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. 2014;22(1):17-20.
doi: 10.1590/S1413-78522014000100002.

Analysis of stress induced by screws in the vertebral fixation system

Sarah Fakher Fakhouri  1 , Marcos Massao Shimano  2 , Cleudmar Amaral de Araújo  3 , Helton Luiz Aparecido Defino  1 , Antônio Carlos Shimano  1
Affiliations

Analysis of stress induced by screws in the vertebral fixation system

Sarah Fakher Fakhouri et al. Acta Ortop Bras. 2014.

Abstract

Objective: To compare, using photoelasticity, internal stress produced by USS II type screw with 5.2 and 6.2 mm external diameters, when submitted to three different pullout strengths.

Methods: Two photoelastic models were especially made. The simulation was performed using loads of 1.8, 2.4 e 3.3 kgf.The fringe orders were evaluated around the screws. In all the models analyzed the shear stress were calculated.

Results: Independently of the applied load, the smaller screw showed higher values of shear stress.

Conclusion: According to the analysis performed, we observed that the place of highest stress was in the first thread of the lead, close to the head of the screws. Experimental study.

Keywords: Biomechanics; Elasticity; Qualitative analysis; Quantitative analysis; Tensile strength.

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Conflict of interest statement

All the authors declare that there is no potential conflict of interest referring to this article.

Figures

Figure 1
Figure 1. 5.2mm (A) and 6.2mm (B) USS vertebral fixation titanium screws (Synthes(r)).
Figure 2
Figure 2. Schematic representation of flexible epoxy photoelastic models.
Figure 3
Figure 3. Schematic representation of polariscope used in photoelastic analysis.
Figure 4
Figure 4. Scheme of mapping grid used on tests showing the fifteen points analyzed in pedicle screws.
Figure 5
Figure 5. Standard orders of isochromatic fringes obtained in the analysis of 5.2 mm USS pedicle screw applying a load of 3.3 kgf.
Figure 6
Figure 6. Mean and Standard deviation of shear tension on both screws submitted to three different pullout strengths.
See this image and copyright information in PMC

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