Table 3.

Numbers at risk and cumulative percent revision for the operation groups

Operation group		1 year	2 years	3 years	4 years	5 years
1–15 operations	CPR	3 (2–5)	4 (3–6)	6 (4–8)	6 (4–8)	6 (4–8)
	Number at risk	548	433	298	191	91
16–30 operations	CPR	3 (2–5)	3 (2–5)	3 (2–5)	3 (2–5)	3 (2–5)
	Number at risk	415	272	172	105	47
31–50 operations	CPR	3 (1–4)	4 (2–6)	5 (3–7)	5 (3–7)
	Number at risk	427	259	187	97
51–100 operations	CPR	2 (1–3)	2 (1–3)	2 (1–4)	3 (2–5)
	Number at risk	561	359	211	86
> 100 operations	CPR	1 (1–1)	1 (1–2.0)	2 (1–3)	2 (1–3)
	Number at risk	1764	960	332	80

Ninety-five percent confidence intervals shown in parentheses; CPR = cumulative percent revision.