Table 2.

The fragility index of patient-related factors for dichotomous events

Grouping variable	Author (year)	Dichotomous event	Arm 1	Arm 2	Sample size arm 1	Sample size arm 2	Events arm 1	Events arm 2	p value or 95% CI (unadjusted/adjusted*)	Statistical test	Fragility index	Mean fragility index	Median fragility index
Age	Aga et al. (2017)	Revision	Age 14–19	Age 20–24	14,733	12,645	985	568	< 0.001*	Cox regression	204	178.5	116.0
		Revision	Age 14–19	Age 25–29	14,733	9280	985	252	< 0.001*	Cox regression	309
		Revision	Age 14–19	Age 30–60	14,733	24,120	985	403	< 0.001*	Cox regression	1089
	Desai et al. (2017)	Revision	Age 13–15	Age 36–49	1300	3350	74	36	< 0.001	Kaplan–Meier	108
		Revision	Age 16–20	Age 36–49	5075	3350	252	36	< 0.001	Kaplan–Meier	100
		Revision	Age 21–25	Age 36–49	3667	3350	117	36	< 0.001	Kaplan–Meier	45
		Revision	Age 26–30	Age 36–49	2513	3350	43	36	0.040	Kaplan–Meier	1
		Revision	Age 13–25	Age 26–49	10,042	7640	443	109	< 0.001	Kaplan–Meier	183
	Fauno et al. (2014)	Revision	Age 13–15	Age > 20	327	11,496	22	233	3.48 (2.24–5.38)/3.23 (2.05–5.08)*	Cox regression	263
		Revision	Age 15–20	Age > 20	2888	11,496	140	233	2.57 (2.09–3.18)/2.50 (2.01–3.11)*	Cox regression	230
	Gifstad et al. (2014)	Revision	Age 15–19	Age 20–24	10,947	8518	480	286	0.77 (0.67–0.90)/0.78 (0.67–0.90)*	Cox regression	39
		Revision	Age 15–19	Age 25–29	10,947	6702	480	145	0.47 (0.39–0.57)/0.47 (0.39–0.57)*	Cox regression	108
		Revision	Age 15–19	Age 30–34	10,947	5471	480	83	0.32 (0.25–0.40)/0.31 (0.25–0.40)*	Cox regression	121
		Revision	Age 15–19	Age 35–39	10,947	5093	480	70	0.29 (0.23–0.37)/0.28 (0.22–0.37)*	Cox regression	119
		Revision	Age 15–19	Age 40–44	10,947	4073	480	48	0.25 (0.19–0.34)/0.25 (0.19–0.34)*	Cox regression	101
		Revision	Age 15–19	Age ≥ 45	10,947	3400	480	30	0.20 (0.14–0.28)/0.19 (0.13–0.28)*	Cox regression	93
	Snaebjornsson et al. (2017)	Contralateral ACLR	Age 13–15	Age 36–49	1300	3350	88	45	0.002	Kaplan–Meier	132
	Soreide et al. (2016)	Revision	Age 15–19	Age > 29	1680	3166	106a	41a	0.001*	Cox regression	116
		Revision	Age 20–29	Age > 29	2647	3166	82a	41a	0.001*	Cox regression	31
Patient sex	Snaebjornsson et al. (2017)	Contralateral ACLR	Female	Male	7669	10,013	266	260	0.001	Kaplan–Meier	35	–	–
Activity at injury	Ahlden et al. (2012)	Revision/contralateral ACLR	Female football players 15–18y	Male football players 15–18y	118	92	26a	9a	0.02	X2 test	2	16.0	5.5
	Gifstad et al. (2014)	Revision	Football	Alpine activities	18,810	6083	527	110	0.65 (0.53–0.79)/0.65 (0.53–0.79)*	Cox regression	32
		Revision	Football	Other sports	18,810	12,103	527	285	0.83 (0.72–0.96)/0.85 (0.73–0.98)*	Cox regression	9
		Revision	Football	Other/unknown	18,810	1033	527	19	0.57 (0.36–0.90)/0.54 (0.34–0.86)*	Cox regression	0
		Revision	Handball	Football	5260	18,810	191	527	1.28 (1.08–1.51)/1.23 (1.04–1.45)*	Cox regression	53
		Revision	Traffic/work	Football	2113	18,810	66	527	1.07 (0.83–1.38)/1.44 (1.12–1.87)*	Cox regression	0

Arm 1 has the highest risk of an event across all analyses

^aNumber has been calculated from a proportion (%)

*Adjusted P value

ACLR anterior cruciate ligament reconstruction, CI confidence interval, y years