Table 3.

Results from the multivariate regression analysis. Results from the multivariate linear regression with change in ODI at 12 months after surgery as dependent variable. P-values from a likelihood ratio test, testing whether or not a given variable is important in explaining variations in the data, is reported. The multivariate regression analysis with Group 1 as a reference, shows that the more intense preoperative leg pain the greater is the probability of achieving a positive clinical outcome

Variable	Coefficient (Confidence interval)	P-value from LR-test
Preoperative leg pain
Group 1	Reference
Group 2	−2.31 (−5.98, 1.36)
Group 3	−4.65 (−8.25, −1-05)
Group 4	−6.95 (− 11.28,-2.61)	0.003
Preoperative ODI	−0.58 (−0.65,-0.51)	< 0.001
Age at surgery	0.08 (0.02–0.15)	0.016
Sex
Male	Reference
Female	0.83 (−0.63,2.28)	0.265
Smoking
No	Reference
Yes	4.76 (3.08,6.44)	< 0.001
BMI	0.24 (0.07,0.41)	0.001
Preoperative back pain
Group 1	Reference
Group 2	4.35 (1.13,7.57)
Group 3	7.11 (3.92,10.30)
Group 4	8.85 (4.65,13.05)	< 0.001
Preoperative EQ. 5D-score	−1.83 (−4.86,1.20)	0.240
Constant	−6.41 (− 14.85,2.03)