Low Level Laser
application to reduce post-operative pain in patients
receiving winograd
type of partial matrixectomy surgery of hallux
Les Jonsson B H Sc (Podiatry). Dip. Podiatry, Dip
Podiatric Surgery, Dip. Soc. Sc. (Psychology). Cert. L.L.T.
Mary Needham, R.G.O.N., Cert., L.L.T.
Introduction
Low level laser was introduced as a part of our surgical
regime to assist with post operative healing following digital surgery. It
was observed that fewer patients returned for post-operative redressings
complaining of post operative pain. A pilot study has been undertaken to
report the level of pain experienced by patients who received a Winograd
type partial matrixectomy of the hallux. To reduce the number of
extraneous variables the surgery was undertaken in the same setting with
the same surgeon and staff with the same operative instructions provided.
Laser Therapy was used within 30minutes of surgery.
Methodology
Each patient was placed on the operating table in the supine
position. The laser probe was placed against the epidermis and applied at
1.8J/cm 2 ,5.7Hz, with wavelength 830 nm and output power 40mW. from a
"Maestro", laser manufactured by Medicom, Praha , Czech Republic . The
probe was applied at 2 points at each surgical site and at one point at
each of the two sites for undertaking the digital anaesthetic block at the
proximal aspect of the great toe. A mixture 5cc of 50/50 2% plain
xylocaine and 0.5% Marcaine was injected dorsal to plantar into the
proximal aspect of the great toe. The feet were prepped and draped in the
normal sterile manner. A partial nail plate avulsion was achieved with
removing 2-3mm of the fibular and/or tibia nail borders. A Betadine scrub
was then undertaken. This was followed with an incision proximal to the
proximal end of the matrix along the course of the new nail edge to the
distal end of the nail. A second incision was made in a semi elliptical
fashion from the proximal end of the first incision along the course of
the original nail border joining with the distal end of the first
incision. Both incisions were made down to bone and all tissue was
removed. Matrix within the cavity was removed. Saline irrigation was
applied to the cavity. The cavity was closed with Proline sutures at
proximal and distal ends with steristrips across the nail section. The
tourniquet was released and blood flow was observed to return to the area.
A dressing of Betadine and Bactagras was applied with 4 x 4 sterile gauze,
followed by gauze bandage and Coban.
Each patient was given oral and written instruction and an
appointment for redressing in 5 to 7 days. Instructions included the
suggestion that the patient take Panadol. Each patient appeared tolerated
the procedure well and left the surgery ambulated.
One returning to the surgery after five to seven days for
redressings, each patient scored on a 10cm Visual Analogue Scale, the
level that best illustrated the highest level of pain that they
experienced following the operation.
Results
Those in the Laser group (N=12) scored an average of 2.1
whereas those in the Non laser group scored an average 7.2 (N=3).
Conclusion
The level of self medication for pain relief was not
monitored and no breakdown of ethnicity, age or sex was recorded for any
patients. The authors note the small number of subjects in this study, in
particularly the “No Laser” group. Given the low pain scores of the laser
group reporting low pain scores, it is expected that these authors will
afford all future eligible patients the opportunity of pre-operative laser
therapy for this and other types of surgery. Other practitioners who do
not use laser, who use like surgical techniques are encouraged to conduct
a similar study on their patients, to make a comparison with the current
study and to report their findings.
PHYSICAL MECHANISMS OF BIOLOGICAL EFFECT OF COHERENT AND
NONCOHERENT LIGHT.
A.N. Rubinov
Stepanov
Institute of Physics
National Academy of Sciences of
Belarus
Skorina Avenue 70, Minsk, Belarus,
e-mail:
Extraordinary
biological action of low intensity laser radiation is well known and
widely used in laser therapy. In spite of a great success in this field
the primary mechanism of laser stimulating effect remains disputable. The
main question to be answered is: whether the observed effects are caused
by absorption of light by some photoreceptors, the excitation of which
starts some chains of biochemical events, or we encounter here with some
other mechanism of interaction of light with biological matter. If the
first is true, i.e. primary interaction of light with biological object is
of pure photochemical nature, then we must find those receptors, study
their properties and look for the light source, which emission is best
overlapped with the absorption band of the receptors. In this case
coherence and polarization of light can not be of importance.
Indeed high coherence of light (i.e. when the phase
of oscillations in electromagnetic wave remains unchanged for a long time)
may be important if the phase of electron oscillations in a substance,
excited by light, is also kept unchanged long enough. Large biomolecules
contain tremendous number of atoms, interaction between which leads to
very fast loss of the electron oscillations phase (during 10-13 sec or
less). Because of this reason high coherence of light is not needed, and
photochemical effects produced by coherent and noncoherent light will be
indistinguishable.
One may use a concept of spectral
properties of light and substance instead of coherence and phase memory.
Then the above statement can be expressed in the following form: as the
spectral absorption bands of organic substances are quite broad (which
means that the phase memory is short) one does not need for exciting a
photochemical reaction the light with very narrow spectral line (coherent
light).
Polarization of light normally is also not
important in photochemical process. It could be important if all (or
majority of) absorbing molecules were oriented in space such a way that
their transition moments happened to be aligned along some preferential
direction. But there is absolutely no reason why the mentioned above
hypothetical photoreceptors would be aligned in a body along one
direction. And for random orientation of photoreceptors in a body the
polarized and nonpolarized light will produce the same effect.
So we may conclude that if the biological effect of
light is based on photochemical processes (i.e. on resonance interaction
of light with absorbing molecules) the coherence and polarization of light
do not play any important role. From this point of view there is no
special reason for using lasers in therapy instead of photodiodes or other
noncoherent light sources. In case of noncoherent light source there is
also no sense in using polarized light.
However
there are enough of data today indicating importance of coherence
(superior qualities of lasers) and polarization at application of light in
therapy [1]. From this follows that there must exist some nonresonant
mechanisms of light interaction with biological matter, which determine
universal action of laser light on a human body. Of course, one can not
deny existence of specific photochemical interactions of light with some
substances in a body (superoxideolis-mutase, catalase, ceruloplasmin,
cytochromes a and a3, cytochromoxidase, endogenic porphyrins, oxygen). But
those specific interactions can hardly explain universal stimulating
biological effect of laser light observed for very wide range of laser
wavelengths.
In case of nonabsorbing medium the
photochemical mechanisms are excluded. Nevertheless light may influence
the properties of such transparent medium. In case of inhomogeneous medium
like a biological one the considerable effect might be caused even at low
intensities of light. Nonresonant action of light on transparent
dielectric objects (for example cells) is based on the interaction of
light induced dipole moments of these objects between themselves or with
the incident light field. Two cases must be distinguished: interaction
with noncoherent and coherent light.
I. Noncoherent light (importance of polarization). Illumination of
particles (cells) with light induces in them oscillations of electrons
which are synchronous for all particles. 
This effect takes place
for both laser and non-laser sources (lamps, photodiodes). If particles
are packed closely enough to each other (as cells in a body) the dipole
moments induced in them interact as is shown in the Fig. 1. As dipole
moments in all particles oscillate synchronously their polarities are kept
identical in respect to each other all time. The result of interaction
strongly depends on light polarization. Both attraction (Fig. 1a) and
repulsion of particles to each other (Fig. 1b) can be realized depending
on orientation of electrical vector of electromagnetic wave relatively the
pair of interacting particles. For linearly polarized light the
orientation of electric field oscillations remains constant which provides
preservation of the type of interaction in time (attraction for the case
of Fig.1a and repulsion in the case of Fig.1b). For circularly polarized
light or nonpolarized light orientation of electrical oscillations in
respect to the particles position changes very fast (from the case of Fig
1a to the case of Fig1b and back). As a result repulsion and attraction
replace each other very quickly and on the average the force of
interaction between particles becomes equal to zero.
So we may make the
first conclusion: noncoherent light may influence ensemble of particles
(biological system) through light induced dipole-dipole interaction.
The effect is realized only for linearly
polarized light and is absent if the incident light is circularly
polarized or nonpolarized.
There is
another possibility of nonresonant action of light on particles – optical
Kerr effect. If polarizability of a particle is anisotropic then the
direction of a dipole moment induced by light in the particle may not
coincide with the direction of electrical vector of light (as is shown in
the Fig.2a). Due to that a torque appears which causes rotation of a
particle until its dipole moment becomes aligned along the electrical
vector of the field (Fig.2b). Linear polarization of the incident light is
also necessary to produce this effect.
In comparison with
the dipole-dipole interaction the optical Kerr effect is less probable at
interaction of low intensity light with biological objects. Because of low
intensity of light, required by biological safety, considerable torque may
appear only for particles of micron scale size. Such large particles
contain large number of electrons whose oscillations are summarized
producing the light induced dipole moment of the whole particle. If the
particle is not a crystal but a biological cell or an organelle then it is
difficult to expect essential anisotropy over the whole volume of a
particle.
So the second conclusion is that in
principle noncoherent light may also act on particles via optical Kerr
effect causing some torque acting on them. The
effect also requires linearly polarized light. But this
mechanism of light action on biological system is less probable in
comparison with dipole-dipole interaction.
Coherent
light.
Both above mechanisms may also act
in case of coherent light. But in addition to that there is a specific
physical mechanism which distinguishes action of laser light on a
biological system from the action of noncoherent one.
The
specific feature of illumination of an object with coherent light is
formation of the so called speckle structure. This is a strong
micron-scale modulation of light intensity, which unavoidably appears at
the surface and in a bulk of optically inhomogeneous medium even at
ideally uniform illumination. Such modulation is a result of the
interference of micro-beams reflected and scattered by heterogeneous
medium (Fig.3).
It is formed only at
illumination of an object with coherent light. The higher degree of the
coherence the higher degree of the intensity modulation in a speckle
structure is observed. At illumination of the same object with noncoherent
light from lamps, photodiodes or so like the speckle structure disappears
and the object appears illuminated uniformly.
Interaction of the speckled light field with
particles leads to appearance of so called gradient forces. The gradient
forces have electric nature and can be easily understood with help of the
Fig. 4.
Let us
assume that some dielectric particle is placed in the homogeneous electric
field. Under the action of the field the particle becomes polarized and
two Coulomb forces acts on separated charges in opposite directions. If
the field is homogeneous the two forces compensate each other, and the
resulting force acting on the particle is equal to zero (Fig. 4a). But if
the electric field is non-uniform and has a gradient along some direction
then Coulomb forces, acting on the particle in the opposite directions, do
not compensate each other any more. In this case the resulting force
(which is called gradient force) is not equal to zero, and drives the
particle towards the stronger field (see Fig. 4b). This is also true for
alternative electric component of electromagnetic wave. The electrons in
the particle follow synchronously oscillations of electric component of
the electromagnetic wave. This is why the resulting force does not change
its direction, in spite of oscillations of electric field in a light wave,
and always points towards the region of the higher field strength (compare
of Figs. 4b and 4c).
From above considerations
follows that if a light field with modulation of intensity in space
(gradient field) is applied to particles, they will be subjected to action
of gradient forces pulling them to the region of maximal intensity. Such
forces are well known in optics and employed in laser tweezers.
Calculations show that at application of low
intensity lasers to a medium at room temperature the gradient forces are
quite important for comparatively large particles whose sizes are of a
micron scale. For small particles like molecules the energy of interaction
connected with gradient forces is much smaller than the thermal energy of
molecules at room temperature, and the action of those forces can be
ignored.
Now we can make another important
conclusion: there is a specific influence of
coherent light on a system of particles (cells in a biological system)
which is based on the action of gradient forces originated by speckle
structure of laser field inside the illuminated object. Polarization of light is also a factor of importance for this mechanism of
action: effect of gradient forces is stronger for linearly polarized light
because in this case the speckle structure of laser field has a higher
contrast.
Theoretical estimation shows that at
typical conditions of illumination of a body with low intensity lasers the
gradient forces plays major role in comparison with the dipole-dipole
interactions.
So finally the above considerations lead us to the
following conclusions:
- Apart from a
photochemical mechanism of light action on biological systems there
exist more universal physical mechanisms based on interactions of light
induced dipole moments of particles between themselves and with
electrical component of light field. Both laser and non-laser light can
produce biological effect via these mechanisms.
- Laser light is the
most efficient at action on biological systems. At that linearly
polarized laser light is expected to produce better effect than
nonpolarized or circularly polarized one.
- Non-laser light
can also produce biological action but of smaller efficiency than the
laser one and only in case if it is linearly polarized.
The
action of gradient laser fields on particle ensembles and biological
systems was considered in [2]. In particular it was shown that action of
gradient laser fields on micron scale particles (cells, organelles large
biomolecules) may influence biological processes through the following
processes:
- change of local
concentration and spatial orientation of particles;
- change of composition of
particles of different type;
- selective increase of the
partial temperature for larger particles;
- small reversible
distortions of particles structure (cellular massage);
- stimulation of
conformational changes in enzymes and other
structures.
Fig. 5 illustrates action of
gradient forces on 6 ? plastic particles in water illuminated by the
interference field of He-Ne laser. One can see that under the action of
gradient laser field all particles are gathered at the maximums of laser
intensity. So the laser field here causes change of local concentration of
particles.
Fig. 6 shows effect of
spatial orientation of particles by a gradient field of Ar-laser. Two
erythrocytes which at the first moment happened to be oriented by their
long sides across the interference fringes (created by interference of two
laser beams) some minutes later became oriented along the fringes.
Fig. 7 demonstrates
splitting of erythrocyte rouleau by the interference field of Ar-laser.
Uniform illumination of an erythrocyte rouleau with a single beam of the
laser does not cause any change in its structure. But as soon as the
interference structure is created (by switching on the second laser beam)
the rouleau is immediately split into separate red blood cells.
There
are also other experiments described in [2] which prove essential
influence of gradient laser fields on some fundamental processes in a
cell.
References
1. J Tunér and
L Hode, "Laser Therapy. Clinical; practice and scientific background",
Prima Books AB, 2002
2. A.N. Rubinov, J. Phys D: Appl. Phys. 36 (2003)
2317-2330.
Captions to
figures
Fig.1. Interaction of dipole
moments induced by light in neighboring particles.
a) – particles
attract each other when electrical vector of light E is parallel to the
line connecting the particles; b) - particles repel each other when
electrical vector of light E is perpendicular to the line connecting the
particles;
Fig.2. Rotation of the
particle characterized by anisotropic polarizability under action of
linearly polarized light. a) – the torque acts on a particle because the
light induced dipole moment P does not coincide with the direction of the
electrical vector E of the light field. b) – particle is aligned with its
dipole moment P along the electrical vector E under action of the torque.
Fig.3. Interaction of
reflected and scattered micro-beams in an inhomogeneous medium, which
causes appearance of speckles of a laser field in the medium.
Fig.4. Polarization of a
dielectric particle under action of uniform (a) and not uniform (b, c)
electric field; b) and c) show that at change of the electric field sign
the direction of the gradient force does not change.
Fig.5. Trapping of 6 ?
plastic particles in water under action of gradient forces in the
interference field of a He-Ne laser; a) – random distribution of particles
at illumination by a single laser beam. b) – distribution of the particles
in the fringes of the two beam interference laser field.
Fig.6. Aligning of
erythrocytes under action of gradient forces in the interference fringes
of Ar laser; a) – the first moment after the interference field has been
switched on; b) – several minutes later – both erythrocytes have oriented
themselves along the interference fringes.
Fig.7. Splitting of the
erythrocyte rouleau under the action of gradient forces of the Ar-laser
interference field; a) an erythrocyte rouleau illuminated by a single
laser beam; b) – splitting of the rouleau into separate erythrocytes at
switching on the interference field.
