Table 2.

Univariable and multivariable analyses of primary outcomes after UKA

Outcome	RA-UKA (n = 1297)	C-UKA (n = 5857)	Unadjusted P	Adjusted aOR	95% CI	Adjusted P
LOS, days (median [IQR])	1 [1–2]	1 [1–2]	–	–	–	–
Prolonged hospitalization (LOS ≥ 2 days), n (%)	412 (30.7)	2,162 (37.2)	< 0.001	0.750	0.647–0.870	< 0.001
Total charges (TOTCHG), USD (median [IQR])	49,368 [36,186–71,616]	47,756 [34,495–70,394]	0.083	–	–	–
High-charge admission (TOTCHG ≥ $72,321), n (%)	323 (24.9)	1,467 (25.0)	0.353	1.007	0.855–1.186	0.993
In-hospital mortality, n (%)	0 (0.0)	1 (0.02)	0.999	–	–	–

LOS and TOTCHG are presented as median (IQR). Prolonged hospitalization was defined as LOS ≥ the 75th percentile (≥ 2 days). High-charge admission was defined as TOTCHG ≥ the 75th percentile (≥ $72,321). Unadjusted P values were calculated using the Wilcoxon rank-sum test for continuous variables and chi-square or Fisher’s exact tests for categorical variables, as appropriate. Adjusted odds ratios (aORs) and 95% confidence intervals (CIs) were estimated using multivariable logistic regression adjusting for age, sex, race, primary payer, admission type, hospital teaching status, comorbidities, and calendar year fixed effects (YEAR 2016–2022). TOTCHG reflects billed hospital charges and does not represent costs or reimbursements. In-hospital mortality was summarized descriptively because of sparse events and the lack of stable adjusted estimation. RA-UKA robotic-assisted unicompartmental knee arthroplasty, C-UKA conventional unicompartmental knee arthroplasty, LOS length of stay, TOTCHG total hospital charges, aOR adjusted odds ratio, CI confidence interval