Table 2.

Age, gender, regional, and annual case volume distribution of study cohorts^†

	Outpatient ACDF (N=1,215)		Inpatient ACDF (N=10,964)		Relative ratio of outpatient ACDF
	n	Incidence (per 100,000)*	n	Incidence (per 100,000)*
Age
Less than 40	61	0.2	355	3.0	0.17
40–44	80	1.8	475	20.1	0.17
45–49	113	2.8	825	28.7	0.14
50–54	167	3.2	1,255	36.0	0.13
55–59	173	4.3	1,446	37.3	0.12
60–64	142	4.3	1,382	34.2	0.10
65–69	227	1.0	2,188	16.1	0.10
70–74	169	1.9	1,698	14.2	0.10
75–79	59	1.9	844	9.4	0.07
80–84	24	1.0	329	5.4	0.07
85–89	0	0	73	3.1	0
90+	0	0	22	0.5	0
Gender
Male	601	1.4	5,265	12.0	0.11
Female	614	1.9	5,699	17.7	0.11
Geographic region
Midwest	264	5.0	2,182	41.5	0.12
Northeast	16	0.1	188	1.0	0.09
South	856	2.1	7,608	18.6	0.11
West	79	0.8	986	9.5	0.08
Case year
2011	168	2.6	1,523	23.3	0.11
2012	207	2.8	1,966	27.3	0.11
2013	276	3.4	2,347	29.7	0.12
2014	338	3.4	2,727	28.3	0.12
2015	235	2.0	2,348	20.5	0.10
2016	12	N/A	54	N/A	0.22

N/A, not applicable; ACDF, anterior cervical discectomy and fusion.

^*Incidence per 100,000 Humana-insured patients.

^†N/A where complete incidence data not available for 2016 calendar year at the time of query.