Cost-utility analysis of posterior minimally invasive fusion compared with conventional open fusion for lumbar spondylolisthesis

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Table 1

Demographics

Variable	Open group			MIS group			P value

	N	Mean	SD	N	Mean	SD
Age (years)	41	57.05	13.38	37	55.11	14.98	.7826^*
Sex (female)	20	—	—	19			.7263^†
Body mass index (kg/m²)	39	30.65	5.72	36	29.84	6.50
No. of levels fused^‡	41	1.49	0.51	37	1.22	0.42	.0133^†
Estimated blood loss (mls)	40	797.75	564.27	37	200.41	165.12	< .0001^*
LOS (days)	41	8.41	5.45	37	6.08	1.86	.0525^*
Adverse events	12	—	—	4	—	—	< .02^†
Operating room time (hours)	41	3.79	1.04	37	3.70	0.90	.6794^§

↵* Whitney-Mann test.
↵† χ² test.
↵‡ Two-level fusions were performed in 20 patients in the open cohort and 12 in the MIS cohort.
↵§ t Test.

Table 3

Cost-utility data

Variable	Open			MIS			P value

	N	Mean	SD	N	Mean	SD
Direct cost (Can $)	40	$18,632.91	6,197.32	36	$14,171.93	3,269.73	.0009^*
Utility score at baseline	29	0.49	0.08	28	0.60	0.09	< .0001^†
Utility score at 1 y	29	0.57	0.10	28	0.72	0.09	< .0001^†