U.S. patent number RE34,037 [Application Number 07/642,582] was granted by the patent office on 1992-08-18 for support for biomedical implant device.
This patent grant is currently assigned to Asahi Kogaku Kogyo K.K.. Invention is credited to Yasuhiko Hirayama, Takeshi Ichitsuka, Masahide Inoue, Tateki Kitaoka, Shozo Koshikawa, Osamu Minoo, Nobuo Nakabayashi, Tatsumichi Takeda.
United States Patent |
RE34,037 |
Inoue , et al. |
August 18, 1992 |
Support for biomedical implant device
Abstract
A support for a biomedical implant device in which the support
has a surface layer composed of a biocompatible calcium phosphate
material such as sintered hydroxyapatite with a porosity of 50-60%
and pore size of 0.5-500 micrometers. Preferably, the surface layer
is formed with projections or recesses of a few hundred micrometers
size.
Inventors: |
Inoue; Masahide (Tokyo,
JP), Ichitsuka; Takeshi (Tokyo, JP),
Hirayama; Yasuhiko (Tokyo, JP), Koshikawa; Shozo
(Tokyo, JP), Kitaoka; Tateki (Ichikawa,
JP), Nakabayashi; Nobuo (Matsudo, JP),
Takeda; Tatsumichi (Koganei, JP), Minoo; Osamu
(Miyoshi, JP) |
Assignee: |
Asahi Kogaku Kogyo K.K. (Tokyo,
JP)
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Family
ID: |
15061148 |
Appl.
No.: |
07/642,582 |
Filed: |
January 17, 1991 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
059445 |
Jun 8, 1987 |
04798585 |
Jan 17, 1989 |
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Foreign Application Priority Data
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Jun 6, 1989 [JP] |
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61-131570 |
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Current U.S.
Class: |
604/175; 604/174;
604/288.02 |
Current CPC
Class: |
A61L
27/12 (20130101); A61L 29/02 (20130101); A61F
2310/00293 (20130101) |
Current International
Class: |
A61L
29/00 (20060101); A61L 29/02 (20060101); A61L
27/00 (20060101); A61L 27/12 (20060101); A61F
2/00 (20060101); A61M 011/00 () |
Field of
Search: |
;604/93,174,175,185,891.1 |
References Cited
[Referenced By]
U.S. Patent Documents
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3673612 |
July 1972 |
Merrill et al. |
3752162 |
August 1973 |
Newash |
4479796 |
October 1984 |
Kallok |
4543088 |
September 1985 |
Bootman et al. |
4610692 |
September 1986 |
Eitenmuller et al. |
4632670 |
December 1986 |
Mueller et al. |
4798585 |
September 1986 |
Eitenmuller et al. |
|
Primary Examiner: Ostrager; Allen M.
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak &
Seas
Claims
What is claimed is:
1. A biomedical implant device for implantation within tissue of a
body, comprising: a support having a surface layer to be contacted
with said tissue and composed of a biocompatible calcium phosphate
material; and a medically operative part at least partially
enclosed by said surface layer.
2. A biomedical implant device as recited in claim 1, wherein said
calcium phosphate material is sintered hydroxyapatite.
3. A biomedical implant device as recited in claim 1, wherein said
calcium phosphate material has a porosity of 5-60%.
4. A biomedical implant device as recited in claim 3 wherein said
porosity is in a range of 20-40%.
5. A biomedical implant device as recited in claim 2, wherein said
calcium phosphate material has a porosity of 5-60%.
6. A biomedical implant device as recited in claim 1, wherein said
calcium phosphate material has a porosity of 5-60% and has voids
with an average pore size of 0.5-500 micrometers.
7. A biomedical implant device as recited in claim 6, wherein said
average pore size is 5-200 micrometers.
8. A biomedical implant device as recited in claim 2, wherein said
calcium phosphate material has a porosity of 5-60% and has voids
with an average pore size of 0.5-500 micrometers.
9. A biomedical implant device as recited in claim 8, wherein said
average pore size is 5-200 micrometers.
10. A biomedical implant device as recited in claim 1, wherein said
support further comprises at least one inner layer inside said
surface layer of a material of greater strength than said surface
layer.
11. A biomedical implant device as recited in claim 10, wherein
said inner layer comprises sintered hydroxyapatite with a porosity
significantly less than that of said surface layer.
12. A biomedical implant device as recited in claim 1, wherein said
surface layer includes a plurality of surface projections having a
average height of 5-1000 micrometers.
13. A biomedical implant device as recited in claim 5, wherein said
surface layer includes a plurality of surface projections having
heights of 5-1000 micrometers.
14. A biomedical implant device as recited in claim 1, wherein said
surface layer includes a plurality of surface recesses having
diameters of 0.5-500 micrometers.
15. A biomedical implant device as recited in claim 5, wherein said
surface layer includes a plurality of surface recesses having
diameters of 0.5-500 micrometers.
16. A biomedical implant device as recited in claim 1, wherein said
medically operative part comprises a catheter and said support acts
as a cuff surrounding said catheter.
17. A biomedical implant device as recited in claim 1, wherein said
medically operative part comprises a drug reservoir and said
support at least partially covers said drug reservoir. .Iadd.
18. A biomedical implant device for implantation within the tissues
of a body, comprising; a support in the form of a cuff having a
surface layer to be contacted with said tissues and composed of a
biocompatible calcium phosphate material. .Iaddend. .Iadd.19. A
biomedical implant device for implantation within the tissues of a
body, comprising; a support having a surface layer to be contacted
with said tissues and composed of a biocompatible calcium phosphate
material, said support being in the form of a catheter cuff, said
cuff including fixing means which, in use, operates to stably
retain a catheter within the body. .Iaddend. .Iadd.20. A drug
reservoir device for implantation within the body of a drug
recipient, comprising; a drug reservoir, a casing formed of a
biocompatible calcium phosphate material and substantially covering
at least one surface of said reservoir and being in contact with
tissues of the body in use, a drug entry location for receiving
quantities of a drug to be delivered to the body, and a drug exit
location through which said drug is supplied to the body. .Iaddend.
.Iadd.21. A biomedical implant device for implantation within the
tissues of a body, comprising; a support in the form of a catheter
cuff having a surface layer to be contacted with said tissues and
composed of a biocompatible calcium phosphate material. .Iaddend.
.Iadd.22. A biomedical implant device for implantation within the
tissues of a body, comprising; a support having a surface layer to
be contacted with said tissues and composed of a biocompatible
calcium phosphate material, said support being in the form of a
cuff, said cuff including fixing means which, in use, operates to
stably contact a member to be held in place in the body by said
cuff. .Iaddend. .Iadd.23. A device as claimed in claim 22, wherein
said fixing
means includes an interior surface of said cuff. .Iaddend.
.Iadd.24. A drug reservoir device for implantation within the body
of a drug recipient, comprising: a drug reservoir, a casing formed
of a biocompatible calcium phosphate material and substantially
covering a surface of said reservoir and being in contact with
tissues of the body in use, a drug entry location for receiving
quantities of a drug to be delivered to the body, and a drug exit
location through which said drug is supplied to the body. .Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a support for retaining biomedical
implant devices such as a catheter for peritoneal dialysis, an
extracorporeal shunt for hemodialysis, a tube for an ascites
recirculation circuit, a drain tube, an air tube for an artificial
heart, an electric circuit tube, and drug reservoir to be implanted
under the skin. In particular, the present invention relates to a
support for such biomedical implant devices that manifests enhanced
biocompatibility and which allows them to be retained in the body
over a prolonged period without permitting bacterial ingress.
2. Background of the Invention
An example of the support conventionally used to fix a biomedical
implant device in the human body is a cuff which is used with a
catheter for peritoneal dialysis. As shown in FIG. 1, a catheter 1
is inserted through the skin 10 of the patient, the subcutaneous
layer of fat 11, the fascia 12, the muscular tunic 13 and the
peritoneum 14. The catheter 1 is retained in the body so as to
permit injection or discharging of a dialyzing solution through the
catheter 1. In this case, a cuff 2 attached to the catheter 1 is
used as a support for functionally retaining the catheter 1 in the
body over an extended period and is generally sutured in living
tissues at the end of a surgical operation. The cuff 2 is typically
made of such materials as knitted or unknitted fabrics of synthetic
or natural fibers, plastic or plastic film.
Another prior art biomedical implant device proposed to date is a
drug reservoir for subcutaneous implantation. As shown in FIG. 2, a
reservoir 15 is implanted below the skin layer 10 and is composed
of a drug cell 16. Holes 17 on projections guide a retaining thread
(suture). The intended drug is injected into the cell 16 through a
silicone or synthetic rubber wall 18. A silicon tube 19 serves as a
passage for introducing the drug into the affected site of part of
the body such as a blood vessel or muscle. Stability of the
retained reservoir 15 is required for a prolonged period in order
to allow for periodic supply of the drug into the reservoir through
the wall 18 with syringe.
Conventional supports such as cuffs that are formed of cellulosic
or synthetic fibers, plastics, titanium or silicone resins show
poor biocompatibility and poor adhesion to living tissues because
of the nature of their constituent materials. As a result, during
prolonged use of biomedical implant devices within the body, they
might be displaced in position or bacterial ingress may occur in
the gap between the device and the surrounding tissues.
SUMMARY OF THE INVENTION
A general object of the invention is to eliminate the above
described problems in a biomedical implant device.
A particular object, therefore, of the present invention is to
provide a support for biomedical implant device that affords
enhanced adhesion to tissues and allows the implanted biomedical
device to be retained stably in the body without permitting
bacterial ingress.
Another object of the present invention is to provide a support
which, in addition to the enhanced adhesion to surrounding tissues,
permits the tissue to be anchored in the support, with subsequent
increase in the stability of the support in the body.
A further object of the present invention is to provide a support
possessed of increased strength and enhanced adhesion to the
biomedical implant device.
These objects are achieved by a biomedical implant device having a
support made of a biocompatible calcium phosphate compound as the
material of the surface layer. The calcium phosphate material may
be porous, thereby allowing anchoring of the tissue. To provide
strength, the support is made in multiple layers. The porous or
solid support may have in its surface many recesses formed by
etching, ion milling or other techniques.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sketch of a conventional catheter with a cuff in the
implanted state.
FIG. 2 is a sketch of a conventional drug reservoir in the
subcutaneously implanted state.
FIGS. 3, 7, 8A and 8B and 9 are cross-sectional views of cuffs
according to four embodiments of the present invention.
FIGS. 4 to 6 are pictorial representations of supports for
biomedical implant device in the state where they adhere to
surrounding tissues.
FIG. 10 is a sketch showing a cross section of the surface layer of
a cuff according to a fifth embodiment of the present
invention.
FIGS. 11A and 11B are a plan and a cross-sectional view,
respectively, of a drug reservoir to be implanted under the skin
according to a sixth embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The support for biomedical implant device of the present invention
is hereinafter described in detail. FIG. 3 shows a cuff 2 prepared
in accordance with one embodiment of the present invention. A
catheter 1 made of a plastic or some other suitable material is
connected to the cuff 2 that is formed of a biocompatible calcium
phosphate material such as sintered hydroxyapatite, bioglass or
sintered tricalcium phosphate (TCP). The cuff 2 which is formed of
sintered hydroxyapatite can be prepared from a hydroxyapatite
powder by the following procedure. A hydroxyapatite powder
comprising irregularly shaped particles of 0.1-1 .mu.m in average
size is blended with a hydroxyapatite powder comprising spherical
particles of 2-20 .mu.m in average size. The blend is intimately
mixed with water and a blowing agent. The mix is expanded and dried
in a thermostatic dryer. A suitable blowing agent is an aqueous
solution of hydrogen peroxide or egg albumin.
The so prepared porous hydroxyapatite is machined into a
cuff-shaped structure which is fired at a temperature of
1,000.degree.-1,250.degree. C. to produce the intended cuff 2. The
cuff has a porosity of 5-60%, preferably 20-40%, with the pore size
being adjusted to 0.5-500 .mu.m, preferably 5-200 .mu.m. The value
of the porosity is determined by comparing the density of the solid
material with that of the porous material. The percentage
difference is the porosity and represents generally the volume
percentage of voids. The cuff 2 is then joined to a catheter 1
which is implanted in the body. Such a cuff exhibits good
biocompatibility while it is being gradually fused to surrounding
tissues with time. Any bacterial ingress that might occur via the
outer surface of the catheter is completely prevented at least by
the cuff 2, with the result that the catheter 1 can be stably
retained in the body over a prolonged period.
Adjustment of the porosity and pore size of the cuff to the
above-specified values ensures spontaneous formation of small voids
in its surface with the result that the effective surface area of
the cuff 2 is sufficiently increased to provide enhanced adhesion
to the surrounding tissues. If the porosity of the cuff is less
than 5%, strong adhesion to the surrounding tissues is not
attained. If the porosity exceeds 60%, the strength of the cuff 2
is drastically decreased. If the pore size of the cuff is less than
0.5 .mu.m, tissue cells are unable to enter the cuff through voids.
If the pore size exceeds 500 .mu.m, the desired anchoring of
tissues in the porous structure of the cuff cannot be attained.
FIGS. 4, 5 and 6 show that the adhesion between the cuff and
surrounding tissues increases as the porosity of the cuff
increases. As can be seen from the comparison of FIG. 4 (20%
porosity), FIG. 5 (30% porosity) and FIG. 6 (56% porosity), strong
adhesion is imparted by the tissues (colored portion) penetrating
into the sintered hydroxy apatite (white portion).
FIGS. 7 shows a cuff according to a second embodiment of the
present invention. A catheter 1 is connected to a cuff 2. The
surface of the cuff 2 is provided with small projections 3 (5-1,000
.mu.m in height) that are formed by cutting or some other machining
technique. The cuff 2 having such small projections 3 on its
surface serve as a brake or impediment resisting movement when it
is implanted in the body. Therefore, the cuff 2 with the
projections 3 allows the catheter 1 to be securely fixed in the
body right after it has been implanted by a surgical operation.
FIGS. 8A and 8B show a cuff according to a third embodiment of the
present invention. A catheter 1 is connected to a cuff 2 that is
provided with holes 3 for facilitating post-operational suturing.
Two variations of such a cuff 2 are shown in the two drawings.
FIG. 4 shows a cuff according to a fourth embodiment of the present
invention. A catheter 1 is connected to a cuff 2 that is composed
of a surface-layer portion 4 and an inner-layer portion 5. The
surface-layer portion 4 is formed of a biocompatible calcium
phosphate material having a comparatively high porosity. The
inner-layer portions 5 is formed of a biocompatible calcium
phosphate material having a comparatively low porosity. The
inner-layer portion 6 may be formed on other materials such as
titanium, alumina and plastics and, if plastic materials are used,
greater facility is ensured when connecting the cuff 2 to the
catheter 1. The advantage of this fourth embodiment is that the
inner-layer portion 6 imparts a greater strength to the cuff 2 so
that the catheter 1 can be stably retained within the body.
FIG. 10 shows a cuff according to a fifth embodiment of the present
invention. A catheter 1 is connected to a cuff 2 that is prepared
from sintered hydroxyapatite which is surface-treated by etching or
ion milling to form recesses 7 in its surface having diameters of
0.5-500 .mu.m. The multiple recesses 7 help increase the surface
area of the cuff 2 so as to provide further enhanced adhesion to
surrounding tissues. The concept of this embodiment is applicable
not only to the case where the cuff 2 has a solid structure but
also to the case where it is made of a porous structure. If
recesses 7 are formed in the porous surface that has been attained
by the sintering described above, the resulting cuff 2 provides not
only good adhesion to surrounding tissues but also effective
anchoring of the issue in the porous surface of the cuff 2, thereby
ensuring greater stability of the catheter in the body.
FIGS. 11A and 11B shows a drug reservoir to be implanted under the
skin according to a sixth embodiment of the present invention.
Components which are the same as those shown in FIG. 2 are
identified by like numerals. The reservoir 15 is surrounded by a
casing 20 that has holes 17 for suturing. The casing 20 is formed
of a biocompatible calcium phosphate material. Any of the
techniques employed in the above-described first to fifth
embodiments is applicable to the casing 20 so that it will display
sufficient biocompatibility and adhesion to the surrounding tissues
to ensure that the reservoir 15 is stably retained in the body over
a prolonged period.
As described in the foregoing pages, the support for biomedical
implant device of the present invention is made of a biocompatible
calcium phosphate material either entirely or at least in the part
which is to contact surrounding tissues when the device is
implanted in the body. As a result, the support has improved
adhesion to the living tissues and allows the implanted biomedical
device to be stably retained in the body without permitting
bacterial ingress.
* * * * *