Elsevier

Clinical Biomechanics

Volume 68, August 2019, Pages 137-143
Clinical Biomechanics

The effect of boundary and loading conditions on patient classification using finite element predicted risk of fracture

https://doi.org/10.1016/j.clinbiomech.2019.06.004Get rights and content
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open access

Highlights

  • Full range of falls is important for an accurate classification of patients.

  • Nonlinear boundary constraint can improve the stratification power.

  • Nonlinear boundary constraint can improve the predicted high strains locations.

  • Boundary constraint has a considerable effect on the predicted strength.

Abstract

Background

Osteoporotic proximal femoral fractures associated to falls are a major health burden in the ageing society. Recently, bone strength estimated by finite element models emerged as a feasible alternative to areal bone mineral density as a predictor of fracture risk. However, previous studies showed that the accuracy of patients' classification under their risk of fracture using finite element strength when simulating posterolateral falls is only marginally better than that of areal bone mineral density. Patients tend to fall in various directions: since the predicted strength is sensitive to the fall direction, a prediction based on certain fall directions might not be fully representative of the physical event. Hence, side fall boundary conditions may not be completely representing the physical event.

Methods

The effect of different side fall boundary and loading conditions on a retrospective cohort of 98 postmenopausal women was evaluated to test models' ability to discriminate fracture and control cases. Three different boundary conditions (Linear, Multi-point constraints and Contact model) were investigated under various anterolateral and posterolateral falls.

Findings

The stratification power estimated by the area under the receiver operating characteristic curve was highest for Contact model (0.82), followed by Multi-point constraints and Linear models with 0.80. Both Contact and MPC models predicted high strains in various locations of the proximal femur including the greater trochanter, which has rarely reported previously.

Interpretation

A full range of fall directions and less restrictive displacement constraints can improve the finite element strength ability to classify patients under their risk of fracture.

Keywords

Finite element analysis
Side fall
Bone strength
Hip fracture

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