U.S. patent application number 12/017430 was filed with the patent office on 2009-09-24 for tissue prosthesis and a method of, and equipment for, forming a tissue prosthesis.
This patent application is currently assigned to COLUMNA PTY LTD. Invention is credited to Johnathon Choi, Ashish Diwan, Sandra Fisher, Zoran Milijasevic.
Application Number | 20090240341 12/017430 |
Document ID | / |
Family ID | 37757246 |
Filed Date | 2009-09-24 |
United States Patent
Application |
20090240341 |
Kind Code |
A1 |
Diwan; Ashish ; et
al. |
September 24, 2009 |
TISSUE PROSTHESIS AND A METHOD OF, AND EQUIPMENT FOR, FORMING A
TISSUE PROSTHESIS
Abstract
A tissue prosthesis 100 comprises an envelope 38 of a
biologically inert, elastically deformable material capable of
being expanded to conform to an interior surface of a cavity 36
formed at a site 10 in a patient's body. A filler material 60 is
received in a fluent state in the envelope 38. The filler material
60 is of the same class of material as the envelope 38 to form,
when cured, together with the envelope 38, a unified structure.
Inventors: |
Diwan; Ashish; (Sydney,
AU) ; Milijasevic; Zoran; (Bayview, AU) ;
Choi; Johnathon; (Carlingford, AU) ; Fisher;
Sandra; (Sydney, AU) |
Correspondence
Address: |
TOWNSEND AND TOWNSEND AND CREW, LLP
TWO EMBARCADERO CENTER, EIGHTH FLOOR
SAN FRANCISCO
CA
94111-3834
US
|
Assignee: |
COLUMNA PTY LTD
Kogarah
AU
|
Family ID: |
37757246 |
Appl. No.: |
12/017430 |
Filed: |
January 22, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/AU2006/001176 |
Feb 15, 2006 |
|
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12017430 |
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60708670 |
Aug 15, 2005 |
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Current U.S.
Class: |
623/23.72 ;
606/99 |
Current CPC
Class: |
A61F 2002/30235
20130101; A61F 2250/0098 20130101; A61F 2/4611 20130101; A61F
2230/0069 20130101; A61F 2002/3008 20130101; A61F 2002/4627
20130101; A61F 2002/30069 20130101; A61F 2002/30561 20130101; A61B
17/8827 20130101; A61F 2002/444 20130101; A61F 2210/0085 20130101;
A61F 2002/4663 20130101; A61F 2002/30583 20130101; A61F 2002/4495
20130101; A61F 2002/467 20130101; A61F 2002/4685 20130101; A61F
2/441 20130101 |
Class at
Publication: |
623/23.72 ;
606/99 |
International
Class: |
A61F 2/02 20060101
A61F002/02; A61B 17/58 20060101 A61B017/58 |
Claims
1. A tissue prosthesis which comprises an envelope of a
biologically inert, elastically deformable material capable of
being expanded to conform to an interior surface of a cavity formed
at a site in a patient's body; and a filler material received in a
fluent state in the envelope, the filler material being of the same
class of material as the envelope to form, when cured, together
with the envelope, a unified structure.
2. The prosthesis of claim 1 in which the envelope is of an
elastomeric material capable of expanding to up to 100 times its
relaxed state.
3. The prosthesis of claim 1 in which the filler material is of an
elastomeric material capable of absorbing shock and withstanding
compressive, tensile, bending and torsional forces.
4. The prosthesis of claim 1 in which the envelope is retained
under tension after being charged with the filler material.
5. The prosthesis of claim 1 in which the envelope and/or the
filler material are of an elastomeric material having a Shore
Hardness in the range of between about 5 to 90 A.
6. The prosthesis of claim 1 in which the envelope and the filler
material are of a silicone rubber material.
7. The prosthesis of claim 1 in which the envelope includes a neck
portion, the neck portion defining a zone of weakness for
facilitating separation of the envelope from a delivery device.
8. The prosthesis of claim 1 in which the envelope includes a flow
control device arranged at an inlet opening to the envelope for
inhibiting back flow of the filler material from the envelope.
9. The prosthesis of claim 8 which includes a flow control defining
member, the flow control defining member being separate from the
envelope and being arranged at the inlet opening to the
envelope.
10. The prosthesis of claim 1 in which the envelope carries a
marker arrangement on an exterior surface for enabling the envelope
to be used to assess dimensions and a shape of the cavity and
positioning of the envelope in the cavity.
11. A tissue prosthesis which comprises an envelope of a
foraminous, chemically inert material shaped to conform to an
interior surface of a cavity formed at a site in a patient's body
in which the envelope is to be placed; and a filler material
received in a fluent state in the envelope, the filler material
being of an elastomeric material which, prior to being cured, is
urged into foramens of the envelope to form an integrated structure
which inhibits relative movement between the envelope and the
filler material, in use, and once the filler material has
cured.
12. The prosthesis of claim 11 in which the envelope is of a
knitted biological or synthetic polymeric material.
13. The prosthesis of claim 11 in which the envelope is coated with
a material of the same class as the filler material.
14. The prosthesis of claim 11 in which the envelope includes a
flow control device arranged at an inlet opening to the envelope
for inhibiting back flow of the filler material from the
envelope.
15. The prosthesis of claim 14 which includes a flow control
defining member, the flow control defining member being separate
from the envelope and being arranged at the inlet opening to the
envelope.
16. A method of forming a tissue prosthesis in situ at a site in a
patient's body, the method comprising: accessing the site in the
patient's body; if necessary, removing tissue from the site to form
a cavity; inserting an envelope of a biologically inert,
elastically deformable material into the cavity; charging a filler
material, in a fluent state, into the envelope to cause the
envelope to expand and conform to the shape of the cavity; and
allowing the filler material to cure, the filler material being of
the same class of material as the envelope so that, when the filler
material has cured, a unified prosthesis is formed.
17. The method of claim 16 which includes accessing the site by
inserting an introducer through an aperture formed in tissue
associated with the site and removing, if required, nuclear tissue
from the site.
18. The method of claim 16 which includes, once the nuclear tissue
has been removed, checking dimensions of the cavity so formed.
19. The method of claim 18 which includes using the envelope,
containing suitable markers, to check the dimensions of the
cavity.
20. The method of claim 16 which includes, once the envelope has
been placed in position, checking the integrity of the
envelope.
21. The method of claim 16 which includes evacuating an interior of
the envelope to inhibit the formation or entrapment of fluid
bubbles in the filler material.
22. The method of claim 16 which includes commencing filling of the
envelope from a distal end of the envelope and progressively
filling the envelope towards a proximal end of the envelope to
inhibit the formation or entrapment of fluid bubbles in the filler
material.
23. The method of claim 17 which includes, once filling of the
envelope has been completed and a filler element withdrawn,
occluding the aperture in the tissue of the site.
24. The method of claim 17 which includes attaching the envelope to
a distal end of a tubular delivery device and everting the envelope
on the distal end prior to insertion of the delivery device into
the introducer for delivery of the envelope into the cavity of the
site.
25. The method of 16 which includes accessing the site
percutaneously in a minimally invasive surgical procedure.
26. The method of claim 25 which is used to perform minimally
invasive intervertebral disc nucleus replacement, the method
comprising: forming an aperture in an annulus fibrosis of the disc
percutaneously; extracting a nucleus pulposus of the disc to form a
disc cavity bounded by the annulus fibrosis of the disc and end
plates of vertebrae between which the disc is located; inserting
the envelope, in a relaxed state, into the cavity through the
aperture; charging the filler material into the envelope to cause
the envelope to conform to the shape of the disc cavity; allowing
the filler material to cure to form, together with the envelope,
the unified prosthesis; and occluding the aperture.
27. The method of claim 16 which includes expanding and stretching
the walls of the envelope and retaining the envelope under tension
after charging it with filler material.
28. Equipment for forming a tissue prosthesis in situ at a site in
a patient's body, the equipment comprising: a delivery device
displaceably receivable in a lumen of an introducer, the delivery
device defining a passageway; an envelope carried at a distal end
of the delivery device, the envelope being of a biologically inert,
elastically deformable material capable of being expanded to
conform to an interior surface of a cavity formed at the site; and
a supply of a filler material chargeable in a fluent state into the
envelope through the passageway of the delivery device, the filler
material being of the same class of material as the envelope to
form, when cured, together with the envelope, a unified
prosthesis.
29. The equipment of claim 28 which includes an aperture forming
element to form an aperture into the site, the aperture forming
element being receivable through the introducer for delivery to the
site.
30. The equipment of claim 28 which includes a tissue removal
mechanism insertable through the aperture for removing tissue, if
required, to form the cavity.
31. The equipment of claim 28 in which the envelope is of an
elastomeric material capable of expanding to up to 100 times its
relaxed state.
32. The equipment of claim 28 in which the envelope is expanded to
be stretched and retained under tension after being charged with
the filler material.
33. The equipment of claim 28 in which the envelope includes a neck
portion, the neck portion defining a zone of weakness for
facilitating separation of the envelope from the delivery
device.
34. The equipment of claim 28 in which the envelope includes a flow
control device arranged at an inlet opening to the envelope for
inhibiting back flow of the filler material from the envelope.
35. The equipment of claim 34 which includes a flow control
defining member, the flow control defining member being separate
from the envelope and being arranged at the inlet opening to the
envelope.
36. The equipment of 28 in which the envelope carries a marker
arrangement on an exterior surface for enabling the envelope to be
used to assess dimensions and a shape of the cavity and positioning
of the envelope in the cavity.
37. The equipment of claim 28 in which the filler material is of an
elastomeric material capable of absorbing shock and withstanding
compressive, tensile, bending and torsional forces.
38. The equipment of claim 28 in which the envelope and the filler
material are of an elastomeric material having a Shore Hardness in
the range of about 5 to 90 A.
39. The equipment of claim 28 in which the envelope and the filler
material are of a silicone rubber material.
40. The equipment of claim 28 which includes a dispenser containing
the supply of filler material.
41. The equipment of claim 28 which includes a sensing arrangement
configured to sense a parameter of the filler material charged into
the envelope.
42. The equipment of claim 41 in which the sensing arrangement
comprises a pressure sensor for sensing the pressure of filler
material charged into the envelope.
43. The equipment of claim 41 in which the sensing arrangement
comprises a temperature sensor for sensing the temperature of the
filler material charged into the envelope.
44. The equipment of claim 41 in which the sensing arrangement is
configured to sense the quantity of filler material charged into
the envelope.
45. The equipment of claim 41 in which the sensing arrangement
comprises a flow rate sensor for sensing the rate of flow of the
filler material into the envelope.
46. The equipment of claim 41 in which the sensing arrangement is
configured to sense the presence of air bubbles in the filler
material charged into the envelope.
47. Equipment for forming a tissue prosthesis in situ at a site in
a patient's body, the equipment comprising: a tubular delivery
device, the delivery device defining a passageway, an envelope of
the prosthesis being mountable to a distal end of the delivery
device to be received in a cavity at the site; a filler member
receivable in the passageway of the delivery device, the filler
member being receivable with clearance in the passageway to define
a gap to enable fluid to be evacuated at least from the envelope;
and a removal mechanism carried by the delivery device for enabling
the envelope to be removed from the delivery device after the
envelope has been charged with filler material via the filler
member.
48. The equipment of claim 47 which includes an introducer and an
aperture forming element to form an aperture at the site, the
aperture forming element being receivable through the introducer
for delivery to the site.
49. The equipment of claim 48 which includes a tissue removal
mechanism insertable through the aperture for removing tissue, if
required, to form the cavity.
50. The equipment of claim 48 in which the introducer and the
delivery device include a retaining arrangement for retaining the
delivery device with respect to the introducer.
51. The equipment of claim 47 which includes a supply of filler
material attachable to a proximal end of the filler member.
52. The equipment of claim 51 in which the filler material is a
mixture of a plurality of parts and in which the supply of filler
material comprises a dispenser defining a plurality of chambers in
each of which one part of the filler material is received prior to
use.
53. The equipment of claim 51 in which the dispenser further
comprises a mixer arranged intermediate an outlet of the dispenser
and the proximal end of the filler member for mixing the filler
material prior to charging it into the envelope.
54. The equipment of claim 47 in which a proximal end of the
delivery device carries a connector for connection to an evacuating
mechanism.
55. The equipment of claim 47 which includes the envelope, the
envelope being of an elastomeric material capable of expanding to
up to 100 times its relaxed state.
56. The equipment of claim 55 in which the envelope is expanded to
be stretched and retained under tension after being charged with
the filler material.
57. The equipment of claim 55 in which the envelope includes a neck
portion, the neck portion defining a zone of weakness for
facilitating separation of the envelope from the delivery
device.
58. The equipment of claim 55 in which the envelope includes a flow
control device arranged at an inlet opening to the envelope for
inhibiting back flow of the filler material from the envelope.
59. The equipment of claim 58 which includes a flow control
defining member, the flow control defining member being separate
from the envelope and being arranged at the inlet opening to the
envelope.
60. The equipment of claim 58 in which a distal end of the filler
member carries an engaging member which engages the flow control
device to at least partially open the flow control device and to
allow the interior of the envelope to be evacuated prior to being
charged with the filler material.
61. The equipment of claim 55 in which the envelope carries a
marker arrangement on an exterior surface for enabling the envelope
to be used to assess dimensions and a shape of the cavity and
positioning of the envelope in the cavity.
62. The equipment of claim 55 in which the filler material is of an
elastomeric material capable of absorbing shock and withstanding
compressive, tensile, bending and torsional forces.
63. The equipment of claim 55 in which the envelope and the filler
material are of an elastomeric material having a Shore Hardness in
the range of about 5 to 90 A.
64. The equipment of claim 55 in which the envelope and the filler
material are of a silicone rubber material.
65. The equipment of claim 47 which includes a sensing arrangement
configured to sense a parameter of the filler material charged into
the envelope.
66. The equipment of claim 65 in which the sensing arrangement
comprises a pressure sensor for sensing the pressure of filler
material charged into the envelope.
67. The equipment of claim 65 in which the sensing arrangement
comprises a temperature sensor for sensing the temperature of the
filler material charged into the envelope.
68. The equipment of claim 65 in which the sensing arrangement is
configured to sense the quantity of filler material charged into
the envelope.
69. The equipment of claim 65 in which the sensing arrangement
comprises a flow rate sensor for sensing the rate of flow of the
filler material into the envelope.
70. The equipment of claim 65 in which the sensing arrangement is
configured to sense the presence of air bubbles in the filler
material charged into the envelope.
71. Equipment for forming a tissue prosthesis in situ at a site in
a patient's body, the equipment comprising: a tubular delivery
device, the delivery device defining a passageway, an envelope of
the prosthesis being mountable to a distal end of the delivery
device to be received in a cavity at the site; a stiffening element
arranged to project from a distal end of the delivery device with
the envelope, in use, being received over the stiffening element to
be supported by the stiffening element; and a removal mechanism
carried by the delivery device for enabling the envelope to be
removed from the delivery device after the envelope has been
charged with filler material via the filler member.
72. The equipment of claim 71 in which the stiffening element is an
elongate element receivable with clearance in the passageway of the
delivery device to define a gap to enable fluid to be evacuated at
least from the envelope to enable fluid to be withdrawn from the
envelope to collapse the envelope on to a distal end of the
elongate element projecting from the distal end of the delivery
device.
73. The equipment of claim 71 which includes a filler member
receivable in the passageway of the delivery device after removal
of the stiffening element, the filler member being receivable,
after removal of the stiffening element, with clearance in the
passageway to define a gap to enable fluid to be evacuated at least
from the envelope.
74. The equipment of claim 71 which includes a tubular filler
member receivable in the passageway of the delivery device, the
filler member being receivable with clearance in the passageway to
define a gap to enable fluid to be evacuated at least from the
envelope and the stiffening element being a elongate element
receivable through the passage of the filler member.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation of International
Application No. PCT/AU2006/001176, filed on Aug. 15, 2006, which
claims the benefit of U.S. Provisional Patent Application Ser. No.
60/708,670, filed on Aug. 15, 2005, the full disclosures of which
are incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0002] This invention relates generally to the repair of tissue in
a body and, more particularly, to a method of, and equipment for,
forming a tissue prosthesis in situ and to a tissue prosthesis. The
invention has particular, but not necessarily exclusive,
application in the field of minimally invasive intervertebral disc
nucleus repair.
[0003] Joints of the musculoskeletal system of the human or animal
body rely on the presence of healthy cartilaginous tissue for
proper operation. Cartilaginous tissue can degenerate due to a
number of causes, eg. age or injury. Degradation of the tissue can
reach a point where movement can cause severe discomfort and
pain.
[0004] In the case of the spinal column, it comprises a series of
26 mobile vertebral bones or vertebrae connected by 75 stable
articulations that control motion. The vertebrae are generally
divided into posterior and anterior elements by thick pillows of
bone called pedicles. The anterior element of the vertebra is a
kidney shaped prism of bone with a concavity directed posteriorly
and has flat superior and inferior surfaces called end plates. An
intervertebral disc is sandwiched between adjacent pairs of
vertebrae forming a joint between the adjacent pair of vertebrae.
These discs are viscoelastic structures comprising a layer of
strong deformable soft tissue. The intervertebral discs are
subjected to a considerable variety of forces and moments resulting
from the movements and loads of the spinal column. Each
intervertebral disc has two components being the annulus fibrosis
circumscribing a nucleus pulposus. The intervertebral disc
cooperates with the end plates of the vertebrae between which it is
sandwiched.
[0005] The primary function of the nucleus pulposus of the disc is
to give the disc its elasticity and compressibility characteristics
to assist in sustaining and transmitting weight. The annulus
fibrosis contains and limits the expansion of the nucleus pulposus
during compression and also holds together successive vertebrae,
resisting tension and torsion in the spine. The end plates of the
vertebrae are responsible for the influx of nutrients into the disc
and the efflux of waste products from within the disc.
[0006] With age or injury, a degenerative process of the disc may
occur whereby its structures undergo morphological and biological
changes affecting the efficiency with which the disc operates.
Thus, the nucleus pulposus may reduce in volume and dehydrate
resulting in a load reduction on the nucleus pulposus, a loss in
intradiscal pressure and, hence, additional loading on the annulus
fibrosis. In a normally functioning disc, the intradiscal pressure
generated results in deformation of the end plates of the adjacent
vertebrae generating the natural pumping action which assists in
the influx of the nutrients and the efflux of waste products as
stated above. A drop in intradiscal pressure therefore results in
less end plate deformation. The nutrients supplied to the discal
tissue is reduced and metabolic wastes are not removed with the
same efficiency. This contributes to a degenerative cascade.
[0007] Radial and circumferential tears, cracks and fissures may
begin to appear within the annulus fibrosis. If these defects do
not heal, some of the nuclear material may begin to migrate into
the defects in the annulus fibrosis. Migration of the nuclear
material into the annulus fibrosis may cause stretching and
delamination of layers of the annulus fibrosis resulting in back
pain due to stimulation of the sinu-vertebral nerve. An
intervertebral disc without a competent nucleus is unable to
function properly. Further, since the spine is a cooperative system
of elements, altering the structure and mechanics at one location
of the spinal column may significantly increase stresses
experienced at adjacent locations thereby further contributing to
the degenerative cascade.
[0008] In the past, operative intervention has occurred to relieve
lower back pain arising from intervertebral disc degeneration. Most
of this operative intervention has been by way of a discectomy
where leaking nuclear material is removed or, alternatively,
fusion. The primary purpose of a discectomy is to excise any disc
material that is impinging on the spinal nerve causing pain or
sensory changes. Fusion means eliminating a motion segment between
two vertebrae by use of a bone graft and sometimes internal
fixation. Biomechanical studies show that fusion alters the
biomechanics of the spine and causes increased stresses to be
experienced at the junction between the fused and unfused segments.
This promotes degeneration and begins the degenerative cycle anew.
Clearly, being an invasive operative procedure, fusion is a risky
procedure with no guarantee of success.
[0009] Due to the minimal success rate of the previous two
procedures, as well as their inability to restore complete function
to the spinal column, alternative treatments have been sought in
the form of artificial disc replacements. Theoretical advantages of
artificial disc replacement over a fusion procedure include
preservation or restoration of segmental motion in the spine,
restoration of intervertebral architecture and foraminal height,
sparing of adjacent segments of the spine from abnormal stresses
and restoration of normal biomechanics across the lumbar spine. The
established artificial disc replacement procedure consists of
techniques that require a surgical incision on the abdomen,
retraction of large blood vessels, a total excision of the anterior
longitudinal ligament, anterior and posterior annulus along with
the nucleus and near total removal of the lateral annulus and
implantation of an articulated prosthesis. This is a major spinal
column reconstruction operation.
[0010] There is therefore a need for a surgical procedure which, as
far as possible, restores the biomechanics of joints such as those
between adjacent vertebrae of the spine by the provision of a
tissue prosthesis mimicking natural, healthy cartilaginous
tissue.
BRIEF SUMMARY OF THE INVENTION
[0011] Throughout this specification the word "comprise", or
variations such as "comprises" or "comprising", will be understood
to imply the inclusion of a stated element, integer or step, or
group of elements, integers or steps, but not the exclusion of any
other element, integer or step, or group of elements, integers or
steps.
[0012] According to a first aspect of the invention, there is
provided a tissue prosthesis which comprises: [0013] an envelope of
a biologically inert, elastically deformable material capable of
being expanded to conform to an interior surface of a cavity formed
at a site in a patient's body; and [0014] a filler material
received in a fluent state in the envelope, the filler material
being of the same class of material as the envelope to form, when
cured, together with the envelope, a unified structure.
[0015] The envelope may be of an elastomeric material capable of
expanding to up to 100 times its relaxed state. Further, the filler
material may be of an elastomeric material capable of absorbing
shock and withstanding compressive, tensile, bending and torsional
forces. The envelope may be expanded to be stretched and retained
under tension after being charged with the filler material.
[0016] In this specification, the term "expanded" and its
variations is to be understood as meaning "stretched
elastically".
[0017] Both the envelope and the filler material may be of an
elastomeric material having a Shore Hardness in the range of
between about 5 to 90 A. Preferably, the envelope and the filler
material are of a silicone rubber material. However, to promote
bonding between the envelope and the filler material, the envelope
and the filler material may be of different grades of silicone
rubber material and may be pre-treated in different ways prior to
use.
[0018] The envelope may include a neck portion, the neck portion
defining a zone of weakness for facilitating separation of the
envelope from a delivery device. Further, the envelope may include
a flow control device arranged at an inlet opening to the envelope
for inhibiting back flow of the filler material from the envelope.
In an embodiment, the prosthesis may include a flow control
defining member, the flow control defining member being separate
from the envelope and being arranged at the inlet opening to the
envelope.
[0019] The envelope may carry a marker arrangement on an exterior
surface for enabling the envelope to be used to assess dimensions
and a shape of the cavity and positioning of the envelope in the
cavity.
[0020] According to a second aspect of the invention, there is
provided a tissue prosthesis which comprises: [0021] an envelope of
a foraminous, chemically inert material shaped to conform to an
interior surface of a cavity formed at a site in a patient's body
in which the envelope is to be placed; and [0022] a filler material
received in a fluent state in the envelope, the filler material
being of an elastomeric material which, prior to being cured, is
urged into foramens of the envelope to form an integrated structure
which inhibits relative movement between the envelope and the
filler material, in use, and once the filler material has
cured.
[0023] The envelope may be of a knitted biological or synthetic
polymeric material. More particularly, the envelope may be of a
knitted polyester material, such as polyethylene terephthalate
(PET). Further, the envelope may be coated with a material of the
same class as the filler material.
[0024] Once again, the envelope may include a flow control device
arranged at an inlet opening to the envelope for inhibiting back
flow of the filler material from the envelope. The prosthesis may
include a flow control defining member, the flow control defining
member being separate from the envelope and being arranged at the
inlet opening to the envelope.
[0025] According to a third aspect of the invention, there is
provided a method of forming a tissue prosthesis in situ at a site
in a patient's body, the method comprising: [0026] accessing the
site in the patient's body; [0027] if necessary, removing tissue
from the site to form a cavity; [0028] inserting an envelope of a
biologically inert, elastically deformable material into the
cavity; [0029] charging a filler material, in a fluent state, into
the envelope to cause the envelope to expand and conform to the
shape of the cavity; and [0030] allowing the filler material to
cure, the filler material being of the same class of material as
the envelope so that, when the filler material has cured, a unified
prosthesis is formed.
[0031] The method may include accessing the site by inserting an
introducer through an aperture formed in tissue associated with the
site and removing nuclear tissue, if required, from the site. The
nuclear material may be removed by mechanical, ultrasonic, laser,
Argon gas or radio frequency ablation, or the like, in combination
with suction and irrigation. For example, mechanical removal may be
effected by using a reaming-type tool.
[0032] Once the nuclear tissue has been removed, the method may
include checking dimensions of the cavity so formed. Thus, the
method may include using the envelope, containing suitable markers,
to check the dimensions of the cavity. This may be effected by
inflating the envelope using a suitable fluid such as a
water/saline solution. Instead of using the envelope with markers,
the method may include using a flexible wire fed down the
introducer and checking the position of the wire using a
fluoroscopic x-ray technique once the wire is in position. In yet a
further way of checking the dimensions of the cavity, the method
may include deploying a jacket of similar dimensions to the
envelope in the cavity, inflating the jacket with the water/saline
solution and, using a fluoroscope, detecting the periphery of the
jacket by radio opaque markers on an outer surface of the
jacket.
[0033] Once the envelope has been placed in position, the method
may include checking the integrity of the envelope, i.e. to ensure
that the envelope does not have any leaks or other defects. This
may be effected by filling the envelope with the water/saline
solution.
[0034] The method may include evacuating an interior of the
envelope to inhibit the formation or entrapment of fluid bubbles in
the filler material. Instead, the method may include commencing
filling of the envelope from a distal end of the envelope and
progressively filling the envelope towards a proximal end of the
envelope (by withdrawing a filler tube or allowing the material
buoyancy to lift the filler tube) to inhibit the formation or
entrapment of fluid bubbles in the filler material. In the latter
case, either a delivery device by which the envelope is introduced
into the cavity or the envelope may define a formation allowing the
escape of air as the envelope is charged with the filler
material.
[0035] The method may include, once filling of the envelope has
been completed and a filler element withdrawn, occluding the
aperture in the tissue of the site. Occluding the aperture may
comprise closing it off by a non-return valve or by crimping closed
a neck portion of the envelope. A removable tube may be nested over
the delivery device and may be propelled distally to remove the
envelope and valve from the delivery device.
[0036] The method may include attaching the envelope to a distal
end of a tubular delivery device and everting the envelope on the
distal end prior to insertion of the delivery device into the
introducer for delivery of the envelope into the cavity of the
site.
[0037] Preferably, the method includes accessing the site
percutaneously in a minimally invasive surgical procedure. Hence,
the method may be used to perform minimally invasive intervertebral
disc nucleus replacement and may comprise: [0038] forming an
aperture in an annulus fibrosis of the disc percutaneously; [0039]
extracting a nucleus pulposus of the disc to form a disc cavity
bounded by the annulus fibrosis of the disc and end plates of
vertebrae between which the disc is located; [0040] inserting the
envelope, in a relaxed state, into the cavity through the aperture;
[0041] charging the filler material into the envelope to cause the
envelope to expand and conform to the shape of the disc cavity;
[0042] allowing the filler material to cure to form, together with
the envelope, the unified prosthesis; and [0043] occluding the
aperture.
[0044] Preferably, the method includes expanding and stretching the
walls of the envelope and retaining the envelope under tension
after charging it with filler material.
[0045] According to a fourth aspect of the invention, there is
provided equipment for forming a tissue prosthesis in situ at a
site in a patient's body, the equipment comprising: [0046] a
delivery device displaceably receivable in a lumen of an
introducer, the delivery device defining a passageway; [0047] an
envelope carried at a distal end of the delivery device, the
envelope being of a biologically inert, elastically deformable
material capable of being expanded to conform to an interior
surface of a cavity formed at the site; and [0048] a supply of a
filler material chargeable in a fluent state into the envelope
through the passageway of the delivery device, the filler material
being of the same class of material as the envelope to form, when
cured, together with the envelope, a unified prosthesis.
[0049] The equipment may include an aperture forming element to
form an aperture into the site, the aperture forming element being
receivable through the introducer for delivery to the site. The
aperture forming element may, for example, be a trocar.
[0050] Further, the equipment may include a tissue removal
mechanism insertable through the aperture for removing tissue, if
required, to form the cavity. As indicated above, the tissue
removal mechanism may comprise mechanical, ultrasonic, laser, Argon
gas or radio frequency ablation mechanisms, or the like in
combination with suction and irrigation. For example, the tissue
removal mechanism may be a reaming-type tool.
[0051] The envelope may be of an elastomeric material capable of
expanding to up to 100 times its relaxed state. The envelope is
preferably expanded to be stretched and retained under tension
after being charged with the filler material.
[0052] The envelope may include a neck portion, the neck portion
defining a zone of weakness for facilitating separation of the
envelope from the delivery device. Further, the envelope may
includes a flow control device arranged at an inlet opening to the
envelope for inhibiting back flow of the filler material from the
envelope. The equipment may include a flow control defining member,
the flow control defining member being separate from the envelope
and being arranged at the inlet opening to the envelope.
[0053] The envelope may carry a marker arrangement on an exterior
surface for enabling the envelope to be used to assess dimensions
and a shape of the cavity and positioning of the envelope in the
cavity.
[0054] The filler material may be of an elastomeric material
capable of absorbing shock and withstanding compressive, tensile,
bending and torsional forces. More particularly, the envelope and
the filler material may be of an elastomeric material having a
Shore Hardness in the range of about 5 to 90 A. The envelope and
the filler material may be of a silicone rubber material.
[0055] The equipment may include a dispenser containing the supply
of filler material.
[0056] Further, the equipment may include a sensing arrangement
configured to sense a parameter of the filler material charged into
the envelope. The sensing arrangement may comprise a pressure
sensor for sensing the pressure of filler material charged into the
envelope, a temperature sensor for sensing the temperature of the
filler material charged into the envelope, be configured to sense
the quantity of filler material charged into the envelope and/or
comprise a flow rate sensor for sensing the rate of flow of the
filler material into the envelope. Further, the sensing arrangement
may be configured to sense the presence of air bubbles in the
filler material charged into the envelope.
[0057] According to a fifth aspect of the invention, there is
provided equipment for forming a tissue prosthesis in situ at a
site in a patient's body, the equipment comprising: [0058] a
tubular delivery device, the delivery device defining a passageway,
an envelope of the prosthesis being mountable to a distal end of
the delivery device to be received in a cavity at the site; [0059]
a filler member receivable in the passageway of the delivery
device, the filler member being receivable with clearance in the
passageway to define a gap to enable fluid to be evacuated at least
from the envelope; and [0060] a removal mechanism carried by the
delivery device for enabling the envelope to be removed from the
delivery device after the envelope has been charged with filler
material via the filler member.
[0061] The equipment may include a tubular introducer and an
aperture forming element, such as a trocar, to form an aperture at
the site, the aperture forming element being receivable through the
introducer for delivery to the site.
[0062] Further, the equipment may include a tissue removal
mechanism insertable through the aperture for removing tissue, if
required, to form the cavity.
[0063] The introducer and the delivery device may include a
retaining arrangement for retaining the delivery device with
respect to the introducer.
[0064] In addition the equipment may include a supply of filler
material attachable to a proximal end of the filler member. The
filler material may be a mixture of a plurality of parts and the
supply of filler material may comprise a dispenser defining a
plurality of chambers in each of which one part of the filler
material is received prior to use. The dispenser may further
comprise a mixer arranged intermediate an outlet of the dispenser
and the proximal end of the filler member for mixing the filler
material prior to charging it into the envelope.
[0065] A proximal end of the delivery device may carry a connector
for connection to an evacuating mechanism such as an evacuation
pump.
[0066] The equipment may include the envelope, the envelope being
of an elastomeric material capable of expanding to up to 100 times
its relaxed state. Preferably, the envelope is expanded to be
stretched and retained under tension after being charged with the
filler material. The envelope may include a neck portion, the neck
portion defining a zone of weakness for facilitating separation of
the envelope from the delivery device.
[0067] Further, the envelope may include a flow control device
arranged at an inlet opening to the envelope for inhibiting back
flow of the filler material from the envelope. The equipment may
include a flow control defining member, the flow control defining
member being separate from the envelope and being arranged at the
inlet opening to the envelope.
[0068] A distal end of the filler member may carry an engaging
member which engages the flow control device to at least partially
open the flow control device and to allow the interior of the
envelope to be evacuated prior to being charged with the filler
material.
[0069] The envelope may carry a marker arrangement on an exterior
surface for enabling the envelope to be used to assess dimensions
and a shape of the cavity and positioning of the envelope in the
cavity.
[0070] The filler material may be of an elastomeric material
capable of absorbing shock and withstanding compressive, tensile,
bending and torsional forces. The envelope and the filler material
may be of an elastomeric material having a Shore Hardness in the
range of about 5 to 90 A. Preferably, the envelope and the filler
material are of a silicone rubber material.
[0071] The equipment may include a sensing arrangement configured
to sense a parameter of the filler material charged into the
envelope. The sensing arrangement may comprise a pressure sensor
for sensing the pressure of filler material charged into the
envelope, a temperature sensor for sensing the temperature of the
filler material charged into the envelope, be configured to sense
the quantity of filler material charged into the envelope and/or
comprise a flow rate sensor for sensing the rate of flow of the
filler material into the envelope. Further, the sensing arrangement
may be configured to sense the presence of air bubbles in the
filler material charged into the envelope.
[0072] According to a sixth aspect of the invention, there is
provided equipment for forming a tissue prosthesis in situ at a
site in a patient's body, the equipment comprising: [0073] a
tubular delivery device, the delivery device defining a passageway,
an envelope of the prosthesis being mountable to a distal end of
the delivery device to be received in a cavity at the site; [0074]
a stiffening element arranged to project from a distal end of the
delivery device with the envelope, in use, being received over the
stiffening element to be supported by the stiffening element; and
[0075] a removal mechanism carried by the delivery device for
enabling the envelope to be removed from the delivery device after
the envelope has been charged with filler material via the filler
member.
[0076] In one embodiment, the stiffening element may be an elongate
element, such as a rod or tube, receivable with clearance in the
passageway of the delivery device to define a gap to enable fluid
to be evacuated at least from the envelope to enable fluid to be
withdrawn from the envelope to collapse the envelope on to a distal
end of the elongate element projecting from the distal end of the
delivery device.
[0077] The equipment may include a filler member receivable in the
passageway of the delivery device after removal of the stiffening
element, the filler member being receivable, after removal of the
stiffening element, with clearance in the passageway to define a
gap to enable fluid to be evacuated at least from the envelope.
[0078] In another embodiment, the equipment may include a tubular
filler member receivable in the passageway of the delivery device,
the filler member being receivable with clearance in the passageway
to define a gap to enable fluid to be evacuated at least from the
envelope and the stiffening element being an elongate element
receivable through the passage of the filler member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0079] Embodiments of the invention are now described by way of
example only with reference to the accompanying drawings in
which:
[0080] FIGS. 1-8 show schematic illustrations of various steps of a
method, in accordance with an embodiment of the invention, for
forming a tissue prosthesis in situ at a site in a patient's
body;
[0081] FIG. 9 shows a schematic illustration of a delivery device
for use in the method;
[0082] FIG. 10 shows a schematic, sectional side view of part of
equipment, in accordance with another embodiment of the invention,
for forming a tissue prosthesis, in situ at a site in a patient's
body;
[0083] FIG. 11 shows a schematic, sectional side view of another
embodiment of the equipment;
[0084] FIG. 12 shows a schematic, side view and end view of part of
the equipment;
[0085] FIG. 13 shows a sectional side view of an envelope, attached
to a delivery device, the envelope forming part of a tissue
prosthesis, in accordance with yet a further embodiment of the
invention;
[0086] FIG. 14 shows a sectional side view of another mounting of
the envelope on the delivery device;
[0087] FIGS. 15-17 show different shapes of envelopes for use in
the tissue prosthesis;
[0088] FIG. 18 shows a plan view of another embodiment of equipment
for forming a tissue prosthesis, in situ, at a site in a patient's
body;
[0089] FIG. 19 shows a sectional side view taken along line XIX-XIX
in FIG. 18;
[0090] FIG. 20 shows, on an enlarged scale, a sectional side view
of the part of the equipment encircled by circle `A` in FIG.
19;
[0091] FIG. 21 shows, on an enlarged scale, a sectional side view
of the part of the equipment encircled by circle `B` in FIG.
19;
[0092] FIG. 22 shows a sectional side view of yet a further
embodiment of equipment for forming a tissue prosthesis, in situ,
at a site in a patient's body;
[0093] FIG. 23 shows on an enlarged scale, a sectional side view of
the part of the equipment encircled by circle `C` in FIG. 22;
and
[0094] FIG. 24 shows on an enlarged scale, a sectional side view of
the part of the equipment encircled by circle `D` in FIG. 22.
DETAILED DESCRIPTION OF THE INVENTION
[0095] While this invention has been developed specifically for the
field of minimally invasive intervertebral disc nucleus
replacement, it will readily be appreciated that the invention has
applications in other fields requiring tissue prostheses. However,
for ease of explanation, embodiments of the invention will be
described below with reference to minimally invasive intervertebral
disc nucleus replacement.
[0096] An intervertebral disc 10 is arranged between adjacent
vertebrae 12 and 14. The disc 10 comprises an annulus fibrosis 16
made up of concentric layers of fibrous tissue. The annulus
fibrosis 16 circumscribes a nucleus pulposus 18 of the disc 10, the
nucleus pulposus 18 being of soft tissue. The disc 10 is sandwiched
between end plates 20 of the vertebrae 12 and 14. Relative movement
between the vertebrae 12 and 14 causes compression of the nucleus
pulposus 18 by the end plates 20. This serves to assist in the
influx of nutrients into the disc 10 and the efflux of waste
products from within the disc 10.
[0097] In a method of forming a tissue prosthesis, in situ, in
accordance with an embodiment of the invention, a damaged nucleus
pulposus 18 of the disc 10 is removed and is replaced by an
artificial prosthesis. Thus, in an initial step as shown in FIG. 1
of the drawings, an introducer 22 is inserted percutaneously into
abutment with the disc 10. An aperture forming element in the form
of a trocar 24 is inserted into a lumen 26 of the introducer 22. A
point 28 of the trocar pierces the annulus fibrosis 16 of the disc
10 forming an aperture 30 (FIG. 2) in the annulus fibrosis 16 of
the disc 10.
[0098] After the formation of the aperture 30 the trocar 24 is
removed from the introducer 22. Once the trocar 24 has been
removed, a nucleotomy is performed on the disc 10. The nucleotomy
involves the removal of nuclear tissue constituting the nucleus
pulposus 18. While various methods of removing the nucleus pulposus
can be used, the example shows the use of a mechanical device 32.
The mechanical device 32 comprises a reaming tool 34. The
mechanical device 32 is inserted through the lumen 26 of the
introducer and the aperture 30 in the annulus fibrosis 16 of the
disc 10 into the nucleus pulposus 18. The reaming tool 34 is
operated to remove the nucleus pulposus as shown in FIG. 4 of the
drawings so that a cavity 36 remains. The cavity 36 is bounded by
the annulus fibrosis 16 and the end plates 20 of the vertebrae 12
and 14. Residue 64 of the nucleus pulposus 18 remains resulting in
the cavity 36 having irregular walls.
[0099] An envelope 38 of an elastomeric material, more
particularly, a silicone rubber material is mounted on a distal end
of a tubular delivery device 40. The tubular delivery device 40
defines a passageway 42. The envelope 38 is made from the silicone
rubber material which is biologically inert and which can
elastically deform up to 100 times the size of the envelope 38 in
its relaxed state.
[0100] In one embodiment, as shown in greater detail in FIG. 10 of
the drawings, the envelope 38, in its relaxed, or deflated, state,
is a snug fit over a distal end 44 of the delivery device 40. A
first sleeve 46 is arranged coaxially over the delivery device 40
adjacent the distal end 44 of the delivery device 40. This sleeve
46 has a plurality of openings 48 defined in it. These openings 48
cooperate with openings 50 at the distal end 44 of the delivery
device 40. A further sleeve 52 is mounted coaxially about the
sleeve 46 and communicates with an evacuation device (not shown)
via an evacuating tube 54. Proximal ends of the sleeves 46 and 52
are sealed against an outer surface of the delivery device 40 via
seals 56. A further seal 58 is arranged between a distal end of the
sleeve 52 and the sleeve 46.
[0101] When filler material, referenced generally by the reference
numeral 60, is injected into the envelope 38, a low pressure is,
simultaneously or prior to injection, imparted to the distal end of
the delivery device 40 to evacuate fluid, more particularly, air,
from within the envelope 38. This assists in airless mixing and
ensures that the formation of air bubbles in the filler material 60
is inhibited. Evacuation of air also inhibits entrapment of air
within the envelope 38 by the incoming filler material 60 and
facilitates the flow of the filler material 60 into the envelope
38. As the filler material 60 is charged into the envelope 38
through the filling openings 50, air is drawn out of the envelope
38 by operation of the evacuation device via the evacuation tube
54. The air is received between the outer surface of the delivery
device 40 and the sleeve 46. This air passes through the openings
48 in the sleeve 46 and through the evacuation tube 54.
[0102] The filler material 60 is also of a silicone rubber material
which is able to absorb shocks and withstand compressive, tensile,
bending and torsional forces imparted to it by movement of the
vertebrae 12 and 14. In addition, due to the fact that the filler
material 60 is the same class or type as the material of the
envelope 38, once the filler material has cured in the envelope 38,
a unified or single, integrated structure is formed which is
resistant to delamination and relative movement between the
envelope 38 and the filler material 60.
[0103] The envelope 38 is made from a silicone rubber material
having the following characteristics: [0104] a Shore hardness (A
scale) in the range from about 20-50; [0105] a tensile strength in
the range from about 2700 kPa to 11000 kPa; [0106] an elongation of
between about 400% and 800%; and [0107] a tear strength of between
about 1700 kg/m and 4500 kg/m.
[0108] The filler material 60 is also of a silicone rubber material
which, prior to use, is stored in two separate parts. The filler
material 60, comprising the combined parts, when mixed in a ratio
of 1:1 and cured, has the following characteristics: [0109] a Shore
hardness (A scale) in the range from about 20 to 40, more
particularly, about 25 to 30 and, optimally, about 28; [0110] a
tensile strength in the range form about 7000 kPa to about 9500
kPa, more particularly, about 8000 kPa to about 9000 kPa and,
optimally, about 8500 kPa; [0111] an elongation in the range from
about 550% to 700%, more particularly, about 600% to 650% and
optimally, about 640%; and [0112] a tear strength in the range from
about 1000 to 2000 kg/m, more particularly, about 1250 kg/m to 1750
kg/m and, optimally, about 1500 kg/m.
[0113] One example of a suitable material for the filler material
has the following characteristics after mixing the parts in a 1:1
ratio and after curing: [0114] a Shore hardness (A scale) of 28;
[0115] a tensile strength of 8439 kPa; [0116] an elongation of
639%; and [0117] a tear strength of 1500 kg/m.
[0118] The filler material 60 is treated to contain 5%, by volume,
barium sulphate to appear radio-opaque under X-ray, CT, fluoroscopy
and MRI. In addition, the filler material 60 contains a catalyst
and has a scorch time of between about 1.5 to 2.5 minutes with a
curing time of about 5 minutes. When the filler material 60 is
charged into the envelope 38 it causes inflation or expansion of
the envelope 38 in an elastically deformable manner. Expansion of
the envelope 38 can occur to such an extent that, where necessary,
the expanded envelope 38 distracts the vertebrae 12 and 14 to
restore the original spacing between the vertebrae 12 and 14. By
using radio-opacity in the filler material 60, distraction of the
vertebrae 12 and 14 can be monitored in real time using a
fluoroscope or the similar equipment.
[0119] Further, the envelope 38 conforms to the shape of the cavity
36. Because the envelope 38 expands within the cavity 36 and
conforms closely to the shape of the cavity 36, the envelope 38
self anchors within the cavity 36 and "extrusion" of a unified
prosthesis 100, comprising the envelope 38 and the filler material
60, formed through the aperture 30 previously formed in the annulus
16 of the disc is inhibited.
[0120] The material for the envelope may, depending on the grade or
class of material used, be post cured for a period of time. This is
effected by placing the moulded envelope 38 into an oven, for
example, for a period of about 1 to 4 hours at a temperature of
about 150.degree. C. to 180.degree. C.
[0121] By having the material of the envelope 38 and the filler
material 60 of the same type, but different grades or classes,
chemical bonding between the materials is enhanced which encourages
the formation of the prosthesis 100.
[0122] The filler material 60 is dispensed from a dispensing source
such as a dispenser 62.
[0123] As described above, when the nucleus pulposus 18 has been
removed, a residue 64 remains about the inner surface of the
annulus fibrosis and on the end plates 20 of the vertebrae 12 and
14. This residue 64 is of an irregular shape. Therefore, in
charging the envelope 38 with the filler material 60, it is
necessary to monitor the charging of the filler material 60 into
the envelope 38. This is done by a sensing arrangement. In one
embodiment of the invention, the sensing arrangement comprises a
pressure sensor 66 at an inlet to the envelope 38. In another
embodiment, the sensing arrangement comprises a volume sensor 68
arranged at an outlet of the dispenser 62 for monitoring the volume
of filler material 60 dispensed. The sensing arrangement could, in
addition or instead, be a flow rate sensor which monitors the rate
of flow of the filler material 60.
[0124] Yet a further method of monitoring filling of the envelope
38 is monitoring back flow of filler material 60 from between the
envelope 38 and the distal end of the delivery device 40. As the
filler material 60 oozes out it may loosen the envelope 38 allowing
the delivery device 40 to be removed.
[0125] It is also necessary to monitor the shape and size of the
cavity 36 taking the residue 64 into account. This can be achieved
in a number of ways. One of the ways in which this can be achieved
is by having radio opaque markers 70 arranged on the envelope 38.
Prior to charging the envelope 38 with the filler material 60, the
envelope 38 can be expanded to conform to the shape of the cavity
36 by means of a water/saline solution or a radio opaque solution.
The markers 70, being radio opaque, are monitored under a
fluoroscope to determine the shape and size of the cavity 36.
[0126] Other methods of assessing the size of the cavity 36 include
the use of a flexible wire inserted down the lumen 26 of the
introducer 22, the wire being monitored by a fluoroscope. Yet a
further way of monitoring the shape and size of the cavity 36 is by
use of a dedicated jacket, of similar dimensions to the cavity 36,
which is inserted into the cavity 36 and inflated using the
water/saline solution or the radio opaque solution. The jacket
carries radio opaque markers which are monitored by a
fluoroscope.
[0127] After the shape and size of the cavity 36 have been
determined, the filler material 60 is dispensed from the dispenser
62 and is monitored via the sensing arrangements 66 or 68, as the
case may be. As illustrated in FIG. 7 of the drawings, the filler
material 60 causes elastic expansion or inflation of the envelope
38 so that the envelope 38 conforms to the shape of the cavity 36
and bears against the residue 64 of the nucleus pulposus remaining
in the cavity 36. The envelope 38, having been elastically expanded
by the filler material 60, remains under tension around the filler
material 60 while conforming to the shape of the cavity 36.
[0128] Backflow filler material 60 from the interior of the
envelope 38 is controlled either by a valve 72 as shown in FIG. 13
of the drawings or by a clamping device 74 as shown in FIG. 7 of
the drawings. The valve 72 is a duckbill valve and acts as a one
way valve so that backflow of filler material 60 from the envelope
38 is inhibited.
[0129] Once the envelope 38 has been filled and has expanded so
that it conforms closely to the shape of the cavity 36 and is
received snugly in the cavity 36, the filler material 60 is allowed
to cure for a predetermined period of time of, for example, about
10 minutes. After curing of the filler material 60, the delivery
device 40 is removed leaving the aperture 30 occluded as shown at
76 in FIG. 8 of the drawings. The unified tissue prosthesis 100 so
formed is fully cured after about 24 hours.
[0130] To facilitate removal of the delivery device 40 from the
envelope 38, the envelope 38 has a zone of weakness in the form of
a circumferential groove 78 (FIG. 14) formed at a proximal end. As
the delivery device 40 is withdrawn, when its distal end comes into
register with the groove 78, the delivery device 40 is twisted
relative to the envelope to cause a break at the groove 78 to form
the occlusion 76 in the aperture 30 of the annulus fibrosis 16 of
the disc 10.
[0131] FIG. 12 shows another way of delivering the envelope 38 into
the cavity 36. In this embodiment of the invention, the envelope 38
is everted to lie within the distal end of the delivery device 40
to facilitate its insertion into the cavity 36. A similar
arrangement is shown in FIG. 9 and FIG. 14 of the drawings.
[0132] In FIG. 11 of the drawings, another embodiment of equipment
for forming the tissue prosthesis 100 is shown. In this embodiment,
a filler tube 80 is used. The tube 80 is received in the passageway
42 of the delivery device 40. A sleeve 82 is arranged coaxially
about the delivery device 40. A first displacement device, such as
a trigger, 84 is provided for controlling relative movement between
the delivery device 40 and the tube 80. A second displacement
device, which may also be in the form of a trigger, 86 controls
relative movement between the delivery device 40 and the sleeve
82.
[0133] The equipment, as shown in FIG. 11 of the drawings, is for
use where an evacuating device is not used. Thus, to fill the
envelope 38, the tube 80 is urged towards the distal end of the
envelope 38 and charging of the filler material 60 into the
envelope 38 commences at the distal end of the envelope 38. Filling
of the envelope 38 progresses from its distal end towards its
proximal end. Thus, as filler material 60 is charged into the
envelope 38, the tube 80 is slid proximally relative to the tube 40
by manipulating the trigger 84 or slides back through buoyancy of
the filler material. Once the envelope 38 is in its fully inflated
state, the envelope 38 is urged off the distal end of the delivery
device 40 by manipulating the trigger 86. As the tube 80 is
withdrawn from the valve 72 and the envelope 38 is removed from the
distal end of the delivery device 40, the valve 72 closes to form
the occlusion 76.
[0134] To facilitate expulsion of air when an evacuating system is
not being used, the envelope 38 has a bead 88 (FIG. 12) formed
along that portion which seats on the distal end of the delivery
device 40 to create passages 90 through which air can be discharged
as the envelope 38 is charged with the filler material 60.
[0135] As described above, the envelope 38 is of a silicone rubber
material which can be inflated up to 100 times its relaxed size
without rupturing. In another embodiment, the envelope 38 is of a
less expansible material such as a biological or a synthetic
polymeric material. A suitable synthetic polymeric material may,
for example, be a polyester such as polyethylene terephthalate
(PET). The envelope 38 is of a knitted PET material so that, when
the filler material 60 is charged into the envelope 38, the filler
material fills foramens or interstices in the envelope 38 to form
an integrated structure which resists relative movement between the
filler material 60 and the envelope 38. Alternatively, the knitted
PET material may be coated with silicone allowing the filler
material 60 to integrate with the coating.
[0136] FIGS. 15 to 17 show different shapes of envelopes 38 which
can be used depending on which intervertebral disc 10 is to have
its nucleus pulposus 18 replaced.
[0137] Referring now to FIGS. 18 to 21 of the drawings, yet a
further embodiment of equipment for forming a tissue prosthesis, in
situ, at a site in a patient's body is illustrated. With reference
to the previous drawings, like reference numerals refer to like
parts, unless otherwise specified.
[0138] In this embodiment, the equipment 110 comprises a delivery
device in the form of an envelope tube 112. The envelope tube 112
carries the envelope 38 at its distal end.
[0139] A filler member in the form of a filler tube 114 is slidably
received within a passage 116 of the envelope tube 112. As
illustrated more clearly in FIG. 21 of the drawings, the filler
tube 114 has a smaller outer diameter than an inner diameter of the
envelope tube 112 to form an annular gap 118 between the filler
tube 114 and the envelope tube 112.
[0140] A removal mechanism in the form of a push-off tube 120 is a
snug fit on the outer surface of the envelope tube 112.
[0141] In this embodiment, the envelope 38 is of a two part
construction comprising a sleeve 122 (FIG. 21) to which an envelope
defining member 124 is adhesively bonded as shown by an annular
adhesive layer 126. The sleeve 122 defines the valve 72.
[0142] A distal end of the filler tube 114 carries an engaging
member 128 which engages and opens the valve 72 so that the annular
gap 118 is in flow communication with an interior 130 of the
envelope 38. A distal end of the push-off tube 120 terminates short
of a proximal end of the sleeve 122 of the envelope 38. However, it
is also to be noted, as will be described in greater detail below,
that the envelope tube 112 is displaceable relative to the push-off
tube 120 in the direction of arrow 132.
[0143] Instead of the engaging member 128, the valve 72 could have
a small opening (not shown) in it. The size of the opening in the
valve 72 is selected to allow the passage of air through it but is
sufficiently small that the viscosity of the filler material will
inhibit the passage of the filler material through it.
[0144] Yet a further way of evacuating the interior 130 of the
envelope 38 is to insert the filler tube 112 into the interior 130
of the envelope 38 and to have a slit (not shown) in the filler
tube 114 upstream of the valve 72. Thus, if the valve 72 seals
about the filler tube 112, air can still be drawn from the interior
130 of the envelope 38 into the gap 116 via the slit when the
evacuation device is operated.
[0145] A proximal end of the envelope tube 112 carries a connector
134. The connector 134 is a Y-connector having a primary member 136
and a secondary member 138 projecting from the primary member 136.
The envelope tube 112 is fast with the primary member 136 of the
connector 134. The secondary member 138 of the connector 134 is in
flow communication with the passage 116 of the envelope tube 112
and, hence, in use with the gap 118 between the envelope tube 112
and the filler tube 114. The secondary member 138 is connectable to
an evacuation device (not shown) such as an evacuation pump for
creating a low pressure in the gap 118 and, via the engaging member
128 opening the valve 72, the interior 130 of the envelope 38 prior
to filler material being charged into the interior 130 of the
envelope 38.
[0146] As shown more clearly in FIG. 20 of the drawings, the
connector 134 includes a retaining mechanism 140 for retaining the
envelope tube 112 in position relative to the introducer 22. The
retaining mechanism 140 comprises a receiving formation 142 carried
at a proximal end of the introducer 22. The retaining mechanism 140
further includes a clip portion 144 forming the distal end of the
connector 134 which clips into the receiving formation 142 to
retain the envelope tube 112 in position relative to the introducer
22.
[0147] A proximal end of the push-off tube 120 carries a gripping
formation 146 which is accessible externally of the retaining
mechanism 140 for enabling the push-off tube 120 to be held while
the envelope tube 112 is moved in the direction of the arrow 132
after charging of the envelope 38 with the filler material.
[0148] The equipment 110 further includes a dispensing device 148
for dispensing filler material. The dispensing device 148 includes
a dispenser 150 feeding into a mixing device in the form of a
static mixer 152. A distal end of the static mixer 152 carries the
filler tube 114. A Luer lock arrangement 154 is arranged at the
distal end of the static mixer 152 and connects the dispensing
arrangement 148 to the connector 134.
[0149] The filler material is of a silicone rubber, as indicated
above. To inhibit curing of the filler material prior to its being
charged into the envelope 38, the filler material is retained in
two, separate parts. Thus, the dispenser 150 includes two
reservoirs 156 in each of which a part of the filler material is
initially received. Each reservoir 156 has a plunger 158 associated
with it for dispensing the parts from the reservoirs 156 into the
static mixer 152 where the parts are mixed prior to being charged
into the envelope 38. It is to be noted that the plungers 158 are
displaceable together with each other via a suitable displacing
device (not shown) such as a pneumatic gun.
[0150] Thus, in use, the filler material to be charged into the
envelope 38 is provided in the dispensing arrangement 148. The
dispensing arrangement 148 is connected to the connector 134 via
the Luer lock 154. An envelope 38, in a deflated condition, is
mounted on the envelope tube 112. After the nucleotomy has been
performed on the disc 10, the envelope tube 112 with the envelope
38 on its distal end is inserted through the introducer 22 so that
the envelope 38, in its deflated condition, is received within the
cavity 36 of the disc 10. The filler tube 114 is inserted into the
interior of the filler tube 112 so that the engaging member 128
engages the valve 72 and opens the valve 72. By opening the valve
72, the interior 130 of the envelope 38 is placed in fluid
communication with the gap 118 between the envelope tube 112 and
the filler tube 114.
[0151] An evacuation device (not shown) is attached to the
secondary member 138 of the connector 134 and a vacuum is drawn.
This creates a low pressure within the gap 118 and the interior 130
of the envelope 38 and inhibits the formation of air bubbles in the
prosthesis 100 as the filler material is charged into the envelope
38.
[0152] The filler material is dispensed from the dispensing device
148 into the filler tube 114 and into the interior 130 of the
envelope 38. This causes the envelope 38 to expand elastically to
conform to the shape of the cavity 36 of the disc 10 with the
envelope 38 being retained under tension by the filler
material.
[0153] After charging of the filler material into the interior 130
of the envelope 38, the filler tube 114 is withdrawn. Withdrawal of
the filler tube 114 causes withdrawal of the engaging member 128
allowing the valve 72 to close to inhibit leakage of filler
material from the interior 130 of the envelope 38.
[0154] After curing, the envelope tube 112 is moved relative to the
push off tube 120 in the direction of the arrow 132 by holding the
push off tube 120 using the gripping device 146. This urges the
sleeve 122 of the envelope 38 off the end of the envelope tube 112
as the envelope tube 112 is withdrawn relative to the push off tube
120. The valve 72 occludes the opening to the envelope 38 and the
aperture 30 previously formed in the annulus fibrosis 16 of the
disc 10. The equipment 110, including the introducer 22, is then
withdrawn from the patient's body and the procedure is
complete.
[0155] Referring now to FIGS. 22 to 24 of the drawings, still a
further embodiment of equipment for forming a tissue prosthesis, in
situ, at a site in a patient's body is illustrated. Once again,
with reference to the previous drawings, like reference numerals
refer to like parts, unless otherwise specified.
[0156] In this embodiment, the equipment 110 includes a stiffening
element in the form of a stiffening rod or tube 160. Prior to
insertion of the filler tube 114 into the envelope tube 112, the
stiffening rod 160 is inserted into the passage 116 of the envelope
tube 112. A distal end 162 of the stiffening rod 160 projects
beyond a distal end of the envelope tube 112 and terminates at a
distal wall in the interior 130 of the envelope 38. A gap 161 is
created between the envelope tube 112 and the stiffening rod 160.
The gap 161 and the interior 130 of the envelope 38 are evacuated
by operation of the evacuation device to cause the envelope 38 to
collapse on to the distal end 162 of the stiffening rod 160. This
facilitates insertion of the envelope 38 into the introducer 22 and
into the cavity 36 of the disc 10.
[0157] Once the envelope 38 has been located within the cavity 36,
the evacuation device is turned off to release the envelope 38 from
the distal end 162 of the stiffening rod 160 and this allows the
stiffening rod 160 to be withdrawn. The filler tube 114 can then be
inserted into the envelope tube 112, as described above, to enable
filler material 60 to be charged into the envelope 38.
[0158] In another embodiment (not illustrated), the stiffening rod
160 is dimensioned to fit in the interior of the filler tube 114.
With this arrangement, the gap 118 between the envelope tube 112
and the filler tube 114 is evacuated, as described above, with the
stiffening rod 160 projecting through the distal end of the
envelope tube 112 and the envelope 38 being collapsed over the
distal end 162 of the stiffening rod 160.
[0159] A proximal end 164 of the stiffening rod carries a cap
connector 166 which connects to the Y connector 134 to retain the
stiffening rod 160 in position relative to the envelope tube 112
and/or the filler tube 118, as the case may be. The cap connector
166 seals hermetically against a proximal end of the Y connector to
enable the gap 161 and the interior 130 of the envelope 38.
[0160] It is an advantage of the invention that a method and
equipment are provided which facilitates minimally invasive
formation of a tissue prosthesis in situ. In addition a tissue
prosthesis is provided which is resistant to delamination. In
particular, in the case where the tissue prosthesis has an envelope
and filler material of the same class of material, a unified,
integrated structure is provided which is resistant to delamination
and relative movement between the envelope and the filler material.
The unified structure and the fact that the envelope is elastically
deformed and is retained under tension also renders the envelope
resistant to creasing increasing the operational efficiency of the
prosthesis by being better able to distribute forces to the annulus
fibrosis of the disc.
[0161] In addition, the use of a silicone rubber envelope is
particularly advantageous due to the fact that, when a nucleotomy
has been performed, residue remains behind which is irregular in
shape. It is beneficial to have a prosthesis which expands and
conforms as closely as possible to the shape of the cavity in order
that compressive, tensile, bending and torsional forces can be
accommodated by the disc. In addition, the provision of a tissue
prosthesis expanding and closely conforming to the shape of the
cavity results in an improvement in stimulation and deformation of
the end plates of the vertebrae and thereby aiding in restoration
of the natural pumping action which assists in the influx of
nutrients and the effluxion of waste products from within the
disc.
[0162] It is yet a further advantage of the invention that the
tissue prosthesis can be formed in situ in a minimally invasive
manner. The need for invasive surgical procedures is therefore
obviated and there is the added advantage of more rapid
post-operative recovery and the reduced need for a prolonged period
in hospital.
[0163] The equipment of the invention further provides an
efficient, easy to use manner of forming the tissue prosthesis. By
having the tubes etc nested, a clinician is more easily able to
manipulate the equipment to place and form the tissue
prosthesis.
[0164] It will be appreciated by persons skilled in the art that
numerous variations and/or modifications may be made to the
invention as shown in the specific embodiments without departing
from the spirit or scope of the invention as broadly described. The
present embodiments are, therefore, to be considered in all
respects as illustrative and not restrictive.
[0165] It will be appreciated by persons skilled in the art that
numerous variations and/or modifications may be made to the
invention as shown in the specific embodiments without departing
from the spirit or scope of the invention as broadly described. The
present embodiments are, therefore, to be considered in all
respects as illustrative and not restrictive.
* * * * *