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Pulsed Magnetic Field Therapy The use of Magnetic
Fields to aid the healing of bones has been long practised with good results,
particularly when applied to non-unions. The FDA in America approved the use of
PMFT in the treatment of fractures and non-union fractures in 1979. It is a
non-invasive therapy which induces low frequency electrical currents in bone.
The whole subject of magnetic fields is extensive and a deep study is beyond
the scope of this synopsis. However, there are some readily understandable
concepts. Pulsed magnet field therapy (PMFT), sometimes referred to as pulsed
electro-magnetic field therapy (PEMFT) is defined in the treatment of fractures
as the application of time-varying magnetic fields that induce voltage
wave-form patterns in bone similar to those resulting from weight bearing and
mechanical deformation. The electrical voltage is induced at right angles to
the pulsed or dynamic magnetic field. This is termed electro-magnetic
induction. The strength of the magnetic field in clinical applications is from
30 gauss (30G) to as much as 1000G - the earth's magnetic field in comparison
is in the region of 0.5G - and a frequency range of 1Hz to about 200 Hz is
typically used. All the studies quoted here are regarding pulsed magnetic
fields and NOT static magnetic fields. The main requirement is that there is
some dynamic interaction i.e. relative movement between the field and target
tissue. In long bones, the marrow produces DNA -bearing immature blood cells
which transform to become bone. Under normal conditions, therefore, the healing
of fractures takes the form of regeneration as opposed to repair. Magnetic
fields will penetrate virtually everything so a POP or Baycast cast is no
obstacle to treatment with this modality. The physiotherapist would need to
mark the approximate area of the fracture, referring to the X-rays for
guidance.
Gossling et al in a literature review in 1992 concluded that PMFT was at
least as effective as surgery in cases of non-union with an overall success
rate of 81% against 82% for surgery, although infected non-unions showed a
success rate of 81% with PMFT against 69% for surgery.
Basset et al in 1982 researched results in treating ununited fractures and
failed arthrodeses with PMFT. In a large group of patients with an average of
4.7 years non-union, 3.4 previous surgical failures and a 35% infection rate,
bony healing took place in 75% of the patients treated with PMFT.
Pulsed Laser Therapy "Laser" stands for
Light Amplification by Stimulated Emission of Radiation. The main differences
between Laser light and high-intensity light is that Lasers emit a coherent
beam i.e. all photons are in phase and synchronised, the light is monochromatic
i.e. one single, very specific wavelength and the Laser is applied with a
specific dosage in mind, usually measured in Joules per square centimetre. Some
Lasers are used in contact with, or very close to, skin and usually have an
optical lens giving a divergent beam, frequently in the region of 6 degrees,
while some more powerful Lasers emit a non-divergent beam which can scan along
easily set parameters along X and Y axes to cover a larger area. The use of a
non-divergent beam means that the inverse square law does not apply although
clearly it does in the case of the 6 degree divergent beams.
The usual therapeutic wavelengths are in the far red to near infra- red
(FR/NIR) wavelengths, ranging from about 600nm (visible red) to 1000nm
non-visible infra-red). Most therapeutic Lasers typically have outputs ranging
from 5mW (0.05W) to 1000mW (1.0W) and treatment times can vary from mere
seconds to several minutes. Some more powerful scanning Lasers such as those
used in this clinic can deliver 3W, non-divergent, continuous output and have
the capability to produce a thermal burn if applied inappropriately. Some
research studies indicate tissue response may be dose dependent as well as
being dependent on the irradiation time and irradiation mode. Dickson et al
showed a 300% increase in ALP ( alkaline phosphatase) expression in rat femoral
fractures irradiated at 10-15 J/cm2 using a 820-830nm laser. Alkaline
phosphates levels indicate bone-forming cell (osteoblast) activity. The main
effect is photo-chemical and not thermic. Photon irradiation by light in the
FR/NIR spectral range has been found to modulate various biological processes
in cell culture and animal models. The mechanism of photo-bio-modulation by
FR/NIR at the cellular level has been ascribed to the activation of
mitochondrial respiratory chain components. Growing evidence suggests that
cytochrome oxidase is a key photo-acceptor of light in the FR/NIR spectral
range. Cytochrome oxidase is an integral membrane protein having a strong
absorbance in the FR/NIR spectral range, detectable in vivo by NIR
spectroscopy.
Far red cellular irradiation has been shown to increase electron transfer in
cytochrome oxidase, increase levels of mitochondrial respiration and ATP
synthesis in isolated mitochondria and also to up-regulate cytochrome oxidase
activity in cultured neuronal cells.
This photo-stimulation also induces a cascade of signalling events such as
activation of immediate early genes, transcription factors, cytochrome oxidase
subunit gene expression as well as other enzymes and pathways related to
increased oxidative metabolism.
Photo-stimulation of mitochondrial electron transfer is known to increase
the generation of reactive oxygen species which may function as signalling
molecules to provide communication between mitochondria and cytosol and
nucleus.
Yaakobi and Oron showed that osteoblast/osteoclast population was altered by
a 120% increase in ALP and 40% reduction in TRAP in the rat tibia. TRAP
(tartarate-resistant acid phosphatase) is an indicator of bone-absorbing cell
(osteoclast) activity. Histomorphometric analysis showed volume fraction of new
reparative compact bone in the irradiated animals as being 27+/- 9% against
9+/- 7% at 10 days, 88+/-9% against 44+/-9% at 13 days and 94+/- 6% against
58+/-5% at 15 days. The wavelength used in this study was in the far red
spectrum of 630-640nm.
Khadra et al investigated the weight percentages of calcium and phosphorus
in rabbit tibial bone irradiated by an 810nm GaAlAs laser. These were found to
be higher in the irradiated group compared to the control group with P=0.037
for calcium and P=0.034 for phosphorus, suggesting bone matured faster in the
irradiated group.
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