Table 2.

Incidence risk ratios for UKA:TKA by primary variable of interest

Variable of interest	IRR	95% CI	p-Value
Race/ethnicity
Black	0.64	0.58–0.71	< 0.001
Hispanic	0.93	0.84–1.01	0.10
Asian or Pacific Islander	0.97	0.82–1.15	0.72
Native American	0.94	0.68–1.28	0.68
Other	0.99	0.85–1.14	0.84
Socioeconomic status
Income Q1	0.85	0.79–0.90	< 0.001
Income Q2	0.87	0.82–0.93	< 0.001
Income Q3	0.95	0.90–1.01	0.10
Payer status
Medicare	0.83	0.79–0.88	< 0.001
Medicaid	0.93	0.84–1.03	0.15
Self-pay	0.93	0.70–1.25	0.65
No charge	1.30	0.54–3.11	0.55
Other	1.07	0.96–1.18	0.20

Reference groups were white (race/ethnicity), income Q4 (socioeconomic status), and private insurance (payer status). CI, confidence interval; IRR, incidence rate ratio