Table 4.

Comparison of Radiographical Outcomes Between IS and S2AI.

	IS (n = 17), Mean ± SD	P a,b	S2AI (n = 46), Mean ± SD	P a,b	P a,c	Interobserver Agreement
Pre Cobb	20.6 ± 10.0	.04	22.6 ± 14.5	<.001	.61	0.87
Post Cobb	10.8 ± 3.6		10.2 ± 8.5		.26	0.85
Change in Cobb	−9.8 ± 11.5		−12.4 ± 12.5		.93
Pre LL	32.4 ± 13.9	<.001	38.6 ± 18.5	.01	.07	0.73
Post LL	46.7 ± 9.7		45.3 ± 9.8		.08	0.75
Change in LL	14.3 ± 13.7		6.7 ± 18.9		.06
Pre TK	32.7 ± 13.8	.007	34.0 ± 20.6	.004	.70	0.83
Post TK	45.4 ± 14.6		40.6 ± 11.7		.18	0.81
Change in TK	12.7 ± 19.0		6.6 ± 18.0		.43
Pre PT	26.6 ± 7.6	.33	29.3 ± 9.8	.43	.22	0.71
Post PT	28.3 ± 6.8		28.4 ± 7.8		.04	0.72
Change in PT	1.7 ± 6.4		−0.9 ± 11.2		.67
Pre SS	26.7 ± 8.3	.36	34.1 ± 9.9	.06	<.001	0.75
Post SS	27.9 ± 5.2		30.1 ± 9.0		.83	0.73
Change in SS	1.1 ± 6.5		−4.0 ± 11.5		.10
Pre PI	53.3 ± 14.1	.07	63.4 ±12.3	.001	.06	0.71
Post PI	56.3 ± 11.6		57.4 ± 9.6		.60	0.74
Change in PI	2.9 ± 6.7		−6.0 ± 12.5		.008
Pre PI-LL	20.9 ± 17.2	.03	24.8 ± 18.8	.01	.75	0.72
Post PI-LL	9.6 ± 7.9		12.1 ± 9.7		.50	0.74
Change in PI-LL	−11.3 ± 13.9		−12.7 ± 19.7		.98
Pre SVA	9.4 ± 6.2	.26	10.4 ± 7.7	.02	.56	0.86
Post SVA	6.6 ± 4.8		7.5 ± 3.9		.41	0.89
Change in SVA	−2.8 ± 8.0		−2.8 ± 6.9		.97

Abbreviations: IS, iliac screw; S2AI, S2-alar-iliac; Pre, preoperative; Post, postoperative; Cobb, Cobb angle; LL, lumbar lordosis; TK, thoracic kyphosis; PT, pelvic tilt; SS, sacral slope; PI, pelvic incidence; PI-LL, pelvic incidence–lumbar lordosis mismatch; SVA, sagittal vertical axis.

^a P values in boldface indicate statistical significance.

^bComparison between preoperative and postoperative outcomes.

^cComparison between IS and S2AI.