Article Figures & Data
Figures
- Fig. 1
Model details (ligaments and mesh).
- Fig. 2
Experimental setup (clamps not represented for clarity).
- Fig. 3
Screw trajectory parameters.
- Fig. 4
Six simulated configurations.
- Fig. 5
Sagittal view of the global displacements of the SIJ (translations in mm) for the simulations at 1000 N: a) uninstrumented (reference) and b) instrumented with one screw inserted obliquely at the proximal insertion point.
- Fig. 6
Local displacements (translations in mm) of 14 points of the SI facet of the sacrum with respect to the iliac bone after a vertical loading of the sacrum of 1000 N: a) unistrumented; b) instrumented (configuration 1). The displacement vectors are magnified for clarity.
- Fig. 7
SIJ local displacements in the sagittal plane and % of reduction with respect to the uninstrumented reference.
- Fig. 8
Average SIJ local rotations and % of rotation reduction with respect to the uninstrumented reference.
- Fig. 9
Stresses (MPa) on the left ilium and sacrum trabecular bone (configuration 5, loaded at 800 N). The virtual axis of rotation is located below the figure.
- Fig. 10
Interosseous ligament modifications in the model to enable device insertion.
Tables
Cortical Bone Trabecular Bone Ligaments Pubic Symphysis SIJ Articular Cartilage Density (kg.m-3) 2 0.2 2 2 1.05 Young Modulus (MPa) 2625 48.75 40 397 150 Poisson Ratio 0.3 0.25 0.3 0.3 0.2 Yield Stress (MPa) 105 1.95 - - - Hardening modulus (MPa) 875 16.3 - - - Hardening exponent 1 1 - - - Failure plastic strain 0.04 0.04 - - - Tangent Young Modulus (MPa) - - 10 155 - Tangent Poisson ratio - - 0.37 0.37 - Viscoelastic constant - - 28 28 - Navier Constant - - 1.105 1.105 - - Table 2
Comparison of experimentally measured (mean) and simulated S1 endplate displacement reduction due to the screws.
1 screw configuration 2 screw configuration Experimental Simulations Difference Experimental Simulations Difference 600 N 14.98% 13.86% 1.12% 17.71% 14.36% 3.35% 800 N 12.09% 14.75% 2.66% 14.27% 15.46% 1.19%
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