Predicting Pedicle Screw Pullout and Fatigue Performance: Comparing Lateral Dual-Energy X-Ray Absorptiometry, Anterior to Posterior Dual-Energy X-Ray Absorptiometry, and Computed Tomography Hounsfield Units

Article Figures & Data

Download figure
Open in new tab
Download powerpoint
Figure 1
Hounsfield unit value measurement.
Download figure
Open in new tab
Download powerpoint
Figure 2
Anterior to posterior (left) and lateral (right) dual-energy x-ray absorptiometry scan measurements.
Download figure
Open in new tab
Download powerpoint
Figure 3
Biomechanical testing.
Download figure
Open in new tab
Download powerpoint
Figure 4
Univariate linear regression analysis of computed tomography (CT)-Hounsfield units vs pullout strength. The correlation between each was stastistically significant.
Download figure
Open in new tab
Download powerpoint
Figure 5
Univariate linear regression model of anterior to posterior (AP) dual-energy x-ray absorptiometry (DEXA) bone mineral density vs pullout strength.
Download figure
Open in new tab
Download powerpoint
Figure 6
Univariate linear regression model of lateral-dual-energy x-ray absorptiometry (DEXA) bone mineral density vs pullout strength.

Table 1

Linear regression model: correlations with pull-out strength.

Variable	Houndsfield Units vs Pullout Strength (N)	Anterior to Posterior Dual-Energy X-ray Absorptiometry Bone Mineral Density vs Pullout Strength (N)	Lateral Dual-Energy X-ray Absorptiometry Bone Mineral Density vs Pullout Strength (N)
Slope (x)	13.8	3071.4	2433.8
R	0.881	0.838	0.632
P	<0.001	<0.001	0.006
R ²	0.78	0.70	0.40

Table 2

Fisher R to Z transformation.

Variable	Computed Tomography vs Lateral DEXA	Anterior to Posterior DEXA vs Lateral-DEXA	Computed Tomography vs Anterior to Posterior-DEXA
R ²	0.78 vs 0.40	0.70 vs 0.40	0.78 vs 0.70
P	0.009	0.032	0.120
Z-score	2.371	1.857	0.171

Abbreviation: DEXA, dual-energy x-ray absorptiometry.
Note: Calculation of the difference between 2 correlation coefficients with 1 variable in common using 1-tailed Steiger Z test.