Table 3.

Estimated hazard ratios for revision over 3 years after primary THA in a population-based study of 39,125 operations

Ordinal number group Operation	No. of operations	No. of revisions	Unadjusted HR (95% CI)	Age- and sex-adjusted HR (95% CI)
Minimum of stem and cup order numbers
1–15	5,967	228	1.3 (1.1–1.6)	1.3 (1.1–1.5)
16–30	3,980	123	1.1 (0.9–1.3)	1.1 (0.9–1.3)
31–50	4,185	135	1.1 (0.9–1.3)	1.1 (0.9–1.3)
51–100	6,820	220	1.1 (1.0–1.3)	1.1 (1.0–1.3)
101–	18,173	527	1.0	1.0
Maximum of stem and cup order numbers
1–15	2,428	89	1.2 (1.0–1.5)	1.2 (1.0–1.5)
16–30	1,868	59	1.1 (0.8–1.4)	1.0 (0.8–1.4)
31–50	2,264	86	1.3 (1.0–1.6)	1.2 (1.0–1.5)
51–100	4,226	153	1.2 (1.0–1.4)	1.2 (1.0–1.4)
101–	28,339	846	1.0	1.0
Stem and cup order number separately in the same model
Stem
1–15	3,653	141	1.3 (1.1–1.5)	1.1 (0.9–1.4)
16–30	2,536	76	1.0 (0.8–1.3)	0.9 (0.7–1.2)
31–50	2,740	93	1.1 (0.9–1.4)	1.0 (0.8–1.3)
51–100	4,707	162	1.1 (1.0–1.3)	1.1 (0.9–1.3)
101–	25,489	761	1.0	1.0
Cup
1–15	4,742	176	1.3 (1.1–1.5)	1.2 (1.0–1.4)
16–30	3,312	106	1.1 (0.9–1.4)	1.1 (0.9–1.4)
31–50	3,709	128	1.2 (1.0–1.4)	1.1 (0.9–1.4)
51–100	6,339	211	1.2 (1.0–1.4)	1.1 (1.0–1.3)
101–	21,023	612	1.0	1.0