Finite element analyses of human vertebral bodies embedded in polymethylmethalcrylate or loaded via the hyperelastic intervertebral disc models provide equivalent predictions of experimental strength

Journal
Journal of biomechanics  
Volume
47
Issue
10
Start Page
2512
End Page
2516
Citation
Journal of Biomechanics 47 (10): 2512-2516 (2014)
Publisher DOI
10.1016/j.jbiomech.2014.04.015
Scopus ID
2-s2.0-84902179231
PubMed ID
24818795
Publisher
Elsevier Science
Quantitative computer tomography (QCT)-based finite element (FE) models of vertebral body provide better prediction of vertebral strength than dual energy X-ray absorptiometry. However, most models were validated against compression of vertebral bodies with endplates embedded in polymethylmethalcrylate (PMMA). Yet, loading being as important as bone density, the absence of intervertebral disc (IVD) affects the strength. Accordingly, the aim was to assess the strength predictions of the classic FE models (vertebral body embedded) against the in vitro and in silico strengths of vertebral bodies loaded via IVDs. High resolution peripheral QCT (HR-pQCT) were performed on 13 segments (T11/T12/L1). T11 and L1 were augmented with PMMA and the samples were tested under a 4° wedge compression until failure of T12. Specimen-specific model was generated for each T12 from the HR-pQCT data. Two FE sets were created: FE-PMMA refers to the classical vertebral body embedded model under axial compression; FE-IVD to their loading via hyperelastic IVD model under the wedge compression as conducted experimentally. Results showed that FE-PMMA models overestimated the experimental strength and their strength prediction was satisfactory considering the different experimental set-up. On the other hand, the FE-IVD models did not prove significantly better (Exp/FE-PMMA: R =0.68; Exp/FE-IVD: R =0.71, p=0.84). In conclusion, FE-PMMA correlates well with in vitro strength of human vertebral bodies loaded via real IVDs and FE-IVD with hyperelastic IVDs do not significantly improve this correlation. Therefore, it seems not worth adding the IVDs to vertebral body models until fully validated patient-specific IVD models become available.
Subjects
Failure strength
Finite element prediction
Human vertebra
Intervertebral disc
Mechanical testing
DDC Class
000: Allgemeines, Wissenschaft
570: Biowissenschaften, Biologie
610: Medizin
Funding Organisations
Bundesministerium für Bildung und Forschung
Swiss National Science Foundation (SNF)
More Funding Information
This work was supported by the German Federal Ministry of Education and Research (BMBF) under Grant 01EC1005 and by the Swiss National Science Foundation (SNF), grant no. 483 325230_147153.