Biomedical Engineering Reference
In-Depth Information
of mechanical loading on bone remodeling, further understanding of the
underlying mechanism is needed.
Pulsed electromagnetic fields (EMFs) have been widely used for the
treatment of non-united fractures and congenital pseudarthrosis. Several
electrical stimulation systems, such as air-cored and iron-cored coils and
solenoids, have been used around the world and claimed to be effective.
Electrical parameters such as pulse shape, magnitude, and frequency
differ widely, and the exact bone-healing mechanism is still not clearly
understood. The application of EMF devices to stimulate osteogenesis is
based on the idea of exciting the natural endogenous streaming potentials
in bones. In the beginning, an electric current is applied directly onto dis-
eased bone via electrodes, and then a periodic wave is produced by forc-
ing electric current through a wire coil placed over the fracture. Periodic
changes of the current then produce the required EMF in bone through
Faraday induction.
The most effective medical devices used today are time-dependent EMF,
especially pulsed EMF (PEMF). Their frequency range is 1-100 Hz. The phys-
iological frequency ranges from 8 to 30 Hz, which is caused by natural mus-
cle contraction. The subsequently induced EMF in bone tissue is mostly used
in clinical therapies. The osteogenesis effect caused by a PEMF device is of
great significance to patients, especially those who have already undergone
failed surgical intervention [26].
Based on random and prospective clinical studies, the US Food and Drug
Administration (FDA) has approved PEMF as a safe and effective way to treat
non-union and osteoporosis diseases [27,28], although the specific molecular
mechanism is not yet fully understood.
In summary, the current understanding of bone remodeling is primarily
based on experimental results in vivo and in vitro. A great deal of research
has been conducted on the interactions of autocrine, paracrine, and endo-
crine activities of receptors and ligands in bone remodeling; the role of
bone cells involved in this process at the cellular and genetic level; and the
influence of different stimuli and factors such as mechanical stimuli, PEMF,
and PTH on bone formation in bone remodeling. Based on these observa-
tions, many hypotheses have been proposed as to the role played by differ-
ent signaling pathways and the communication between bone cells in bone
remodeling. However, due to the complexity of the bone regulation system,
which involves numerous factors and interactions, understanding of system
behavior is still fragmentary.
Mathematical modeling is a powerful tool for reducing ambiguity as to
causes and effects in complex systems. It allows one to test various experi-
mental and theoretical hypotheses that might be difficult (such as time- or
money consuming) or impossible to test in vivo or in vitro. The development
of a pharmaceutical treatment for bone diseases can also be enhanced by
computational system biology that uses mathematical modeling to integrate
experimental data into a system-level model, enabling various interactions
