Anterior direct decompression significantly relieves spinal cord high signal in patients with ossification of the posterior longitudinal ligament: a case-control study

Table 2 Linear regression analyses for lower CR2 values

	95% CI		P value
Uni-variable analyses
Demographic data
Sex (male/female)	− 0.01	0.221	0.924
Age	− 0.015	0.003	0.195
Hypertension	− 0.071	0.204	0.334
Diabetes	− 0.195	0.135	0.716
BMI	− 0.375	0.422	0.905
Smoking history	− 0.249	0.077	0.295
Surgical approach	− 0.349	− 0.113	0.000^#
Preoperative measured imaging parameters
C2–7 Cobb angle	− 0.009	0.002	0.185
SVA	− 0.008	0.008	0.995
mK-line INT	− 0.043	0.005	0.122
Preoperative SCR	0.092	0.445	0.004^#
CR1	0.156	0.784	0.004^#
CNR	− 0.76	0.844	0.918
Multi-variable analyses
Surgical approach	− 0.321	− 0.118	0.000**
Preoperative SCR	0.127	0.41	0.000**
CR1	− 0.018	0.501	0.067

^#, variables that achieved a significance level of p < 0.1 in the univariate analysis
*statistical significance (p < 0.05). **statistical significance (p < 0.01)
BMI = body mass index. SCR = the signal change ratio between the localized high signal and normal spinal cord signal at the C7-T1 levels. CR1 = the regression of high cord signals at 6 months postoperatively (i.e., CR1 = (Preoperative SCR—SCR at 6 months postoperatively)/ Preoperative SCR). CR2 = the regression of high cord signal at 2 years postoperatively (i.e., CR2 = (Preoperative SCR—SCR at 2 years postoperatively)/ Preoperative SCR). CNR = canal narrowing ratio. SVA = sagittal vertical axis. mK-line INT = modified K-line interval

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