Factors that influence long term instrumentation stability in patients with unstable thoracolumbar injuries

Table 1 Characteristics of the enrolled group

Characteristics	Value
Age (years)	m = 40 (σ = 15.01; range: 18-71 years)
Male to female ratio	117/87
Patients with radiodensity of cancellous bone below 110 HU	63%-30.9%
Intermediate fixation used	93%-45.6 %
Laminectomy	66%-32.4%
Total facet joints and ligamentum flavum removal	48%-23.5%
Extensive decompression with laminectomy and at least one level total facetectomy and ligamentum flavum removal	37%-18.1%
Reconstruction of the anterior column	76%-37.2%
Anterior decompression	31%-15.1%
Monosegmental short fixation	10%-4.9%
Bisegmental fixation	139%-68.1%
Three segment fixation	21%-10.3%
Four segment fixation	34%-16.7%
Lumbosacral fixation	6%-2.9%
Residual kyphotic deformity	38%-18.6%

HU: Hounsfield units.

Table 2 Parameters of general logistic regression

Components of regression model	Regression coefficient	OR per unit change (95%CI)
Intercept	-1.5227, P = 0.0537	-
Number of instrumented levels	0.6215, P = 0.0076	1.8617 (1.1819-2.9324)
Lumbosacral fusion	2.3039, P = 0.0292	10.0136 (1.2655-79.2374)
Residual deformity over 10°	1.3772, P = 0.0028	3.9636 (1.6161-9.7213)
Intermediate fixation	0.8377, P = 0.0457	2.3110 (1.0162-5.2553)
Anterior reconstruction	-1.2827, P = 0.0095	3.7491 (1.3725-3.6062)
Radiodensity HU	-0.0142, P = 0.0029	0.9869 (0.9768-0.9951)
Laminectomy	0.8809, P = 0.0448	2.4130 (1.0210-5.7029)
Anterior decompression performed	-0.0726, P = 0.9071	0.9299 (0.2729-3.1688)

OR: Odds ratio; CI: Confidence interval; HU: Hounsfield units.

Table 3 Parameters of general discriminant model for the assessment of risk factors for clinically significant instrumentation failure

Components of regression equation	Regression coefficient	Statistical significance	Beta coefficient
Intercept	0.5679	P = 0.0008	-
Residual deformity of over 10°	0.0529	P = 0.0518	0.1216
Anterior fusion bipolar, Tan 1-2	0.0027	P = 0.9323	0.0063
Partial or complete ankyloses of facet joints within instrumented area	-0.1684	P = 0.0006	-0.4612
Anterior decompression performed	0.0219	0.5109	0.0463
Anterior reconstruction	-0.0780	0.0040	0.0207
Extensive posterior decompression with laminectomy and at least one level total facetectomy	0.1194	P = 0.0003	0.2716
Lumbosacral fusion	0.0799	0.2133	0.0796
Radiodensity in HU	0.0002	0.6894	0.0239
Length of fixation (number of levels)	0.0362	0.6894	0.0239
Intermediate fixation	-0.1262	0.0025	-0.2036

HU: Hounsfield units.