Table 1.

Number of patients (n) according to age at operation, and number of person-years (PY) according to the age at follow-up. The non-metal-on-metal cohort consisted of implants with metal-on-polyethylene, ceramic-on-polyethylene, and ceramic-on-ceramic bearing surfaces

	Metal-on-metal cohort				Non-metal-on-metal cohort				Total
	Men		Women		Men		Women		Men		Women
Age	n	PY	n	PY	n	PY	n	PY	n	PY	n	PY
0–9	1	1	–	–	–	–	–	–	1	1	–	–
10–19	5	16	3	16	–	–	–	–	5	16	3	16
20–29	25	136	16	69	4	17	7	29	29	153	23	98
30–39	159	558	67	309	30	119	20	116	189	677	87	425
40–49	741	3,746	471	2,078	143	730	157	578	884	4,476	628	2656
50–59	2,277	11,787	1,643	8,578	850	3,880	922	4,416	3,127	15,667	2,565	12,994
60–69	2,257	19,652	1,581	14,090	2,260	13,980	2,739	16,099	4,517	33,632	4,320	30,189
70–79	763	9,403	594	6,773	3,044	25,854	5,397	39,047	3,807	35,257	5,991	45,820
80–	65	1,276	48	1,036	698	13,610	1,953	33,884	763	14,886	2,001	34,920
Total	6,293	46,573	4,423	32,948	7,029	58,190	11,195	94,168	13,322	104,763	15,618	127,116

PY: person-years