Factors that influence the results of indirect decompression employing oblique lumbar interbody fusion

Table 1 Preoperative and postoperative radiographic parameters of the enrolled group according to the results of computed tomography examination

	Preoperative value	Postoperative value	Statistical	Р value
Vertebral canal square in axial plane mm2	m = 102.4468 ± 8.6091	m = 150.3774 ± 8.9059	t-test for matched samples	< 0.0001
	SD = 67.7880	SD = 70.1252
	95%CI: 85.2319, 119.6617	95%CI: 132.5689, 168.1859
Left lateral recess depth in axial plane mm	M = 3.90	M = 4.95	Wilcoxon test	< 0.0001
	25%-75%: (2.8, 4.8)	25%-75%: (3.7, 6.2)
Left lateral recess depth in axial plane mm	M = 3.45	M = 4.95	Wilcoxon test	< 0.0001
	25%-75%: (2.7, 5.0)	25%-75%: (3.8, 6.2)
Disc height along the midline of anterior boarders of vertebral bodies	m = 6.6677 ± 0.3016	m = 12.0161 ± 0.2734	t-test for matched samples	< 0.0001
	SD = 2.3751	SD = 2.1531
	95%CI: 6.0646, 7.2709	95%CI: 11.8693, 12.963
Disc height along the midline of posterior boarders of vertebral bodies	m = 4.4500 ± 0.2496	m = 7.1871 ± 0.2749	t-test for matched samples	< 0.0001
	SD = 1.9656	SD = 2.1649
	95%CI: 3.9508, 4.949	95%CI: 6.6373, 7.736

M: Median; m: Mean.

Table 2 The parameters of linear regression model for postoperative vertebral canal square in patients who were treated with anterior column reconstruction and reduction

Component of linear regression equation	Beta coefficient	Regression coefficient	Р value
Intercept		39.2163	0.0001
Preoperative vertebral canal square	0.8486	0.8893	< 0.0001
Difference in the upper vertebral body anterior slip	0.1782	6.2508	0.0029
Difference in the disc space height along the anterior boarder, midline	-0.0302	-0.7912	0.6087
Difference in the disc space height along the posterior boarder, midline	-0.0460	-1.3984	0.4312

Table 3 The results of covariance analysis for the postoperative right lateral recess depth

Component of ANCOVA regression	Beta coefficient	Regression coefficient	Р value
Intercept		1.8432	< 0.0001
Preoperative lateral recess depth	0.7401	0.8139	< 0.0001
Weishaupt 4 degenerative changes in the facet joints	0.1746	0.4954	0.0041

Table 4 The results of covariance analysis for the postoperative right lateral recess depth

Component of ANCOVA regression	Beta coefficient	Regression coefficient	Р value
Intercept		1.3199	0.0384
Preoperative lateral recess depth	0.6515	0.8145	< 0.0001
Weishaupt 4 degenerative changes in the facet joints	0.1746	0.4954	0.0041
Difference in the disc space height along the anterior boarder, midline	0.1886	0.1477	0.0384

Table 5 The parameters of linear regression model for postoperative vertebral canal square in patients who were treated with anterior reconstruction without reduction applied

Component of linear regression equation	Beta coefficient	Regression coefficient	Р value
Intercept		6.4119	0.5567
Preoperative vertebral canal square, mm2	0.9527	0.9968	< 0.0001
Difference in the disc space height along the anterior boarder, midline	0.11073	1.8073	0.1181
Difference in the disc space height along the posterior boarder, midline	0.1689	4.2827	0.0287

Table 6 The parameters for the discriminant regression function for the failure of the indirect decompression prediction

Component of the regression equation	Regression coefficient	Р value	Beta coefficient
Intercept	0.5591	< 0.0001	-
Postoperative square of the vertebral canal below 80 mm2	0.2777	0.0001	0.5783
Lateral recess depth below 3 mm	0.1008	0.0088	0.2671
Vertebral canal square mm2	-0.0005	0.3351	-0.1013
Right lateral recess depth, mm	0.0221	0.2670	0.1426
Left lateral recess depth, mm	-0.0037	0.8763	0.0207