U.S. patent number 3,818,513 [Application Number 05/300,967] was granted by the patent office on 1974-06-25 for implantable joint prosthesis.
This patent grant is currently assigned to Rhone-Poulenc S.A.. Invention is credited to Jean Pillet.
United States Patent |
3,818,513 |
Pillet |
June 25, 1974 |
IMPLANTABLE JOINT PROSTHESIS
Abstract
Implantable prosthesis of a joint comprising a central flexible
hollow body portion, in the form of a tube of silicone elastomer,
into the ends of which are inserted medullary pins of the same
material, to extend outwardly from the body portion for insertion
into the medullary ducts of the bones to be joined. The pins may be
adhesively secured to the bones, or at least partly surrounded by a
textile sheath colonizable by bone tissue. The cavity may be filled
with sterile air or liquid.
Inventors: |
Pillet; Jean (Paris,
FR) |
Assignee: |
Rhone-Poulenc S.A. (Paris,
FR)
|
Family
ID: |
9084967 |
Appl.
No.: |
05/300,967 |
Filed: |
October 26, 1972 |
Foreign Application Priority Data
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|
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Oct 27, 1971 [FR] |
|
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71.38605 |
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Current U.S.
Class: |
623/23.41;
128/DIG.21 |
Current CPC
Class: |
A61F
2/42 (20130101); Y10S 128/21 (20130101); A61F
2/30907 (20130101); A61F 2002/30069 (20130101); A61F
2002/30125 (20130101); A61F 2002/30563 (20130101); A61F
2230/0008 (20130101); A61F 2002/3008 (20130101); A61F
2002/30593 (20130101); A61F 2220/005 (20130101); A61F
2250/0098 (20130101); A61F 2002/30448 (20130101) |
Current International
Class: |
A61F
2/42 (20060101); A61F 2/00 (20060101); A61F
2/30 (20060101); A61f 001/24 () |
Field of
Search: |
;3/1
;128/92C,DIG.21 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"Calnan-Nicolle Encapsulated Finger Joint", Advertisement by Zimmer
Orthopaedic Ltd., The Journal of Bone and Joint Surgery, British
Vol. 53-B, No. 3, August 1971..
|
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Frinks; Ronald L.
Attorney, Agent or Firm: Cushman, Darby & Cushman
Claims
I claim:
1. Implantable prosthesis of a joint comprising a central flexible
hollow body portion, defining a central unobstructed cavity,
enabling the central portion to be bent with flattening of the
opposite walls and two medullary pins extending outwardly from said
central portion, each dimensioned effective to be inserted into the
medullary ducts of the bones to be joined.
2. Implantable prosthesis of a joint as claimed in claim 1, wherein
said central body portion is in the form of a tubular sleeve,
having ends, and wherein said medullary pins are inserted into said
ends.
3. Implantable prosthesis of a joint as claimed in claim 1, wherein
said central body portion is formed of silicone elastomer.
4. Implantable prosthesis of a joint as claimed in claim 1, wherein
said central flexible hollow body portion is of substantially
elliptical transverse cross-section, the ratio of the major axis
length to minor axis length being between 1 and 2.
5. Implantable prosthesis of a joint as claimed in claim 1, wherein
said pins are interconnected solely by said flexible hollow body
portion.
Description
The present invention relates to an implantable prosthesis of a
joint.
It has already been proposed to replace deficient or destroyed
natural joints by flexible prostheses for insertion in the
medullary ducts and comprising a flexible central mass extended by
two medullary pins, the prosthesis consisting of a single piece of
silicone elastomer or equivalent material (i.e., simultaneously
offering resistance to alternating flexion, mechanical stability
and suitable innocuousness).
In use it has been found that such a prosthesis is not entirely
satisfactory since the central mass presents a couple of excessive
resistance to flexion relative to the resistance of the terminal
pins. Consequently the prosthesis tends to bend at the level of the
pin rather than at the level of the central mass, even when this
mass is weakened by a groove parallel to the bending axis.
Moreover, if the pin is not sufficiently anchored (notably by
colonizable of bone tissue) it tends to slide longitudinally in the
medullary duct and to pull out partially during the flexion.
According to the present invention there is provided implantable
prosthesis of a joint comprising a central flexible hollow body
portion, defining a central unobstructed cavity enabling the
central portion to be bent with flattening of the opposite walls,
and two medullary pins extending outwardly from said central
portion, each dimensioned effective to be inserted into the
medullary ducts of the bones to be joined.
The flexible portion preferably is of substantially elliptic
transverse cross-section and of a longitudinal section of
rectangular to diamond shaped configuration; more particularly the
longitudinal section may be an ellipse or more simply a rectangle,
optionally ending in arcs of a circle, an ellipse or a
parabola.
Generally the ratio of the major axis to the minor axis of the
internal and external transverse cross-sections may be between 1
and 2, the major axis being parallel to the bending axis. Good
results have been obtained with a ratio of 1.5 to 1.2.
The wall thickness of the central body portion is a function of the
elasticity of the material employed and of the result desired. With
silicone elastomers of medicinal quality of 85 to 110 kg/cm.sup.2
breaking strength, 380 to 550 percent elongation (AFNOR T 46 002),
47 to 60 percent recovery (DIN 53 512), the wall thickness may vary
between 1/10 and 1/3 and preferably between 1/6 and 1/4 of the
outer diameter for a tube of circular section. This thickness is
not necessarily the same over all of the periphery, it can in
particular be greater at the side of the centre of flexion, a ratio
of wall thicknesses of up to 2:1 being possible.
The length of the central body portion depends on the desired
effect, an average length of 1 to 21/2 times (preferably 1 to 11/2
times) the diameter generally being suitable in the case of a body
portion having a cavity which is a cylindrical. Most often a body
portion of the shortest possible length is chosen, the portion of
joint which is to be replaced being itself the shortest
possible.
At either side of the central transverse plane of the body portion,
and preferably beyond the above defined length, the wall of the
tube may gradually thicken toward the interior until at the two
ends of the cavity a conical or curved wall as indicated above is
formed.
The tubular portion may initially be filled with sterile air. After
implantation water may diffuse through the wall into the tubular
portion. It is thus possible initially to introduce into the cavity
a sterile, physiologically compatible liquid, for example an
isotonic saline solution containing 1 percent of zinc sulphate.
The medullary extremities may be of any material and shape
currently utilized for implantable prostheses. They may be
cylindrical or slightly conical, flexible or rigid, preferably have
a surface which is colonizable or adapted to be glued by the
well-known surgical adhesives. They may, for example, be of
silicone elastomer sheathed in a tricot of polyester fibre which
has been adhesively affixed or of potentially porous ceramic
material (described for example in Chemical Engineering, June 16,
1969, p. 42 or in Chemical and Engineering News, Mar. 15, 1971, p.
15).
Implanting of the prosthesis is accomplished according to customary
techniques.
The prosthesis according to the invention enables the bending line
to be well localized, it only offers a weak resistance to flexion
and in particular permits bending of large amplitude. Moreover, in
contrast to solid, flexible prostheses, it has its maximum
restoring couple in a position near the extension which is an
important advantage when the muscle or extensor tendon are
deficient. It is believed that these advantages are due to the fact
that the flexion of the prosthesis causes a two-fold deformation,
first flattening of the tube and then bending of the flattened
walls, and to the fact that this latter bending affects two layers
which are partly movable relative to one another. It is to be noted
that filling the cavity with liquid imposes a constant volume on
the cavity which limits the tube being crushed and enhances the
bending resistance. Moreover, the presence of the cavity improves
absorption of terminal shocks.
In order that the invention will more readily be understood, the
following description is given, merely by way of example, reference
being made to the accompanying drawing, in which the sole FIGURE is
a cross-section through one embodiment of prosthesis according to
the invention.
The example of joint prosthesis illustrated in the drawing
comprises a flexible central tubular portion 1 and two medullary
pins 2 and 3. The portion 1 is a tube of circular section of
silicone elastomer, outer diameter 8 mm, inner diameter 4 mm,
length 14 mm. The pins 2 and 3 are rods of the same kind of
elastomer, diameter 4 mm, length 20 mm, embedded 5 mm. in the tube.
At the time of assembly the surfaces and junction angles are coated
with a moisture-curable silicone adhesive which results in
integrating the assembly and in suppressing abrupt sectional
variations. The cavity 4 may be filled with isotonic saline
solution with the aid of a syringe, prior to total curing of the
adhesive. As illustrated the surface of the medullary pins 3 is
covered with a sheath 5 of material colonizable by the bone
tissue.
The articulation may, of course, be obtained from two preformed
pieces, one corresponding for example to the whole of portions 1
and 2, or it may even be obtained directly as a single piece, for
example in a revolving mould.
The elastomer may contain certain radio-opaque charges which
facilitate the post-surgery control.
* * * * *