Subject-specific finite element models implementing a maximum principal strain criterion are able to estimate failure risk and fracture location on human femurs tested in vitro

ABSTRACT Objective: To investigate the most reliable stress or strain parameters in subject-specific finite element (FE) models to predict success or failure of orthodontic mini-implants (OMIs). Materials and Methods: Subject-specific FE analysis was applied to 28 OMIs used for anchorage. Each model was developed using two computed tomography data sets, the first taken before OMI placement and the second taken immediately after placement. Of the 28 OMIs, 6 failed during the first 5 months, and 22 were successful. The bone compartment was divided into four zones in the FE models, and peak stress and strain parameters were calculated for each. Logistic regression of the failure (vs success) of OMIs on the stress and strain parameters in the models was conducted to verify the ability of these parameters to predict OMI failure. Results: Failure was significantly dependent on principal strain parameters rather than stress parameters. Peak maximum principal strain in the bone 0.5 to 1 mm from the OMI surface was the best predictor of failure (R2 = 0.8151). Conclusions: We propose the use of the maximum principal strain as a criterion for predicting OMI failure in FE models.

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Subject-specific finite element models of long bones: An in vitro evaluation of the overall accuracy

Journal of Biomechanics ◽

10.1016/j.jbiomech.2005.07.018 ◽

2006 ◽

Vol 39 (13) ◽

pp. 2457-2467 ◽

Cited By ~ 171

Author(s):

Fulvia Taddei ◽

Luca Cristofolini ◽

Saulo Martelli ◽

H.S. Gill ◽

Marco Viceconti

Keyword(s):

Finite Element ◽

Finite Element Models ◽

Long Bones ◽

In Vitro Evaluation ◽

Subject Specific

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Subject-Specific Inverse Dynamics of the Head and Cervical Spine During in Vivo Dynamic Flexion-Extension

Journal of Biomechanical Engineering ◽

10.1115/1.4023524 ◽

2013 ◽

Vol 135 (6) ◽

Cited By ~ 7

Author(s):

William J. Anderst ◽

William F. Donaldson ◽

Joon Y. Lee ◽

James D. Kang

Keyword(s):

Finite Element ◽

Cervical Spine ◽

Inverse Dynamics ◽

Total Force ◽

Finite Element Models ◽

Moment Arms ◽

Flexion Extension ◽

Subject Specific

The effects of degeneration and surgery on cervical spine mechanics are commonly evaluated through in vitro testing and finite element models derived from these tests. The objectives of the current study were to estimate the load applied to the C2 vertebra during in vivo functional flexion-extension and to evaluate the effects of anterior cervical arthrodesis on spine kinetics. Spine and head kinematics from 16 subjects (six arthrodesis patients and ten asymptomatic controls) were determined during functional flexion-extension using dynamic stereo X-ray and conventional reflective markers. Subject-specific inverse dynamics models, including three flexor muscles and four extensor muscles attached to the skull, estimated the force applied to C2. Total force applied to C2 was not significantly different between arthrodesis and control groups at any 10 deg increment of head flexion-extension (all p values ≥ 0.937). Forces applied to C2 were smallest in the neutral position, increased slowly with flexion, and increased rapidly with extension. Muscle moment arms changed significantly during flexion-extension, and were dependent upon the direction of head motion. The results suggest that in vitro protocols and finite element models that apply constant loads to C2 do not accurately represent in vivo cervical spine kinetics.

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