Note: Descriptions are shown in the official language in which they were submitted.
3 ~ ~
This application is a divisional of copending Canadian Patent
application serial No. 357,039 filed on July 25, 1980 in the name of Electro-
Biology, Inc.
This invention relates to the treatment of living tissues and/or
cells by altering their interaction with the charged species in their
environment. In particular, the inven~ion relates to a controlled modification
of cellular and/or tissue growth, repair and maintenance behavior by the
application of encoded electrical information. Still more particularly, this
invention provides for the application by a surgically non-invasive direct
inductive coupling, of one or more elec~rical voltage and concomitant current
signals conforming to a highly specific pattern.
Several attempts have been made in the past to elicit a response
of living tissue to electrical signals.
Investigations have been conducted involving the use of direct
current, alternating current, and pulsed signals of single and double polarity.
Invasive treatments involving the use of implanted electrodes have been
followed, as well as non-invasive techniques utilizing electrostatic and
electromagnetic fields. Much of the prior work that has been done is described
in Volume 238 of the Annals of The New York Academy of Sciences published 11
October 1974 and entitled "Electrically Mediated Growth Mechanisms in Living
Systems" (Editors A. R. Liboff and R. A. Rinaldi). See also "Augmentation of
Bone Repair by Inductively Coupled Electromagnetic Fields" by C. Andrew L.
Bassett, Robert J. Pawluk and Arthur A. Pilla published in Volume 184, pages
575-577 of Science ~3 May 1974).
The invention herein is based upon basic cellular studies and
1 - r~
6 ~ 1 ~
analyses which involve a detailed consideration of the interactions of charged
species, such as divalent cations and hormones at a cell's interfaces and
junctions.
Basically, it has been established that, by changing the electrical
and/or electrochemical environment of a living cell and/or tissue, a
modification, often a beneficial therapeutic effect, of the growth, repair and
maintenance behavior of said tissue and/or cells can be achieved. This
modification or effect is carried out by subjecting the desired area of tissues
and/or cells to a specifically encoded electrical voltage and concomitant
current, whereby the interactions of charged species at the cells' surfaces
are modified. Such modifications engender a change in the state or f~mction ~`
of the cell or tissue which may result in a beneficial influence on the
treated site. For example, in the specific case of bone growth and repair, it
is possible with one electrical code, hereinafter referred to as Mode 1, to
change the interaction of the ion such as Ca2 with a cell's membranes.
Whereas, with another electrical code, hereinafter referred to as Mode 2, a
modification in the same cell's protein-synthesis capabilities can be a:Efected.
For example, tissue-culture experiments involving the study o~
embryonic chick-limb rudiments show that the use of a Mode 1 code signal
elicits enchanced Ca2 release of up to 50% from the competent osteogenic cell.
This effect is highly specific to the parameters of the electrical code of
Mode 1. Thus, this code influences one major step of ossification, i.e., the
mineralization of a bone-growth site. Similar tissue-culture studies using
Mode 2 code signals have demonstrated that this code is responsible for
enhanced protein production from similar competent osteogenic cells. This
latter effect is also highly specific to the parameters of the electrical code
. .~i, ~., .
., ' ~
1 1663 1 ~
of Mode 2. In other words, this code affects certain metabolic processes for
these types of cells such as those involved in calcium uptake or release
from mitochrondria as well as the syn~hesis of collagen, a basic structural
protein of bone.
These studies show that the electrical codes of Mode 1 and Mode 2
elicit individual tissue and cellular responses, indicating that each code
contains a highly specific informational content therein. Based upon these
and other studies, it has been possible to utilize Mode 1 or Mode 2 signals or a
particular combination of Mode 1 and Mode 2 signals to achieve a specific
response required to enable the functional healing of a bone disorder. These
electrical modes have been applied successfully to human and animal patients
for non-healing fractures such as congenital pseudarthrosis and non-unions as
well as fresh fractures. Successes achieved in the congenital pseudarthrosis
cases are particularly noteworthy, since normally 80% oE children thus
afflicted require amputation, since conventional treatments such as bone
grafting and internal fixation are unsuccessful.
While there have been many investigations in the past of the
response of living tissues and/or cells to 01ectrical signals, clinical
results to date using prior techniques have not been uniformly successful or
generally accepted withln the appropriate professional community. Several
reasons con~ribute to this state. First, it has not been realized heretofore
that electrical signals of very specific informational content are required
to achieve a spejcifically desired beneficial clinical effect on tissue and/or
cells. Second, most of the prior techniques utilize implanted electrodes,
which by virtue of unavoidable faradaic ~electrolysis) effects are often more
toxic than beneficial in the treated site. Furthermore, the cells and/or
3 :1 ~
tissues are subjected to a highly uncontrolled current and/or voltage
d;stribution, thereby co~promising the ability of the cells to respond, should
they do so, to the applied signal. This highly uncontrolled current and/or
voltage distribution also applies in the case of capacitatively coupled
signals.
In contrast, the surgically non-invasive direct inductive coupling
of electrical i~formational content of specific electrical codes as involved
in the present invention produces within living tissue and/or cells a
controlled response.
In brief~ the present invention involves the recognition that the
growth, repair and maintenance behavior of living tissues and/or cells can be
modified beneficially by the application thereto of a specific electrical
information. This is achieved by applying pulse waveforms of voltage and
concomitant current of specific time~frequency-amplitude relations to tissue
and/or cells by a surgically non-invasive means through use of a varying
electromagnetic field which is incluctively coupled through direct induction
into or upon the tissue and/or cells under treatment. The information
furnished to the cells and/or tissues by these signals is designed to
influence the behaviour of non-excitable cells such as those involved in
tissue growth, repair, and maintenance. These growth, repair and maintenance
phenomena are substantially different from those involved in excitable cellular
activity (e.g., nerves, muscles, etc.)~ particularly with respect to the type
of perturbation required. Thus, the voltages and concomitant currents
impressed on the cells and/or tissues are at least three orders of magnitude
lower than those required to effect cellular activities such as cardiac pacing,
bladder control, etc.
11~631~
The invention and that of copending Canadian Patent application
serial No.357,039 will now be described in greater detail with reference to
the accompanying drawings, in which:
Figure 1 is a simplified view showing the treatment of a bone
in accordance with the invention;
Figure 2 is a perspective view of the treatment unit shown in
Figure l;
Figure 3 is a view ~from the rear) of the unit shown in Figure 2,
showing the positioning of a coil therein used for treatment purposes;
Figure ~ is a block diagram of an electrical system for energizing
the coil shown in Figure 3 for Mode 1 treatment;
Figure 5 is a block diagram of an electrical system for energizing
the coil shown in Figure 3 for Mode 2 treatment;
Figures5a and 5b are pulse waveform diagrams for Mode 1 and Mode 2
treatments, respectively, showing presently preferred pulses as induced in
living tissues and cells;
Figure 6 shows alternative forms of negative pulse portions for
Mode 2 treatment;
Figure 7 is a front view of a body-treatment device, being an
em~odiment in substitution for that of Figure 1, and shown unfolded, in
readiness for wrapped application to an afflicted body region;
Figure 7A is a sectional view, taken at 7A-7A of Figure 7;
Figure 8 is a perspective view of a locating element for use with
the device of Figure 7;
Figure 9 is a simplified schematic illustration of a method of use
of the device and element of Figures 7 and 8;
Figure 10 is a simplified right-sectional view through a body-limb
3 ~ ~
cast to which the device and element of Figures 7 and 8 have been applied;
Figures 11 and 12 are simplified views in perspective showing
further body-treatment devices, for particular purposes;
Figure 13 is a diagram to illuminate discussion of dual-coil
placement considerations;
Figures 14, 15 and 16 are similar pairs of views a and _,
respectively schematically representing front and side elevational views for
each of three different generally elliptical dual-coil configurations; and
Figures 17 to 20, appearing on the same drawing sheet as Figure 11,
are views similar to Figures 11 and 12 to show coil arrangements for further
body treatment devices.
DETAILED DESCRIPTION
Referring to Figures 1 to 3, the leg 10 of a person having a broken
bone, as indicated as at 12, is shown as representative of the application of
the invention to the stimulation of bone growth for healing purposes. A
treatment head 14 is positioned outside tha skin oE the person, and is held
in place by use of a strap 16 (secured to head 14 by fasteners 16a) which may
include ~elcro material 18 thereon so that the strap may be wrapped about the
leg and about the treatment head to maintain the treatment head in position
against the leg. The treatment head 14 may include a foam material 20 on the
inside surface thereof for the purpose of cushioning and ventilating the
treatment head against the leg. It will be noted ~hat the treatment head 14 is
generally curved OII the anterior surface thereof so that it conforms to the
shape of the leg under treatment
The treatment head 14 includes therein a coil 22 which may be of
any suitable shape. As shown in Figure 3 the coil 22 is generally rectangular
* Trade Mark
- 6 -
'.
1 ~i63 1 ~
in shape so as to define a "window" within the interior portion of the turns
of the coil. The coil 22, may lie in a plane or it may generally be curved to
conform to the curvature of the treatment head 14. The coil 22 includes
terminals 24 which extend away from the treatment head 14 to be coupled to
a cable 26 for connection to a suitable energizing circuit, as will be
explained below in more detail. A diode 27 may be included within the cable
26 for connection across the coil 22 as will also be explained below.
The treatment head 14 is positioned on the patient so that the
"window" formed by the coil 22 is adjacent the break 12, i.e., adjacent the
tissue under treatment. The coil 22 is energized, as will be explained in more
detail below, and induces an electrical potential within the tissue under
treatment. It has been found that a particular type of signal should be
induced within the tissue and this is achieved by energizing the coil 22 by a
circuit, such as shown in Figure 4 or Figure 5, to produce the pulse signal
shown in Figure Sa or Figure 5b.
Referring to Figure 4, a variable dc supply 30 is coupled through
a gate 32 to the treatment coil 22 (or coilsJ as the case may be, and as will be
explained in more detail below). ~he gate 32 is under the control of control
units 34 and 36 which cause a pulse signal consisting of repe*itive pulses of
electrical potential to be applied to the treatment coil 22. Each pulse, as
shown in Figure 5a, is composed of a "positive" pulse portion Pl followed by
"negative" pulse portion P2 because of the stored electrical energy within
the treatment coil. In the circuit of Figure 4, a diode clamping unit 38
may be employed to limit the pea~ potential of that negative pulse portion. ~he
diode clamping unit 38 may be one or more diodes connected across the coil 22,
-- 7 --
:iL16~3~ ~
and may be advantageously located within ~he cable 26. The diode 27 shown in
Figure 1 constitutes such a clamping unit 38.
In Figure 5a, the signals at the treatment coil 22 and hence the
induced signal within the tissue to be treated are shown. At time tl, it is
assumed that gate 32 is gated on by an appropriate signal from control unit
36 ~designated a pulse width control unit) so that the electrical potential
across the treatment coil 22 is raised from about zero volts along pulse
segment 39 to a potential designated vl in Figure 5a. The signal across the
treatment coil decays in a second pulse segment along the portion of the curve
designated 4~ in Figure 5a. The slope of that curve is determined by the L/R
time constant of the circuit of Figure 4, i.e., the inductance of the treatment
coil and the effective resistance of the circuit, including distributed
factors of capacitance, inductance and resistance. For treatment of many
tissues and cells~ it is believed desirable to adjust the circuit parameters so
that the portion 40 of the curve is as flat as possible, rendering the signal
applied to the treatment coil 22 as rectangular in shape as possible. At the
time t2, the gate 32 is gated off by the control unit 36. Just prior to being
gated off, the signal across the treatment coil is at the potential v2 shown
in Figure 5a. The potential across the treatment coil drops from the level v2
in a third pulse segment 41 to a potential of opposite polarity designated
v3 in Figure 5a. The magnitude of the opposite polarity potential v3 may be
limited by the diode clamping unit 38 to a relatively small value as compared
with value vl. The signal across the treatment coil 22 then decays from the
potential level v3 to the zero or reference potential level, finally
effectively reaching that level at time t3. A predetermined period passes
~ _ :
l~66~la
before the pulse-repetition rate control unit 34 generates an appropriate
timing signal to trigger the control unit 36 to generate a signal to turn gate
32 on again ~o continue the cycle just explained.
The control units may typically be monostable multi-vibrators,
e.g., to generate appropriate timing signals and which may be variable to
control pulse duration and repetition rate within desired limits. Further,
the use of a variable dc supply 30 permits variation of the amplitude of the
pulse signal as desired.
When pulse-train operation ~ode 2) is employed, additional timing
circuitry similar to units 34 and 36 in Figure 4 is employed to provide the
burst-segment width and the burst-segment repetition rate. Referring to
Figure 5, control units 35 and 37 control gate 33 to produce a signal applied
to coil~s) 22 of the wave form type as shown in Figure 5b. The circuit is
otherwise the same as in Figure 4, except that the diode-clamping unit 38 is
omitted to permit the large negative-pulse portions as shown in Figure 5b. The
control unlts 35 and 37 determine the number of pulses in a burst and the time
between successive bursts.
It has been found that the signal across the treatment coil 22, and
hence the iDduced signal within the tissue under treatment, should satisfy
certain criteria. These criteria will be specified with respect to the signal
as _nduced in the tissue and/or cells under treatment. Such induced signal may
be monitored, if desired, by use of an auxiliary monitoring pickup coil ~not
shown) which is positioned at a distance from the treatment coil 22
corresponding to the distance of the tissue under treatment rom that coil, as
will be explained in more detail below. In any event, it has been found that
_ g _
:1~6~3~
the following criteria should be satisfied for effective treatment of living
tissues and cells, in particular, hard tissue such as bone.
~ n the following presentation, the signals shown in Figures 5a and
5b constitute the pulses of electrical potential and concomitan* current
generated by the coil and impressed upon the tissues and/or cells. These
pulses have one polarity upon "energization" of the coil (termed herein the
"positive" pulse portion and shown as the positive-going portion of the waveform
on Figures 5a and Sb). These pulses have an opposite polarity upon "de-energiz-
ation'l of the coil ~termed herein the "negative" pulse portion and shown as
the negative-going portion of the waveforms of Figures 5a and 5b). The terms
"positive" and "negative" are intended to be relative only, and are used
herein only for the purpose of indicating that pulse portions of opposite
polarity, with respect to a reference potential level, are involved.
It has been determined that the "positive" pulse portions should
bear a predetermined rela~ionship to the "negative" pulse portions in order to
modify beneficially and with uniform results the behavior of living tissues
and cells. This pre determined relationship has been achieved by the
utilization of two different signal modes, as well as combinations thereof.
In Mode l~see Figure 5a), the asymmetrical waveform induced in
tissue or cells by the alternata energization and de-energization of arl
electromagnetic coil is repeated at a frequency such that the overall duty
cy~le is no less than about 2%. This frequency, in Mode 1, has typically been
about,10-100 Hz with duty cycles of 20-30%. The basic relationship for Mode 1
of the respective frequency amplitude content of the "positive" and "negative"
pulse portions is as follows: pulse signal should be of a particular shape,
namely, each "positive" pulse portion should be composed of at least three
? `
_ 10 -
'
:~ ~663~ ~
segments, e.g.,the segments 39, 40 and 41 in Figure 5a. As noted above, it
has been found that a substantially rectangular shaped "positive" pulse signal
portion is particularly useful in the treatment of tissue and cells. However,
it is possible that other pulse configurations ~other than a simple two-segment
spike) may be useful. The peak amplitude of the final segment of each
"positive" pulse portion, e.g., the potential v2 in Figure 5a should be no
less than about 25% of the peak amplitude of the first segment 39 of the
"positive" pulse portion, e.g., the potential vl in Figure 5a.
The peak "negative" portion amplitude is denoted by v3 in Figure 5a.
This peak amplitude should be no more than about l/3 the peak amplitude of the
"positive" pulse portion. The time duration of each "positive" pulse portion
(the period that elapses between times tl and t2 in Figure 5a) should be no
longer than about l/9 the time duration of the :Eollowing "negative" pulse
portion (the time elapsing between times t2 and t3 in Figure 5a), Because
the treatment system utilizes an electro-magnetic coil, the energy of each
"positive" pulse portion is equal to the energy o:E each "negative" pulse
portion, i.e., the area in Figure 5a embraced by the "positive" pulse portions
is equal to ~he area embraced by the "negative" pulse portions. By satisfying
the criteria just mentioned, the ~nergy of each "negative" pulse portion is
dissipated over a relatively long period of time, and the average amplitùde of
that negative pulse portion is limited. It has been found that such average
negativé amplitude should be no greater than about l/6 the average amplitude o~
the "positive" pulse portion.
These relationships also ensure that the "positive" and "negative" pul-
se portions haue the proper frequency-amplitude characteristics within themselves
- 11 -
~ ~fi63 ~ 8
and to each other such that a beneficial modification of the behavior of
tissues and cells is accomplished.
Besides the relationships just mentioned~ it has been found that
the average magnitude of the "positive" pulse portion peak potential should be
within the range of about O.OOOl to O.Ol volt per centimeter of tissue or cells,
corresponding to between about O.l and lO microampere per square centimeter of
treated tissue and/or cells (based upon typical cell and tissue resistivities).
It has been found that higher or lower pulse potentials will not result in a
beneficial effect. It has also been found that the duration of each "positive"
pulse portion(the time elapsed between times tl and t2 in Figure 5a) should be
at least about 200 microseconds. If the time duration of each "positive"
pulse portion is less than about 200 microsecondsJ the tissues and cells are
not stimulated sufficiently to modify the repair or other processes. From a
practical standpoint, the "positive" pulse portion duration should not be
greater than about l millisecond. It has also been found that the repetition
rate of the pulses should be within the range oE about 65 to 75 Hz for bone
and other hard tissues. Pulse treatments within this range have been found
to be particularly effective with reproducible results for tissues and cells
of this type. In general, however, pulse repetition rate should be between
about lO and lO0 Hz for good results in tissues and cells.
For the treatment of bone disorders, and particularly for the
treatment of pseudarthrosis, it has been found that for Mode l an optimum induced
"positive" pulse signal portion having a peak amplitude of between about l and
3 millivolts per centimeter of treated tissue (l to 3 microamperes per square
centimeter of treated tissue and/or cells~ with the duration of each "positive"
:~ `
- 12 -
13L6~3~ a
pulse portion being about 30U microseconds and the duration of each of the
"negative" pulse portions about 3300 microseconds~ and a pulse repetition rate
of about 72 Hz, represents a presently preferred and optimum induced pulse
treatment as long as the pulse-shape requirements noted above are met. Total
treatment times may vary. It is presently believed that pulse-signal
treatments for periods each lasting for at least about 15 minutes J with one or
more periods of treatment during a prescribed number of days, may be effective
in stimulating tissue and cell behavior. A preferred treatment regime using
Mode l has been found to be a minimum of 8 hrs/day for a period of four months
in difficult cases, and two weeks in less difficult cases.
In Mode 2 treatment (Figure 5b) the asymmetrical waveform induced
in tissue or cells by the alternate energization and de-energization of an
electromagnetic coil is applied in a pulse-train modality, which contains
bursts (pulse groups) of as~nmetrical waveforms. Each burst of asymmetrical
pulses has a duration such that the duty cycle of the burst portion is no less
than about 1%. The burst frequency has typically been about from 5-50 ~1z.
The basic relationshipsfor Mode 2 of the respective frequency-
amplitude content of the "positive" and "negative" pulses within the burst
section of the pulse train are as follows: each "positive" pulse portion
2~ should be composed of at least three segments, e.g., the segments 39', 40' and
41' in Figure 5b. For this mode, it has also been found that a substantially
rectangular shaped "positive" pulse-signal portion is particularly useful in
the treatment of tissues and cells. However~ it is possible that pulse
configurations other than a simple two segment spike may be useful. The peak
amplitude of the final segment of each "positive" pulse portion, e.g , the
potential v2 in Figure 5b, should be no less than about 25% of the peak
amplltude of the first segment 39' of the "positive" pulse portion, e.g.,
the potential vl in Figure 5b.
The peak "negative" amplitude is denoted by V3 in Figure 5b.
This "negative" peak amplitude should be no more than about 40 times the
"positive" peak amplitude (in this case vl). This requirement may be met
by utilizing "negative" pulse portions having several different waveshape
forms e.g., substantially rectangular, trapezoidal with exponential decay,
bell-shaped, or single-spike with exponential decay, as in representative
waveforms a, b, c and d in Figure 6.
The duration of each "positive" pulse portion (the time that
elapses between times tl and t2 in Figure 5b) should be at least about 4 times
the duration of the following "negative" pulse portion (the time that elapses
between times t2 and t3 in Figure Sb). As noted above, since the treatment
system utilizes an electromagnetic coil, the energy of each "positive" pulse
portion is equal to the energy of each "negative" pulse portion, i.e., the
area in Figure 5b embraced by the "posi~ive" pulse portions is equal to the
area embraced by the "negative'' pulse portions.
The pulse-repetition rate of the pulses within the burst segment
of the Mode 2 pulse train (the time elapsing between times tl and t4) can be
between about 2000 Hz and 10,000 Hz.
The width of the burst segment o the pulse train (the time
elapsed between tl and t5) should be at least about 1% of the time elapsed
between tl and t6.
By satisfying the criteria just mentioned, these relationships also
ensure that the "positive" and "negative" pulse portions have the proper
- 14 -
..~
3 1 8
frequency~amplitude characteristics within themselves and to each other such
that a beneficial modification of the behavior of tissues and cells is
accomplished.
Besides the relationships just mentioned, it has also been found
that the average magnitude of the "positive" peak potential should be within
the range of about 0.00001 to 0.01 volts per centimeter of tissues and/or
cells (between about 0.01 and 10 microampere per square centimeter of treated
tissue and/or cells).
It has been found that higher or lower pulse potentials will not
result in a beneficial effect on tissues and/or cells. It has also been
found that the duration of each "positive" pulse portion in the burst segment
of the pulse train (i.e., the time elapsed between tl and t2 in Figure 5b)
should be at least about 1000 microseconds. It has also been found that the
repetition rate o~ the burst segment should be within the range of about 5-15
Hz for bone and other hard tissues.
Each negative-pulse portion within the burst segment of the pulse
train should be of a duration no greater than about 50 microseconds and of an
average amplitude no greater than about 50 mv/cm of treated tissue and/or cells
(about 50 microamperes per square centimeter of treated tissue and/or cells).
For the treatment of bone disorders, and particularly for the
treatment of pseudarthrosis and non-unions, it has been found that an optimum
induced "positive" pulse signal ~ortion having a peak amplitude of between about
1 and 3 millivolts/centimeter of treated tissue (i.e.,l to 3 microamperes per
square centimeter of treated tissue and/or cells), with the du~ation of each
"positive" pulse portion being about 200 microseconds, and the duration of
each of the "negative" pulse portions being about 30 microseconds, and a time
- 15 -
~ ~6631 ~
elapsed between times t3 and t~ of Figure 5b of lQ microseconds, and a pulse
repetition rate of about 4000 H~, and a burst segment width of aoout 5
milliseconds, and a burst repetition rate of about 10 Hz, represents a
presently preferred and optimum induced pulse treatment in bone for Mode 2, as
long as the pulse requirements noted above are met.
It is also believed that a single asymmetrical pulse as described in
the burst segment of Mode 2 can be employed at a repetition rate similar to that
used in Mode 1 for beneficial modification of tissue growth and repair.
Treatment of living tissues and cells by the above methods herein3
in particular for hard tissue such as bone, has demonstrated an increased repair
response and generally un;form results have been attained throughout all
patient and animal treatments. Particularly beneficial results have been obtained
in the cases of treatment of pseudarthrosis in which a bone union has been
achieved following previous unsuccessful attempts by other treatment methods
and in which amputation has been discussed as a possible alternative to
regain function.
In practice, it is believed desirable to utili~e as large a coil
"window" as possible and to position the coil such that an adequate flux
density is impressed upon the tissue and/or cells being treated. As is known,
a time-varying magnetic-field induces a time-varying voltage field orthogonal
to it. That is, the geometry of the magnetic-field lines determin~ the
geometry of the induced-voltage field. Because a relatively uniform induced-
voltage field is desired, the geometry of the magnetic-field lines should be as
uniform as possible, which may be achieved by rendering the si~e of the coil
relatively large with respect to the area under treatment. At this particular
time, it is not believed that there need be a particular orientation between
- 16 -
~ ~ 6 ~t~l ~
the magnetic-field lines and the tissue and/or cells being treated.
It is believed that the uniformity of the induced-voltage field
possible through electromagnetic treatment is responsible in many respects
for the good treatment results which have been obtained, in distinction to the
non-uniform fields which may and probably do result with other types of
treatments, for example utilizing electrostatic fields or by the creation of
a potential gradient through the use of electrodes implanted within or on
tissues or cells. In particular, an induced voltage field is present in a
vacuum as well as in a conducting medium or an insulator. The field
characteristics will in general be the same (within one percent) in these three
cases, except in the case for which an induced current flow is sufficiently
great to create a back electromotive force to distort the magnetic field lines.
This condition occurs when the conducting medium has a high conductivityJ
e~g., a metal, and is large enough to intercept a substantial number of
magnetic-field lines. Living systems, i.e., tissue and/or cells, are much
less of a conductor than a typical metal ~generally by at least 105, i.e.
five orders of magnitude). Because of these considerations, the geometry of
the magnetic field present in tissue and/or cells is undisturbed and remains
unchanged as the tissue and/or cell growth process continues. Thus, with non-
invasive electromagnetic treatment, it is believed that the potentialgradient that is produced within the tissue and/or cells is constant
regardless of the stage or condition of the treatment.
Such uniformity of induced potential is virtually impossible to be
achieved through the use of implanted electrodes or by electrostatic coupling
or by a transformer coupled to electrodes, or by implanted coils coupled to
electrodes. Since these latter types of treatments are dependent upon
,. ` '
~16~31~
conductivity, which will vary within tissue and/or cells, the induced
potential gradient will not be constant as the condition of the tissue
and/or cells changes. Additionally, at any particular time within tissue and/or
cells, individual localities of the material being treated will have different
conductivity characteristics, which will result in differing potential
gradients throughout the material treated.
For these reasons, it is believed that a surgically non-invasive
electromagnetic treatment of tissue and/or cells is greatly preferable to
electrical treatment by other means.
Regarding typical coil parameters, it is believed that for typical
bone breaks, coil windows of about 2.0" x 2.75" ~for an adult) and 2" x 1.5"
(for a child) are suitable. The wire employed in the coils may be B~S gauge
12 copper wire that is varnish-coated to insulate the turns one from another.
Coils of about 60 turns for an adult and 70 turns for a child seem to be
suitable. For treatments in the oral cavity, coil sizes would be correspondingly
smaller.
It is believed that the inductance of the treatment coil should be
between about 1-5000 microhenriesJ and preferably between about 1000 and
3000 microhenries, with sufficiently low resistance ~e.g., 10 2 to 1 oh~) and
a high input coil driving signal between about 2 and 30 volts, to induce the
appropriate pulse potential in the tissue and/or cells treated. The lesser
the inductance of the treatment coil, the steeper the slope of the curves 40 and
~0' as shown in Figures 5a and 5b; the greater the inductance, the flatter or
more rectangular is the "positive" pulse that is produced.
The monitoring of the induced potential may be by actual
electrodes making contact with the tissue and/or cells being treated or by use
3 1 ~
of a pickup coil positioned adjacent to the treatment coil 22 at a distance
corresponding to the distance of the material under treatment from the coil.
A typical pickup coil that has been employed is circular, about one-half
centimeter in diameter, with about 67 to 68 turns of wire. The potential
developed by the coil is divided by the length of the wire (in centimeters)
to provide an induced voltage per centimeter number that is closely related to
the volts per centimeter induced in the tissue and/or cells under treatment.
A typical treatment utilizing a coil having a "window" 2" x 2.75"
and 60 turns of number 17 gauge wire J including a diode at the coil such as the
diode 27 in Figure 1, produced the following induced voltages in a pickup coil*
for the pulse times~in microseconds) as follows (voltages and times are with
reference to ! the waveform of Figure 5):
Induced Voltagevl v2 v3 tl-t2 t2-t3
Maximum ~at face
of treatment coil) 22 17 3.7 300 4200
5/8" from Eace of
treatm~nt coil 15 11.5 2.5 300 ~200
1 1/2" from face
of treatment coil ; 6.0 4.2 1.0 300 ~200
The use of pulsing electromagnetic fields to control bone formation
in a variety of conditions, now, is on a sound experimental and clinical basis.
Thus far, the developments have had application in treating successfully
congenital and acquired pseudarthrosis and fresh fractures in humans, increasing
_
* These voltage values may be translated into millivolts per centimeter of
tissue, by dividing by a factor of substantially ten~
- 19 -
116~
the rate of fracture and reactive periostitis repair in animals, and
reducing bone loss in disuse osteoporosis of long bones. Success with the
method hinges on the discovery of pulse patterns with specific time-frequency-
amplitude relationships as outlined above.
EXAMPLES
In order to demonstrate efficacy, the utilization o~ direc-t
i~dUcti~e coupling of electromagnetically induced pulsing voltages and
concomitant current via Modes 1 and 2 and combinations thereof for hard tissue
growth and repair was initially applied in cases of congenital and acquired
pseudarthrosis, In a group of patients, only individuals who had been treated
previously by one or more unsuccessful surgical attempts (grafting, internal
fixation~ were accepted. For most of these patients, amputation had been
recommended by at least one qualified orthopedist. Throughout this study, the
necessity for pulse specificity was illustrated again and again. For example,
when lack of ossification was the primary problem (usually the case for
congenital pseudarthrosis), Mode 1 treatment was utilized with final functional
bony union occurring only when the parameters of the pulse corresponded to
those given above. On the other hand, when lack of bony matrix was the
primary problem, Mode 2 treatment was employed in order to achieve the production
of collagen which is the primary supporting protein in bone structure. ~ince
protein production and ossification are two completely different steps in bone
formation, the highly selective nature of each of the signals utilized in
Modes 1 and 2 could be synergistically combined when neither matrix production
nor ossification were present in a given patient's treatment history. Thus~ a
combination of Modes 1 and 2 was utilized with benefit in this type of
situation.
- 20 -
~ ~63:~ ~
In the case of congenital pseudarthrosis, the typical patient is
~etween one and ten years of age. The afflicted part is normally the distal
tibia of one extremity. The patients were presented with an average of three
prior unsuccessful surgical procedures and had the condition for an average
of 5 years, and all were candidates for amputation.
The treatment of such a patient was normally carried out using
Mode 1 treatment regime since the primary problem was due to a lack of
ossification in the affected area.
The patient is prescribed the appropriate equipment by the
attending orthopedic surgeon and carries out his treatment on an out-patient
basis. Treatment time is typically 12 to 16 hours a day for about an
average of 4 months.
Some 20 of this type of disorder have been treated to date with
successful ossification achieved in approximately 90% of the treated
individuals.
For acquired pseudarthrosis, either traumatic or operative,
patients are mostly adults and had an average number of three failed operations
and an average of 2.5 years from onset of non-union. Amputation had been
discussed for seventy percent of these individuals. Since in some cases the
primary problem was lack of bony matrix, typically visible radiographically as
gaps in the bone of more than 2 mm in the fracture site, such a patient was
treated commencing with Mode 2 modality. When it was thought that sufficient non-
ossified bony matrix was present Mode 1 modality was employed to gain rapid
immobilization of the fracture site.
Because of the particular pathology of several patients in this
group, a combination of Modes 1 and 2 was employed with this treatment being
- 21 -
~L 16~;3 :1 ~
specifically Mode 2 followed by Mode 1. As in the case of congenital
pseudarthrosis, the proper equipment was prescribed by the attending
orthopedic surgeon and treatment was performed on an out-patient basis,
Treatment time is typically 10 - 14 hours/day for periods ranging from 3 to
9 months.
Some 30 of this type of disorder have been treated to date with
successful bony union observed in 75% of the treated individuals.
These clinical results clearly demonstrate that once the
particular pathology of a bone disorder is diagnosed it can be selectively
beneficially treated by the application of properly encoded changes in
electrical environment.
Similar findings have been obtained from a study of bilateral
femoral and radial osteotomies in 160 rats. These animals were divided into
two major groups; field exposed and control for an interval of 1~ days after
operation. Following sacrifice, the extent of fracture repair was judged on
the basis of X-ray and histologic evaluation, coupled with non-destructive
mechanical testing. These animal models were employed to evaluate the
effectiveness o~ treatment modalities of Modes 1 and 2 and combinations
thereof. Generally, when the osteotomy gap was less than 1.0 mm, a Mode 1
signal was effective since very little bony matrix was required for
solidification. On the other hand, for wider osteotomies, substantially
increased matrix production was observed over control animals when Mode 2
was employed. A combination of Modes 1 and 2 was employed in the latter case
to obtain a stiffer repair site for an equivalent treatment time.
This was further evaluated by ~he response of these bones to
mechanical testing This was performed by subjecting the bone of the rats
- 22 -
1 ~S~l ~
following sacrifice to cantilever loading at various deformations in accordance
with the testing procedures described in "Acceleration of Fracture Repair hy
Electromagnetic Fields. A Surgically Non-invasive Method" by C. A. L. Bassett,
R.J. Pawluk and A. A. Pilla, published on pp. 242-262 of the Annals of The
New York Academy of Sciences referenced ahove. The specimens were deformed in
the antero-posterior, lateral-medial, postero-anterior, medial-lateral and
again the antero-posterior positions.
The average response of a femur to this test at a deformation of
0.05 inch is shown in Table I as follows:
Table I
Mechanical Load Values In Electrical
Stimulation of Artificial Osteotomies
In Adult Female Rat Femur
Load at 0.05 in.
Stimulation Defo:rmation
Control ~untre~ted) 42 gms. ~ 5.2 gms.
Mode 1 Signal ~Figure 5a) 580 gms. ~ 65 gms.
In addition to radiographic and mechanical evidence of the
effectiveness of the signal employed, histologic evidence further attests
to this effectiveness.
Hemotoxylin and eosin stained longitudinal specimens show a much
higher degree of maturation for the Mode l signal than in the control case.
For wider osteotomy gaps~ treatment times of fourteen days showed
that the active animals had a significantly larger callus than controls.
Histologic evidence shows that the increase is at least 150% over controls.
Limited tooth extraction studies have been performed and show that
pulses of the Mode 1 type may have a highly beneficial effect on the rate of
' . '
1 ~663 1 ~
healing and on bone loss in the oral cavity. The latter effect in the oral
cavity is particularly important for the maintenance of mandibular and
maxillar crestal bone height, a very important factor for implant fixation.
These observations all point to the fact that electromagnetic
fields with highly specific pulse characteristics can be non-invasively
inductively coupled to biological systems to control cell behavior. In the
initial application of these principles, effects on bone cells have been
investigated~ Other biological processes, however, may eventually be proven
to be controlled by similar techniques, e.g., malignancy, neuro-repair,
inflammatory processes and immune response, among others.
In summary, it is believed that a unique electromagnetic and
surgically non-invasive treatment technique has been discovered. Induced
pulse characteristics appear to be highly significant, especially those
relating to the time-frequency-amplitude relationships of the entire pulse
~or pulse sequence. It is believed that selection of particular time-frequency-
amplitude relationships may be the key to successful treatments of varying
cellular behavior in a variety of tissues.
Throughout the specification for Mode 1, a preferred pulse
repetition rate of between about 65 and 75 Hertz had been specified for bone
and other hard tissue, The exact limits of the pulse-repetition rate are not
known for all types of tissues and cells. It is believed that preferred
operating ranges will vary depend mg on the tissue and cell type. Positive
results have been obtained, for example, in soft-tissue treatment at 20 Hertz.
It will be appreciated ~hat the methods and apparatus described
above are suscepti~le of modification. For example, while Figures 1 and 2
illustrate a treatment unit which may be strapped to the leg, treatment units
- 24 -
incorporated in casts, e.g., may be employed. Further, treatment may be carried
out by use of one or more coils of varying shapes positioned adjacent to tissue
and/or cells to be treated. In fact, some treatments of humans have involved
coils positioned upon opposite sides of a bone break. Coils with metal cores
may also be used. In the case of treatment within the oral cavity, it is
believed that double coils are advantageous, positioned, for example, on
opposite sides of a tooth socket to stimulate repair of that socket. Some
specifically beneficial treatment units and procedures will be described in
connection with ~igures 7 to 16.
Figures 7 and 7A illustrate a body-treatment or applicator device
which is most beneficially applied to the treatment of bone breaks or non-unions
in arm or leg members, i.e., wherein the bone region to be treated is relatively
elongate. The device comprises two coil-mounting units 50-51 each of which
contains an electrical coil of the character already described, and they are
flexibly interconnected to permit ready adaptability to opposite sides of the
region to be treated. Each of the units 50 - 51 may be of like construction,
essentially involv:ing a rigid potting o:E its coil turns in a consolidating mass
of cured elastomeric or plastic material; however, in the preferred form, each
unit, such as unit 50, comprises a casing consisting of flanged concave-front
and convex-back panels 52-53, with the peripheral flange 54 of front panel 52
in continuous telescoping overlap to the similar flange 55 of back panel 53.
Registering and abutting inwardly projecting boss or foot formations in pa~els
52-53, as at 56, enable the two panels to be bolted together in the precisely
spaced relation shown in Figure 7A. The respective inner and outer panels of
unit 51 are precisely the same as for unit 50, except that as a further feature
of the invention a rectangular recess 57 is inwardly formed in panel 52, for a
,
' '
locating or key purpose to be later explained. The secured boss or foot
formations at 56 are preferably offset inwardly from the flanged peripheries of
panels 52 - 53, thereby defining peripherally spaced means for locating the
inner limit of turns of coil 58 within the flange 55 of back panel 53. The
coil turns may be rigidly bonded in place, to and within flange 55, or they may
be adequately retained by compressible material such as urethane foam,
compressed as the bolted connections are established at 56.
The flexible interconnection of units 50 - 51 is shown to include
an electrical cable 59 for establishing the electrically parallel inter-
connection of like coils 58 in the respective units 50 - 51, the polarity of
such interconnection being such that magnetic-flux lines within the two coils
58 and in the space therebetween are flux-aiding when the front ~concave)
panels of units 50 - 51 are in face-to-face relation. Removable connection of
the coils 58 to the energizing circuitry of E~igures ~ or 5 is shown by way of
the single plug and socket means 24 - 26, via unit 51. Typically,each of the
two coils 58 has an inductance in the order of 5000 microhenries, so that in
their preferred parallel relation the inductance presented to the output of
the applicable one of the circuits of Figures ~ and 5 is 2500 n~icrohenries.
The flexible interconnection of units 50 - 51 also includes
articulating strap means, as of Velcro material, to enable simple adaptation
to the dimensional requirements of each patient's particular circumstances.
Thus, uni~ S0 is shown with a first such strap element 60 secured to its back
panel 53 and having a free end extending a distance Ll to one lateral side of
uni~ 50; similarly, unit 51 is shown with another str~p element fixed to its
back panel and having a first free end 61 of length Ll extending laterally for
adjustable overlapping connection to the free end of strap 60. The opposite
~ 26 ~
ll663~a
end 62 of the strap carried by unit 51 is also free but of substantially
greater length L2, to permit full circumferential completion of the strap
co~mection as the means of removably applying both units 50 - 51 to the body-
member treatment region; preferably, the length L2 is sufficient to enable
the ~elcro-material region 63 at the inner or front face of the free end 62 to
circumferentially envelop the body member and to enable region 63 to have
removable Velcro engagement with~a suitably equipped back surface of the same
strap member, as at the region of its fixed mounting to the back panel of
unit 51.
The coils 58 are shown to be of generally elliptical configuration.
These coils should be of sufficiently large internal dimensions, in relation
to their ultimately installed positioning for bone treatment, as to assure
relatively uniformly distributed concentrated flux within the treatment zone.
Elementary principles and preferred dimensional relationships for a two-coil
flux-aiding circular configuration will be ]ater discussed, with a view to
minimizing the establishment of stray-flux lines between the two coils. It
suffices here to point out that by employing ~he cylindrically concave-convex
configurations described for panels 52-53, the coils 5~ are necessarily also
conormed to a geometrical shape which is cylindrically arcuate, the major-axis
direction of the ellipse being parallel to the axis about which each coil 5~ is
cylindrically arcuate. Thus, when units 50~51 are positioned for body
treatment, the concave sides o both coils 58 are in face-to-face relation,
with the minor-axis spaced coil regions m~_ of unit 50 in closer adjacency to
the corresponding minor-axis spaced coil regions m'-_'of unit 50 than is
the case for coil-to-coil spacing of corresponding major~axis spaced coil
regions ~-~ and ~ '; as a result of this relation, any tendency to establish
. . ~ '' , ' ~ .
.
stray-flux lines between corresponding minor-axi.s coil regions m-n' and _'-n
is minimized.
Specific use of the body-treatment device of Figures 7 and 7A
will be more clearly understood through additional reference to Figures 9 and
10, utilizing a locating-block or keying device (shown in Figure 8) which may
be expendable and of suitable molded plastic such as polypropylene. The
locating device of Figure 8 comprises a rectangular-prismatic block 65 which is
dimensioned for removable locating reception in the rectangular recess
formation 57 that is cen*ral to the concave panel 52 of unit 50. Integrally
formed with and extending in opposite longitudinal directions from the base of
prism 65 are elongate mounting strips 66 which are relatively stiffly compliant
for slight bending adaption to particular body or cast configurations. Also,
the thickness and material of strips 66 should be such as to permit sheared
cut off to shorter length, as may be needed for some applications. A
pressure-sensitive tape 67, which may incorporate metal foil, wire or other
material opaque to radiological irradiation i.s shown to be removably adhered
to the peripheral edge of block 65.
In the initial s~ages of use of the device of Figure 7, i.e.,
during the period in which the separate halves o~ a bone break or non-union are
to be fixedly retained for electromagnetically induced treatment of the
invention, the afflicted limb, for example, the leg 70 of ligure 9, is first
placed in a cast 71 which overlaps the afflicted region. The leg is then
placed on a table 72 so that the afflicted region can be viewed under
radiological irradiation, schematically designated by an arrow, with the legend
"X~Rays", instantaneous and current viewing being provided by suitable video-
scanning and display means 73-7~. The device of Figure 8 is then placed.upon
.. ' ~
~1~63~
a local region of the cast 71 such that the opaque periphery of prism 65 is
viewable at 74 as a rectangular frame, surrounding the central zone of the
bone break or non-union region to be treated. ~hen the opaque frame is seen in
the display in proper surrounding registry with the afflicted bone region, i.e.,
after such positioning adjustments as may be needed to assure such registry, the
strip ends 66 are fastened to the cast 71, as by maans of adhesive tape
suggested at 68. The cast 71 may then be further developed over the strip ends
66 to assure permanence of the locating prism as a fixed part of cast 71.
~len prism 65 is thus fixed to cast 71, strip 67 may be removed and discarded,
and the patient is ready for the device, of Figure 7, which is assembled by
first locating (i.e., keying) unit 50 via recess 57 to the prism 65, by then
adjusting the ~elcro overlap 60-61 to position unit 51 in diametrically
opposite relation to unit 50 (on the other side of cast 71), and by then
using the s*rap end 62 for completion and securing of the circumferential
overlap described for the inner-surface region 63. The electrical connection is
then completed at 2~-26, and treatment may commence in the manner already
described. It should be noted thatJ if the surface of the concave panel of
each unit 50-51 is not soft-textured, there may be a tendency to generate
chalk dust upon local mechanical fretting of the cast 71~ with repeated
assembly and disassembly of units 50-51 theretoJ Such fretting can be
minimized by adhering a foamed-plastic or the like yieldable liner to the
concave panel of one or both units 5O-51J such a liner being shown at 75
in Figure 10. Still furtherJ the use of a foamed-plastic liner will assure
greater patient comfort while frictionally contributing to stable placement
and retention of the treatment coils.
Figure 11 depicts a body-treatment device which is particularly
- 29 -
: ~ .' ' ~ ' . , . ' '
. ' ' . . ~ :
suited to the treatment of bone affliction in the region of the heel. For
simplici~y in Figure 11, the showing is limited to relatively rigid structural
components, and the foamed-plastic lining carried by such structure for patient
comfort ~i.e., to avoid chafing~ has been omitted. Basically, the rigid
structure of Figure 11 comprises a tubular shell 80, as of methylmethacrylate,
being open at its longitudinal ends and locally open at 81, over an angular
span ~about the shell axis~ and intermediate the longitudinal ends of shell 80.
An "S"-shaped strap 82, which may be of the same material as shell 80, has
its upper end secured at 83 to the back end of shell 80, at opening 81, and
its lower end 84 extends along the diametrically opposite region of the inner
surface of shell80,todefine a plate for basic support of the bottom of a
foot 85, to be inserted via the opening 81. The respective courses of two
arcuately curved elliptical coils 86-86' are schematically indicated by heavy
dashed lines. These coils will be understoocl to be bonded to shell 80 in
vertically opposed relation, the upper coil 86 being bonded to the inner
surface of shell 80J just inside the edge of opening 81, and the lower coil
86' being similarly bonded at the diametrically opposite location. Coils 86-86'
thus have a permanent relation to each other, much the same as described for
the coils 58 of units 50-51, once the latter are in body-assembled relation;
alld it will be understood that coils 86-86' are preferably electrically
connected in parallel, in flux aiding polarity, being excited by one or the
other of the energizing circuits of Figures 4 and 5.
In addition to the described coil-positioning and foot-supporting
structure, the device of Figure 11 includes side-bumper guards 87-88 which
may be bowed strips of the same plastic material as shell 80, suitably bonded
at both ends to the respective longitudinal ends of shell 80. Strips 87-88 are
~ 30 _
~63la
preferahly stiffly yieldable, to cushion the treated region from mechanical
shock in the event of unwitting contact with furniture or other objects.
Figure 12 is a simplified diagram similar to Figure 11 to illustrate
another another body-treatment device, configurated for application to an
afflicted ankle region, or to a lower tibia/femur region. Again, the basic
rigid structure is seen to comprise a tubular shell 90, as of suitable plastic.
A single local side-wall opening 91 in shell 90 has a straight lower edge,
contiguous to a bottom plate or rest 92 which diametrically spans the lower
end of shell 90. Opposed electrical coils 93-94 are bonded to the inner
surface of shell 90 at an elevation such that the alignment 95 of their
centers of symmetry will geometrically intersect the cen~er of the afflicted
region, preferably as confirmed by X-ray observation on the alignment 95.
The configuration of coils 93-9~ may be circular or elliptical, but is
preferably cylindrically arcuate, in conformance with the local shell surface
to which each of them is bonded; in the event of elliptical coil configurations,
the major-axis orientation is preferably vertical, consistent with the
discussion above as to coils 58 in Figure 7. Interconnection and excitation
of coils 93-94 is as descrlbed for other two-coil devices.
It will be seen that the described devices and techniques represent
major advances in surgically non-invasive treatment of body cells, particularly
as they may be involved in bone repair and healing. With respect to the body-
treatment~devices which have been described, we have not yet established the
full range of dimensional limitations, but certain beneficial ranges can be
described in general terms, particularly for dual-coil embodiments 9
illustratively disclosed in connection with Figures 7 to 12.
On an elemental basis, it is convenient to consider the circular-
.;
- 31 -
.. . . . .
3 ~ ~
coil situation depicted in Figure 13, wherein like circular coils A-B of
inside diameter Dl are positioned on a common central axis of symmetry, at
parallel planes which are spaced apart by the distance S, and wherein the
coils A-B are excited in :Elux-aiding relation If the spacing S is sufficiently
small in relation to the diameter Dl, then substantially all flux lines
within coils A-B will extend continuously therebetween, on a generally straight
alignmen~ which may even neck down as suggested by the profile 96. If the
spacing S is greater ~again in relation to the diameter Dl), some stray-flux
lines 97 will develop, to the detriment of the development of uniform high-
density flux in the central span S. Generally, in view of the necking down(96), and in view of the treatment zone being generally at the center of span
S, it is convenient to consider the coils A-B as being desirably effective in
producing the uniform flux distribution over an imaginary cylinder 98 of
diameter D2, tangent to the neck-down profile 96. From our experience to date,
we can state that for body application of the character presently described,
the span S should be equal to or less than the diameter Dl, and of course D2
~the effective diameter of the zone of body treatment) will always be
considerably less than Dl, being substantially equal to Dl onl~ when coils A-B
are closely adjacent. As a practical consideration in the application of
dual coils to the body, we consider that the nominal inside diameter Dl of the
coils should be at least 1.5 times the diameter D2 of the effective body-
treatment zone, and this has been found to be a reliable approach for coil
spacing S substantially equal to the inside diameter Dl.
Having thus considered criteria factors for the simplified case of
flat circular coils, it is possible to develop general criteria applicable to
elliptical coils which are "hrapped" in general conformance with a
~ . .
- 32 _
116~3~
cylindrical arc. Figure 14 schematically depicts the coil-58 relationship
discussed for Figure 7, wherein the cylindrical arc of "wrapped" coil
curvature is about a central axis 100, which is parallel to the major axis
of the coil ellipse. And Figure 15 schematically depicts a coil-58'
relationship wherein the cylindrically arcuate curvature of the coils is
parallel to the minor axis of each coil. In both cases, the typical
resultant treatment-zone section is suggested by dashed outline in the
front view (Figure 14a and Figure lSa).
For purposes of deducing central magnetic-field distribution
between opposed coils 58, their major-axis regions ~designated p-q-p'-q' in
Figure 7) may be deemed to be at maximum separation Sl and their minor-axis
regions (designated m-n-m'-n' in Figure 7) may be deemed to be at minimum
separation S2, as viewed in Figure 14b. This being the case, major-axis-
region contributions to the magnetic field may be deemed to apply for the
span S ~of Figure 13) e~ual to Sl(of Figure 14b) in the context of an
effective inside diameter Dmaj which corresponds to the major axis of the
ellipse; by the same token, minor-axis-~region contributions to the magnetic
field may be deemed to apply for a span S2 (of Figure 15b) in the context of
an effective inside diameter ~min which corresponds to the minor axis of
the ellipse. For sectional considerations at planes intermediate those
o the major axes and of the minor axes, the field will follow distribution
considerations intermediate those controlling distribution in planes of the
major axes and of the minor axes, respectively.
Reasoning applied above as to magnetic-ield distribution for the
Figure 14 configuration can also be applied to that of Figure 15, except of
course that patterns will differ by reason of the cylindrical curvature about
.j ~
- 33 -
~ ~63~ ~
an axis parallel to the minor elliptical axis.
The arrangement of Figure 16 depicts use of two generally
cylindrically arcuate coils 58" wherein the cylindrical arcs are nested in
spaced relation appropriate to the desired application, electrical connection
being again understood to be for flux-aiding. The coil arrangement of
Figure 16 will be understood to have application over a generally cylindrically
arcuate treatment zone, as in the case of a jaw segment or group of teeth,
the latter being suggested schematically at 101 in Figure 16b. Depending
upon the size of coils 58", it will be understood that they may be retained
in fixed spacing, using a suitable bracket (suggested at 102) which bridges
only teeth in the case of insertion of both coils in the mouth, and which
bridges teeth as well as the adjacent cheek (via the mouth) in the case of
one coil inside and the other coil outside the mouth. It will also be
understood that for purposes of certain desired flux distribution within
the mouth, as for dental and/or jaw osteogenesis, the inner coil 58" may be
of smaller physical size than the outer coil 58".
It will be understood that the foregoing discussion of general
principles is with a view to illustration and not limitation,and that
modif1cations may be made without departing from the scope of the invention.
For example, if for certain purposes, it is not possible to construct both
coils of a dual-coil embodiment so as to completely match in geometry and
electrical properties, as suggested above for a dental or jaw application,
t~ere can still be a useful employment of the invention, using magnetic-flux
distribution which may not be as uniform asjdiscussed in connection with
Figures 13 to 16, but which nevertheless derives benefit from the flux-
aiding cooperation of two coils in opposite sides of the afflicted region
- 3~ -
3 1 ~
under treatment, such benefit flowing of course from the excitation of such
co~ls hy the specially characteri~ed inputs discussed in connection with
FIgures 4 to 6.
Figures 17 to 20 are concerned with coil configurations applicable
to flux development along and therefore generally parallel to the
longitudinal direction of a body member to be treated. In Figure 17, a single
coil of like plural turns 105 is helically developed along the length of a
supporting tubular member 106 of suitable plastic or other non-magnetic
material. The turns 105 may be on the inner or the outer surface of tube
106, and the axial length of the winding should be such as to overlap both
longitudinal ends of the bone fracture or the like to be treated.
In Figure 18, a single winding is again shown carried by one of
the cylindrical surfaces of a tubular member 108~ but the latter is locally
cut at an opening 109 (as in the manner described at 81 in Figure 11~ to
permit insertion of a joint region such as the elbow, with the forearm
projecting out one axial end of tubular member 108, and wi~h the upper arm
projecting radially outward via opening 109. The single winding is shown as
a first plurality 110 of helical turns continuously connected by an axially
expanded turn 111 to a second plurality 112 of similar turns, the
pluralities 110-112 being positioned on opposite longitudinal sides of the
opening 109 and at a spacing which is at least no greater than the
effective diameter of the turns 110-112.
The arrangement of Figure 19 is similar to that of Figure 18 except
that the respective pluralities of turns 110-112 are electrically connected
in parallel, in flux-aiding relation. A central access port will be
understood to be provided in tubular member 108 at a location opposite the
,.
~ 35 ~
,.. .
:
opening 109~ to permit excitation wiring connections to be provided external
to all turns~ i.e.) no supply lines passing within any of the turns at
110~112.
In the arrangement of Figure 20, two coil subassemblies 115-116
are constructed for assembly to the respective ends of a longitudinally split
compliant-supporting member 117 of non-magnetic material. The longitudinal
split at 118 permits a degree of flexibility in application to a body member,
as for example during the course of its assembly past the heel region to a
leg part to be treated. Each of the coil subassemblies is shown to be a
relatively rigid annular assembly of a winding to a potting of cured
hardenable material, and formed with a counterbore 119 at which the coil
subassembly is telescopically assembled over the end of the adjacent end
of tubular member 117. The inner end of each counterbore defines an inward
flange to limit coil assembly, and to determine repeatably accurate spaced
retention of the two coil subassemblies.~ Electricàl connections to the coil
subassemblies are shown to be parallel, and should be in flux-aiding
relation, and a flexible-cable interconnection is suggested at 120.
It will be understood that various simplifying techniques have
been adopted to make for more readily understood reference to the drawings.
For example, in the rigid-frame coil-supporting embodiments of Figures 11,
12, and~l7 to 20, it will be ~understood that in application to the body
certain cushioning liner materials such as urethane foam are preferably
adhered to the descrlbed structure for comfortable engagement with the body
at the region of application, but to have shown such liners would only
encumber the drawings. Also, in connection with Figure 9, the showing of the
cast 71 is merely illustrative, in that the key device 65 may be otherwise
v ~ .
.. ..
- 3~ -
- ~ , , ~:
3 1 ~
externall~ mounted~ as for exam~le to an external fixation device such as a
puttee~ or to the body limb itself ~i.e., without a cast, as in latter
stages o~ a bone repair), and the cast may ~e of materials other than
plaster, e.g., the material known as orthoplast.
J ~ 37 -
