On the limits of finite element models created from (micro)CT datasets and used in studies of bone-implant-related biomechanical problems

Marcián, Petr; Borák, Libor; Zikmund, Tomáš; Horáčková, Ladislava; Kaiser, Jozef; Joukal, Marek; Wolff, Jan

Affiliations

¹Institute of Solid Mechanics, Mechatronics and Biomechanics, Faculty of Mechanical Engineering, Brno University of Technology, Brno, Czech Republic

²CEITEC - Central European Institute of Technology, Brno University of Technology, Czech Republic

³Department of Anatomy, Faculty of Medicine, Masaryk University, Brno, Czech Republic

⁴Department of Oral and Maxillofacial Surgery, Division for Regenerative Orofacial Medicine, University Hospital Hamburg-Eppendorf, Hamburg, Germany

⁵Fraunhofer Research Institution for Additive Manufacturing Technologies IAPT, Hamburg, Germany

Abstract and keywords

Patient-specific approach is gaining a wide popularity in computational simulations of biomechanical systems. Simulations (most often based on the finite element method) are to date routinely created using data from imaging devices such as computed tomography which makes the models seemingly very complex and sophisticated. However, using a computed tomography in finite element calculations does not necessarily enhance the quality or even credibility of the models as these depend on the quality of the input images. Low-resolution (medical-)CT datasets do not always offer detailed representation of trabecular bone in FE models and thus might lead to incorrect calculation of mechanical response to external loading. The effect of image resolution on mechanical simulations of bone-implant interaction has not been thoroughly studied yet. In this study, the effect of image resolution on the modeling procedure and resulting mechanical strains in bone was analyzed on the example of cranial implant. For this purpose, several finite element models of bone interacting with fixation-screws were generated using seven computed tomography datasets of a bone specimen but with different image resolutions (ranging from micro-CT resolution of 25 μm to medical-CT resolution of 1250 μm). The comparative analysis revealed that FE models created from images of low resolution (obtained from medical computed tomography) can produce biased results. There are two main reasons: 1. Medical computed tomography images do not allow generating models with complex trabecular architecture which leads to substituting of the intertrabecular pores with a fictitious mass; 2. Image gray value distribution can be distorted resulting in incorrect mechanical properties of the bone and thus in unrealistic or even completely fictitious mechanical strains. The biased results of calculated mechanical strains can lead to incorrect conclusion, especially when bone-implant interaction is investigated. The image resolution was observed not to significantly affect stresses in the fixation screw itself; however, selection of bone material representation might result in significantly different stresses in the screw.

Keywords: Finite element method; Computational modeling; Computed tomography; Image resolution; Bone tissue; Mechanical strain

Links

DOI: 10.1016/j.jmbbm.2021.104393

PubMed: 33647729

WoS: 000635269700003

History

Received: 2020-07-23

Revised: 2021-02-10

Accepted: 2021-02-10

Online: 2021-02-18

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Cited By (1)

Year	Entry
2022	Ortner L. Comparison of Peri-Implant Loading in Screw-Bone Constructs Predicted by Homogenized and Micro FE Models [Master's thesis]. Vienna University of Technology; May 11, 2022.