TABLE II.

Univariate and Multivariate Associations Between Baseline Variables and Risk of Revision Total Hip Replacement Among Medicare Beneficiaries Undergoing Primary Total Hip Replacement from July 1995 through June 1996

	Bivariate*		Multivariate†
Variable	Hazard Ratio	95% Confidence Interval	Hazard Ratio	95% Confidence Interval
Sex
Male	1.26	1.18, 1.34	1.23	1.15, 1.31
Female	1.0
Age
65-75 yr	1.49	1.40, 1.60	1.47	1.37, 1.58
>75 yr	1.0
Race
White	0.90	0.79, 1.03
Nonwhite	1.0
Medicaid eligibility
Yes	0.92	0.80, 1.06
No	1.0
Comorbidity (Charlson score)
>1	1.02	0.93, 1.12
0–1	1.0
Hospital volume‡
1–25	1.14	1.07, 1.23
26–50	1.01	0.94, 1.10
>50	1.0
Surgeon volume‡
1–5	1.24	1.15, 1.34	1.21	1.12, 1.32
6–12	1.09	1.02, 1.18	1.08	1.00, 1.17
>12	1.0		1.0	–

^*Hazard ratios obtained from bivariate Cox proportional hazards models. †Hazard ratios obtained from multivariate Cox proportional hazards model. N = 49,136 for the multivariate model.

^‡Listed volumes indicate only Medicare patients who had total hip replacement.