U.S. patent application number 10/984566 was filed with the patent office on 2005-09-22 for multi-stage biomaterial injection system for spinal implants.
This patent application is currently assigned to Disc Dynamics, Inc.. Invention is credited to Ahrens, Michael, Bao, Qi-Bin, Bowman, Bruce R., Hook, Scott, Hudgins, Robert Garryl, Johnson, Dennis, Kohler, Robert, Lehuec, Jean-Charles, Martz, Erik, Melink, Daniel, Myint, Khin, Sherman, John.
Application Number | 20050209602 10/984566 |
Document ID | / |
Family ID | 37177834 |
Filed Date | 2005-09-22 |
United States Patent
Application |
20050209602 |
Kind Code |
A1 |
Bowman, Bruce R. ; et
al. |
September 22, 2005 |
Multi-stage biomaterial injection system for spinal implants
Abstract
A method and apparatus for fluidly coupling a reservoir
containing a flowable biomaterial to a mold. The flow of the
flowable biomaterial into the mold is controlled in accordance with
a first operating parameter. At least one injection condition is
monitored. The flow of the flowable biomaterial is controlled in
accordance with a second operating parameter in response to one or
more of the injection conditions reaching a threshold level. The
second operating parameter is maintained during at least a portion
of the curing of the flowable biomaterial. In some embodiments, the
second operating parameter may optionally include permitting a
portion of the flowable biomaterial to be expelled from the
mold.
Inventors: |
Bowman, Bruce R.; (Eden
Prairie, MN) ; Kohler, Robert; (Lake Elmo, MN)
; Martz, Erik; (Savage, MN) ; Melink, Daniel;
(Prior Lake, MN) ; Myint, Khin; (Shakopee, MN)
; Ahrens, Michael; (Neustadt i.H., DE) ; Lehuec,
Jean-Charles; (Pessac, FR) ; Sherman, John;
(Wayzata, MN) ; Hook, Scott; (Edina, MN) ;
Johnson, Dennis; (Shakopee, MN) ; Bao, Qi-Bin;
(Marquette, MI) ; Hudgins, Robert Garryl;
(Burnsville, MN) |
Correspondence
Address: |
FAEGRE & BENSON LLP
PATENT DOCKETING
2200 WELLS FARGO CENTER
MINNEAPOLIS
MN
55402
US
|
Assignee: |
Disc Dynamics, Inc.
Eden Prairie
MN
|
Family ID: |
37177834 |
Appl. No.: |
10/984566 |
Filed: |
November 9, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60555382 |
Mar 22, 2004 |
|
|
|
Current U.S.
Class: |
606/90 ;
623/17.16 |
Current CPC
Class: |
A61F 2002/4688 20130101;
A61F 2/441 20130101; A61F 2002/467 20130101; A61F 2002/4694
20130101; A61F 2210/0004 20130101; A61B 17/8805 20130101; A61F
2250/0098 20130101; A61F 2/4601 20130101; A61F 2002/30062 20130101;
A61F 2002/4677 20130101; A61F 2210/0085 20130101; A61F 2002/4663
20130101; A61B 2090/064 20160201; A61F 2002/3008 20130101; A61F
2/4611 20130101; A61F 2002/4627 20130101; A61B 17/8827 20130101;
A61F 2002/465 20130101; A61B 17/8836 20130101; A61F 2002/4693
20130101; A61F 2002/30583 20130101 |
Class at
Publication: |
606/090 ;
623/017.16 |
International
Class: |
A61B 017/88; A61F
002/44 |
Claims
What is claimed is:
1. An apparatus adapted to deliver a flowable biomaterial to an
intervertebral disc space, comprising: a reservoir containing the
flowable biomaterial fluidly coupled to the intervertebral disc
space; at least one sensor adapted to monitor at least one
injection condition of the flowable biomaterial; a controller
programmed to; monitor the at least one sensor; control the flow of
the flowable biomaterial into the intervertebral disc space in
accordance with a first operating parameter; controlling the flow
of the flowable biomaterial in accordance with a second operating
parameter in response to one or more of the injection conditions
reaching a threshold level; and maintaining the second operating
parameter during at least a portion of the curing of the flowable
biomaterial.
2. The apparatus of claim 1 comprising a mold located in the
intervertebral disc space fluidly coupled to the reservoir
containing the flowable biomaterial.
3. The apparatus of claim 2 wherein the first operating parameter
comprises delivering the flowable biomaterial to the mold so that
the mold substantially fills the intervertebral disc space.
4. The apparatus of claim 1 wherein the first operating parameter
comprises delivering the flowable biomaterial at a pressure
sufficient to distract the intervertebral disc space.
5. The apparatus of claim 1 wherein the controller is programmed to
waiting a predetermined period of time after the at least one
injection condition reaches the threshold level before initiating
the second operating parameter.
6. The apparatus of claim 1 wherein the controller controls the
delivery of the flowable biomaterial in accordance with a third
operating parameter that maintains the flowable biomaterial at a
predetermined pressure in the intervertebral disc space for a
predetermined period of time after the at least one injection
condition reaches the threshold level and before the second
operating parameter.
7. The apparatus of claim 1 wherein the second operating parameter
permits a portion of the flowable biomaterial to be expelled from
the intervertebral disc space.
8. The apparatus of claim 1 wherein the second operating parameter
delivers additional flowable biomaterial into the intervertebral
disc space.
9. The apparatus of claim 1 wherein the controller controls
pretreatment of the flowable biomaterial.
10. The apparatus of claim 1 comprising a source of ultraviolet
light and/or heating directed at the flowable biomaterial prior to
delivery to the intervertebral disc space.
11. The apparatus of claim 1 comprising a mixing device located
between the reservoir of flowable biomaterial and the
intervertebral disc space.
12. The apparatus of claim 1 wherein the flowable biomaterial
comprises a plurality of components.
13. The apparatus of claim 1 comprising a purging device adapted to
direct a predetermined quantity of the flow of biomaterial away
from the intervertebral disc space.
14. The apparatus of claim 1 wherein the first operating parameter
comprises a first operating pressure.
15. The apparatus of claim 14 wherein the second operating
parameter comprises a second operating pressure lower than the
first operating pressure.
16. The apparatus of claim 14 wherein the intervertebral disc space
exerts pressure on the flowable biomaterial in the intervertebral
disc space greater than the second operating pressure.
17. The apparatus of claim 1 wherein the controller monitors the
pressure of the flowable biomaterial between the reservoir and the
intervertebral disc space.
18. The apparatus of claim 1 wherein the controller monitors the
pressure of the flowable biomaterial in the intervertebral disc
space.
19. The apparatus of claim 1 wherein the controller is programmed
to monitor at least one injection condition comprises monitoring at
least one of the pressure, the flow rate, elapsed time, or the
total volume of the flowable biomaterial flowing between the
reservoir and the intervertebral disc space.
20. The apparatus of claim 1 wherein the first operating parameter
comprises a first injection pressure of about 50 psi to about 270
psi.
21. The apparatus of claim 1 wherein the second operating parameter
comprises a second injection pressure of about 0 psi to about 150
psi.
22. The apparatus of claim 1 wherein the threshold level of the
injection condition is about 80 psi to about 150 psi.
23. The apparatus of claim 1 wherein the controller is programmed
to record data corresponding to at least one of the injection
conditions during the flow of flowable biomaterial.
24. The apparatus of claim 1 wherein the controller is programmed
to upload to a computer data corresponding to at least one of the
injection conditions recorded during the flow of flowable
biomaterial.
25. The apparatus of claim 1 wherein the controller is programmed
to determine that the at least one injection condition comprises an
out of specification condition and to indicate an out of
specification condition.
26. The apparatus of claim 1 wherein the controller is programmed
to determine that the at least one injection condition comprises an
out of specification condition and to alter the flow of flowable
biomaterial to the intervertebral disc space.
27. The apparatus of claim 1 wherein the controller is programmed
to determine that the at least one injection condition comprises an
out of specification condition and to withdraw at least a portion
of the biomaterial from the invertebral disc space.
28. The apparatus of claim 1 comprising a switch to manually switch
the flow of flowable biomaterial to the second operating parameter
in response to one or more of the injection conditions reaching a
threshold level.
29. The apparatus of claim 1 wherein a controller automatically
controls the delivery of the flowable biomaterial in accordance
with the second operating parameter in response to one or more of
the injection conditions reaching a threshold level.
30. The apparatus of claim 1 wherein the controller adjusts the
threshold level as a function of mold size.
31. The apparatus of claim 1 wherein the controller adjusts the
threshold level as a function of patient parameters.
32. The apparatus of claim 1 wherein the first operating parameter
comprises a plurality of variable.
33. The apparatus of claim 1 wherein the second operating parameter
comprises a plurality of variables.
34. The apparatus of claim 1 comprising: an evaluation mold adapted
to be positioned in the intervertebral disc space prior to the
delivery of the biomaterial; a liquid adapted to be delivered to
the evaluation mold so that the mold substantially fills the
intervertebral disc space; wherein the controller is programmed to
remove the liquid from the evaluation mold and measure the amount
of liquid present in the evaluation mold.
35. The apparatus of claim 34 wherein one or both of the liquid and
the evaluation mold have radiopaque properties.
36. The apparatus of claim 34 wherein the controller is programmed
to estimate the volume of biomaterial required to fill the
intervertebral disc space and to comparing the amount of liquid
present in the evaluation mold with an estimated volume of the
intervertebral disc space measured using imaging techniques.
37. The apparatus of claim 1 comprising an evaluation mold located
in the intervertebral disc space, wherein the controller is
programmed to deliver a liquid under pressure to the evaluation
mold sufficient to distract the intervertebral disc space, to hold
the volume of liquid in the evaluation mold constant for a period
of time, and to add additional liquid to the evaluation mold when
the pressure in the mold drops to a predetermined level.
38. The apparatus of claim 37 wherein the controller is programmed
to repeat the steps a plurality of cycles.
39. The apparatus of claim 1 comprising an evaluation mold located
in the intervertebral disc space wherein the controller is
programmed to continuously deliver a liquid to the evaluation mold
at a constant pressure, to measure the rate at which the liquid is
delivered to the evaluation mold, and to estimate the compliance of
the intervertebral disc space as a function of the changing rate at
which the liquid is delivered.
40. The apparatus of claim 1 comprising: a guide wire positioned in
the mold; and an image of the intervertebral disc space containing
the guide wire.
41. The apparatus of claim 40 wherein the guide wire comprises an
imaging target.
42. The apparatus of claim 2 comprising: a radiopaque sheath over
the mold; and an image of the intervertebral disc space containing
the radiopaque sheath.
43. The apparatus of claim 42 wherein the radiopaque sheath
comprises at least one bend adapted to direct the mold to selected
regions of the intervertebral disc space.
44. The apparatus of claim 2 comprising at least one bend in a
delivery tube connecting the reservoir to the mold.
45. The apparatus of claim 2 comprising at least guide wire located
in a delivery tube connecting the reservoir to the mold.
46. The apparatus of claim 1 wherein the intervertebral disc space
includes an annulus with an inlet connected to a cavity formed
therein, the apparatus comprising: a delivery tube fluidly coupling
the reservoir to the cavity in the annulus; and a flange located on
a distal end of the delivery tube biased against the inlet to the
cavity.
47. The apparatus of claim 1 wherein the intervertebral disc space
includes an annulus with an inlet connected to a cavity formed
therein, the apparatus comprising: a delivery tube fluidly coupling
the reservoir to the cavity in the annulus; and a distal end of the
delivery tube having an expandable portion positioned adjacent the
inlet to the annulus, the expandable portion being adapted to
expand in response to the delivery of flowable biomaterial.
48. A apparatus of claim 1 wherein the intervertebral disc space
includes an annulus with an inlet connected to a cavity formed
therein, the apparatus comprising a delivery tube fluidly coupling
the reservoir containing the flowable biomaterial to the cavity in
the annulus.
49. An apparatus adapted to deliver a flowable biomaterial to an
intervertebral disc space, comprising: a reservoir containing the
flowable biomaterial fluidly coupled to the intervertebral disc
space; at least one sensor adapted to monitor at least one
injection condition of the flowable biomaterial; a controller
programmed to; monitor the at least one sensor; control the flow of
the flowable biomaterial into the intervertebral disc space in
accordance with a first operating parameter; determine that the at
least one injection condition comprises an out of specification
condition; and generating a signal of the out of specification
condition.
50. The apparatus of claim 49 comprising a mold located in the
intervertebral disc space fluidly coupled to the reservoir
containing the flowable biomaterial.
51. The apparatus of claim 49 wherein the controller is programmed
to automatically altering the flow of flowable biomaterial to the
mold in response to the out of specification condition.
52. The apparatus of claim 49 comprising a manual switch adapted to
alter the flow of flowable biomaterial to the mold.
53. The apparatus of claim 49 wherein the controller opens a purge
device located between the reservoir and the mold in response to
the out of specification condition.
54. An apparatus adapted to deliver a flowable biomaterial to a
mold located in an intervertebral disc space, comprising: a
reservoir containing the flowable biomaterial fluidly coupled to
the mold; an actuator providing a flow of the flowable biomaterial
into the mold in accordance with a first operating parameter; at
least one sensor monitoring at least one operating parameter of the
flowable biomaterial; a display adapted to indicate that the at
least one injection condition has reached a threshold level; and a
switch that controls the flow the flowable biomaterial in
accordance with a second operating parameter.
55. The apparatus of claim 54 wherein the switch is adapted for
manual operation by the surgical staff.
Description
[0001] The present application claims the benefit of U.S.
Provisional Application Ser. No. 60/555,382 entitled MULTI-STAGE
BIOMATERIAL INJECTION SYSTEM FOR SPINAL IMPLANTS filed on Mar. 22,
2004.
FIELD OF THE INVENTION
[0002] The present invention relates to a method and apparatus for
filling an intervertebral disc space with an in situ curable
biomaterial using a biomaterial injection system to form an implant
device and to a method for replacing, in whole or in part, an
intervertebral disc using the present method and apparatus.
BACKGROUND OF THE INVENTION
[0003] The intervertebral discs, which are located between adjacent
vertebrae in the spine, provide structural support for the spine as
well as the distribution of forces exerted on the spinal column. An
intervertebral disc consists of three major components: cartilage
endplates, nucleus pulpous, and annulus fibrosus. The central
portion, the nucleus pulpous or nucleus, is relatively soft and
gelatinous; being composed of about 70 to 90% water. The nucleus
pulpous has a high proteoglycan content and contains a significant
amount of Type II collagen and chondrocytes. Surrounding the
nucleus is the annulus fibrosus, which has a more rigid consistency
and contains an organized fibrous network of approximately 40% Type
I collagen, 60% Type II collagen, and fibroblasts. The annular
portion serves to provide peripheral mechanical support to the
disc, afford torsional resistance, and contain the softer nucleus
while resisting its hydrostatic pressure.
[0004] Intervertebral discs, however, are susceptible to a number
of injuries. Disc herniation occurs when the nucleus begins to
extrude through an opening in the annulus, often to the extent that
the herniated material impinges on nerve roots in the spine or
spinal cord. The posterior and posterio-lateral portions of the
annulus are most susceptible to attenuation or herniation, and
therefore, are more vulnerable to hydrostatic pressures exerted by
vertical compressive forces on the intervertebral disc. Various
injuries and deterioration of the intervertebral disc and annulus
fibrosus are discussed by Osti et al., Annular Tears and Disc
Degeneration in the Lumbar Spine, J. Bone and Joint Surgery,
74-B(5), (1982) pp. 678-682; Osti et al., Annulus Tears and
Intervertebral Disc Degeneration, Spine, 15(8) (1990) pp. 762-767;
Kamblin et al., Development of Degenerative Spondylosis of the
Lumbar Spine after Partial Discectomy, Spine, 20(5) (1995) pp.
599-607.
[0005] Many treatments for intervertebral disc injury have involved
the use of nuclear prostheses or disc spacers. A variety of
prosthetic nuclear implants are known in the art. For example, U.S.
Pat. No. 5,047,055 (Bao et al.) teaches a swellable hydrogel
prosthetic nucleus. Other devices known in the art, such as
intervertebral spacers, use wedges between vertebrae to reduce the
pressure exerted on the disc by the spine. Intervertebral disc
implants for spinal fusion are known in the art as well, such as
disclosed in U.S. Pat. Nos. 5,425,772 (Brantigan) and U.S. Pat. No.
4,834,757 (Brantigan).
[0006] Further approaches are directed toward fusion of the
adjacent vertebrate, e.g., using a cage in the manner provided by
Sulzer. Sulzer's BAK.RTM. Interbody Fusion System involves the use
of hollow, threaded cylinders that are implanted between two or
more vertebrae. The implants are packed with bone graft to
facilitate the growth of vertebral bone. Fusion is achieved when
adjoining vertebrae grow together through and around the implants,
resulting in stabilization.
[0007] Apparatuses and/or methods intended for use in disc repair
have also been described but none appear to have been further
developed, and certainly not to the point of commercialization.
See, for instance, French Patent Appl. No. FR 2 639 823 (Garcia)
and U.S. Pat. No. 6,187,048 (Milner et al.). Both references differ
in several significant respects from each other and from the
apparatus and method described below. For instance, neither
reference teaches switching the flow of biomaterial between
discrete operating parameters or methods of detecting ruptures in
the mold. Further, neither reference teaches shunting an initial
portion of a curing biomaterial in the course of delivering the
biomaterial to the disc space.
[0008] Prosthetic implants formed of biomaterials that can be
delivered and cured in situ, using minimally invasive techniques to
form a prosthetic nucleus within an intervertebral disc have been
described in U.S. Pat. No. 5,556,429 (Felt) and U.S. Pat. No.
5,888,220 (Felt et al.), and U.S. Pat. Publication No. US
2003/0195628 (Felt et al.), the disclosures of which are
incorporated herein by reference. The disclosed method includes,
for instance, the steps of inserting a collapsed mold apparatus
(which in a preferred embodiment is described as a "mold") through
an opening within the annulus, and filling the mold to the point
that the mold material expands with a flowable biomaterial that is
adapted to cure in situ and provide a permanent disc replacement.
Related methods are disclosed in U.S. Pat. No. 6,224,630 (Bao et
al.), entitled "Implantable Tissue Repair Device" and U.S. Pat. No.
6,079,868 (Rydell), entitled "Static Mixer".
BRIEF SUMMARY OF THE INVENTION
[0009] The present invention relates to a method and apparatus for
filling an intervertebral disc space with an in situ curable
biomaterial. The biomaterial injection system can be used, for
example, to implant a prosthetic total disc, or a prosthetic disc
nucleus, in a manner that leaves the surrounding disc tissue
substantially intact. The phrase intervertebral disc prosthesis is
used generically to refer to both of these variations. Optionally,
the device and system of the invention are adapted for minimally
invasive use. Various implant procedures, implant molds, and
biomaterials related to intervertebral disc replacement suitable
for use with the present invention are disclosed in U.S. Pat. No.
5,556,429 (Felt); U.S. Pat. No. 6,306,177 (Felt, et al.); U.S. Pat.
No. 6,248,131 (Felt, et al.); U.S. Pat No. 5,795,353 (Felt); U.S.
Pat. No. 6,079,868 (Rydell); U.S. Pat. No. 6,443,988 (Felt, et
al.); U.S. Pat. No. 6,140,452 (Felt, et al.); U.S. Pat. No.
5,888,220 (Felt, et al.); U.S. Pat. No. 6,224,630 (Bao, et al.),
and U.S. patent application Ser. Nos. 10/365,868 and 10/365,842,
all of which are hereby incorporated by reference.
[0010] The present method of filling an intervertebral disc space
with a flowable biomaterial includes the step of fluidly coupling a
reservoir containing the flowable biomaterial to the intervertebral
disc space. The delivery of the flowable biomaterial into the
intervertebral disc space is controlled in accordance with a first
operating parameter. At least one injection condition is monitored.
The delivery of the flowable biomaterial is controlled in
accordance with a second operating parameter in response to one or
more of the injection conditions reaching a threshold level. The
second operating parameter is maintained during at least a portion
of the curing of the flowable biomaterial.
[0011] In one embodiment, the method includes fluidly coupling the
reservoir containing the flowable biomaterial to a mold located in
the intervertebral disc space. The first operating parameter
delivers the flowable biomaterial to the mold so that the mold
substantially fills the intervertebral disc space.
[0012] In another embodiment, a predetermined period of time is
permitted to lapse after the at least one injection condition
reaches the threshold level before initiating the second operating
parameter. This dwell time comprises a third operating parameter.
The length of this dwell time can be fixed or can vary from
patient-to-patient.
[0013] The first operating parameter preferably applies sufficient
pressure to rapidly fill the mold and to expand the mold to fill
the disc space. A first injection condition triggers a second
operating parameter, which maintains adequate pressure for a
certain dwell time to completely fill the disc space and to
distract the intervertebral disc space. Following the dwell time, a
third operating parameter optionally permits a portion of the
flowable biomaterial to be expelled from the intervertebral disc
space, followed by a second dwell time that continues until the
biomaterial adequately cures.
[0014] The present method optionally includes pretreating the
flowable biomaterial. The biomaterial can also be exposed to
ultraviolet light, heating and/or mixed prior to delivery to the
intervertebral disc space.
[0015] In one embodiment, the flow of biomaterial is directed away
from the intervertebral disc space until a predetermined quantity
of biomaterial is delivered to a chamber in a purge device. In one
embodiment, the first operating parameter includes the step of
applying a first operating pressure to the flowable biomaterial in
the reservoir and applying a second operating pressure, lower than
the first operating pressure, to the flowable biomaterial in the
reservoir. In another embodiment the intervertebral disc space
exerts a pressure on the flowable biomaterial in the intervertebral
disc space greater than the second operating pressure.
[0016] The step of monitoring at least one injection condition
typically includes monitoring the pressure of the flowable
biomaterial between the reservoir and the intervertebral disc space
and/or the pressure of the flowable biomaterial in the
intervertebral disc space. The step of monitoring at least one
injection condition can be monitoring at least one of the pressure,
the flow rate, elapsed time, or the total volume of the flowable
biomaterial flowing between the reservoir and the intervertebral
disc space.
[0017] The present method also includes the step of recording data
corresponding to at least one of the injection conditions during
the flow of flowable biomaterial. The injection condition data is
optionally uploaded to a computer. The present method also includes
determining whether any of the injection conditions is in an out of
specification condition and indicating an out of specification
condition. Alternatively, the flow of biomaterial is altered and/or
the biomaterial is withdrawn from the intervertebral disc space in
response to an out of specification condition.
[0018] The flow of flowable biomaterial can be manually switched to
the second operating parameter in response to one or more of the
injection conditions reaching a threshold level or automatically
switched by a controller. The present method optionally includes
adjusting the threshold level as a function of patient parameters.
The first and second operating parameter typically comprises a
plurality of variables, such as for example, injection pressure,
biomaterial temperature, and the like.
[0019] The present method also includes positioning an evaluation
mold in the intervertebral disc space prior to the delivery of the
biomaterial. A liquid is delivered to the evaluation mold so that
the mold substantially fills the intervertebral disc space and
measurements, such as for example disc height, pressure, and the
like, are taken. The liquid is removed from the evaluation mold and
the volume of liquid injected and/or removed is measured. The
evaluation mold is then removed from the intervertebral disc space.
The liquid is preferably delivered under pressure sufficient to
distract the intervertebral disc space. The liquid and/or the
evaluation mold optionally have radiopaque properties. The present
invention also includes use of the present biomaterial injection
system to control delivery and/or removal of the liquid to the
evaluation mold.
[0020] In the preferred embodiment, imaging can be used to measure
the distraction of the intervertebral disc space, to evaluate
whether the mold substantially fills the intervertebral disc space,
to evaluate the geometry of the intervertebral disc space, and/or
to supply information to the surgeon regarding adequacy of the
nucleus removal. The evaluation mold can either be positioned in
the implant mold, directly in the annulus, or within the disc space
in the case of complete disc removal. In another embodiment, the
intervertebral disc space containing the evaluation mold and the
liquid is imaged and at least one of the first operating parameter
and/or the second operating parameter are established based on the
imaging of the intervertebral disc space. In one embodiment, the
intervertebral disc space is imaged to estimate the volume of
biomaterial required. That estimate can then be compared to the
amount of liquid removed from the evaluation mold.
[0021] In another embodiment, a liquid is delivered under pressure
to the evaluation mold sufficient to distract the intervertebral
disc space. The volume of liquid in the evaluation mold may be held
constant for a period of time. Additional liquid is added to the
evaluation mold when the pressure in the mold drops to a
predetermined level. The steps of delivering, holding and adding
additional liquid is preferably repeated a plurality of cycles.
[0022] In another embodiment, a liquid is continuously delivered to
the evaluation mold at a constant pressure. The rate at which the
liquid is delivered to the evaluation mold is measured. The
compliance of the intervertebral disc space is measured as a
function of the rate of change of the delivery of liquid.
[0023] The present method also includes positioning a guide wire in
the mold and imaging the intervertebral disc space containing the
guide wire. The guide wire optionally includes an imaging
target.
[0024] The present method also includes positioning a radiopaque
sheath over the mold before the delivery of the biomaterial. The
intervertebral disc space containing the radiopaque sheath is
imaged and the radiopaque sheath is removed before delivering the
biomaterial.
[0025] The present invention is also directed to an apparatus
adapted to deliver a flowable biomaterial to an intervertebral disc
space. The apparatus includes a reservoir containing the flowable
biomaterial fluidly coupled to the intervertebral disc space, at
least one sensor adapted to monitor at least one injection
condition of the flowable biomaterial, and a controller. The
controller is programmed to monitor the at least one sensor and to
control the flow of the flowable biomaterial into the mold in
accordance with a first operating parameter. In response to one or
more of the injection conditions reaching a threshold level, the
controller controls the flow of the flowable biomaterial in
accordance with a second operating parameter and maintains the
second operating parameter during a certain time period or dwell
time before switching to the third operating parameter and
maintaining the third operating parameter during at least a portion
of the curing of the flowable biomaterial.
[0026] In one embodiment, the apparatus includes a mold located in
the intervertebral disc space fluidly coupled to the reservoir
containing the flowable biomaterial. The controller is programmed
so that the first operating parameter delivers the flowable
biomaterial to the mold so that the mold substantially fills the
intervertebral disc space.
[0027] In one embodiment, the controller is programmed to initiate
a second operating parameter during which the system waits a
predetermined period of time after the first operating parameter
(i.e., the at least one injection condition reaches the threshold
level at a second operating parameter) before initiating the third
operating parameter. In another embodiment, the controller is
programmed to deliver the flowable biomaterial in accordance with a
third operating parameter that maintains the flowable biomaterial
at a predetermined pressure in the intervertebral disc space for a
predetermined period of time after the at least one injection
condition reaches the threshold level and before the second
operating parameter. Operating parameters can be linear,
non-linear, continuous, discontinuous, or any other configuration
necessary to achieve the desired injection profile. The operating
parameter can also be modified real-time based on feedback from the
sensors monitoring the injection conditions.
[0028] The controller is preferably programmed so that the first
operating parameter comprises a pressure sufficient to distract the
intervertebral disc space. In another embodiment, the controller is
programmed so that the second operating parameter permits a portion
of the flowable biomaterial to be expelled from the intervertebral
disc space. The controller is also optionally programmed to control
pretreatment of the flowable biomaterial.
[0029] The apparatus optionally includes a source of ultraviolet
light and/or heating directed at the flowable biomaterial prior to
delivery to the intervertebral disc space. The present apparatus
also optionally includes a mixing device located between the
reservoir of flowable biomaterial and the intervertebral disc
space. The present apparatus also optionally includes a purging
device adapted to direct a predetermined quantity of the flow of
biomaterial away from the intervertebral disc space.
[0030] In one embodiment, the controller is programmed so that the
second operating parameter applies a second operating pressure to
the biomaterial in the reservoir that is lower than the first
operating pressure applied under the first operating parameter. The
controller can monitor the pressure of the flowable biomaterial
between the reservoir and the intervertebral disc space and or in
the intervertebral disc space. The controller is preferably
programmed to monitor at least one injection condition comprises
monitoring at least one of the pressure, the flow rate, elapsed
time, or the total volume of the flowable biomaterial flowing
between the reservoir and the intervertebral disc space.
[0031] The controller is preferably programmed to record data
corresponding to at least one of the injection conditions during
the flow of flowable biomaterial. In one embodiment, the controller
is programmed to upload to a computer data corresponding to at
least one of the injection conditions recorded during the flow of
flowable biomaterial.
[0032] The controller may also be programmed to determine whether
the at least one injection condition comprises an out of
specification condition and to indicate an out of specification
condition. Alternatively, the controller is programmed to alter the
flow of flowable biomaterial or to withdraw at least a portion of
the biomaterial from the intervertebral disc space in response to
an out of specification condition.
[0033] The controller preferably adjusts the threshold level as a
function of patient parameters. The first, second and third
operating parameters typically comprises a plurality of
variable.
[0034] The present invention may also include an evaluation mold
adapted to be positioned in the intervertebral disc space prior to
the delivery of the biomaterial and a liquid adapted to be
delivered to the evaluation mold so that the mold substantially
fills the intervertebral disc space. The controller is preferably
programmed to remove the liquid from the evaluation mold and to
measure the amount of liquid removed from the evaluation mold. The
liquid and/or the evaluation mold optionally have radiopaque
properties.
[0035] In one embodiment, the controller is programmed to estimate
the volume of biomaterial required to fill the intervertebral disc
space and to compare the amount of liquid removed from the
evaluation mold with an estimated volume of the intervertebral disc
space measured using imaging techniques.
[0036] In another embodiment, the controller is programmed to
deliver a liquid under pressure to the evaluation mold sufficient
to distract the intervertebral disc space, to hold the volume of
liquid in the evaluation mold constant for a period of time, and to
add additional liquid to the evaluation mold when the pressure in
the mold drops to a predetermined level. The controller is
preferably programmed to repeat the steps a plurality of cycles and
estimate the compliance of the intervertebral disc space or spinal
unit. In one embodiment, the operating parameters are modified in
response to the estimate of compliance.
[0037] In another embodiment, the controller is programmed to
continuously deliver a liquid to the evaluation mold at a constant
pressure, to measure the rate at which the iiquid is delivered to
the evaluation mold, and to estimate the compliance of the
intervertebral disc space as a function of the changing rate at
which the liquid is delivered.
[0038] In one embodiment, the present invention includes a guide
wire positioned in the mold. In another embodiment, a radiopaque
sheath is positioned over the mold.
[0039] The present invention is also directed to a controller
programmed to determine whether at least one injection condition
comprises an out of specification condition and to generate a
signal of the out of specification condition.
[0040] The present invention is also directed to an apparatus
adapted to deliver a flowable biomaterial to a mold located in an
intervertebral disc space. The apparatus includes a reservoir
containing the flowable biomaterial fluidly coupled to the mold, an
actuator providing a flow of the flowable biomaterial into the mold
in accordance with a first operating parameter and at least one
sensor monitoring at least one operating parameter of the flowable
biomaterial. The apparatus also includes a display adapted to
indicate that the at least one injection condition has reached a
threshold level and a switch that controls the flow the flowable
biomaterial in accordance with a second operating parameter.
[0041] As used herein the following words and terms shall have the
meanings ascribed below:
[0042] "biomaterial" will generally refer to a material that is
capable of being introduced to the site of a joint and cured to
provide desired physical-chemical properties in vivo. In one
embodiment the term will refer to a material that is capable of
being introduced. to a site within the body using minimally
invasive mechanism, and cured or otherwise modified in order to
cause it to be retained in a desired position and configuration.
Generally such biomaterials are flowable in their uncured form,
meaning they are of sufficient viscosity to allow their delivery
through a delivery tube of on the order of about 1 mm to about 6 mm
inner diameter, and preferably of about 2 mm to about 3 mm inner
diameter. Such biomaterials are also curable, meaning that they can
be cured or otherwise modified, in situ, at the tissue site, in
order to undergo a phase or chemical change sufficient to retain a
desired position and configuration;
[0043] "cure" and inflections thereof, will generally refer to any
chemical transformation (e.g., reacting or cross-linking), physical
transformation (e.g., hardening or setting), and/or mechanical
transformation (e.g., drying or evaporating) that allows the
biomaterial to change or progress from a first physical state or
form (generally liquid or flowable) that allows it to be delivered
to the site, into a more permanent second physical state or form
(generally solid) for final use in vivo. When used with regard to
the method of the invention, for instance, "curable" can refer to
uncured biomaterial, having the potential to be cured in vivo (as
by catalysis or the application of a suitable energy source), as
well as to the biomaterial in the process of curing. As further
described herein, in selected embodiments the cure of a biomaterial
can generally be considered to include three stages, including (a)
the onset of gelation, (b) a period in which gelation occurs and
the biomaterial becomes sufficiently tack-free to permit shaping,
and (c) complete cure to the point where the biomaterial has been
finally shaped for its intended use.
[0044] "minimally invasive mechanism" refers to a surgical
mechanism, such as microsurgical, percutaneous, or endoscopic or
arthroscopic surgical mechanism, that can be accomplished with
minimal disruption of the pertinent musculature, for instance,
without the need for open access to the tissue injury site or
through minimal incisions (e.g., incisions of less than about 4 cm
and preferably less than about 2 cm). Such surgical mechanism are
typically accomplished by the use of visualization such as
fiberoptic or microscopic visualization, and provide a
post-operative recovery time that is substantially less than the
recovery time that accompanies the corresponding open surgical
approach;
[0045] "mold" will generally refer to the portion or portions of an
apparatus of the invention used to receive, constrain, shape and/or
retain a flowable biomaterial in the course of delivering and
curing the biomaterial in situ. A mold may include or rely upon
natural tissues (such as the annular shell of an intervertebral
disc) for at least a portion of its structure, conformation or
function. The mold, in turn, is responsible, at least in part, for
determining the position and final dimensions of the cured
prosthetic implant. As such, its dimensions and other physical
characteristics can be predetermined to provide an optimal
combination of such properties as the ability to be delivered to a
site using minimally invasive mechanism, filled with biomaterial,
prevent moisture contact, and optionally, then remain in place as
or at the interface between cured biomaterial and natural tissue.
In one embodiment the mold material can itself become integral to
the body of the cured biomaterial. The mold can be elastic or
inelastic, permanent or bio-reabsorbable.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0046] FIG. 1 is a schematic illustration of the method and
apparatus of the present invention.
[0047] FIG. 2 is an exemplary delivery tube and mold in accordance
with the present invention.
[0048] FIG. 3 is a schematic illustration of one embodiment of a
biomaterial reservoir in accordance with the present invention.
[0049] FIG. 4 is a schematic illustration of a purge device in
accordance with the present invention.
[0050] FIG. 5 illustrates the purge device of FIG. 4 in an open
configuration.
[0051] FIG. 6A is a schematic illustration of an alternate method
and apparatus of the present invention.
[0052] FIG. 6B is schematic illustration of a delivery tube that
seals against the annulus in accordance with the present
invention.
[0053] FIG. 6C is schematic illustration of the delivery tube of
FIG. 6B sealed against the annulus.
[0054] FIG. 7 is a schematic illustration of a communication system
between a central computer and a plurality of controllers in
accordance with the present invention.
[0055] FIGS. 8A-8C illustrate an imaging and mold positioning
technique in accordance with the present invention.
[0056] FIG. 9 illustrates an alternate imaging technique in
accordance with the present invention.
[0057] FIG. 10A-10B illustrate an alternate imaging technique using
a radiopaque sheath in accordance with the present invention.
[0058] FIG. 11 is an exemplary injection profile in accordance with
the present invention.
[0059] FIGS. 12-14 are schematic illustrations of one method in
accordance with the present invention.
[0060] FIG. 15 illustrates an alternate embodiment of the present
method and apparatus.
[0061] FIGS. 16A-16B illustrate an alternate delivery tube for
posterior access into the annulus in accordance with the present
invention.
[0062] FIGS. 17A-17B illustrate an alternate delivery tube for
lateral access into the annulus in accordance with the present
invention.
[0063] FIG. 18 illustrates an alternate delivery tube in accordance
with the present invention.
[0064] FIG. 19 illustrates another alternate delivery tube in
accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0065] FIG. 1 illustrates one embodiment of a biomaterial injection
system 1 in accordance with the present invention. The biomaterial
injection system 1 includes a reservoir 3 containing the
biomaterial 23 fluidly coupled to an implant mold 13 by a delivery
tube 11. The deflated implant mold 13 is dimensioned to be
positioned within the intervertebral disc space 19. The mold is
filled with uncured biomaterial 23 in order to provide a
replacement disc. As the biomaterial 23 is delivered to the implant
mold 13, the mold 13 expands to substantially fill the
intervertebral disc space 19, and in particular, fill the cavity 24
formed in the annulus 25 as a result of removal of some or all of
the nucleus.
[0066] Intervertebral disc space refers generally to the space
between adjacent vertebrae. The embodiments illustrated herein are
equally applicable to both a complete disc replacement and to a
full or partial nucleus replacement. A replacement disc refers to
both a complete disc replacement and to a full or partial nucleus
replacement.
[0067] The reservoir 3 is adapted to hold the biomaterial 23, and
in some embodiments, the reservoir 3 heats and/or mixes the
biomaterial 23. In some embodiments, the biomaterial 23 is
pretreated before use. The biomaterial 23 can either be pretreated
before being placed in the reservoir 3 or the pretreatment can be
performed in the reservoir 3. For example, the biomaterial 23 can
be heated, mechanically agitated, or both, such as heating in a
rotating oven before being placed in the reservoir 3. For some
polyurethane biomaterials, for example, sealed packages of
biomaterial 23 are heated while rotating in an oven at about
75.degree. C. for about 3 hours, maintained at 75.degree. C.
degrees C. without rotating for an additional 3 hours, and then
kept in the oven at about 37.degree. C. until surgical
implantation. During the second 3 hour period, the package of
biomaterial 23 is preferably retained in the oven without rotating
and in an upright position during heating so that bubbles rise to
the top. The flowable biomaterial 23 containing the bubbles is
preferably purged before it reaches the mold, as will be discussed
below.
[0068] A chamber 5 is optionally located in-line between the
reservoir 3 and the mold 13. The chamber 5 can be used to heat, mix
and/or stage the biomaterial 23. In some embodiments, the chamber 5
can be used to initiate curing of the biomaterial 23, such as for
example by exposing the biomaterial 23 to an ultraviolet light
source or a heat source 5b.
[0069] An actuator 21 is mechanically coupled to the reservoir to
expel the biomaterial 23 from the reservoir 3 and into the delivery
tube 11. The actuator 21 can be a pneumatic or hydraulic cylinder,
a mechanical drive such as an electric motor with a ball screw, a
drive screw or belt, or a variety of other mechanisms well know to
those of skill in the art. Control of the actuator 21 is typically
the primary operating parameter used to create the desired
injection profile. Other possible operating parameters that can be
controlled by the controller 15 include releasing biomaterial 23
through one or more of the purge devices 7a, 7b, biomaterial
temperature, biomaterial viscosity, and the like.
[0070] As used herein, "operating parameter" refers to one or more
independent variables that can be controlled during the injection
of biomaterial. The operating parameters can be linear, non-linear,
continuous, discontinuous, or any other configuration necessary to
achieve the desired injection profile. The operating parameter can
also be modified real-time based on feedback from the sensors
monitoring the injection conditions. For example, a control
algorithm, such as Proportional Integral Derivative (PID) control,
can be used to evaluate the injection condition data in light of
the desired injection profile.
[0071] For embodiments where the actuator 21 is a pneumatic
cylinder, it should be noted that many hospitals and clinics do not
have sources of compressed air greater than 50 pounds per square
inch (hereinafter "psi"). Thus, in some embodiments the pneumatic
cylinder needs to magnify the available compressed air source by a
factor of about 3. Thus, an initial pressure of about 50 psi
becomes about 150 psi in the reservoir 3.
[0072] The delivery tube 11 preferably includes at least one purge
device 7a. In the illustrated embodiment, the purge device 7a is
located downstream of the chamber 5. In another embodiment, a
secondary purge device 7b is located closer to the mold 13. The
purge devices 7a and 7b are referred to collectively as "7".
Suitable purge devices can include but are not limited to,
reservoirs, three-way valve systems, and the like. The purge
devices 7 can divert or redirect the flow of biomaterial 23 aside
in order to purge a portion, which can include an initial portion
that may be inadequately mixed or contain bubbles. The purge
devices 7 can also be employed if there is a system failure, such
as rupture of a mold 13, to quickly divert biomaterial from the
intervertebral disc space.
[0073] The purge devices 7a, 7b can be operated manually or
automatically. In the preferred embodiment one or both are operated
by controller 15 and/or using the mechanism in FIGS. 4 and 5/. In
one embodiment, the purge device 7a is operated manually by the
surgical staff and the purge device 7b is operated by the
controller 15.
[0074] In the illustrated embodiment, the biomaterial injection
system 1 preferably includes one or more sensors 9a, 9b, 9c, 9d,
9e, 9f, 9g and 9h (referred to collectively as "9") located at
strategic locations in the present biomaterial injection system 1.
In the illustrated embodiment, sensor 9a is located between the
reservoir 3 and the chamber 5. Sensor 9b is located between the
chamber 5 and the purge device 7a. Another sensor 9c is located
downstream of the purge device 7a. Sensor 9d is located close to
the mold 13. In the preferred embodiment, the sensor 9d is located
as close to the mold 13 as possible. The pressure sensor 9g is
located substantially in the mold 13. The sensor 9h is optionally
located in the intervertebral disc space 19, but outside the mold
13. The sensor 9e is located in the reservoir 3 and the sensor 9f
is located in the actuator 21.
[0075] Each of the individual sensors 9 can measure any one of a
plurality of injection conditions, such as for example biomaterial
color, biomaterial viscosity, pressure, quantity and/or size of air
bubbles in the biomaterial, flow rate, temperature, total volume,
duration of the flow of the biomaterial 23, or any other injection
condition that characterizes a proper injection profile. As used
herein, "injection condition" refers to one or more dependent
variables that are effected by one or more operating parameters. An
"injection profile" refers to values of one or more injection
conditions evaluated over time. An exemplary injection profile is
illustrated in FIG. 11.
[0076] Output from the sensors 9 is preferably delivered to
controller 15. The controller 15 preferably attaches a time/date
stamp to all injection condition data. Not all of the sensors 9
necessarily perform the same function. For example, the sensors 9a
and 9d may monitor pressure, while the sensor 9b monitors
temperature and the sensor 9c monitors flow.
[0077] The sensors 9 can be in-line with the delivery tube 11,
fluidly coupled to the delivery tube 11, coupled to the delivery
tube 11 by a diaphragm, or engaged with the delivery tube using a
variety of other techniques. The sensors 9 may be disposable or
reusable. A suitable pressure sensor 9 can include any device or
system adapted to measure or indicate fluid pressure within a
surgical fluid system and adapted for attachment to a delivery
mechanism 11. Examples of suitable pressure sensors include, but
are not limited to, those involving a suitable combination of
pressure gauge, electronic pressure transducer and/or force
transducer components. Such components that can be adapted to
permit the accurate and substantially real time measurement of
pressure in a remote fluid, by shunting a sample of such fluid, can
also be used particularly where the fluid is itself undergoing a
change in properties in the course of its ongoing cure.
[0078] The various components of the biomaterial injection system 1
are preferably fabricated from polymeric or other materials that
provide an optimal combination of properties such as compatibility
with the biomaterial 23 and the ability to be sterilized and/or to
be disposable.
[0079] Operation of the actuator 21 is preferably monitored and/or
directed by the controller 15. Output from the sensors 9 is
preferably delivered to the controller 15 to create a closed-loop
feed back system. The controller 15 preferably includes a processor
and a memory device. The controller 15 can be a special purpose
computer, a general purpose computer such as a personal computer,
independent signal conditioning circuits, threshold comparator
circuits and switch circuits. In some embodiments, the controller
15 is a user interface to effect manual control of the system
1.
[0080] The controller 15 preferably includes one or more displays
16 that communicate injection conditions to the surgical staff. The
controller 15 can also provide audio indications of the injection
condition data shown on the displays 16. In another embodiment, the
surgical staff manually overrides the operation of the controller
15 so as to permit one or more operating parameters to be
controlled manually based on data obtained from the displays
16.
[0081] As illustrated in FIG. 2, the biomaterial injection system 1
also preferably includes a secondary tube 11' that evacuates air
from the mold 13 before the biomaterial is delivered. The secondary
tube 11' can either be inside or outside the delivery tube 11.
Removal of air from the mold 13 through the secondary tube 11' is
preferably controlled by the controller 15. Connection to the
sensor 9g in the mold 13 can optionally be connected through the
secondary tube 11'.
[0082] FIG. 3 illustrates an embodiment where the reservoir 3
includes two or more discrete compartments 37a and 37b. Each
compartment 37a, 37b is engaged with a piston 35a, 35b coupled to
an actuator 21. As the actuator 21 advances the pistons 35a, 35b
into the compartments 37a, 37b, respectively, components 23a, 23b
of the biomaterial 23 flow into the chamber 5 where they are
mixed.
[0083] The mixing of the two or more components 23a, 23b of the
biomaterial 23 can initiate a chemical curing reaction. Although
the reservoir of FIG. 3 is illustrated with two compartments 37a,
37b, three or more compartments can be used for applications where
the biomaterial has more than two components.
[0084] Alternatively, the biomaterial may be a single component
system that can be located in one or more of the compartments 37a,
37b. Single component biomaterials can be cured using, for example,
ultraviolet light, ultrasonic energy, or heat. In one embodiment,
the chamber 5 can optionally include an ultraviolet light source, a
heater, or any other device or source of energy that initiates the
curing process of the biomaterial 23.
[0085] FIG. 4 is a schematic illustration of an exemplary automatic
purge device 70 in accordance with the present invention. The purge
device 70 can optionally be substituted for the purge device 7a.
Delivery tube 11 is fluidly coupled to inlet 72 using connecting
structure 74. In the illustrated embodiment, connecting structure
74 is a plurality of threads. In an alternate embodiment, the
connecting structure 74 can be a quick-connect device, or variety
of other structures. The inlet 72 on the purge device 70 is fluidly
coupled to chamber 76 by passageway 78. Piston 80 is located in the
chamber 76. The purge device 70 is in a closed configuration with
valve 82 obstructing the flow of biomaterial 23 to outlet 84.
Outlet 84 also includes a connecting structure 86, such as
threads.
[0086] As biomaterial is delivered to the inlet 72 under pressure,
it is advanced through the passageway 78 into the chamber 76. The
volume of the chamber 76 is designed to accommodate the optimum
amount of biomaterial 23 that is typically purged prior to delivery
to the mold 13. Once the chamber 76 is filled with biomaterial 23,
force 88 is applied to the piston 80. As the piston 80 is driven
toward surface 90 on housing 92 by the pressure of the biomaterial
23, connecting member 94 displaces the valve 82 along with the
piston 80. Vent hole 81 allows air to escape from behind the piston
80 as it advances in the housing 92.
[0087] FIG. 5 illustrates the purge device 70 of FIG. 4 in an open
configuration. The piston 80 has been advanced all the way to the
surface 90, causing the valve 82 to create an opening 96 through
which the biomaterial 23 can be advanced to the outlet 84. Pressure
transducer 98 is optionally located on the inlet side 72 of the
valve 82 to measure the pressure of the bio-material 23 both
before, during and after the valve 82 is opened.
[0088] FIG. 6A illustrates the biomaterial injection system 1 of
FIG. 1, except that the annulus 25 acts as the mold to retain the
biomaterial. As the biomaterial 23 is delivered to the annulus 25
it substantially fills the cavity 24. In one embodiment, the
interior surface of the cavity 24 in the annulus 25 is coated with
a reinforcing material 27, such as a curable polymer, prior to the
delivery of the biomaterial. The reinforcing material 27 preferably
adheres to the interior surface of the cavity 24. The reinforcing
material 27 can be flexible and can be either permanent or
bio-absorbable. In one embodiment, the reinforcing material 27 also
adheres to the biomaterial, securing the biomaterial forming the
implant to the inner surface of the cavity 24.
[0089] In another embodiment, the delivery tube 11 is sized to fit
the inlet 26 formed in the annulus 25 snuggly to allow the
biomaterial 23 to be delivered under pressure without leaking. In
the embodiment of FIGS. 6B and 6C, flange 250 is located near
distal end 252 of the delivery tube 11 to reduce or eliminate
leakage of the biomaterial 23 from the cavity 24. Also illustrated
in FIGS. 6B and 6C, distal end 252 of the delivery tube 11 adjacent
to the inlet 26 includes a thin wall that expands when subjected to
the pressure of the biomaterial 23 (see FIG. 6C). The expanded
distal end 252 of the delivery tube 11 forms a seal with the inlet
26. The flange 250 and the thin-walled distal end 252 can either be
used alone or in combination with each other.
[0090] As discussed above, the controller 15 preferably monitors
and records the injection condition data and attaches a time/date
stamp. FIG. 7 illustrates an embodiment in which a plurality of
controllers 15a, 15b, 15c . . . (referred to collectively as "15")
communicate with a remote computer 18 using a variety of
communications channel 22, such as for example the Internet, phone
lines, direct cable connection, wireless communication, and the
like. The injection profiles 20a, 20b, 20c, 20d . . . (referred to
collectively as "20") for a plurality of patients are optionally
uploaded to the computer 18 for storage and processing.
Pre-surgical and post-surgical data about each patient is also
preferably uploaded to the computer 18. Patient parameters
typically includes weight, age, disc height after the procedure,
disc degree index, disc compliance, and the like.
[0091] By linking the historic injection profiles 20 with the
patient's pre-surgical and post-surgical patient parameters, a
database is created that can be searched by surgeons for the
injection profile 20 that most closely matches the current
patient's parameters. Once the optimum profile is selected, it can
optionally be downloaded to the controller 15 prior to performing
the present method.
[0092] Preliminary Analysis of the Patient
[0093] The optimum injection profile and the corresponding
injection conditions may vary as a function of patient parameters,
such as for example, the patient's weight, age, gender, disc
height, disc degeneration index, disc compliance, general clinical
goals, patient-specific clinical goals, and the like. For example,
a diseased disc may require a higher injection pressure and a
higher termination pressure to restore more disc height and a
longer dwell time at the threshold and/or termination pressure.
Alternatively, if a bone scan indicates reduced bone density or
that the vertebral bodies are otherwise compromised, a lower
injection pressure may be indicated. The present invention includes
creating an injection profile as a function of patient parameters
and clinical goals. In some embodiments, a custom injection profile
is created for each patient.
[0094] One mechanism for selecting the appropriate injection
profile for the patient is to conduct an analysis on the annulus
25. Imaging or palpitation of the annulus, preferably after
nuclectomy, is optionally performed before the delivery of the
biomaterial to assess annular integrity. In one embodiment, an
instrument is used that applies a known force to the annular wall
25 and measures the amount of deflection. In one embodiment, an
evaluation mold 13' (which may be the same mold or a different mold
than the implant mold 13), is inserted into the patient's annulus
25 after the nuclectomy is completed, such as illustrated in FIG.
1. The evaluation mold 13' is inflated with a contrast medium that
is easily imaged or other liquid, such as saline, to a target
pressure (see e.g., FIGS. 4-6). Inflation and deflation of the
imaging mold 13' is preferably controlled by the present
biomaterial injection system 1, and annular deflection is measured
either automatically or manually. Alternatively, operations related
to the evaluation mold 13' can be handled manually.
[0095] In some embodiments, the evaluation mold 13' and/or the
delivery tube 11 have radiopaque properties. The radiopaque
properties can be provided by constructing the evaluation mold 13'
and/or the delivery tube 11 from a radiopaque material or including
radiopaque markings, such as inks, particles, beads, and the like
on the evaluation mold 13' and/or the delivery tube 11 to
facilitate imaging. An image, such as an x-ray, MRI, CAT-scan, or
ultrasound, is then taken of the patient's intervertebral disc
space 19 to check if the nuclectomy (i.e., the cavity 24) is
symmetrical, of adequate size, of the desired geometry and/or if
the required amount of distraction has been achieved. This
information is used by the surgeon to decide when the proper amount
of nucleus material has been removed from the annulus 25.
[0096] The volume of contrast medium necessary to fill the cavity
24 and to achieve the desired amount of distraction, as verified by
the image sequence, provides an indication of the volume of
biomaterial 23 necessary for the procedure. In another embodiment,
imaging is used to estimate the amount of nucleus that needs to be
removed. The volume of liquid necessary to fill the evaluation mold
13' is then compared to the estimated volume measured using imaging
techniques and a determination is made whether additional nucleus
material should be removed.
[0097] In another embodiment illustrated in FIGS. 8A-8C, an imaging
device 100 including an evaluation mold 13' is positioned in the
mold 13. After the mold 13 is positioned in the cavity 24 of the
cavity 24 of the annulus 25 between the vertebrae 17, delivery tube
11' containing an evaluation mold 13' is inserted into the delivery
tube 11. The evaluation mold 13' is preferably a small pliable,
stretchable contrast balloon. A contrast medium 102 (see FIG. 10B)
is delivered through the tube 11' into the evaluation mold 13' to
fill the nominal volume of the mold 13. The mold 13 and/or the
delivery tube 11 may also have radiopaque properties.
[0098] The contrast medium 102 is preferably delivered at a
pressure sufficient to fully expand the mold 13 into the cavity 24.
The evaluation mold 13' also serves to position the mold 13 within
the annulus 25. As best illustrated in FIG. 8B, the fully expanded
evaluation mold 13' corresponds generally to the shape of the
cavity 24 within the annulus 25 that will be filled by the implant.
Imaging, as discussed above, is then performed to confirm the shape
of the cavity within the annulus 25 and placement of the mold 13
within the annulus 25. The quantity of contrast medium 102 can be
used to estimate the volume of the cavity 24 within the annulus
25.
[0099] As illustrated in FIG. 8C, the contrast medium 102 is then
removed from the evaluation mold 13'. The tube 11' and evaluation
mold 13' are then removed from the delivery tube 11 in preparation
for delivery of biomaterial 23 into the mold 13. The procedure of
FIGS. 8A-8C can also be performed in connection with the embodiment
of FIG. 6A, where the evaluation mold 13' is positioned directly in
the cavity 24, rather than in the mold 13.
[0100] FIG. 9 illustrates an alternate imaging method using imaging
device 110 in accordance with the present invention. A guide wire
or wire stylus 112 with an optional imaging target 114 at a distal
end 116 is inserted into the delivery tube 11. The imaging target
114 can be a variety of shapes, preferably easily recognizable
geometric shapes such as for example a sphere. Imaging techniques
are then used to confirm the positioning of the evaluation mold 13'
or the mold 13 in the annulus 25. The guide wire 112 can also be
used to evaluate the geometry of the intervertebral disc space
created by removal of nucleus material and/or to press the mold 13
into position within the annulus 25.
[0101] FIGS. 10A and 10B illustrate an alternate imaging technique
using imaging device 120 in accordance with the present invention.
The delivery tube 11 and mold 13 are provided with a radiopaque
sheath 122. The delivery tube 11 and/or the mold 13 may also have
radiopaque properties. In the illustrated embodiment, the
radiopaque sheath 122 includes bend 124 that directs the mold 113
at a predetermined angle relative to the longitudinal axis of the
delivery tube 11. Once positioned in the cavity 24 formed in the
annulus 25, imaging techniques can be used to determine placement
of the assembly in the cavity. Once positioning has been confirmed,
the radiopaque sheath 122 can be withdrawn along the delivery tube
11 in preparation for delivery of biomaterial to the mold 13.
[0102] Compliance Testing
[0103] The evaluation mold 13' can also be used to measure the
compliance of the annulus 25. For example, the evaluation mold 13'
can be pressurized with a fixed volume of saline or a liquid
contrast medium to the level anticipated during delivery of the
biomaterial. Images of the intervertebral disc space 19 are
optionally taken at various pressures to measure the distraction of
the adjacent vertebrate 17. After a period of time, such as about
three to about five minutes, the tissue surrounding the
intervertebral disc space 19 generally relaxes, causing the
pressure measured in the evaluation mold 13' to drop. Additional
saline or contrast medium is then introduced into the evaluation
mold 13' to increase the pressure in the intervertebral disc space
19 to the prior level. The tissue surrounding the intervertebral
disc space 19 again relaxes as measured by the reduction in
pressure within the evaluation mold 13'. By repeating this
procedure several times, the surgeon can assess the compliance of
the intervertebral disc space 19 and/or the annulus 25, and the
likely volume of biomaterial 23 necessary for the procedure.
[0104] In another embodiment, compliance is measured by
continuously adding a liquid to the evaluation mold 13' at a rate
sufficient to maintain a generally constant pressure in the
biomaterial delivery system 1 and/or in the intervertebral disc
space. The change in the rate at which liquid needs to be added to
maintain a constant pressure provides information that can be used
to estimate compliance of the annulus 25 and/or the intervertebral
disc space 19.
[0105] A healthy, compliant annulus can typically handle several
pressurization/relaxation cycles. A diseased annulus 25 may show
less relaxation (e.g., less compliance) after being pressurized.
Depending upon the status of the annulus 25 and the intervertebral
disc space 19, a patient-appropriate injection profile can be
selected.
[0106] This compliance evaluation can be either controlled manually
or by the controller 15. The compliance data collected can be used
to determine the operating parameters to produce the injection
profile best suited to the patient.
[0107] Injection conditions
[0108] The present biomaterial delivery system 1 permits one or
more operating parameters to be controlled to achieve the desired
injection conditions. The injection conditions are monitored,
recorded and controlled real-time. The injection conditions may
include, for example, biomaterial temperature and viscosity,
biomaterial flow rate, biomaterial pressure, volume of biomaterial,
distraction pressure, total distraction, and time, such as for
example distraction time. These injection conditions can vary over
the course of the medical procedure, so a plurality of injection
conditions are preferably monitored and recorded as a function of
time. The injection conditions can also be evaluated as a function
of any of the other injection conditions, such as for example,
pressure as a function of volume or flow. In the present invention,
the pressure in the mold 13 is one possible injection condition for
determining when to terminate the flow of biomaterial 23.
Alternatively, the volume of biomaterial 23 delivered to the mold
13 can also be used for this purpose.
[0109] Once an optimum injection profile for the patient is
determined (see e.g., FIG. 11), the controller 15 preferably
controls one or more operating parameters so that the injection
conditions are maintained within a predetermined margin of
error.
[0110] The injection conditions can be used to signal that the
procedure is out of specification. Alternatively, the controller 15
can calculate trends or slopes of the injection conditions to
predict whether a particular injection condition will likely be out
of specification. As used herein, "out of specification" refers to
one or more injection conditions that have deviated from the
desired injection profile and/or are exhibiting a trend that
indicates a future deviation from the injection profile.
[0111] In those situations where the injection conditions can not
be brought under control, such as for example if the mold 13
malfunctions, the procedure is aborted and the biomaterial 23 is
preferably withdrawn from the patient before it cures. As used
herein, malfunction refers to ruptures, fractures, punctures,
deformities, kinks, bends, or any other defect that results in more
or less biomaterial being injected into the patient than would
otherwise occur if the mold was operating as intended.
Alternatively, if the malfunction occurs in a location other than
the mold, such as in the delivery tube 11 or if the mold kinks and
can not be deployed and expanded to fill the intervertebral disc
space, or if the vacuum tube 11' is obstructed an air in the mold
13 can not be evacuated, less biomaterial will be injected into the
mold than is desired.
[0112] The controller 15 monitors one or more sensors 9 to
determine if the injection conditions are under control. If any one
or a combination of the injection conditions are out of
specification, a number of corrective actions can be taken. If the
deviation from the preferred injection profile is minor, the
controller 15 can attempt a correction. During a given medical
procedure where the resistance to the flow of biomaterial 23 is
essentially fixed, the primary mechanisms for controlling the
injection conditions are 1) decreasing, increasing or reversing the
drive pressure exerted on the reservoir 3 by the actuator 21; 2)
releasing biomaterial 23 through one or more of the purge devices
7a, 7b; and 3) changing the temperature, and hence the viscosity,
of the biomaterial 23.
[0113] If the deviation is above a particular threshold, the
controller 15 may signal the surgical staff. Alternatively, the
surgical staff can monitor the displays 16 for any out of
specification injection conditions. The displays 16 preferably
highlight the injection condition(s) that have deviated from the
preferred injection profile. In those instances where an injection
condition is seriously out of specification, the controller 15 will
signal that the procedure should be aborted and/or automatically
abort the procedure. Typically, the actuator 21 will decrease or
reverse the drive pressure on the reservoir 3 in anticipation of
aborting the procedure. If the procedure is aborted, any
biomaterial 23 in the mold 13 and/or the intervertebral space 19 is
removed, either through the purge device 7b or manually by the
surgeon. The mold 13 is also removed.
[0114] FIG. 11 illustrates a simulated injection profile 70 that
illustrates the benefits of the present biomaterial delivery system
1. The injection profile 70 includes three injection condition
curves for flow rate 72, injection pressure 74 and total volume 76
all as a function of time 78. In the illustrated example, the flow
72 is calculated by the controller 15, the injection pressure 74 is
measured as the sensor 9b and/or 9c, and the volume 76 is measured
by the sensor 9f. In another embodiment, the injection profile may
include flow, pressure or volume curves measured at other locations
along the biomaterial injection system 1.
[0115] At the beginning of time sequence 81, the biomaterial 23 is
immediately upstream of the purge device 7a. During time sequence
81, the biomaterial 23 begins to enter the purge device 7a. During
time sequence 82, the biomaterial 23 is filling the purge device.
The flow rate 72 is relatively constant and the total volume 76 of
biomaterial continues to increase. The sudden increase of injection
pressure 74 between the end of time sequence 81 and the beginning
of time sequence 82 is the result of internal resistance to the
flow of biomaterial 23 at the purge device 7a.
[0116] At time sequence 83, the purge device 7a switches the flow
of biomaterial 23 to the delivery tube 11, resulting in a rapid
spike in injection pressure 74. At time sequence 84, the
biomaterial 23 fills the delivery tube 11. Injection pressure 74
increases due to resistance to the flow of biomaterial 23 through
the delivery tube 11. At time sequence 91, the biomaterial 23
reaches the folded mold 13, resulting in a rapid increase in
injection pressure 74 as the mold unfolds.
[0117] At time sequence 85 the biomaterial 23 begins to fill the
mold 13. The slight drop in injection pressure 74 is the result of
the biomaterial 23 flowing freely into the mold 13. The expanding
mold 13 hits the inner wall of the annulus at time sequence 86. The
flow rate 72 continues to drop and the total volume 76 of
biomaterial 23 continues to increase at a generally constant rate.
At time sequence 87, the injection pressure 74 of the biomaterial
23 continues to increase at a different rate as it displaces the
vertebrae 17 and distracts the intervertebral disc space 19. The
muscles and tendons attached to the vertebrate 17 are stretched
elastically by the injection pressure 74 of the biomaterial 23 in
the mold 13.
[0118] At time sequence 88, the threshold injection pressure 74 is
reached. Time sequence 88 represents the maximum distraction of the
intervertebral disc space 19. In the illustrated example, the drive
pressure exerted by the actuator 21 on the reservoir 3 during time
sequences 81 through 88 is generally constant. Once the injection
pressure 74 at time sequence 88 is reached, a transition is
triggered where the drive pressure at the actuator 21 is reduced
from a first operating parameter to a second operating parameter.
As a result, the injection pressure 74 is reduced. The flow rate 72
is about zero and the total volume 76 of biomaterial is at a
maximum.
[0119] In another embodiment, once the injection pressure 74 at
time sequence 88 is reached, a transition is triggered from a first
operating parameter to a second operating parameter where the drive
pressure at the actuator 21 is held constant for some period of
time, such as for example 3-120 seconds. At the end of the dwell
time, the drive pressure is reduced from the second operating
parameter to a third operating parameter. Again, the injection
pressure 74 is reduced and the flow rate 72 is about zero and the
total volume 76 of biomaterial is at its final volume.
[0120] At time sequence 89 the drive pressure exerted on the
biomaterial 23 in the reservoir 3 by the actuator 21 is reduced.
This reduction can alternatively be achieved by releasing a portion
of the biomaterial 23 through a purge device 7a, 7b. The pressure
created in the intervertebral disc space 19 acting on the mold 3 is
now greater than the injection pressure 74 of the biomaterial 23 in
the biomaterial delivery system 1. Consequently, tension of the
muscles and tendons surrounding the vertebrate 17 provides a
compressive force that results in a flow of biomaterial 23 out of
the mold 13, as indicated by the negative flow rate 72 during time
sequence 89 and a decrease in total volume 93.
[0121] At time sequence 90 the injection pressure 74 of the
biomaterial 23 is generally constant. The pressure exerted by the
mold 13 and biomaterial 23 is nearly in balance with the pressure
exerted by the vertebrate 17 on the mold 13. The flow rate 72 and
the change in total volume 76 are both about zero. With the system
1 now in stasis, the biomaterial 23 begins to cure. Once the
biomaterial 23 is at least partially cured, the delivery tube 11 is
removed.
[0122] FIGS. 12-14 schematically illustrate one embodiment of the
present invention. The embodiments of FIGS. 12-14 are illustrated
as a complete disc replacement. The embodiments of these Figures
are equally applicable to a full or partial nucleus
replacement.
[0123] In these embodiment, the biomaterial injection system 1
initially operates at a first operating parameter. When one of the
injection conditions reaches a threshold level, such as for example
a threshold pressure as measured in the mold 13, the controller 15
switches or transitions to second operating parameter. In an
alternate embodiment, the threshold trigger could be flow rate,
time, volume or temperature of the biomaterial. In the embodiment
of FIGS. 12-14, the trigger from the first to the second operating
parameter causes the controller to reduce the pressure applied by
the actuator 21 on the biomaterial 23 in the reservoir 3.
[0124] In another embodiment, the second operating parameter is a
dwell cycle where the pressure is maintained as some predetermined
level for a predetermined period of time. At the end of the dwell
cycle, the controller switches to a third operating parameter,
which includes reducing the pressure applied by the actuator 21 on
the biomaterial 23 in the reservoir 3.
[0125] FIG. 12 illustrates a first operating parameter during which
the deflated mold 13 is filled with biomaterial 23 until it
conforms to the shape of the intervertebral disc space 19. In one
embodiment the first operating parameter includes a drive pressure
created by the actuator 21 which results in an injection parameter
(i.e., injection pressure) measured at the sensor 9e of about 150
psi. Alternatively, the first operating parameter includes a drive
pressure created by the actuator that results in an injection
pressure in the range of about 100 psi to about 270 psi.
[0126] The relatively high injection pressure provides a number of
benefits, including rapid filling of the mold 13 to reduce the
chance of leaving voids or under-filled regions. The biomaterial
injection system 1 continues to operate at the first operating
parameter until one of the injection conditions reaches a threshold
level that triggers use of the second operating parameter.
[0127] FIG. 13 depicts the time sequence in the procedure when the
pressure of the biomaterial 23 measured at the sensors 9b, 9c, and
preferably the sensor 9d, triggers the controller 15 to change to
second operating parameter. Once the injection pressure measured at
the sensors 9b, 9c or 9d rises to a particular level, the drive
pressure exerted by the actuator 21 is reduced to a predetermined
level.
[0128] The injection pressure used to determine a suitable
threshold typically corresponds to the distraction pressure brought
about by the delivery of biomaterial 23 within the disc space 19.
The injection condition in this instance is the injection pressure
measured at the sensors 9c or 9d, such as for example about 80 psi
to about 150 psi. In one embodiment, the injection pressure
triggers the controller 15 to transition to the second operation
condition. In another embodiment, the second operating condition
holds the injection pressure at a predetermined level for a
predetermined dwell time.
[0129] FIG. 14 illustrates the second operating parameter (or a
third operating parameter where the second operating parameter is a
dwell cycle). In the embodiment of FIG. 14, the second operating
parameter includes a reduction in drive pressure exerted by the
actuator 21. The tension built up in the tissues surrounding the
vertebrate 17 is permitted to act on the mold 13 to expel a portion
of the biomaterial 23 out of the intervertebral disc space 19 and
back into the delivery tube 11. In one embodiment, the injection
pressure measured at sensor 9a during the second operating
parameter is about 0 psi to about 120 psi, and typically about 10
psi to about 50 psi.
[0130] It is possible to measure the pressures discussed above
using any of the sensors 9a-9d and 9g-9h. Doing so would require
calibrating the biomaterial injection system 1 so that a measured
pressure at one of the sensors 9 is correlated to the actual
pressure in the intervertebral disc space 19, such as measured by
sensor 9g or 9h. The factors required for such a calibration
include the size of the mold 13, the resistance to fluid flow
between the reservoir 3 and the mold 13, the flow rate, the
viscosity and temperature of the biomaterial 23, the cure time of
the biomaterial, and a variety of other factors. For example, with
regard to mold size, the transition from the first operating
parameter to the second operating parameter occurs when the
injection conditions measured at the sensor 9b is about 100 psi to
about 125 psi for a mold 13 with a volume of about 1.8 cubic
centimeters; about 105 psi to about 130 psi for a mold 13 with a
volume of about 2.7 cubic centimeters; and about 110 psi to about
135 psi for a mold with a volume of about 4.0 cubic
centimeters.
[0131] FIG. 15 illustrates an alternate method and apparatus for
performing the present invention where the actuator 21 is attached
to an external source of compressed air 57. The controller 15
includes a directional control valve 49 that extends or retracts
the pneumatic actuator 21 and a pressure control switch 51 to
change between the first operating parameter and the second
operating parameter. At least two pressure regulators 53, 55 are
used to regulate the pressure reaching the pressure control switch
51. The first pressure regulator 53 provides the first pressure
injection and the second pressure regulator 55 provides the second
pressure injection. In an embodiment where the operating parameters
comprise multiple variables, multiple pressure regulators will
typically be required.
[0132] Initially, the pneumatic actuator 21 is supplied with
compressed air through the first pressure regulator 53. When one or
more of the sensors 9a-9d detects a threshold pressure, the
pressure control switch 51 selects compressed air from the second
pressure regulator 55 to drive the pneumatic actuator 21. In one
embodiment, the directional control valve 49 is a normally open,
four-way valve such as those available under the trade name of
Four-Way Valve (SV271) available from Omega Engineering, Inc.
Stamford, Conn.
[0133] Mold Placement
[0134] In a related embodiment, the mold, or a kit that contains or
is adapted for use with such a mold, can include tools adapted to
position the mold 13 in situ. In one embodiment, the tool is a
guide wire, such as for example the guide wire shown in FIG. 9,
that is placed through the delivery conduit 11 itself, or
preferably through an air passageway that terminates at or near the
point of contact with the mold 13. The guide wire can be designed
to substantially assume the curved contour of the extended but
unfilled mold, and to provide a plane of orientation, in order to
both facilitate placement of the mold and provide an outline of the
periphery of the mold in position and prior to filling. Thereafter,
the guide wire can be removed from the site prior to delivery of
the biomaterial and air evacuation. The use of a guide wire in this
manner is particularly facilitated by the use of an air passageway
that is unconnected to, and positioned outside of, the biomaterial
delivery tube. In another embodiment, the delivery tube 11 includes
one or more curves that facilitate placement of the mold 13.
[0135] Optionally, and in order to facilitate the placement of the
collapsed mold 13 within a sheath, the invention further provides a
rod, e.g., a plastic core material or a metal wire, dimensioned to
be placed within the mold 13, preferably by extending the rod
through the conduit. Once in place, a vacuum can be drawn on the
mold 13 through the air passageway in order to collapse the mold 13
around the rod. Simultaneously, the mold 13 can also be twisted or
otherwise positioned into a desired conformation to facilitate a
particular desired unfolding pattern when later inflated or filled
with biomaterial. Provided the user has, or is provided with, a
suitable vacuum source, the step of collapsing the mold 13 in this
manner can be accomplished at any suitable time, including just
prior to use.
[0136] In certain embodiments it will be desirable to collapse the
mold 13 just prior to its use, e.g., when using mold materials that
may tend to stick together or lose structural integrity over the
course of extended storage in a collapsed form. Alternatively, such
mold materials can be provided with a suitable surface coating,
e.g., a covalently or noncovalently bound polymeric coating, in
order to improve the lubricity of the surface and thereby minimize
the chance that contacting mold surfaces will adhere to each other.
In another embodiment, the outer surface of the mold 13 can be
coated with a material that bonds to the inner surface of the
cavity 24 in the annulus 25.
[0137] FIG. 16A illustrates the delivery tube 200 and mold 13 with
a bend 202 at the connection 204 between the mold 13 and the
delivery tube 11. In the illustrated embodiment, the bend 202
extends along about 3-5 millimeters of the delivery tube 200 near
the connection 204 and has a curvature of about
30.degree.+/-15.degree.. As illustrated in FIG. 16B, this
configuration is particularly well suited for posterior entry into
the annulus 25. The embodiment of FIG. 16A can also be achieved
with a straight, flexible delivery tube and a curved guide wire 206
in the delivery tube 200.
[0138] FIG. 17A illustrates a curved delivery tube 210. As
illustrated in FIG. 17B, this configuration is particularly well
suited for lateral entry of the mold 13 into the annulus 25. The
curve of the delivery tube 210 can also be achieved by using a
flexible delivery tube containing a curved guide wire. In another
embodiment, the guide wire may be malleable.
[0139] FIG. 18 illustrates a delivery tube 220 with multiple bends
222, 224, 226. The bends 222, 224, 226 can be co-planar or located
in multiple planes. The bend 226 is located near the connection 228
with the mold 13, similar to FIG. 16A. FIG. 19 illustrates the mold
13 attached to an alternate delivery tube 230 with bends 232, 234.
Similarly, the bends 232, 234 can be co-planar or located in
multiple planes. Alternatively, the embodiments of FIGS. 18 and 19
can be achieved by using a flexible delivery tube containing a
curved guide wire.
[0140] Biomaterials
[0141] The method of the present invention can be used with any
suitable curable biomaterial such as a curable polyurethane
composition having a plurality of parts capable of being
aseptically processed or sterilized, stablely stored, and mixed at
the time of use in order to provide a flowable composition and
initiate cure, the parts including: (1) a quasi-prepolymer
component comprising the reaction product of one or more polyols,
and one or more diisocyanates, optionally, one or more hydrophobic
additives, and (2) a curative component comprising one or more
polyols, one or more chain extenders, one or more catalysts, and
optionally, other ingredients such as an antioxidant, hydrophobic
additive, dyes and radiopaque markers. Upon mixing, the biomaterial
is sufficiently flowable to permit it to be delivered to the body
and fully cured under physiological conditions. A suitable
biomaterial also includes component parts that are themselves
flowable at injection temperature, or can be rendered flowable, in
order to facilitate their mixing and use. Additional discussion of
suitable biomaterials can be found in U.S. patent application Ser.
Nos. 10/365,868 and 10/365,842, previously incorporated by
reference.
[0142] The biomaterial used in this invention can also include
polyurethane prepolymer components that react in situ to form a
solid polyurethane ("PU"). The formed PU, in turn, includes both
hard and soft segments. The hard segments are typically comprised
of stiffer oligourethane units formed from diisocyanate and chain
extender, while the soft segments are typically comprised of more
flexible polyol units. These two types of segments will generally
phase separate to form hard and soft segment domains because these
segments tend to be thermodynamically incompatible with one
another.
[0143] Those skilled in the relevant art, given the present
teaching, will appreciate the manner in which the relative amounts
of the hard and soft segments in the formed polyurethane, as well
as the degree of phase segregation, can have a significant impact
on the final physical and mechanical properties of the polymer.
Those skilled in the art will therefore further appreciate the
manner in which such polymer compositions can be manipulated to
produce cured and curing polymers with a desired combination of
properties within the scope of this invention. In some embodiments
of the present invention, for instance, the hard segment in the
formed PU ranges from about 20% to about 50% by weight and more
preferably from about 20% to about 30% by weight and the soft
segment from about 50% to about 80% and more preferably from about
70% to about 80% by weight, based on the total composition of the
formed PU. Other embodiments may be outside of these ranges.
[0144] The biomaterial typically includes a plurality of component
parts and employs one or more catalysts. The component parts,
including catalyst, can be mixed to initiate cure, and then
delivered, set and fully cured under conditions such as time and
exotherm sufficient for its desired purpose. Upon the completion of
cure, the resultant biomaterial provides an optimal combination of
properties for use in repairing or replacing injured or damaged
tissue. In a further embodiment, the biomaterial provides an
optimal combination of properties such as compatibility and
stability, in situ cure capability and characteristics (e.g.,
extractable levels, biocompatibility, thermal/mechanical
properties), mechanical properties (e.g., tensile, tear and fatigue
properties), and biostability.
[0145] Many mixing devices and methods have been used for
biomaterials having a plurality of parts such as bone cement and
tissue sealant. Mechanical mixing devices, such as the ones
disclosed in U.S. Pat. No. 5,797,679 (Grulke, et al.) and U.S. Pat.
No. 6,042,262 (Hajianpour), have been used for bone cement mixing.
These mechanical mixing devices, however, can take a long time to
get thorough mixing and can be difficult to operate in sterile
field, especially for biomaterials having a plurality of parts with
short cure time. On the other hand, some prior art two-part
polyurethanes have a gel time of about 30 minutes. Without a proper
seal method to seal off the delivery tube, a cure time of 30
minutes can be too long for operating room use.
[0146] It is important that mixing of the biomaterial occurs
quickly and completely in the operating room in a sterile fashion.
Biomaterial with induction times of less than 60 seconds and cure
times of less than 5 minutes require a different mixing and
delivery device than biomaterials of about 15 minutes of cure time.
For biomaterial having two-part issocyanate-based polyurethane
biomaterials, due to the sensitivity of NCO to OH ratio to the
final properties of the cured biomaterial, there are several
features that are important to the final properties of the in situ
cured biomaterial. Several factors appear to have an impact on the
in situ curable biomaterial mixing and delivery such as the number
of mixing elements, purging of the initial volume from the static
mixer and the effect of polymer flow during delivery using a static
mixer.
[0147] The compatibility of the biomaterial can also be achieved by
having more than the traditional two parts, e.g., three or more
parts, and mixing them all together prior to polymer application.
By storing the incompatible components in different cartridges
and/or preconditioning each component according to individual
requirements, it often can minimize the concern of component
incompatibility. One example of a three-part biomaterial is to
separate the polyol and chain extender in a two-part
biomaterial.
[0148] In situ curability is largely dependent on the reaction
rate, which can be measured by induction time and cure time. In
general, fast cure (short induction time) will improve in situ
curability by providing more complete polymerization, less
leachable components, and better mechanical properties (e.g., less
"cold layer" formed due to the cold surface of the implant).
However, induction time should also be balanced with adequate
working time needed for biomaterial injection, distraction, to
provide enough time to access the injection conditions, identify if
the injection conditions fall inside or outside an acceptable
range, and if falling outside the acceptable range, halting or
reversing the injection process.
[0149] Particularly for use in the disc, it has been determined
that shorter induction times tend to provide improved biomaterial
properties. For such uses, the induction time can be between about
5 and about 60 seconds, for instance, between about 5 and about 30
seconds, and between about 5 and about 15 seconds. By comparison,
the total cure time for such biomaterial can be on the order of 5
minutes or less, 3 minutes or less, and one minute or less. In one
embodiment of the present invention, however, the cure time can be
on the order of about 15 minutes. In either case the cure time can
be greater than 15 minutes by adjusting the amount of catalyst
used.
[0150] The method of the present invention can be used for a
variety of applications, including for instance, to provide a
balloon-like mold for use preparing a solid or intact prosthesis,
e.g., for use in articulating joint repair or replacement and
intervertebral disc repair. Alternatively, the method can be used
to provide a hollow mold, such as a sleeve-like tubular mold for
use in preparing implanted passageways, e.g., in the form of
catheters, such as stents, shunts, or grafts.
[0151] The present invention also provides a method and system for
the repair of natural tissue that involves the delivery of
biomaterial using minimally invasive mechanism, the composition
being curable in situ in order to provide a permanent replacement
for natural tissue. Optionally, the biomaterial is delivered to a
mold that is positioned by minimally invasive mechanism and filled
with biomaterial composition, which is then cured in order to
retain the mold and cured composition in situ.
[0152] As can be seen, the annular shell can itself serve as a
suitable mold for the delivery and curing of biomaterial.
Optionally, the interior surface of the annular shell can be
treated or covered with a suitable material in order to enhance its
integrity and use as a mold. One or more inflatable devices, such
as the molds described herein, can be used to provide molds for the
delivery of biomaterial. The same inflatable devices used to
distract the joint space can further function as molds for the
delivery and curing of biomaterial.
[0153] The method of the present invention can also be used to
repair other joints, including diarthroidal and amphiarthroidal
joints. Examples of suitable diarthroidal joints include the
ginglymus (a hinge joint, as in the interphalangeal joints and the
joint between the humerus and the ulna); throchoides (a pivot
joint, as in superior radio-ulnar articulation and atlanto-axial
joint); condyloid (ovoid head with elliptical cavity, as in the
wrist joint); reciprocal reception (saddle joint formed of convex
and concave surfaces, as in the carpo-metacarpal joint of the
thumb); enarthrosis (ball and socket joint, as in the hip and
shoulder joints) and arthrodia (gliding joint, as in the carpal and
tarsal articulations).
[0154] Implant Procedure
[0155] An illustration of the surgical use of one embodiment of the
intervertebral prosthesis system of the invention is as follows
[0156] 1) A nuclectomy is performed by surgically accessing the
nucleus through one or more annulotomies and removing at least a
portion of the nucleus of the disc to form a cavity. The cavity is
preferably symmetrical relative to the spine.
[0157] 2) The distal (patient end) portion of a device of this
invention is inserted into the surgical site and intervertebral
space. In one embodiment, the distal tip contains a deflated mold.
The mold is then inserted into the intervertebral disc space by
pushing the distal end of the biomaterial delivery portion in a
longitudinal direction through the annulotomy in the direction of
the disc to the extent necessary to position the mold only into the
nuclear cavity.
[0158] 3) Optionally, if pre-distraction of the intervertebral disc
is needed when the patient has pre-existing disc height loss, it
can be accomplished using any suitable intervertebral distraction
mechanism, including both external and internal mechanism. Internal
distraction can be accomplished by using an apparatus similar to
that of the invention, e.g., by first delivering a suitable
solution (e.g., saline or contrast solution) into the mold in order
to exert a force sufficient to "distract" the intervertebral joint
to the desired extent. After the distraction, the solution can be
removed from the mold by applying vacuum. It is optional either to
use the same mold for hosting the injectable biomaterial or to
replace the distraction mold with a new mold.
[0159] 4) The components of a biomaterial delivery system are
assembled as generally illustrated in FIG. 1a.
[0160] 5) The controller applies a first pressure to the
biomaterial in the reservoir.
[0161] For embodiments that use multi-part biomaterials, the
biomaterial components are forced by positive pressure out of the
reservoir and through a static mixer. The initially inadequately
mixed portion of the mixed biomaterial are preferably shunted
through a purge device. Once the initial portion of the biomaterial
has been shunted, the valve is redirected to permit the biomaterial
to continue onward through the flow path and into the mold.
[0162] 6) When the fluid pressure of the biomaterial in the
biomaterial delivery system and/or the mold reaches a threshold
operating parameter, such as the measured injection pressure, the
controller reduces the pressure on the reservoir to a second
pressure. The second pressure permits the tissues of the
intervertebral disc space to expel a portion of the biomaterial out
of the mold and back into the biomaterial injection system.
[0163] 7) When the desired pressure has been reached, the
parameters are maintained during the curing phase of the
biomaterial.
[0164] 8) The delivery tube is detached from the mold, thereby
leaving the filled mold containing the cured biomaterial in situ to
function as an intervertebral disc prosthesis.
[0165] 9) The patient is sutured and closed and permitted to
recover from the surgery.
[0166] Patents and patent applications disclosed herein, including
those cited in the Background of the Invention, are hereby
incorporated by reference. Other embodiments of the invention are
possible. It is to be understood that the above description is
intended to be illustrative, and not restrictive. Many other
embodiments will be apparent to those of skill in the art upon
reviewing the above description. The scope of the invention should,
therefore, be determined with reference to the appended claims,
along with the full scope of equivalents to which such claims are
entitled.
* * * * *