Infuence of the Radius of Curvature and Residual Stresses on Pedicular Spinal Implant Rods

Authors

DOI:

https://doi.org/10.14295/vetor.v30i1.12880

Keywords:

Pedicular Implants, Finite Elements, Residual Stresses

Abstract

Pedicle rods are used in spinal implants in order to stabilize and correct deformities. In several clinical applications, pedicle rods are molded (cold forming) at the time of surgery, in order, for example, to provide sagittal alignment to the patient. However, the normative test related to these implants (ASTM F1717-04) evaluates the straight configuration (without conformation). The present work seeks to verify the influence of such bending on the rods’ stress state, affecting the implant lifespan. In this work, two effects are evaluated: the influence of the new geometries (by varying radii of curvature) and the influence of residual stresses resulted from bending. The influence of geometry was investigated using finite element modeling using ANSYS Mechanical APDL software. The influence of residual stresses was estimated based on a simplified model proposed by the balance of moments for a circular cross-section. It was found that both effects are significant. For the geometric effects, the rod closest to the point of force application resulted on a lower tractive tension in the posterior part of the implant, while for residual stresses, the effect was the opposite. Greater bending increased in tensile stresses. The present work results point out that it would bebeneficial to use precast pedicle rods in such a way that the manufacturing processes would minimize their residual stresses.

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Published

2021-04-22

How to Cite

Masiero, L. V., Habib, A. Z., Aliaga, L. C. R., & Lima, L. V. P. de C. (2021). Infuence of the Radius of Curvature and Residual Stresses on Pedicular Spinal Implant Rods. VETOR - Journal of Exact Sciences and Engineering, 30(1), 49–59. https://doi.org/10.14295/vetor.v30i1.12880

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