Potential contribution of pedicle screw design to loosening rate in patients with degenerative diseases of the lumbar spine: An observational study

Table 3 Parameters included in the general logistic regression model

Parameter	Regression coefficient	OR per unit change with 95%CI
Intercept	−4.819065; Р = 0.3617	-
Radiodensity, HU	−0.0271586; P < 0.0001	0.9732 (0.9623-0.9842)
Number of fused levels	1.111651; P < 0.0001	3.0394 (1.7566-5.2590)
Bilateral total facet joints removal (at least one level)	1.124871; Р = 0.4359	3.0798 (1.0023-9.2781)
Laminectomy	0.4418158; Р = 0.5333	1.5555 (0.5090-4.7533)
Posterior fusion performed without interbody fusion	−0.4247137; Р = 0.4550	0.6540 (0.2128-2.0097)
Maximal external screw diameter	−5.966555; Р = 0.3798	0.0026 (0.000009-0.7153)
Maximal internal screw diameter	6.430714; P = 0.0253	620.61 (2.2363-172234.6)
Helical pitch	4.611687; Р = 0.0081	100.6538 (3.3668-3009.1310)
Thread type (buttress vs V-shape)	−1.034237; Р = 0.9949	0.1070 (0.0090-1.2659)
Design cyl/cyl	0.1446205; P = 0.8568	1.1566 (0.2378-5.6156)
Design cyl/con	−1.731799; Р = 0.2767	0.1769 (0.0077-4.0602)
Design con/con	0.2718265; P = 0.7594	1.3124 (0.2282-7.5451)

CI: Confidence interval; con/con: Conical core and thread.; cyl/con: Cylindrical thread and conical core; cyl/cyl: Cylindrical core and thread; HU: Hounsfield unit; OR: Odds ratio.