPT 27446) from 2013 to 2018 was collected from the National Surgical Quality Improvement Program (NSQIP). Variables collected included patient demographics, American Society of Anesthesiology classification, functional status, NSQIP morbidity probability, operative time, length of stay, 30-day reoperation, and readmission rates. There was an increase in outpatient UKAs performed (920 in 2013; 11,080 in 2018) (p < 0.0001). Analysis of variance from 2013 to 2018 revealed significant decrease in patient body mass index (BMI) (32.5 in 2013; 31.5 in 2018) (p < 0.01) and NSQIP morbidity probability (0.014 in 2013; 0.011 in 2018) (p < 0.0001). Operative time increased (79.1 minutes in 2013; 84.4 minutes in 2018) (p < 0.01), but length of stay decreased (0.9 days in 2013; 0.5 days in 2018) (p < 0.0001). The number of all-cause and related readmissions decreased significantly (p < 0.045; p < 0.01). Age, male gender, BMI >40 and chronic obstructive pulmonary disease (COPD) were significant predictors for 30-day readmission. BMI >40 was a significant predictor for discharge destination. UKA has seen a rise in incidence from 2013 to 2018 with an increasing number of outpatient UKAs. Operative times and 30-day readmissions have both decreased in this time. BMI > 40 is predictive for discharge destination after UKA, while age, male gender, BMI >40, and COPD are independent risk factors for 30-day readmission.
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