Article Figures & Data
Figures
- Fig. 1
The screws and tap. The pedicle screws (5.5x45 mm) and cortical screws (5.5x30 mm) were inserted after tapping (5.5 mm).
- Fig. 2
The custom-designed apparatus allowed a non-constraint motion for the spine in all three planes of motion during pure moment application. The reflective markers were used to detect interlevel motion. The inset illustrates the position of the specimen and fixture during sagittal and lateral bending. During switching from lateral bending to sagittal bending, the specimen was rotated 90° around its caudo-cephelad axis.
- Fig. 3
Each specimen was instrumented (L1-4) and tested with both standard and cortical trajectory pedicle screws. Due to the difference in screw start points and insertion trajectories, there was minimal interaction between the constructs.
- Fig. 4
The interlevel ROM for destabilized and instrumented spines (L1-4) as normalized with intact in sagittal bending. Instability was significantly reduced by both fixation systems. There was no difference in ROM between both constructs (mean ± standard deviation).
- Fig. 5
The interlevel ROM for destabilized and instrumented spines (L1-4) as normalized with intact in lateral bending. Instability was significantly reduced by both fixation systems. There was no difference in ROM between both constructs (mean ± standard deviation).
- Fig. 6
The interlevel ROM for destabilized and instrumented spines (L1-4) as normalized with intact in axial rotation. Instability was significantly reduced by both fixation systems. There was no difference in ROM between both constructs (mean ± standard deviation).
- Fig. 7
The sagittal cross-sectional view of cortical trajectory. The superior and inferior cortices of the pedicle isthmus provide dense bone and might contribute increased screw stability.
Tables
Spine ID Age Gender T-Score 1 69 M -3.50 2 69 F -3 3 50 M -1.3 4 80 F -0.6 5 78 M 2.8 6 78 M -0.5 7 72 F -1.3 8 79 M 0.2 L4-3 L3-2 L2-1 Sagittal intact 8.76±3.58 8.37±2.77 7.43±2.29 destab 13.01±1.45 10.52±2.59 12.67±2.84 PS 3.18±1.78 0.28±1.09 1.53±1.63 CS 2.58±1.60 1.73±0.65 3.55±2.97 Lateral intact 9.37±2.51 9.82±3.44 7.36±1.50 destab 14.77±4.92 11.09±2.46 11.84±2.62 PS 1.40±0.56 0.32±0.53 0.68±0.98 CS 1.93±0.77 0.96±0.25 3.51±1.91 Axial intact 4.28±2.61 4.91±3.25 2.50±1.06 destab 12.50±4.75 11.46±3.75 9.73±4.12 PS 2.15±0.99 0.83±1.13 1.29±1.28 CS 2.10±1.01 2.76±1.46 3.45±1.61 Sagittal Lateral Axial PS CS PS CS PS CS Slope 0.25 0.17 0.03 0.08 0.29 0.28 Intercept -0.07 0.04 0.13 0.12 -0.16 -0.09 P-value 0.02 0.05 0.24 0.14 0.01 0.00 R 2 0.24 0.16 0.03 0.07 0.32 0.41 Are the slopes different (P-value)? 0.56 0.49 0.99
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