Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This is a divisional of copending Canadian patent application Serial
No. 311,778 filed September 21, 1978 in the name of Werner 1~raus.
The present invention relates to a surgical prosthesis, and more
particularly to an osteosynthesis implantate, which, after its manufacture, can
be associated with an electrical pick-up element to provide a small electrical
voltage across the implantate and surrounding tissue of the patient to
stimulate healing processes.
The term "tissue" as used herein includes soft tissue as well as
bone tissue, unless it clearly appears otherwise.
It has previously been proposed - see the referenced United States
Patents 3,745,995 and 3,820,534 - to provide an inductive receiving coil,
preferably having a ferromagnetic core, for association with osteosynthesis
implantates. The receiving coil has two or more connecting terminals, connected
to electrodes which are attached to an injured or danaged bone which is fixed
in relative position by the osteosynthesis implantate. Such an implantate may,
for example, be a bone nail, securing together the ends of a fractured bone by
extending through the marrow duct. After the operation of introducing the bone
nail, and of closing the wound, a low-frequency electrical current is induced
in the coil which flows through the electrodes and the damaged bone region, and
promotes healing and reformation of bone substance.
Such osteosynthesis implantates are known as electro-osteosynthesis
implantates and are provided with the receiving coil and the electrode connec-
tions, as delivered from the manufacturer. The manufacture of any one electro-
osteosynthesis implantate requires individual, special manufacture in which the
electrical winding elements and the osteosynthesis implantate are individually
associated. Such implantates may, also, be in the form of flat or bendable
plates. The winding section is individually and securel3r connected to the
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implantate by adhesion, clamping connection or welding; likewise, the electrodes
or electrode connection are so adhered or connected. Surgical clinics, trauma
stations in hospitals, and the like, require a large stock of different types
of electro-osteosynthesis implantates, for example bone nails of many different
lengths in many different diameters. Such electro-osteosynthesis implantates
are expensive and stocking and storage of a large number of such items in
many different sizes, the requirements for which are hardly predictable, is
a substantial drain on limited financial resources of public and private health
facilities. Frequently, therefore, the patient is subjected to multiple
surgical procedures since electro-osteosynthesis implantates were frequently
introduced into the patients only in a second operation, after the initial
operation of fixation of the bone has taken place, the type and size of the
required electro-synthesis implantate has been determined and the appropriate
unit has been ordered and received from the manufacturer.
Developments in surgical devices have been undertaken to reduce the
financial load on health facilities and to reduce the requirement for stocking
of specific electro-implantates. United States Patent 3,820,534 describes a
belt-like element which is furnished with electrodes and a connecting element
on which a coil is secured. After implantation of a bone nail, for example,
the belt-like element is placed around the bone, and the connecting coil can be
connected to the bone nail with one terminal. It has also been proposed to
provide a loose pick-up coil which is embedded in a biologically tissue-
compatible plastic material and which can be connected to bone screws by means
of snap-button type connections. The bone screws function as electrodes across
which an electric current will flow ~see eerman Disclosure Document DE-OS
23 11 817). United States Patent 3,918,440 describes such a loose receiving
coil in combination with bone screws, in which the head of the bone screws is
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insulated so that it can be used for attachment of a bone plate. The screws,
themselves, form the electrodes which are insulated with respect to the bone
plate.
The loosely implanted pick-up coil, as well as the belt-like element,
and the snap button or push-button type connections are an entirely satisfactory
substitute for premanufactured electro-osteosynthesis implantates. Use of the
belt-like element introduces additional complexity; the loose pick-up coil is
difficult to secure.
It is an object to provide an attachment element for an ordinary
osteosynthesis implantate, specifically a bone plate, which attachment can be
applied to the plate so that it can be converted into an electro-implantate
during the progress of an operation and which then will be a fully equivalent
and effective substitute for a premanufactured electro-implantate.
Briefly, in accordance with the invention, there is provided an
attachment for converting an osteosynthesis plate into an electrified osteo-
synthesis plate, the attachment comprising at least one body of electrically
insulating material, an induction pick-up coil located in the body and having
at least two terminals, a plurality of members supported by and protruding from
the body and adapted to secure mechanically the body to the plate, one of said
at least two terminals being provided with a connecting device for electrical
and mechanical connection to a bone screw insulated with respect to the plate,
the bone screw serving as a tissue electrode for electrically connecting the
one terminal to the tissue of a patient, and means for electrically connecting
another of the at least two terminals also to the tissue of the patient.
The attachment permits the surgeon to fix the bone in standard manner
by an osteosynthesis plate implantate in accordance with standard surgical
procedure, and using the ordinarily available implantates. He can then deter-
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mine whether it would be desirable to have an electrical implantate and, if so,
the osteosynthesis plate can be supplied with the attachment in accordance with
the present invention and the implantate will then function as an electro-
implantate without requiring any further changes or modifications, or a subse-
quent operation.
A standard osteosynthesis plate and the attachment in accordance
with the present invention, together, are substantially simpler and further less
expensive than the combined electro-osteosynthesis implantates.
The present invention together with that of copending application
Serial No. 311,778 will now be described in greater detail with reference to
the accompanying drawings, in which:
Figure 1 is a top view of a standard bone nail in accordance with
German Industrial Standard DIN 55801, Porm B;
Figure 2 is a schematic simplified longitudinal section of an elec-
trification attachment for the bone nail of ~igure l;
Figure 3 is a cross section in the plane of III-III of Figure 2;
Figure 4 is a top view of a bone nail of Figure 1, partly in phantom
view;
Figure 5 is a cross section in plane V V of Figure 4;
Figure 6 is a side view of a modified embodiment of the attachment
of Figure 2, in which the electrical circuit inherent in the element is
separately shown in view B, and the structural arrangement is shown in view A;
Figures 7 and 8 are two schematic electrical diagrams suitable for
use in the electrical attachment;
Figure 9 is a highly schematic perspective view of an osteosynthesis
plate, shown in broken lines, to which the electrification attachment in accor-
dance with the present invention has been added;
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Figure 10 is a schematic top view of another arrangement of an
osteosynthesis plate; and
Figure 11 is a top view of an elastic electrode connection holding
arrangement, in which view A illustrates the holding arrangement in relaxed
state, and view B the same arrangement in stretched, or stressed state.
The invention will best be understood when considering first an
embodiment for attachment to a standard bone nail, as shown in Figure 1. The
cross section of the bone nail of ~igure 1 is approximately clover leaf-shaped,
or pear-shaped (Figure 5). The bone nail 10 has a longitudinal slot 12, a
tapering, somewhat pointed tip 14 and an enlarged terminal end 16.
In accordance with the present invention, the known and conventional
bone nail 10 is converted into an electro-bone nail by the attachment 20 -
see Figures 2 and 3. Damaged or diseased or fractured bone tissue is electro-
dynamically stimulated in the region of injury or disease to stimulate
reformation of bone tissue and improve and accelerate the healing process.
The attachment 20, in accordance with the present invention, has a
body 22 made of a biologically compatible, tissue-compatible plastic, such as
polyethylene, or a carbon-fluoropolymer. A receiving coil 24, shaped like a
solenoid, is embedded in the body 22. The receiving coil 24 is only schemati-
cally shown in Pigures 2 and 3, and there illustrated as a single-layer coil;
of course, it may be a coil wound of a plurality of tightly arranged windings.
The circuit and the electrical terminals have been omitted from the illustra-
tion of Figures 2 and 3 for simplicity, and will be explained below.
The coil 24 preferably is a cored coil, and has a magnetic core 26
made of a magnetically soft material, having soft-iron characteristics, such
as a ferrite, or an iron-nickel alloy. lt may also be a permanent-magnet
material which, then, preferably, is brought into a partially saturated con-
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dition and permits modification of the wave shape of the voltage applied to the
electrodes and hence of the currents being supplied to the body tissue.
Embodiment of Figures 2 and 3: The body 22 has three leaf-likeJ
spring electrodes 28 secured thereto, for example by being set into a groove
of the body ~see Figure 2) which are bowed outwardly. The electrodes 28 are
connected together and to one end terminal or end point of the winding 24 and
provide electrical connection of the attachment to the metal bone nail 10, by
bearing against the inside wall, as illustrated in Figure 5. The dimensions of
the body 22 and the outward bulge of the electrodes 28 are preferably so select-
ed that the same attachment 20 can be used for bone nails of a wide range of
diameters, preferably the entire range of diameters of bone nails which are
used in surgical procedures. ~t most, however, two such bodies 20 need be pro-
vided, one for a thinner group of bone nails and another for a group of bone
nails having a wider diameter. The spring electrodes 28 permit deflection, and
hence reliable electrical contact, as well as reliable seating within the bone
nail.
The body 22 is formed with an extension 30 which, in cross section,
is essentially T-shaped ~Figure 3~ and which fits through the slot 12 of the
bone nail 10. The upper cross portion 34 of the T-extension 30 (Figure 5) is
bent downwardly so that it fits at least approximately around the curvature of
the bone nail 12. Since the body 20, with the integral extension 30, is made
of a soft plastic, the pre-bowing of the cross portion 34 can be such that it
fits the thinnest nail, since it will then expand, or resiliently bow outwardly
to fit over nails of larger diameter. ~n longitudinal extent, the cross portion
34 can be flat (Figures 4, S) or can be slightly bowed (Figure 2). An electrode
36 is applied to the outside of the bowed cross extension 34, connected to
another point on the winding 24 of the attachment. The electrode 36 is the
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counter electrode or soft-tissue electrode of the attachment.
Embodiment of Pigure 4: A plurality of separate counter electrodes
36a, 36b can be provided, each one connected to different points on the winding
of the coil 24. In all other respects, the structure is similar to that of the
embodiment of Figures 2 and 3.
The body 22 is preferably formed at its end with recesses, notches
or grooves 38 to permit attachment of an insertion or removal tool, and to
facilitate insertion or removal of the attachment 20 into or from the nail 10.
In a preferred form, the surgeon ls provided, together with the
attachment 20, with an additional filler strip which, for example, may be formed
similar to an I-beam, that is, have a double T-profile in cross section~ and
so dimensioned that it cannot pass through the narrow end 14 of the bone nail.
The filler strip is then trimmed to the desired length by the surgeon during
the operation and introduced into the nail 14 together with the attachment 20 in
order to ensure proper spacing of the attachment 20 from the end 14 of the nail,
or in order to ensure spacing between a plurality of attachment elements 20
which can be se~uentially, axially introduced into the nail 10. The filler
strip is preferably made of the same material as that of thé body 20, and soft
enough so that it can be cut by surgical scissors to the desired length, being
supplied, for example, in coil or rod form.
The body 22 with the T-pro~ection 30 and the electrode 36, or the
electrodes 36a, 36b, are so dimensioned that they fit within the diameter of
the surgical drill with which the opening for the bone nail 10 is drilled.
The entire length of the attachment 20 preferably is between about
3 to 5 cm. The material is somewhat resilient and the dimensions are preferably
so arranged that, coupled with the elasticity of the material of the body 22,
it is possible to introduce the attachment simply and effortlessly even over
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a bent-over end formed at the upper end of a bent bone nail and from there
into the there widened slot 12. The outer diameter of the attachment is larger
than the lower opening of the end 14 of the conically tapering bone nail, so
that the attachment device cannot slip upon introduction, or when pulling the
nail.
The bone nail 10 is galvanically connected over the electrodes 28
with the coil 24 and forms one of the electrodes, engaging the bone. The other
electrode 36, or the electrodes 36a, 36b, may have galvanic, semiconductive
or capacitive connection with the adjacent tissue of the patient. If semi-
conductive orcapacitative contact is desired, the electrodes 36 are suitably
coated at the outside with either a thin coating of semiconductor material or
with a thin coating of an insulator. A galvanic contact is desirable in tissue
poorly supplied with blood, or having few blood vessels. In tissue having
better blood supply, a semiconductive contact is desirable. This can be obtain-
ed by coating the electrode with a thin layer of aluminum oxide (A1203),
biological carbon, calcium phosphate, or the like. Tf the tissue to be contact-
ed has high blood supply, a capacitative contact may be desirable since rise
of current beyond the physiologically compatible value of about 100,u amperes
is prevented. Galvanic contact, due to the high conductivity of tissue well
supplied with blood might result in an excessive current flow.
Embodiment of Figure 6: The attachment has four tissue electrodes
36a, 36b, 36c, 36d. The projection 30 which carries these electrodes is sub-
divided into four parts 30a, 30b, 30c, 30d (see view A). The body 22 is con-
stricted between the respective pro~ections, as seen at 40a, 40b, 40c. As seen
in the electrical connection of Pigure 6, view B, one end of the coil 24 is
connected to the electrode 28 which is used to connect the entire unit to the
bone nail 10. The electrodes 28 are identical to those described in connection
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with Figures 2 and 3. The soft-tissue electrodes 36 to 36d are connected to
winding terminals of the coil 24 which have increasingly longer distances from
the end of the coil 24 connected to the electrodes 28.
The attachment in accordance with Pigure 6 can be fitted to bone
nails of any length by cutting or trimming the body 22' at any one of the con-
strictions 40a, 40b, 40c, which function as break point, so that the extent of
contact of the tissue electrodes can be matched to the extent of the region of
the fracture which is to be subjected to an electrical current. The soft-tissue
electrodes 36b to 36d are connected to the coil 24 by connecting lines 42, for
example in the form of thin foils, which can be readily severed.
Circuit arrangements, with reference to Figures 7 and 8: The circuit
of Figure 7 permits application to the electrodes of a-c with a superimposed d-c.
As seen, coil 24 is connected in series with a semiconductor rectifier 50 and
two voltage divider resistors 52, 54. The tap point 56 of the voltage divider
thus has a d-c potential appear thereat. The magnitude will depend on the a-c
induced in the coil 24 and the dimension of the voltage divider resistors 52,
54. The tap 56 is additionally connected by a capacitor 58 to the junction of
the diode rectifier 50 and the coil 24 50 that the d-c voltage appearing at the
tap 56 is superimposed on the a-c supplied by the coil 24. The tap 56 and
the terminal 60 of the coil 24 are connected, respectively, to the electrodes
36, 28 (Figures 2, 3; 4-6~ so that the bone nail is negative with respect to
the soft-tissue electrode. The diode 50 preferabl~ is a miniature semiconductor
diode with low threshold voltage, for example of 50 mV. The circuit is suit-
ably so dimensioned that the d-c component is about 20% of the peak amplitude
of the a-c voltage; in a preferred form, the d-c component is approximately 10
of the peak amplitude of the a-c voltage which may be about i V or possibly
e~en higher.
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The embodiment of F~gure 8 is a modlfication of the circuit for an
insert in accordance with Pigure 4J in which the a-c is applied to the junction
56 from a tap 62 of the coil 24. The capacitor then need not be used. a-c can
be applied to the terminal 56 also over a separate winding, for example formed
on another layer of winding 24, and connected between terminals 60 and 56.
The rectifier diode 50 is connected to the winding 24 over a conduc-
tor loop which, physically, extends into a projecting portion 66 of the body
22, or 22', respectively, as schematically indicated in broken lines in Figure
8. If the surgeon decides that no d-c should be applied, he can cut the pro-
1~ jection 66 during the surgical procedure, thus interrupting connection between
coil 24 and the rectifier diode 50, so that the applied electric current will
be only a-c, without a d-c component.
Embodiment of ~lgure 9- The attachment can be used not only with a
bone nail, but also with an osteosynthesis plate 70, shown in broken lines in
Figure 9. The attachment 72 has a body 74 ~ade of biologically tissue-compatible
material, similar to body 22, in which a receiving coil is located. The re-
ceiving coil has been omitted from ~igure 9 for clarity. The body 74 preferably
has an approximately rectangular cross section which has a thickness not sub-
stantially in excess of that of the plate 70. One or more pairs of knife
contact electrodes 76 project from one side of the body 74. Preferably, these
contacts 76 are made of springy metal which simultaneously provide electrical
connection to the plate 70 as well as ensuring attachment of the body 74 on the
plate 70. The electrodes 76, similar to the electrodes 28 of Figures 1-6, form
electrical contact between the coil in the body 74 and the plate 70. An
additional spring electrode 28' may be provided which, similar to the electrodes
28 of the embodiment of Figures 2 and 3 is bowed or bulged outwardly and set
in at an edge of the body 74, to bear against the edge of plate 70 when the
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attachment 72 is associated with the plate 70. The body 74 has additional
strip-like springy projections 78, made of plastic, and for example molded
integrally on the body 74. The pro~ections 78 carry connection arrangements
80, connected over the projections 78 by electrical leads embedded therein with
the coil 24 in body 74, similar to the electrodes 36a to 36d, Figure 6. The
connection arrangements 80 permit connection of the coil 74 to bone screws,
not shown. The bone screws are insulated with respect to the plate 70 and,
simultaneously, form electrodes and attach the plate 70 to the bone. These
screws may be constructed as described in the aforementioned United States
Patent 3,918,440. Projections 78 which are not needed can be trimmed. The
projections may have different lengths, as shown, and be so constructed that the
location of the connection arrangements 80 corresponds to the position or dis-
tribution of the holes in a standard osteosynthesis plate.
Embodiment of Figure lO: Two bodies 74a, 74b, each one similar to
body 74 (Figure 9) and each one having a coil 24a, 24b, are located at opposite
sides of a plate 70 ~not shown, and omitted for clarity). The lower ends of
the receiving coils have electrodes 76 and, if desired, electrodes 28 attached
thereto, similar to the illustration of Pigure 9, and also omitted from Figure
10. The sense of winding or connection of the coils 24a, 24b may be the same,
or opposite, so that the terminals 80 of facing projections 78 will either
carry the same, or different voltage levels. The two bodies 74a, 74b are
connected at their ends - only one is shown - by a spring 82 made of plastic
material so that the attachment arrangement can be used for plates of different
widths.
Embodiment of Figure ll: The projections 78', which carry the
connection arrangement 80, are preferabl~ so constructed that they are made of
two elastic, oppositely howed strips, made of plastic. In quiescent state,
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they are widely bent - see Figure 11J view A. The strips act like a spring so
that the position of the connection arrangement 80 can be matched to different
distances of the connection openings between the edge of the plate and the
openings for the bone screws themselves, with which the contact elements 80 are
to be connected.
Vse and application: When using the attachment in accordance with
Figures 9 and 10, the bone plate 70 is first secured to the bone to be joined,
or set. Insulated bone screws having heads which fit the connection arrange-
ment 80 are used at those portions where electrodes are deemed desirable.
Thereafter, the attachment body 74, or 74a, 74b, is attached to the plate by
sliding it on the longitudinal edge of the plate; the insulated bone screws are
then connected with the connection 80 of the projections 78, or 78' (Figure 11).
Those connection elements which are not desired or used are cut off together
with the respective projections 78, 78'.
The attachment permits the surgeon to decide during the operation
whether healing of a fractured or otherwise injured bone will be promoted by
introducing an electrical current to the region of fracture or disease, and if
electrodynamic activation of osteosynthesis is desirable.
If the attachment is to be used for an osteosynthesis implantate
made of a non-conductive material, such as ceramic then the electrode which is
designed for contact with the implantate is, instead, contacted with a large-
area electrode foil, or sheet electrode which, preferably, is in contact with
the soft tissue of the patient, preferably with the soft tissue immediately
adjacent to the bone which is to heal. When using the embodiment in accordance
with Figure 4 or 5, one of the electrodes 36a, 36b .... can be used as the
tissue counter electrode.
The body 22, or 72, respectivel~, may also be made of metal and, for
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example, may include a housing made of a tlssue-compatible material such as a
cobalt-chrome alloy, chrome-nickelmanganese steel; titanium, or the like. The
body can then be used directly as the electrode for connection to a metallic
osteosynthesis implantate, or as a large-area, soft-tissue electrode. The other
electrodes are then suitably insulated from this conductive body, for example
by a thin coating of biologically compatible plastic.
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