Table 4.

Correlation between sagittal parameters and NDI scores

	Sagittal parameters	Correlation (Spearman r)	P
Preoperative NDI scores	Preoperative T1 s	0.489	0.001**
	Preoperative C2–7SVA	0.206	0.191
	Preoperative C2–7 lordosis	0.245	0.117
	Preoperative Cranial tilting	0.154	0.331
	Preoperative Cervical tilting	0.449	0.003**
Follow-up NDI scores	Follow-up T1 s	0.421	0.006**
	Follow-up C2–7SVA	0.106	0.503
	Follow-up C2–7 lordosis	0.190	0.228
	Follow-up Cranial tilting	0.115	0.470
	Follow-up Cervical tilting	0.156	0.325

SVA sagittal vertical axis, T1 s T1 slope

**Correlation is significant at the P < 0.01 level (2-tailed)