Micro-CT and micro-FE analysis of pedicle screw fixation under different loading conditions

Anchorage of pedicle screw instrumentation in the elderly spine with poor bone quality remains challenging. In this study, micro finite element (µFE) models were used to assess the specific influence of screw design and the relative contribution of local bone density to fixation mechanics. These wer...

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Bibliographic Details
Published in:Journal of biomechanics 2018-03, Vol.70, p.204-211
Main Authors: Chevalier, Y., Matsuura, M., Krüger, S., Fleege, C., Rickert, M., Rauschmann, M., Schilling, C.
Format: Article
Language:English
Subjects:
Biomechanics
Bone density
Bone implants
Bones
Cancellous bone
Computed tomography
Computer simulation
Concentration (composition)
Finite element method
Fixation
Geriatrics
Loading
Mathematical models
Micro finite element analysis
Micro-CT
Older people
Pedicle screw
Pedicle screws
Pull-out
Quality
Radius
Screws
Spine
Stiffness
Tomography
Torsion
Vertebrae
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Summary:Anchorage of pedicle screw instrumentation in the elderly spine with poor bone quality remains challenging. In this study, micro finite element (µFE) models were used to assess the specific influence of screw design and the relative contribution of local bone density to fixation mechanics. These were created from micro computer tomography (µCT) scans of vertebras implanted with two types of pedicle screws, including a full region-or-interest of 10 mm radius around each screw, as well as submodels for the pedicle and inner trabecular bone of the vertebral body. The local bone volume fraction (BV/TV) calculated from the µCT scans around different regions of the screw (pedicle, inner trabecular region of the vertebral body) were then related to the predicted stiffness in simulated pull-out tests as well as to the experimental pull-out and torsional fixation properties mechanically measured on the corresponding specimens. Results show that predicted stiffness correlated excellently with experimental pull-out strength (R2 > 0.92, p 
ISSN:0021-9290
1873-2380
DOI:10.1016/j.jbiomech.2017.12.023