Effect of different femur shapes on the development of cam-type deformities

The development of a combined bone growth and remodeling algorithm to investigate the effect of different femur shapes generated by a SSAM on the development of cam-type deformities

Master thesis (2021)

Authors

N.H.A. Rutten Mechanical Engineering

Contributors

A.A. Zadpoor Biomaterials & Tissue Biomechanics - Mechanical, Maritime and Materials Engineering (supervisor 1)
N. Tümer Biomaterials & Tissue Biomechanics - Mechanical, Maritime and Materials Engineering (supervisor 2)
Faculty
Mechanical Engineering
Copyright: © 2021 Niek Rutten
Computational modelling Femur Bone adaptation Bone growth SSAM Statistical shape and appearance model FEM simulation Cam deformities
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Published Date

09-09-2021

Language

English

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Faculty

Mechanical Engineering

Abstract

Introduction: A combined bone growth and remodeling model should be created, to investigate the effect of different femur shapes on the risk of developing cam type deformities. The different femur shapes needed for this study can be created using a statistical shape and appearance model (SSAM). The workflow of the combined bone growth and remodeling model has been (semi)-automated for increased efficiency and other future uses. Methods: An algorithm was created that leads the user through a (semi)-automated workflow, where the necessary features are added to the simulation. The model uses remodeling and growth simulations in sequence to estimate both the change in density distribution and in shape. The used loading conditions correspond to the 10% gait cycle phase. The remodeling is driven by strain energy density, and the growth by the osteogenic index. Results: The resulting density distributions are similar to those found in other studies, while the growth model predicts larger changes in the neck-axis angle than other studies. The growth was also predicted for two MRI pilot scans and the predicted growth was similar to the growth found in follow up scans of the same children. To investigate the influence of the bone shape on the development on cam-deformities, three different shape modes were varied and their influence on the osteogenic index in the growth plate was analyzed. The results from this study indicate that an increased femoral neck-axis angle increase the growth stimulation in the cam region of the growth plate. Discussion: The created bone adaptation model performs mostly as expected, only the included growth model occasionally performs unreliably. To improve its reliability, recommendations have been given to improve its behaviour. Because of the increased growth stimulation in the cam region of the growth plate, the results indicate that femurs with a large neck-axis angle have an increased risk of developing cam type deformities. The effect of other shape characteristics is unclear, and more research is recommended to investigate the effect of other characteristics, such as the femoral anteversion.