U.S. patent number 3,786,806 [Application Number 05/308,739] was granted by the patent office on 1974-01-22 for thermoconstrictive surgical appliance.
Invention is credited to Frank P. Alicandri, Alan A. Johnson.
United States Patent |
3,786,806 |
Johnson , et al. |
January 22, 1974 |
THERMOCONSTRICTIVE SURGICAL APPLIANCE
Abstract
The application of a plate of thermoconstrictive material for
extra-medullary fixation of fractured bones is described. The
plate, consisting of a nickel-titanium alloy, is subjected to
deformation by a tensile stress below its critical transition
temperature. Upon securing the plate over the fracture, heat is
applied at or above the transition temperature thereof so as to
return it to its original state, thereby drawing the fractured bone
ends together.
Inventors: |
Johnson; Alan A. (Pullman,
WA), Alicandri; Frank P. (Teaneck, NJ) |
Family
ID: |
23195193 |
Appl.
No.: |
05/308,739 |
Filed: |
November 22, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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72651 |
Sep 16, 1970 |
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Current U.S.
Class: |
606/78 |
Current CPC
Class: |
A61L
31/022 (20130101); A61B 17/8004 (20130101); A61B
2017/00867 (20130101); A61F 2002/30092 (20130101); A61F
2210/0019 (20130101); F16B 1/0014 (20130101) |
Current International
Class: |
A61B
17/68 (20060101); A61B 17/80 (20060101); A61L
31/02 (20060101); A61F 2/00 (20060101); A61B
17/00 (20060101); F16B 1/00 (20060101); A61f
005/04 () |
Field of
Search: |
;128/92D,92R,92B,92BC
;3/1 ;75/175.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Yasko; J.
Attorney, Agent or Firm: Bartholy; Frederick E.
Parent Case Text
This application is a continuation-in-part of our pending
application, Ser. No. 72,651 filed on Sept. 16, 1970 now abandoned.
Claims
What is claimed is:
1. A surgical appliance for the extra-medullary fixation and
compression of the juxtaposed ends of a fractured bone, said
appliance comprising:
1. means connected to a plate to be specified hereinafter for
attaching said plate to a fractured bone on either side of the
fracture and
2. a plate which is
a. shaped to conform to the exterior of the fractured bone in a
manner overlapping the fracture,
b. formed of an alloy which exhibits a martensitic transformation
at a temperature in the range tolerable by the human body, and
c. plastically deformed in the direction of an imaginary line
connecting said attachment means by a predetermined amount
sufficient to draw the juxtaposed ends of the fractured bone into
forceful contact when the plastic deformation is removed by means
of martensitic transformation,
whereby the juxtaposed ends of the fractured bone may be forcefully
compressed by raising the temperature of said plate to a
temperature at which the alloy of which it is formed exhibits a
martensitic transformation.
2. A surgical appliance as claimed in claim 1 wherein said plate is
formed of a nickel-titanium alloy.
3. A surgical appliance as claimed in claim 2 wherein the alloy of
which said plate is formed also contains a small amount of
cobalt.
4. A surgical appliance as claimed in claim 1 wherein:
1. said plate is of oblong configuration and has transverse bores
therein near either end thereof for the accommodation of retaining
screws and
2. said means for attaching said plate to the fractured bone
comprises retaining screws passed through the transverse bores in
said plate and into the bone.
5. A surgical appliance as claimed in claim 4 wherein the plastic
deformation of said plate is confined to the region between the
transverse holes at either end thereof.
6. A surgical appliance as claimed in claim 1 wherein the plastic
deformation of said plate is confined to the region between said
means for attaching said plate to the fractured bone on either side
of the fracture.
7. The method of applying compression between the juxtaposed ends
of a fractured bone which comprises the steps of:
1. plastically deforming a plate which is
a. shaped to conform to the exterior of a fractured bone in a
manner overlapping the fracture,
b. formed of an alloy which exhibits martensitic transformation at
a temperature in the range tolerable by the human body, and
c. has attachment means connected thereto for attaching said plate
to the fractured bone on either side of the fracture in the
direction of an imaginary line connecting said attachment means by
a predetermined amount sufficient to draw the juxtaposed ends of
the fractured bones into forceful contact when the plastic
deformation is removed by means of martensitic transformation;
2. placing the juxtaposed ends of the fractured bone in abutting
relationship;
3. attaching said plate over the fracture to both bone portions;
and
4. applying an amount of heat to said plate sufficient to cause the
martensitic transformation of the alloy of which it is formed,
thereby causing constriction of said plate and the compression of
the juxtaposed ends of the fractured bone.
Description
This invention relates to surgical appliances and, more
particularly, to orthopedic clamping devices or splints for the
extra-medullary fixation of fractured bones.
Devices of the above type have been used in various forms for
holding two sections of a fractured bone in proper alignment and in
abutting relation to insure the knitting together of the fractured
ends.
Aside from the requirement of maintaining static condition of the
bone sections which the surgeon has carefully placed in proper
alignment, it is important that the contracting action of the
related muscles be further aided by forceful compression of the
juxtaposed ends.
Fracture healing in long bones is accelerated when compression is
applied between the fractured bone ends. At present, a widely
accepted method employs the use of an internally applied
compression bone plate. The plate is affixed by screws to one side
of the fractured bone with the plate overlapping the fracture site
and extending to the other side of the fractured bone. Before
screwing the other side down to the bone, a hand clamp device,
available in various designs, is applied to the upper end of the
unfastened plate. Compression is now applied to the plate, drawing
the fractured bone ends together and thereby effecting compression
and rigid fixation to the fractured bone ends. Screws are now
inserted in the bone plate on the clamped side, the clamp is
removed and the wound closed. This technique is widely accepted in
orthopedic practice. However, it has certain disadvantages in that
it requires an incision larger than the bone plate, extra
manipulation due to the large clamping device, additional screw
holes to hold the clamp in place, and generally increased operating
time.
Accordingly, it is the primary object of this invention to
eliminate the above-mentioned disadvantages by providing a bone
plate which requires no clamping devices of any kind for achieving
compression of the reduced fracture.
It is a particular feature of the invention that the fixation
element, generally in the form of a plate, has such physical
properties as to effect compression by virtue of its metallurgical
composition and properties.
A particular advantage of the invention resides in the fact that
the use of the fixation element is extremely simple, requiring
manipulation prior to its application to the bone surface and not
during the operation.
Other objects, features, and advantages will be apparent from the
following description of the invention, pointed out in
particularity in the appended claims, and taken in connection with
the accompanying drawings, in which:
FIG. 1 is a pictorial representation of a femur with the bone plate
affixed overlapping the fractured ends.
FIG. 2 is a top view of the plate in a prestrained or preformed
condition ready for application.
FIG. 3 shows the plate of FIG. 2 affixed to two separated ends of a
bone.
FIG. 4 shows the plate in constricted condition firmly holding the
bone portions together, exerting compressive force.
FIG. 5 is a schematic representation of a type of tensile stress
producing apparatus suitable for the deformation of the bone
plate.
FIG. 6a is an isometric view illustrating the general configuration
of one form of plate.
FIGS. 6b and 6c illustrate other configurations of plates which may
be advantageous in certain cases.
It is known that certain alloys of nickel and titanium exhibit
thermo-reactive properties in that, when deformed to a desired
configuration, they will return to the original configuration upon
being subjected to heat at certain critical temperatures. This
behavior of nickel-titanium alloys has given rise to considerable
metallurgical investigations and reference to it may be found in
the literature, e.g., in the Journal of Applied Physics, Vol. 36,
No. 10, Oct. 1965, the article entitled "Crystal Structure and a
Unique `Martensitic` Transition of TiNi," describes the crystal
structure of Ti-Ni compounds and contains a large number of
literature references on the subject.
The above-described properties of such alloys may be taken
advantage of in accordance with the present invention by selecting
such compositions which exhibit martensitic transformations at
temperatures in the range tolerable by the human body. The critical
temperature may be varied at will by varying the ratio of nickel to
titanium or by replacing a small proportion of the nickel with
cobalt.
Experiments performed have shown that a Ni-Ti alloy prepared as
shown in the following example has the desired characteristics to
be used as fixation elements in orthopedic surgery.
Appropriate quantities of nickel and titanium, or of nickel,
titanium and cobalt, are weighed and placed in the hearth of an
arc-melting furnace which operates with tungsten electrodes under a
reduced pressure of argon. The hearth, which is generally of copper
and is water-cooled, contains a depression into which the metals
may flow when heated with the arc. After solidification the alloy
is turned over and melted again. This procedure is repeated several
times to promote homogeneity.
The resulting casting is heated, typically to 700.degree. C., and
then rolled into a flat sheet using a conventional rolling mill.
Blanks for bone plates are then cut out of the sheet using a
conventional milling machine. A drill is used to make the screw
holes. After fabrication in this manner the finished bone plates
are recrystallized by vacuum encapsulation in quartz, or some other
appropriate material, annealed at some appropriate temperature,
such as 1,000.degree. C., and cooled to room temperature.
A separate alloy casting is fabricated into rod form using a
conventional hot swaging technique. Self-tapping screws for use
with the bone plates are then machined from these rods.
When the above-prepared compound is deformed plastically at room
temperature, and then its temperature raised within the range of an
appropriate higher value, it regains the configuration which it had
before its deformation at room temperature.
The above Ni-Ti compound may easily be fabricated into plates or
rods of various sizes and it is to be understood that the surgical
appliance herein described in the form of a bone plate is a Ni-Ti
alloy of the above composition.
The literature references explain in detail the various
compositions of such alloys. Some having the temperature range for
memory effect for surgical use are commercially available under the
trade name "Nitinol."
As examples, the following compositions have been found suitable
for surgical use.
A. An alloy containing 50 atomic per cent of nickel and 50 atomic
per cent of titanium.
B. An alloy containing 49 atomic per cent of nickel, 1 atomic per
cent of cobalt, and 50 atomic per cent of titanium.
C. An alloy containing 49 atomic per cent of titanium, 1 atomic per
cent of cobalt, and 50 atomic per cent of nickel.
The presence of cobalt has the tendency of lowering the transition
temperature.
The above are merely given as useful examples and may be varied in
order to obtain the most desirable temperature range for the memory
effect.
Referring to the figures, it is seen that in FIG. 1 the plate 10,
of generally oblong configuration, overlaps the fracture 11 and is
secured by means of screws 12 and 13 to one portion of the bone 14
and by means of screws 15 and 16 to the other portion thereof. This
is the conventional method of application of a metallic splint and
the bone plate in accordance with the present invention is affixed
in the same manner.
In FIG. 2 the plate 10 is depicted in a strained condition, having
been plastically elongated in the mid-section from its original
length shown in phantom line to its present length shown in solid
line. This is the deformed condition of the plate fabricated of the
aforementioned Ni-Ti alloys. The shaded area 18 purports to show
the elongation or tensile stressed portion. This is generally
chosen to be remote from the area occupied by the bores or screw
holes 22, 23, 25, and 26 which accommodate the respective screws as
shown in FIG. 1.
In FIG. 3 it is seen that the plate 10, bridging the separated bone
portions 14 and 17, is secured thereto by means of screws 12, 13,
15 and 16. For the sake of illustrating the constrictive action of
the bone plate, the distance between the bone portions 14 and 17 is
exaggerated. In an actual application, the bone ends are carefully
placed in abutting relationship so that there is but slight
separation between them.
FIG. 4 shows the constricted state of the plate 10 when, by virtue
of the application of heat, it returns to nearly its original
length.
It was mentioned before that the bone plate in accordance with the
present invention must be subjected to a deformation or strain so
that, upon application of heat within a suitable range of
temperatures, it will be constricted and thereby return to its
former state. However, experience has shown that in a simple
tensile elongation, the length after thermoconstriction will be
approximately 80 percent of the original length. This
characteristic must naturally be accounted for in its application
for surgical purposes.
In orthopedic practice care must be taken that the elongation be
precisely controlled so that the implanted plate should not produce
an undesirably strong compression of the bone surface. This would
result in seriously disturbing the normal healing processes. In
order to precisely produce the required compressive stress, an
apparatus of the type schematically shown in FIG. 5 and generally
known as a tensile-strain producing machine may be used. It
consists of a stationary jaw 30 affixed to a bed 31. A clamp 32
overlies the jaw 30 and is so dimensioned as to accept the plate 10
to be clamped therein by means of a fastening device such as the
winged screw 34.
A similarly constructed jaw 33 having a clamped member 36 and
winged screw 37 is slidably disposed on the bed 31 in linear
alignment with the jaw 30. The lead screw 38 extends into a
threaded portion of the jaw 33 having a shaft 40 supported in
bearings 41 and 42 placed in the body of the jaw 30. A handle 45
attached to the shaft 40 is provided for turning the lead screw 38,
thereby causing sliding of the jaw 33 toward the jaw 30 in one
direction of movement and away from it in the other direction. In
this manner, the jaw 33, when moved in the direction away from the
jaw 30, will exert a tensile strain on the plate 10 which is firmly
clamped between the jaws, causing elongation thereof in the
mid-section. The clamping members 32 and 36 and the configuration
of the jaws 30 and 33 are so dimensioned as to accept the greater
portion of both ends of the plate 10, leaving only a relatively
small section where no clamping force is exerted. In this manner,
deformation of the plate 10 in the region near the bores which
accept the fastening screws is prevented. Retaining collars 46 and
47 attached to the shaft 40 prevent outward movement thereof by
virtue of the force exerted when the jaw 33 is moved to produce the
required stress on the plate 10. A micrometric scale (not shown
here) is generally used to indicate the rotational displacement of
the shaft 40 in terms of tensile strain produced.
It must be remembered that the inter-metallic compound of which the
plate 10 is fabricated exhibits slight resiliency to the extent to
which the elastic strain induced during elongation recovers. The
force exerted as a result of thermo-constriction is considerable.
Therefore, the tensile stress must be carefully calculated with
respect to the compression force to be exerted on the bone
sections, bearing in mind that, in the constricted state, only
approximately 80 percent of the forced elongation will be
compensated. In actual practice, depending upon the skeletal
structure to which the bone plate is to be applied in order to
achieve proper arthrodesis of the joints, the tensile strain is
generally in the order of a few millimeters.
FIGS. 6a, 6b, and 6c show, simply by way of example, various
configurations which the plates in accordance with this invention
may take. When desired, other configurations for certain specific
orthopedic applications may just as easily be fabricated.
It is essential of course that in surgical practice the plate to be
inbedded in live tissue be completely sterile. This may be achieved
either by conventional heat sterilization in an autoclave or by
means of a cold sterilization liquid, such as benzalkonium
chloride. Sterilization in an autoclave may not be applied to a
pre-deformed plate inasmuch as the heat produced would effect
thermoconstriction. On the other hand, cold sterilization is not
fully reliable in certain cases where orthopedic appliances must be
imbedded in the body.
It is considered preferable to first heat sterilize the plate of
the type herein described and afterward effect the necessary
tensile stress for its elongation under sterile conditions. The
tensile stress apparatus shown in FIG. 5 may be sterilized and
placed in a sterile environment in an appropriate enclosure. In
this manner heat sterilized plates may be strained prior to
surgical implant. After this procedure, the prestrained plate is
applied to the fractured bone after the bone is aligned and screwed
to both ends thereof. While the fracture is held stable by this
plate, thereby eliminating the use of bone clamps, heat is applied
to its mid-section by any suitable means contracting the
prestrained metal and applying compression to the fracture site. No
clamping device is thus used, no extra metal is introduced into the
body, and the incision is smaller. Finally, the wound is now closed
as with the conventional plate. This Ni-Ti plate is easier to
handle technically than those now available. It has further
applications in areas where the present plate cannot be used, such
as in smaller bones, i.e., fingers, where compression may be
helpful for the fusion of joints. In forearm fractures, where two
bones are involved, use of the conventional double plating
technique is very cumbersome and many times, after compression is
applied to one of the fractured bones, the other fractured bone is
made to overlap and cannot be fixed by plates. By the use of the
plates in accordance with this invention, each bone of the forearm
may be plated separately, held aligned, and each bone in turn is
compressed.
While preferred embodiments have been described, it will be
apparent that various changes and modifications can be made without
departing from the true spirit and scope of the present invention.
It is intended that the invention be limited only by the appended
claims.
* * * * *