U.S. patent number 3,745,995 [Application Number 05/026,809] was granted by the patent office on 1973-07-17 for apparatus and method for aiding formation of bone forming material.
Invention is credited to Werner Kraus.
United States Patent |
3,745,995 |
Kraus |
July 17, 1973 |
APPARATUS AND METHOD FOR AIDING FORMATION OF BONE FORMING
MATERIAL
Abstract
An apparatus and method for aiding formation of bone forming
material in the region of a bone structure of a living being,
especially a human being, has at least one pick-up coil having
first and second terminals, each of which being d.c.-coupled to at
least one electrode, each pair of electrodes connected to a
respective at least one electrode. Each pair of electrodes
straddles a region of the bone structure within which enhanced
formation of bone structure, specifically callus, is desired. Field
generating means is provided for inducing in the pick-up coil an
a.c. current having gentle, gradual slopes, a frequency preferably
below 100 c/s, and a magnitude which produces a current density of
no more than 10 microamperes per square millimeter at the
electrodes.
Inventors: |
Kraus; Werner (D-8 Munich 13,
DT) |
Family
ID: |
5730828 |
Appl.
No.: |
05/026,809 |
Filed: |
April 9, 1970 |
Foreign Application Priority Data
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Apr 10, 1969 [DT] |
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P 19 18 299.1 |
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Current U.S.
Class: |
602/2; 623/23.49;
607/51 |
Current CPC
Class: |
A61B
17/58 (20130101); A61N 1/378 (20130101); A61N
1/372 (20130101); A61N 1/40 (20130101); A61N
2/02 (20130101) |
Current International
Class: |
A61B
17/58 (20060101); A61N 1/40 (20060101); A61N
1/378 (20060101); A61N 1/372 (20060101);
A61n () |
Field of
Search: |
;128/82.1,83,87,92,404,418,419,420,421,1 ;3/1 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Bioelectric Potentials in Bone, by Friedenberg et al. The Journal
of Bone & Joint Surgery, Vol. 48A, No. 5, July 1966. .
The Effect of Direct Current on Bone by Frienberg et al. Surgery,
Gynecology & Obstetrics, July 1968, pp. 97-102. .
Effects of Electric Currents on Bone in Vivo by Bassett et al.,
Nature, Nov. 14, 1964, Vol. 204, p. 652-654. .
"Induction Pacemaker for Control of Complete Heart Block" by G.
Holswade et al., Journal of Thoracic & Cardiovas, Surg. Vol.
44, No. 2, Aug. 1962, p. 246, 252..
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Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Yasko; J.
Claims
What is claimed is:
1. An apparatus for aiding formation of bone forming material in
the region of a bone structure of a living being, comprising, in
combination; at least one pick-up coil having first and second
terminals, at least one first electrode of elongated slender shape
electrically connected to said first terminal and adapted to be
inserted into the bone structure; said second terminal being
adapted to be conductively connected to the bone structure; a
second electrode adapted to be positioned at least partially on the
side of the bone structure which is opposite to said first
electrode for being d.c.-coupled to a portion of the living being;
and means for inducing in said pick-up coil, and between said
electrodes, an a.c. current having gradual, gentle slopes, a
frequency below 1,000c/s, and a magnitude which produces a current
density of no more than 10 microamperes per square millimeter at
said electrodes.
2. The apparatus according to claim 1 wherein said current inducing
means comprises a field coil coupled to an a.c. signal
generator.
3. The apparatus according to claim 1 wherein said current inducing
means comprises the stray fields of the mains.
4. The apparatus according to claim 2 wherein said a.c.signal
generator comprises means for superimposing on said a.c.signal a
modulating signal having a frequency of at least three times the
frequency of said a.c. signal.
5. The apparatus according to claim 1 for treating a, bone
structure having an opening which is a gap caused by a fracture,
wherein said second electrode is a metal splint adapted to be
attached to the bone structure for fixing it.
6. The apparatus according to claim 5 wherein said metal splint
comprises a plate-like member having a circumferential groove
housing said pick-up coil.
7. The apparatus according to claim 5 wherein said pick-up coil is
wound around a core of a material of low reluctance, said core
forming an open-ended magnetic circuit.
8. The apparatus according to claim 1, further including a
capacitor connected in parallel to said pick-up coil to form a
resonant circuit tuned substantially to the frequency of the
induced current.
9. The apparatus according to claim 1, wherein the frequency is
below 150 c/s and preferably between 1 and 65 c/s.
10. The apparatus according to claim 1, wherein said frequency is
between about 10 and 30 c/s.
11. The apparatus according to claim 1, wherein said harmonics
content is below 20 percent and preferably below 10 percent.
12. The apparatus according to claim 1, wherein said current
density at said electrodes is below 10 microamperes per square
millimeter, and preferably between 3 and 7 microamperes per square
millimeter.
13. The apparatus according to claim 1, wherein the coil and the
coil leads are insulated up to the point where the electrodes are
adapted to enter into the bone structure.
14. The apparatus according to claim 1 wherein said pick-up coil is
mechanically connected to a medical splint adapted to reinforce and
fix the bone structure.
15. The apparatus according to claim 1 wherein said frequency is
between 10 c/s and 1,000 c/s.
16. In an apparatus for aiding formation of bone forming material
in the region of a bone structure of a living being including a
splint for positioning the bone, and means for securing the splint
to the bone, the improvement comprising at least one first
electrode of elongated slender shape adapted to be inserted into
the bone structure; a second electrode adapted to be positioned at
least partially on the side of the bone structure which is opposite
to said first electrode for being d.c.-coupled to a portion of the
living being; and, at least one pick-up coil having a first
terminal and a second terminal, said first terminal being connected
to said first electrode and said second terminal being adapted to
be conductively connected to the bone structure, said coil being
adapted to be arranged in inductive relationship with a signal
generating means for inducing within said coil an a.c. current
having gradual, gentle slopes, a frequency below 1,000 c/s, and a
magnitude which produces a current density of no more than 10
microamperes per square millimeter at said electrodes.
17. The apparatus as defined in claim 16, further comprising: a
screw having at least its outer surface made of insulating material
and connecting the splint to the bone structure and wherein said
first electrode is located within said screw so that said first
electrode is insulated from the splint.
18. The apparatus as defined in claim 16, wherein the splint is a
plate-like member made of a non-magnetic material and said second
terminal is connected to the splint.
19. The apparatus as defined in claim 18, wherein said plate is a
sheet-metal member having a thickness not greater than 3
millimeter.
20. The apparatus as defined in claim 16 further comprising a
rod-shaped magnetic core and wherein said pick-up coil is wound on
said magnetic core.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus and method for aiding
formation of bone forming material in a region of the bone
structure of a living being, such as a human being or an
animal.
In the medical field it is often desired to speed up formation of
bone forming material, e.g. in healing a fracture, or to induce the
bone forming material to form at all, as in the case of
pseudo-arthrosis or osteoporosis.
The apparatus and method described herein provide the possibility
of accelerating the formation of bone forming material and
correspondingly cutting down the period of time necessary for
recovering from a fracture, as well as the possibility to induce
formation of bone where this ability has been impeded by a disorder
such as osteoporosis.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a
novel apparatus for helping bone disorders to mend, e.g. fractures
or osteoporosis or other disorders of the mineral metabolism.
Another object of the present invention is to provide apparatus and
methods to abbreviate the period of time which is necessary to
bring a fractured limb into a state where it can be used again.
A further object of the invention is to provide an improved splint
which promotes healing of the splinted fracture and is
simultaneously of reduced size and weight, so that the wound trauma
is reduced and the aftereffects of the fracture are alleviated.
Features of the present invention include an apparatus for aiding
formation of bone forming material in a region of the bone
structure of a living being which comprises at least one pick-up
coil having first and second terminals. At least one first
electrode of elongated, slender shape adapted to be inserted into
the bone structure is connected to the first terminal. A second
electrode is positioned at least partially on the side of the bone
structure which is opposite to said first electrode, and is
d.c.-coupled to a portion of said living being adjacent to said
bone structure. Means are provided for inducing in the pick-up coil
or coils a current having gentle, gradual slopes; e.g. a current in
the form of a sine wave having a low harmonics content which may be
as low as 20 percent, preferably lower than 10 percent or in the
form of a triangular wave, a frequency below 1,000 c/s, preferably
below 100 or 60 c/s, and a magnitude which produces a current
density of no more than 10 microamperes per square millimeter,
preferably between 3 and 7 microamperes per square millimeter, at
the electrodes.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic elevation view, partially in cross section,
of an apparatus according to the present invention applied to a
fractured bone;
FIG. 2 is a schematic perspective view of an embodiment of a novel
splint according to the present invention attached to a broken
bone;
FIG. 3 is an enlarged cross-sectional view taken generally along
the line III--III in FIG. 2;
FIG. 4 is a somewhat enlarged cross-sectional view taken generally
along the line IV--IV in FIG. 2;
FIG. 5 is a schematic elevation view, partly in cross section, of a
further embodiment of a novel splint structure;
FIG. 6 is a schematic view partly in cross section, of still
another embodiment of a novel splint applied to a fractured bone to
be mended;
FIG. 7 is a schematic perspective view of yet another embodiment of
a new splint structure attached to a broken bone.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
There is shown in FIG. 1 a bone 10 of a living being, e.g. an femur
(thigh bone) of a human being, which has gaps 12, 14 caused by a
fracture.
The parts of the fractured bones are fixed in the normal position
by means of two opposed splints 16, 18 which may be fixed to the
parts of the broken bone by means of screws as usual in the medical
art. The splints may be made of a stainless steel material or a
Co-Cr-alloy known as "Vitallium" and may have the form of a curved
plate.
To the main surface of splint 16, which is opposite to the bone 10,
is attached a pick-up arrangement which includes a rod-like
magnetic core 20 bearing three pick-up coils 22, 24, 26. The core
and the coils are encapsulated in an appropriate plastic material
28. The core is made of a material having low reluctance, such as a
magnetically soft ferrite or Permalloy. A first terminal of coil 22
is electrically connected, or d.c. coupled, to splint 16, and the
second terminal of coil 22 is connected through an insulated wire
30 to two rod-like electrodes 32. The insulation of the wire 30
extends up to the point where the conductor enters the bone 10, or
more specifically the gap 12 between the bone portions separated by
the fracture.
The first (the upper in FIG. 1) terminal of coil 24 is connected to
an insulated wire which passes into the bone 10 through a hollow
screw 34 insulated against the splint 16. The wire extends
preferably into the endostale bone or marrow cavity of the bone 10
and is bare beginning from the point where it leaves screw 34. The
other (lower) terminal of coil 24 is connected to a screw 36 which
is insulated against splint 16, but has a bare tip which extends
into the bone 10, preferably as far as into the endostale bone or
marrow cavity, and forms an electrode.
The lower terminal of coil 26 is again connected to splint 16, and
the other terminal of coil 26 is connected through an insulated
wire 38 both to a rod-like electrode 40, which extends radially
into gap 14, and to the second splint 18 which may be fixed to the
portions of bone 10 by screws (not shown) in the usual manner.
A tube-like field coil 42 is provided which may be slipped over the
broken limb into the position shown in FIG. 1. Field coil 42
comprises a plurality of windings encompassing the broken limb and,
thus, magnetic core 20 bearing pick-up coils 22, 24 and 26. The
field coil 42 is connected to an a.c. signal generator 44 which may
be of known construction and supplies to coil 42 an alternating
current, e.g. a sinusoidal current having a low harmonics content
which may be less than 20 percent, preferably less than 10 or 5
percent. The signal delivered by the a.c. signal generator has a
frequency of less than 1,000 c/s, preferably less than 100 or 60
c/s, e.g. between 1 or 10 c/s and 40 c/s. The signal generator 44
may comprise a modulator for superimposing higher frequency
oscillations onto the basic signal; these oscillations or
undulations may have a frequency which is at least three times the
frequency of the basic signal.
When excited by signal generator 44, field coil 42 produces an
alternating magnetic field symbolized in FIG. 1 by field lines 48
which are picked up by core 20 and induce alternating currents in
the coils 22, 24, 26, so that alternating currents or potentials
are produced between the spaced electrodes connected to the
terminals of said coils. It is these alternating currents or
potentials having gradual, gentle slopes, low harmonics content and
low frequency, which greatly enhance the formaton of bone forming
material, or callus. Callus forming rates which are more than three
to five times faster than the normal rates have been observed in
human beings to which the present apparatus and method were applied
for healing a fracture. Further callus formation could be induced
in pathological cases where normal callus formation had failed, as
in the case of pseudo-arthrosis.
The recovery of the broken bone is further aided by the magnetic
field which is produced by field coil 42 and which is essentially
parallel to the structural elements of the bone to be formed.
A further embodiment of a splint for use in the present apparatus
and method is depicted in FIGS. 2, 3 and 4. Splint 50 has the form
of an elongated, curved plate which is attached to a broken bone 52
by screws 54. The splint 50 has a circumferencial groove 56 (see
FIG. 3) into which one or several pick-up coils 58 are wound.
Groove 56 housing the pick-up coil or coils 58 is enclosed with an
appropriate plastic material or resin 60, e.g. an epoxy resin. The
coil ends extend into bores of the bone or the gaps in the bone
caused by the fracture, as shown in FIG. 4. The portion of the
wires between the coil proper and the point of entrance into the
bone or gap is insulated, e.g. by a teflon insulation, the bare tip
of the wire forming an electrode. One of the coil ends may be
connected to a screw 54 which may or may not be insulated against
the splint.
The pick-up coils cooperate with a field coil (see FIG. 2) which is
positioned in the vicinity of splint 50 and functions in a manner
similar to coil 42 shown in FIG. 1.
FIG. 5 shows a splint 60 which is externally applied to an injured
limb, i.e. to the skin 62 thereof. The splint 60 may be of any
suitable material, e.g. a plastic or resin material which is
hardened in situ, and comprises pointed spine-like members 64, the
roots of which are embedded in the material forming the splint 60
proper. The pointed ends 66 of members 64 are inserted into the
broken bone 68, preferably as far as the marrow channel as shown in
FIG. 5, to fix the bone in its proper position. Simultaneously, the
pointed ends 66 being of metal serve as electrodes and are
connected to respective pick-up coils 70 which are similar to those
described in connection with FIG. 2. The portions of members 64
which are outside of bone 68 are insulated against the tissue 72
surrounding the bone 68. In operation, a current is induced in
coils 70, e.g. by a pick-up coil as shown in FIG. 2 or by the
stray-fields which exist in the environment and are caused by the
mains, electrical appliances,and so on.
FIG. 6 shows a splint according to the present invention which is
in general similar to the splint shown in FIG. 5 and comprises a
plastics or resin material 80, shaped and cured in situ on the skin
82 of the outer side of an injured hand comprising broken bones 84.
The main difference between the splints according to FIG. 5 and 6
respectively, is that a capacitor 88 is connected in parallel to
pick-up coil 86 for tuning it to the frequency of the induced
currents. The capacitor 88 is embedded in material 80 and provides
for an especially low harmonics content of the induced signal,
which will produce a purely sinusoidal current.
As noted above, a major advantage of the present invention is that
callus is formed so quickly that the broken bone will be able to
recover to a substantial portion of its original strength in a
relatively short time, so that the splint need not supplement the
load carrying function of the bone when the injured individual has
otherwise recovered sufficiently to be able to get up again. Thus,
the splint is only needed for fixing the broken bone in the proper
position during the initial stage of healing and can be made much
lighter and thinner than the presently used splints. The screws
used to attach the splint to the bone may be correspondingly
smaller, which greatly reduces the wound trauma and the after
effects which arise after removal of the splint; e.g. the filling
of the screw holes with bone forming material. Further, the use of
the so-called Kuentscher-nail (a rod-like supporting element,
inserted into the marrow-channel of a broken bone) may be dispensed
with.
FIG. 7 shows a novel splint of such reduced dimensions, the splint
comprises a curved plate-like member 90, made of stainless steel or
"Vitallium," to which pick-up coil means 92 wound around a magnetic
core 94 are attached. Member 90 may be made of sheet material
having a thickness of 1 to 2 mm in contrast to 4 to 6 mm in the
known splints. Member 90 is connected to one terminal of each of
the coils making up coil means 92 through an unsymmetrically
conducting device 99, such as a diode, to make the shape of the
current wave unsymmetrical. Preferably, member 90 is positive
during the current periods having the higher amplitude.
Pick-up coil means 92 is connected by insulated leads 96 to bare,
slender, rod-like electrodes 98 adapted for insertion into a bone
structure (e.g. as shown in FIG. 4) to aid forming or regeneration
of bone material.
The electrode portions which are in contact with the bone structure
consist preferably of a noble-metal alloy, e.g. an alloy of 90
percent by weight Pt and 10 percent by weight Ir, or stainless
alloys such As a Co-Cr-alloy known as "Vitallium." The insulation
may consist of Teflon, and all of the materials which are in
contact with bone or tissue are of course so chosen that they are
compatible with the environment and the living or organic
matter.
The induced current which enters into the bone region may consist,
e.g., of a sinusoidal wave having low harmonics content, a
triangular wave, a series of triangular or essentially sinusoidal
pulses of alternating polarity; the said pulses being separated by
periods of time during which the current is zero or negligible. The
waveforms or pulses need not to be symmetrical.
The invention is not limited to healing fractured bones, it may be
applied with success also for curing other bone disorders where
forming of bone material is to be enhanced or promoted. Thus, the
invention may be applied, e.g., to curing osteoporosis,
regenerating bone structure destroyed by a tumor, to cure an
illness known as "Sudeck'sche Atrophia" and so-called false
articulations (pseudo-arthrosis).
The pick-up coil means may also be positioned adjacent the
peripheral edge, e.g. at the straight long edge portion, of the
plate member of the splint.
EXAMPLE I
A novel splint similar to that shown in FIG. 2 was attached and
electrodes which were in the form of needles consisting of a
platinum-iridium alloy, were applied as shown in FIG. 4 to the
broken right femur (upper thigh bone) of a rabbit. A similar splint
and similar electrodes, however, without being connected to a
pick-up coil or other current source were applied to the like-wise
broken left femur of the same animal. This was carried out in an
operation under narcosis lege artis. The animal was kept in a barn
within which an electric a.c. field was maintained producing in the
windings of the pick-up coil and a.c. current of sinusoidal
waveshape and a frequency of 25 c/s. The maximum current density at
the areas of contact between the electrodes and the tissue or bone
was about 5 microamperes per square millimeter. After having been
kept in the electric field for 3 weeks, the rabbit was killed and
sections of the bones in the planes of the electrodes were
prepared. The sections showed that at least three times as much
callus had formed in the area of those electrodes which were
connected to the pick-up coil in comparison with the area connected
to the other, currentless dummy electrodes.
EXAMPLE II
Similar results as in example I have been achieved in mending an
injured bone of a human being: A splint similar to that shown in
FIG. 7 (without diode 99) was applied to the femur of a male (age
about 50) which had been injured in a car accident about 1 year
ago. The fracture did not heal because callus did not form by
itself.
The applied novel splint comprised a metal plate of usual size to
which a pick-up coil was attached having 200 windings of
teflon-insulated platinum wire (diameter 0.1 millimeters) wound on
a magnetic core consisting of two superimposed Permalloy sheets
each having a length of 50 mm, a width of 4 mm and a thickness of
0.5 mm. The electrodes connected to the terminals of the pick-up
coil and inserted into the gap of the fractured bone were
needle-like members consisting of an alloy of 90 percent by weight
platinum and 10 percent by weight iridium and having a diameter of
about 0.5 to 1 mm.
A field coil was put around the splinted limb and excited by a
sine-wave a.c. current of 25 c/s to produce an a.c. field of about
800 ampere-turns in the region of the pick-up coil.
After the splinted limb had been kept in the electric field and
treated as described for 14 days, an x-ray investigation showed
that plenty of new callus has formed in the area around and between
the electrodes.
The patient who was regarded as incurable before the described
treatment eventually completely recovered.
Other embodiments will occur to those skilled in the art and are
within the following claims.
* * * * *