Biomedical Engineering Reference
In-Depth Information
A Mechanically Stimulated Fracture Healing
Model Using a Finite Element Framework
Alexander Sapotnick and Udo Nackenhorst
Abstract
In this work a biochemical fracture healing model coupled with mechan-
ical stimulation of stem cell differentiation is investigated. A finite element scheme
is applied to the underlaying advection-diffusion-reaction problem, using the Time
Discontinuous Galerkin and Finite Calculus method to ensure stability of the calcu-
lation. Strains within the callus region are computed and used for a characterization
of the local mechanical demand and the resulting stimulation of the healing process.
A theoretical axisymmetric model of a sheep osteotomy is implemented and results
of the presented FEMapproach are discussed. The repair progress will be determined
by the interfragmentary movement (IFM) and the mean tissue densities.
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Keywords
Fracture healing
Bone repair
Biomechanics
Finite element
1 Introduction
The process of fracture healing, if successful, is a well-orchestrated biochemical
response to the injury of the bone. Cells, mesenchymal stem cells in particular, are
recruited from the surrounding tissue and are stimulated to produce new tissues in
the callus region. The effect is a subsequent stabilisation and vascularization of the
fracture site, until the normal load bearing capacity of the bone is regained. Growth
factors play a major role in controlling the cell activities. They serve as attractants,
drawing cells to locations of high growth factor concentration and stimulate stem cell
differentiation. Additionally, the mechanical demand on the callus area influences
the cellular functions. Exposure to high loads, premature or inappropriate loading
inhibits bone growth and re-vascularization.
Typically, the process from the occurrence of the fracture to the bridging of
the fracture gap and re-establishing of the load bearing capacity of the bone takes
