U.S. patent application number 12/753640 was filed with the patent office on 2011-04-14 for devices and injectable or implantable compositions for intervertebral fusion.
This patent application is currently assigned to Light Cure, LLC. Invention is credited to Brian Perri.
Application Number | 20110087231 12/753640 |
Document ID | / |
Family ID | 42826617 |
Filed Date | 2011-04-14 |
United States Patent
Application |
20110087231 |
Kind Code |
A1 |
Perri; Brian |
April 14, 2011 |
Devices and Injectable or Implantable Compositions for
Intervertebral Fusion
Abstract
A device for injecting materials for intervertebral fusions,
kits containing the device, injectable and implantable modified
poly(methyl methacrylate) (mPMMA) materials, and methods of use
thereof, particularly in interverterbral fusions or intravertebral
structural fortification, are described herein. The device contains
an outer canula (20), an inner canula (30) that is in telescoping
relation with respect to the outer canula (20) and removable
therefrom, and one or more barrier forming materials, preferably
two balloons. When the mPMMA material is cured, it produces a
cement with a sufficient porosity to allow for bone growth through
the cement to connect one vertebral endplate to the adjacent
endplate. The mPMMA cement has sufficient compressive strength to
withstand physiologic loads of the body during weight bearing
activity and exhibits a Young's modulus of elasticity which is
slightly less than cortical bone. Additionally, the mPMMA is able
to bind to calcium phosphate and/or BMP.
Inventors: |
Perri; Brian; (Manhattan
Beach, CA) |
Assignee: |
Light Cure, LLC
|
Family ID: |
42826617 |
Appl. No.: |
12/753640 |
Filed: |
April 2, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61166404 |
Apr 3, 2009 |
|
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Current U.S.
Class: |
606/94 ;
604/101.01 |
Current CPC
Class: |
H04W 16/18 20130101;
H04W 24/02 20130101; H04W 84/045 20130101 |
Class at
Publication: |
606/94 ;
604/101.01 |
International
Class: |
A61B 17/58 20060101
A61B017/58; A61M 29/00 20060101 A61M029/00 |
Claims
1. A device for injecting a curable material in an intervertebral
fusion, comprising an outer canula, an inner canula, wherein the
inner canula comprises a first delivery portion and a second
delivery portion, wherein each delivery portion has a proximal end
and a distal end, and one or more barrier forming materials,
wherein the one or more barrier forming materials are attached to
the proximal end of the first delivery portion, and wherein the one
or more barrier forming materials form a barrier upon
inflation.
2. The device of claim 1, wherein the one or more barrier forming
materials are balloons.
3. The device of claim 2, comprising two balloons.
4. The device of claim 3, wherein the balloons form an asymmetric,
discontinuous ring upon inflation, wherein the proximal ends of the
balloons are sufficiently close following inflation to prevent
release of an injectable modified poly(methyl methacrylate)
material from the center of the ring.
5. The device of claim 4, wherein one portion of the ring is higher
than the portion on the opposite side of the ring.
6. The device of claim 1, further comprising a first syringe and a
catheter, wherein the first syringe is attached to the distal end
of the catheter, and the proximal end of the catheter is attached
to the distal end of the first delivery portion.
7. The device of claim 1, further comprising a second syringe,
wherein the second syringe is in fluid communication with the
distal end of the second delivery portion, and wherein the second
syringe comprises a injectable, curable modified poly(methyl
methacrylate).
8. A method for injecting a curable material into an intervertebral
space in need of treatment, comprising (i) inserting into the
intervertebral space a device, comprising an outer canula, an inner
canula, wherein the inner canula comprises a first delivery portion
and a second delivery portion, wherein each delivery portion has a
proximal end and a distal end, and one or more barrier forming
materials, wherein the one or more bather forming materials are
attached to the proximal end of the first delivery portion, and
wherein the one or more barrier forming materials form a barrier
upon inflation, (ii) inflating the one or more barrier forming
materials to form a barrier surrounding a hollow portion, (iii)
injecting the curable material into the hollow portion, and (iv)
curing the material to form a porous cement via an isothermic
reaction.
9. The method of claim 8, wherein the material is a modified
poly(methyl methacrylate).
10. The method of claim 8, further comprising deflating the one or
more barrier forming materials after step (iv).
11. The method of claim 8, wherein step (iv) comprises exposing the
material to a UV light source to initiate the curing step.
12. The method of claim 8, wherein the resulting porous cement has
a sufficient porosity to allow blood to pass through from one
endplate to the adjacent vertebral endplate and to allow for
sufficient bone growth through the cement to create an
endplate-to-endplate fusion.
13. A method of forming an intervertebral fusion in a patient in
need of treatment comprising implanting into the intervertebral
space in need of treatment a modified poly(methyl methacrylate)
implant, wherein the implant is a porous cement with a sufficient
porosity to allow blood to pass through from one endplate to the
adjacent vertebral endplate and to allow for sufficient bone growth
through the cement to create an endplate-to-endplate fusion.
14. The method of claim 13, wherein the implant has a shape
selected from the group consisting of rectangular implant with a
tapered or lordotic cross section; crescent shape with a tapered or
lordotic cross section; oblong, rectangular implant with a tapered
or lordotic cross section; and circular.
15. A kit comprising (i) a powdered precursor for a modified
poly(methyl methacrylate) (mPMMA) or an injectable mPMMA, (ii) a
trocar, (iii) an outer canula, (iv) an inner canula, wherein the
inner canula comprises a first delivery portion and a second
delivery portion, wherein each delivery portion has a proximal end
and a distal end, and (v) one or more barrier forming materials,
wherein the one or more barrier forming materials are attached to
the proximal end of the first delivery portion, and wherein the one
or more barrier forming materials form a barrier upon
inflation.
16. The kit of claim 15 further comprising a first syringe for
inflating the one or more barrier forming materials.
17. The kit of claim 16 further comprising a plunger and a second
syringe for administration of the mPMMA.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority under 35 U.S.C. .sctn.119
to provisional application U.S. Ser. No. 61/166,406, filed Apr. 3,
2009, which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention is in the field of improved materials,
devices and methods for intervertebral fusions and intravertebral
stabilization.
BACKGROUND OF THE INVENTION
[0003] Poly (methyl methacrylate) or poly(methyl
2-methylpropenoate) ("PMMA") is currently used to "cement" and
stabilize vertebral compression fractures (VCF). A VCF is a
fracture in the body of a vertebra, which causes it to collapse. In
turn, this causes intense pain, induced by the movement of the
fracture fragments, and the spinal column above it may develop an
abnormal forward curve called a kyphotic deformity. Additionally,
kyphosis often causes fatigue related muscular back pain as result
of the abnormal biomechanical alignment.
[0004] PMMA cement is surgically administered to a patient during a
surgical technique, such as vertebroplasty or kyphoplasty.
[0005] Vertebroplasty involves the percutaneous injection of PMMA
into a fractured vertebral body via a trocar and canula system. The
targeted vertebrae are identified under fluoroscopy. A needle is
introduced into the vertebrae body under fluoroscopic control, to
allow radiographic visualization. A bilateral transpedicular
approach is typical but the procedure can also be done
unilaterally. Since the PMMA needs to be forced into the cancellous
bone, the techniques may require high pressures and fairly low
viscosity cement. Since the cortical bone of the targeted vertebra
may have a recent fracture, there is the risk of PMMA leakage.
[0006] Kyphoplasty (Kyphon.RTM.) is a modification of percutaneous
vertebroplasty. Kyphoplasty involves, as a preliminary step, the
percutaneous placement of an inflatable balloon tamp in the
vertebral body. Inflation of the balloon creates a cavity in the
bone prior to injection of the PMMA cement. The kyphoplasty
technique generally allows for application of the PMMA cement at
lower pressures than are needed for application using the
vertebroplasty technique.
[0007] Leakage of PMMA during vertebroplasty or kyphoplasty can
result in serious complications, including compression of adjacent
structures that necessitate emergency decompressive surgery. See
Groen, R. et al, "Anatomical and Pathological Considerations in
Percutaneous Vertebroplasty and Kyphoplasty: A Reappraisal of the
Vertebral Venous System", Spine, 29(13): 1465-4471 (2004). The PMMA
leakage could lead to serious adjacent tissue injury, such as a
compressive or thermal neural injury. It has been found that
leakage of PMMA is related to various clinical factors such as the
vertebral compression pattern, and the extent of the cortical
fracture, bone mineral density, the interval from injury to
operation, the amount of PMMA injected and the location of the
injector tip. Leakage or extravasion of PMMA includes paravertebral
leakage, venous infiltration, epidural leakage and intradiscal
leakage.
[0008] PMMA cement is formed by combining powdered PMMA with liquid
methyl methacrylate (MMA) at the time of surgery in the operating
room. Typically, the surgical "scrub" technician mixes the
materials while the patient is asleep on the operating table.
Temperature and humidity affect the time for the PMMA to cure and
form the solid PMMA cement. Typical cure times range from 2 to 10
minutes following mixing the powdered PMMA with liquid MMA. This
variability places a time constraint upon the surgeon during the
surgery. The surgeon must time the use and implantation of the
cement appropriately in order for it to be injected into the body
and placed in the appropriate location and in an appropriate
volume. If it cures too fast, not enough PMMA is able to be
injected or the PMMA is not delivered to the desired location, and
the operation is compromised. Additionally, if the PMMA is injected
under pressure when it is not sufficiently viscous, the risk of
cement embolization is increased compared to if the injected
material has a higher viscosity. Cement embolization results when
PMMA cement enters the vascular system and travels to the lungs or
even the brain and becomes lodged into blood vessels of either of
these organs. The time constraints occur as the surgeon attempts to
inject this polymer carefully into the fractured vertebral body in
a short period of time between when the material's viscosity
increases from when it is considered "too run y" to when it is
considered "too thick" where it becomes difficult to inject and may
actually harden to the point that further injection of PMMA is not
possible or requires higher pressure to inject and possibly
increases the risk for extravasation from the vertebral body.
[0009] Another risk related to using PMMA is due to the exothermic
reaction of PMMA. During curing, PMMA undergoes an exothermic
reaction, which carries potential catastrophic consequences if
thermal damage extends to the dural sac, spinal cord, and/or nerve
roots. However, some clinicians speculate that the thermal curing
process may desensitize the pain fibers from the fractured
vertebral body, yet this has not been proven.
[0010] Intervertebral or spinal fusion is a surgical procedure used
to correct problems with the vertebrae of the spine. The spine is
stabilized by fusing together two or more vertebrae, typically
using intervertebral cages, bone grafts and metal rods and screws.
Spinal implant, such as interbody bone grafts or synthetic cages,
are known in the art and are routinely used by spine surgeons to
keep adjacent vertebrae in a desired spaced-apart relation while
interbody bone ingrowth and fusion takes place. Such spinal fusion
devices are also used to provide weight bearing support between
adjacent vertebral bodies and thereby correct clinical problems.
Such spinal fusion devices are indicated for medical treatment of
conditions, such as degenerative disc disease, discogenic low back
pain and spondylolisthesis. These conditions have been treated by
using constructs, typically made from metals such as titanium or
cobalt chrome alloys such as used in orthopedic implants, and
allograft (from a third party donor) or autograft (from the
patient) bone to promote bone ingrowth and fusion between two or
more vertebrae.
[0011] Many spinal fusion implants are made from titanium alloy and
allograft (donor) bone. However, the former implant devices exhibit
poor radiolucency characteristics, presenting difficulties in
post-operative monitoring and evaluation of the fusion process due
to the artifact produced by metals. Additionally, while these
implant devices are load bearing, they are not osteoconductive. Use
of allograft bone in implants has risks, such as transmission of
infectious diseases or bioresorption and collapse prior to the
patient developing a solid intervertebral fusion. Although,
allograft bone implants exhibit good osteoconductive properties,
they have variable materials properties and are in limited
supply.
[0012] In response to these problems some developers, such as
Zimmer.RTM., Inc., are attempting to use porous tantalum-based
metal constructs (e.g. Trabecular Metal.RTM. implants, which are
fabricated of elemental tantalum metal using a vapor deposition
technique to create a metallic strut configuration that is similar
to trabecular bone), conferring osteoconductivity, but these have
met with limited success owing to the metal artifact which occurs
with postoperative imaging. Additionally, these implants are
prefabricated in particular shapes that can be surgically placed
through an open or mini-open surgical exposure technique. There is
a need for a less invasive method for spinal fusions.
[0013] Further, there is a need for improved materials and devices
for treating disorders of the spine.
[0014] It is an object of the present invention to provide improved
materials and/or devices for use in intervertebral fusions.
[0015] It is a further object of the invention to provide improved
methods for intervertebral fusions.
SUMMARY OF THE INVENTION
[0016] A device for injecting materials for intervertebral fusions,
kits containing the device, injectable and implantable modified
poly(methyl methacrylate) (mPMMA) materials, and methods of use
thereof, particularly in interverterbral fusions or intravertebral
structural fortification, are described herein. The device contains
an outer canula (20), an inner canula (30) that is in telescoping
relation with respect to the outer canula (20) and removable
therefrom, and one or more bather forming materials, preferably two
balloons. When the mPMMA material is cured, it produces a cement
with a sufficient porosity to allow for bone growth through the
cement to connect one vertebral endplate to the adjacent endplate.
The mPMMA cement has sufficient compressive strength to withstand
physiologic loads of the body during weight bearing activity and
exhibits a Young's modulus of elasticity which is slightly less
than cortical bone. Additionally, the mPMMA is able to bind to
calcium phosphate and/or BMP. In yet another embodiment, the mPMMA
is a preformed, pre-cured implant.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIGS. 1A-1D illustrate a system for administering an
injectable material into the intervertebral space in a spinal
fusion. FIGS. 1A and 1B illustrate a canula/trocar assembly,
assembled and disassembled, respectively.
[0018] FIGS. 1C and 1D illustrate a preferred embodiment for a
device for administering an injectable material into the
intervertebral space in a spinal fusion. FIG. 1C shows the syringe,
inner canula, which is inserted into the outer canula when the
device is assembled, and the barrier forming materials (i.e. 2
deflated balloons). FIG. 1D shows the outer canula with the inner
canula inserted inside the outer canula.
[0019] FIGS. 2A-2D illustrate a preferred embodiment for a device
for administering an injectable material into the intervertebral
space in a spinal fusion. FIG. 2A shows the device with the balloon
in a deflated position. FIG. 2B shows the device with the balloons
in the inflated position to form the barrier. FIG. 2C is a side
view of the device with the balloons in the inflated position. FIG.
2D shows the device with the injectable material in the center of
and surrounded by the barrier.
[0020] FIGS. 3A-C are illustrations of the shaped of an implant
designed for lateral intervertebral fusions. FIG. 3A is a side
view; FIG. 3B is a top plan view; and FIG. 3C is a front view.
[0021] FIGS. 4A and B are illustrations of the shape of an implant
designed for transforaminal interbody fusions (TLIF). FIG. 4A is a
side view and FIG. 4B is a top plan view.
[0022] FIGS. 5A and B are illustrations of the shape of an implant
designed for posterior lateral interbody fusions (PLIF). FIG. 5A is
a side view and FIG. 5B is a top plan view.
[0023] FIGS. 6A and B are illustrations of the shape of an implant
designed for anterior intervertebral fusions. FIG. 6A is a side
view and FIG. 6B is a top plan view.
[0024] FIG. 7 is a cross-sectional illustration of a patient's
spine showing the relationship of the barrier relative to the
patient's spine.
[0025] FIG. 8 is an illustration of the percutaneous insertion a
canula/trocar into a patient via using an extra-pedicular
approach.
DETAILED DESCRIPTION OF THE INVENTION
I. Definitions
[0026] As used herein "modified poly(methyl methacrylate" or
"mPMMA" means a material containing poly(methyl methacrylate)
(PMMA) and other comonomers, additives, and/or fillers, and/or PMMA
that is chemically modified such as with different functional
groups, where the material has at least the following properties:
(1) curable upon demand and activated by ultraviolet light and (2)
an isothermic curing reaction to prevent thermal tissue injury, and
where, when the material is cured, it produces a cement with a
sufficient porosity to allow for bone growth onto and through the
cement.
II. Compositions for Intervertebral Fusions
[0027] Compositions for intervertebral or spinal fusions are
described herein. The compositions primarily contain a modified
poly (methyl methacrylate) (mPMMA). Optionally, the compositions
may contain additional materials, such bioactive agents, additives,
or fillers. In one embodiment, the mPMMA is an injectable material.
In another embodiment, the mPMMA is an implantable material with
prefabricated shapes. Preferably the mPMMA is used in a spinal
fusion technique. However, optionally, the mPMMA can be designed to
be suitable for other medical applications, such as to stabilize a
vertebral compression fracture (VCF). The porosity and other
modifications of PMMA are useful in both scenarios.
[0028] A. Injectable Materials
[0029] An injectable form of the mPMMA can be delivered via
injection to the intervertebral space or within the vertebral body
(i.e. intravertebral delivery). The injectable material is
particularly preferred for use in percutaneous or mini-open
intervertebral fusions. Suitable methods for delivery of the
injectable mPMMA to the intervertebral space include using a
posterior percutaneous approach (such as the technique used to
access the disc for discography) or a percutaneous or mini-open
lateral transpsoas approach. These surgical approaches are
particularly useful for intervertebral fusions. Alternatively, the
mPMMA can be injected into the vertebral body for intravertebral
applications, such as the treatment of vertebral compression
fractures. A suitable method for injection into a vertebral body
includes using a percutaneous transpedicular surgical approach,
such as by using a canulated trocar technique.
[0030] The injectable form of the mPMMA preferably has the
following properties: a putty consistency; and a curing time which
is preselected, preferably longer than ten (10) minutes.
Preferably, the curing time is regulated by the surgeon by exposing
the mPMMA to UV light.
[0031] Optionally, the injectable mPMMA also contains a material
selected for its relatively high osteoconductive and osteoinductive
properties, such as a hydroxyapatite or a calcium phosphate
material. Alternatively, such osteoconductive and osteoinductive
materials can be administered separately from the injectable mPMMA,
such as before or after the mPMMA is injected into the desired
location. Following injection into the intervertebral space,
preferably using the device described herein, the mPMMA is cured,
preferably by exposure to UV light, and thereby solidifies forming
a mPMMA cement with a sufficient porosity to allow for bone growth
onto and through the implant, forming a fusion of adjacent
vertebral endplates. Additionally, the mPMMA cement has sufficient
compressive strength to withstand physiologic loads of the body
during weight bearing or activity. The compressive strength
typically ranges from about 50 MPa, i.e. a typical compressive
strength for trabecular or cancellous bone, to about 150 MPa, i.e.
a typical compressive strength for cortical bone; preferably the
compressive strength ranges from about 50 MPa to about 150 MPa.
Further, the mPMMA cement generally has a Young's modulus of
elasticity ranges from 0.8 GPa, i.e. the Young's modulus of
elasticity for trabecular bone, to 15 GPa, i.e. the Young's modulus
of elasticity for allograft cortical bone, or a Young's modulus of
elasticity which is greater than the Young's modulus of elasticity
for cancellous bone but similar to or slightly less than the
Young's modulus of elasticity for cortical bone. Preferably the
Young's modulus of elasticity for the mPMMA is about 3 GPa.
However, the mPMMA may be modified, as needed, to provide a
material with the desired compressive strength and Young's modulus
of elasticity. Preferably, the Young's modulus of elasticity is
selected to correspond with the modulus of elasticity for a
patient's bone. The modulus of elasticity of a patient's bone is a
function of the bone's density. For example, for an osteoporotic
patient, the Young's modulus of elasticity for the mPMMA is lower
than the Young's modulus of elasticity of mPMMA used for a typical
healthy individual. This reduces the risk of the cement itself
inducing a compression fracture as a result of a "modulus mismatch"
of the mPMMA and the patient's bone.
[0032] B. Implantable Materials
[0033] The mPMMA may be in the form of an implantable material,
such as a putty. The implantable mPMMA may be implanted using a
minimally open surgical approach.
[0034] In one embodiment, the mPMMA material is a prefabricated
structural graft. The graft is also cured prior to implantation.
Prefabricated structural grafts can be formed in a various sizes
and shapes for implantation in the intervertebral space, typically
using an open surgical approach. Suitable methods include an
anterior, posterior or lateral intervertebral approach.
[0035] The grafts may be of a suitable size and shape for anterior
lumbar interbody fusion (ALIF) surgery. The grafts may be designed
to be used as anterior cervical interbody grafts, such as for
anterior cervical discectomy and fusion surgery. Banana or
crescent-shaped grafts may be implanted in a patient for
transforaminal lumbar interbody fusion (TLIF). Straight grafts may
be implanted in a patient for posterior lumbar interbody fusion
(PLIF) surgery. Grafts with a generally rectangular shape may be
used in minimally invasive, open transpsoas implantation in the
intervertebral space. Alternatively, rectangular grafts, built with
lordotic angulation and to conform to the lumbar and thoracic
vertebral endplates may be used for implantation for intervertebral
fusions.
[0036] Exemplary shapes for the implantable materials are
illustrated in FIGS. 3-6. Preferred shapes include a generally
rectangular implant with a tapered or lordotic cross section to
suit the required curvature of the intervertebral space (see FIGS.
3A-3C), in the case of a spinal fusion device. For example, this
implant would be used in a lateral intervertebral fusion. Another
preferred shape is a crescent shape (also referred to as
"banana-shaped") implants, optionally with a tapered or lordotic
cross section for improved fit into the inter-vertebral space (see
FIGS. 4A and 4B). This implant can be used in transforaminal
interbody fusions (TLIF). Another preferred shape is a generally
oblong, rectangular implant, optionally with a tapered or lordotic
cross section for improved fit into the inter-vertebral space (see
FIGS. 5A and 5B). This implant can be used for posterior lateral
interbody fusions (PLIF). Another preferred shape is a generally
circular implant (see FIGS. 6A and 613). This implant can be used
for anterior intervertebral fusions.
[0037] The prefabricated implants typically are lordotic to restore
the vertebral alignment as needed, for example used commonly in the
lumbar or cervical spine. Other areas of the spine, such as the
thoracolumbar section, are more likely to require a neutral
alignment, thus parallel or neutral prefabricated grafts are better
suited than the above-described shapes when implanted in the
thoracolumbar section.
[0038] In one embodiment, the implantable material has a
coefficient of friction which is suitable for preventing the
material from moving out of the site of implantation as the spine
experiences physiologic loads. For example, the implantable
material may have a coefficient of friction that ranges from 0.58
to 0.86, which is generally a suitable coefficient of friction to
prevent dislocation of the graft from the site of implantation as
the spine experiences physiologic loads.
[0039] In a preferred embodiment the implantable material contains
one or more means for attaching to tissue (e.g. vertebral end
plate), such as points, hooks or spikes. The one or more means for
attaching to tissue are generally suitable for preventing the
implant material from moving out of the site of implantation (i.e.
dislocation) as the spine experiences physiologic loads.
[0040] In one embodiment, the prefabricated structural graft is
coated with or contains within and/or throughout the graft a
material that has relatively high osteoconductive and
osteoinductive properties, such as a hydroxyapatite or a calcium
phosphate material.
[0041] The mPMMA implant is cured prior to implantation. The mPMMA
implant has a sufficient porosity to allow for bone growth through
the implant. The mPMMA implant has the same compressive strength
and Young's modulus of elasticity as described above with respect
to the injectable mPMMA material.
[0042] C. Bioactive Agents
[0043] In a preferred embodiment, the injectable or implantable
material contains one or more bioactive agents, preferably the
injectable or implantable material contains the one or more
bioactive agents in an effective amount to enhance bone fusion
and/or bone ingrowth at the site of treatment. Suitable bioactive
agents include natural or synthetic osteoconductive,
osteoinductive, osteogenic agents, and other fusion enhancing
agents or beneficial therapeutic agents, such as bone morphogenic
proteins (BMPs), growth factors, bone marrow aspirate, stem cells,
progenitor cells, and antibiotics.
[0044] Other suitable bioactive agents include agents that
preferentially bind to bone morphogenic proteins (BMPs), calcium
phosphate outer surface area covering, FORTEO.RTM. (Eli Lilly and
Company) (teriparatide (rDNA origin) injection, which contains
recombinant human parathyroid hormone (1-34), agents that bind to
rhPTH (1-34), or stem cells.
[0045] In one embodiment, the bioactive agent is encapsulated in
micro- or nano-particles within the mPMMA material. The bioactive
agent may be delivered locally to the site at which the pMMA is
delivered via injection or implantation. Typically the bioactive
agents are delivered to the tissue surrounding the mPMMA when the
micro- or nanoparticles rupture and/or degrade. Preferably, the
micro- or nano-particles are biodegradable and release the
bioactive agent as they degrade. Alternatively, the spheres may be
fractured after the polymer is cured, such as following exposure to
UV light, and thereby release the bioactive agent.
[0046] In a preferred embodiment, the injectable or implantable
material contains one or more osteobiologic materials, such as bone
morphogenetic proteins (BMP), such as, recombinant BMP-2 (rhBMP-2)
(e.g. INFUSE.RTM. Bone Graft by Medtronic.RTM., Memphis, Tenn.),
LIM mineralization protein-1 (LMP-1), demineralized bone matrix
(DBM), growth differentiation factors (GDF), transforming growth
factors (TGF), hydroxyapatite, tri-calcium phosphate (TCP),
bioactive glass, calcium phosphate, calcium sulfates, collagen, or
alginate. In one embodiment, the osteobiologic material comprises a
calcium mineral, such as hydroxyapatite, calcium phosphate or
calcium sulphate. Suitable materials include biodegradable porous
mixtures of hydroxyapatite and tricalciumphosphate, such as
TRICOS.RTM. from Biomatlante (France) or CAMCERAM.RTM. from Cam
Implants, Leiden (Netherlands). Nonporous hydroxyapatite/tricalcium
phosphate granules, pure hydroxyapatite granules (porous or
nonporous), tricalcium phosphate granules (porous or nonporous),
calcium sulfate granules, bone chips (either autograft or
allograft) or xenograft bone chips may also be used.
[0047] D. Additives, Fillers, and/or Excipients
[0048] Optionally, the implantable or injectable material contains
one or more additives, fillers or excipients. In one embodiment,
the implantable or injectable material contains one or more
radio-opaque agents in order to track the material, and in the case
of the injectable material, detect any possible leakage.
[0049] Radio-opaque agents are commercially available and can be
readily synthesized, as is well-known to the man skilled in the
art. Monitoring of the radio-opaque agent may be accomplished with
the methods generally used in the art, for example by X-ray
imaging.
[0050] Suitable radio-opaque agents include standard X-ray contrast
agents such as barium sulfate (BaSO.sub.4), zirconium oxide
(ZrO.sub.2), gold, or titan. In a preferred embodiment the
radio-opaque agent is barium sulphate (BaSO.sub.4). Alternatively,
iodinated radio-opaque agents may also be used. Exemplary
non-ionic, iodinated contrast agents include iodixanol, iohexol,
iopamidol, iopentol, iopromide, iorneprol, iosimide, iotasul,
iotrolan, ioversol, ioxilan, and metrizamide. Examplary ionic,
iodinated contrast agents include diatrizoate, iobenzamate,
iocarmate, iocetamate, iodamide, iodipamide, iodoxamate, ioglicate,
ioglycamate, iopanoate, iophendylate, iopronate, ioserate,
iothalamate, iotroxate, ioxaglate, ioxithalamate, and
metrizoate.
[0051] Preferably the implantable or injectable material contains
an effective amount of a radiopaque agent to provide a uniform
radiopaque background under X-ray radiation.
[0052] Optionally the injectable or implantable material contains
one or more fillers, such as silica, zirconium oxide and barium
sulfate. The addition of fillers result in an increase of the
mechanical properties (e.g., compressive strength and Young's
modulus E) of the resulting cement compared to the mechanical
properties of the same cement in the absence of the fillers.
[0053] In one embodiment, the injectable material contains one or
more thixotropic agents. The thixotropic agent can contain organic
(e.g. hydroxypropylcellulose) or inorganic materials, such as
hydrophilic or hydrophobic silica, smectite and hormite clay.
III. System and Device for Administration of mPMMA
[0054] A system for administering injectable materials in the
intervertebral space, such as in an intervertebral fusion, is
described herein.
[0055] As shown in FIGS. 1A-D, the system (10) contains (i) a
canula-trocar assembly (26), which contains an outer canula (20)
and an inner trocar (25), which is used to place the outer canula
in the desired site; (ii) an inner canula (30), (iii) a catheter
(40), (iv) one or more barrier fowling materials that form a
barrier (50) when inflated, and (v) a syringe (60).
[0056] a. Canula/Trocar Assembly
[0057] In a first step, the system contains a canula-trocar
assembly (26), which contains an outer canula (20) and an inner
trocar (25). The canula-trocar assembly (26) is inserted
percutaneously into the patient, typically via a posterior-lateral
approach, to gain access to the disc space using an extra-pedicular
approach (see FIGS. 1A and B). Once the desired site in the disc
space is reached, the inner trocar (25) is removed, leaving the
outer canula (20) in place, which provides canula access to the
intervertebral disc space.
[0058] i. Outer Canula
[0059] The outer canula (20) is formed from any suitable
biocompatible material. Preferably the outer canula is formed from
a radio-opaque material, such as a metal, to facilitate imaging.
The outer canula (20) has a proximal end (22) and a distal end
(24). The outer canula has an inner diameter of at least 4 to 5 mm
and does not exceed 10 mm and typically has an outer diameter of 6
mm, where the outer diameter ranges from 5 mm to 12 mm. Suitable
ranulas are available from a variety of manufacturers, including
Medtronic.RTM..
[0060] ii. Inner Trocar
[0061] The inner trocar (25) is formed from any suitable
biocompatible material. The diameter of the inner trocar is less
than the inner diameter of the outer canula so that the trocar is
slidable within the outer canula and slidably removable therefrom.
Suitable trocars are available from a variety of manufacturers,
including Medtronic.RTM..
[0062] b. mPMMA Injection Device
[0063] In the next step, the mPMMA injection device (15) is
assembled. This device (15) is illustrated in FIGS. 1C and D and
2A-2D and contains the outer canula (20), an inner canula (30), a
catheter (40), one or more barrier forming materials that form a
barrier (50) when inflated, and a first syringe (60).
[0064] i. Inner Canula
[0065] The inner canula (30) is formed of any suitable inert,
biocompatible material. Preferably the inner canula is formed from
a clear plastic. The inner canula contains two delivery portions
(36 and 38) in the shape of tubes. The outer diameter of the inner
canula is less than the inner diameter of the outer canula. The
inner canula is inserted into the outer canula so that it is in
telescoping relation to thereto and can be slidably removed
therefrom.
[0066] A first delivery portion (36) is designed to deliver a fluid
to inflate the one or more barrier forming materials. Typically,
the first delivery portion has an inner diameter of about 2 mm, and
may range from 1 mm to 5 mm. The second delivery portion (38) is
designed to deliver the injectable mPMMA to the desired site in the
patient. Typically, the second delivery portion has the same inner
diameter as the first delivery portion, such as an inner diameter
of about 2 mm, and may range from 1 mm to 5 mm.
[0067] The first delivery portion has a proximal end (42) and a
distal end (44). The second delivery portion (38) has a proximal
end (32) and a distal end (34). The location of the proximal end
(42) of the first delivery portion and the proximal end (32) of the
second delivery portion (38) are pre-selected so that opening (39)
in the proximal end of the second delivery portion (38) is in the
hollow portion (46) of the barrier (50) that forms when the barrier
forming materials are inflated.
[0068] The barrier forming material(s), typically one or more
balloons, are attached to the distal end (42) of the first delivery
portion (36) of the inner canula (30). The proximal end (44) of the
first delivery portion (36) is attached to a catheter (40), which
is attached to a first syringe (60).
[0069] A second syringe (not shown in figures) is filled with a
suitable volume of the mPMMA to form the bone cement. The syringe
is connected via a suitable connector to the proximal end (34) of
the second delivery portion (38) of the inner canula. In one
embodiment, the syringe is pre-filled with the mPMMA. In another
embodiment, the mPMMA is mixed and then placed into the
syringe.
[0070] ii. Catheter
[0071] The catheter (40) is designed to deliver a fluid, preferably
saline, to the first delivery portion (36) of the inner ranula.
[0072] iii. First Syringe
[0073] The first syringe (60) stores and delivers a fluid,
preferably saline, to the catheter (40) to inflate the barrier
forming materials and thereby form a barrier having the desired
size. The volume of fluid that is delivered is suitable for
inflating the barrier forming materials to the necessary height to
restore the intervertebral disc height and sagittal balance.
Typically the syringe able to contain at least 5 cc of fluid.
Preferably the syringe is a 5 cc syringe.
[0074] Typically, the catheter attaches to a syringe via a valve,
or other suitable attachment device at its distal end (45). In the
preferred embodiment, the attachment device is a 3-way stopcock
(48), which is used to regulate the amount of fluid that is
delivered to fill the barrier forming materials.
[0075] iv. Barrier
[0076] a. Size and Shape
[0077] The barrier (50) may be formed by inflating one or more
balloons. The barrier has a suitable shape and size to restore the
disc height and alignment and retain the cement at the desired
location. In the preferred embodiment, the barrier is in the shape
of an asymmetric ring, where one portion is higher than the
opposite portion on the ring (see e.g. FIGS. 2C and 2D). Within a
patient, the higher portion of the barrier corresponds with the
anterior portion of the patient's spine, while the lower portion of
the barrier corresponds with the posterior portion of the spine. As
shown in FIG. 7, in the preferred embodiment, when the barrier is
formed, the posterior portion (60) of the barrier protects the
neural elements within the spinal canal, and the anterior portion
(62) inflates to a height that is greater than the height of the
posterior portion, thereby introducing lordosis where needed in the
lumbar spine. The height of the barrier varies based on the level
of inflation. In some embodiments, the highest portion of the
barrier typically has a height ranging from 6 to 14 mm, with
preferred heights of 6, 8, 10, 12 and 14 mm. The lowest portion of
the barrier typically has a height ranging from 3 to 8 mm.
[0078] The barrier is typically about 6 to 10 mm thick (i.e., the
difference between the inner and the outer diameters of the
resulting barrier), however, the thickness varies based on the
level of inflation.
[0079] The outer diameter for the barrier will generally correspond
with the width of the vertebrae at its widest dimension. Standard
dimensions for the barrier are: an outer diameter ranging from 15
to 25 mm (measured anterior to posterior) and from 20 to 30 mm
(measured side to side).
[0080] b. Materials
[0081] The barrier is formed from any biocompatible, inflatable
material. Suitable materials are strong enough to resist the high
pressures required for inflation of the balloon in the
intervertebral space and include, but are not limited to,
non-elastic materials, such as polyethylene terephthalate (PET),
nylon, and Kevlar.RTM.. (E. I. du Pont de Nemours and Co.) or other
medical balloon materials (see e.g. U.S. Pat. No. 7,261,720 to
Stevens et al.). The balloon can also be made of semi-elastic
materials, such as silicone, rubber, thermoplastic rubbers and
elastomers or elastic materials such as latex or polyurethane, if
appropriate restraints are incorporated. The restraints can be
continuous or made of discrete elements of a flexible, inelastic
high tensile strength material including, but not limited to, the
materials described in U.S. Pat. No. 4,706,670, which is
incorporated herein by reference.
[0082] In one embodiment, the barrier is formed from a
bioresorbable material, such as poly hydroxyl acids or blends or
copolymers thereof. Preferred poly hydroxyl acids include poly
lactic acid, poly glycolic acid, and copolymers (e.g.
poly(lactide-co-glycolide)) and blends thereof. In one embodiment,
if the barrier is formed from one balloon, the barrier is
preferably bioresorbable, and preferably degrades in less than six
months, more preferably less than one month, following insertion
into the patient's body.
[0083] c. Inflation of the Barrier forming Material(s)
[0084] The one or more barrier forming materials are deflated prior
to insertion into the patient. The barrier forming materials can be
inflated by any suitable means, such as filling with an inert gas
or mixture of gases, such as air, or by injecting a liquid into the
balloon, such as water or saline. Preferably the barrier forming
materials are balloons, which are inflated by injecting saline into
the balloons, more preferably the saline contains a radio-opaque
material, such as barium sulfate (BaSO.sub.4).
[0085] d. Two Balloons for the Barrier
[0086] In a preferred embodiment, the barrier is formed by
inflating two balloons. One balloon forms the left side (52)
(referred to herein as "left balloon") of the barrier and the other
balloon forms the right side (54) of the barrier (referred to
herein as "right balloon") which meet to form a ring when they are
inflated. Each balloon has a distal end (51 and 53) which attaches
to one side of the proximal end (42) of the first portion (36) of
the inner canula (30). The proximal ends (55 and 56) of the
inflated right and left balloons meet to form the barrier (50). In
this embodiment, the barrier (50) is a discontinuous ring that
surrounds a hollow center portion (46).
[0087] Each of the left balloon and the right balloon are
preferably asymmetrical, such that each of each inflated balloon
has a greater height at its proximal end (55 and 56) than at its
distal end (51 and 53) (see e.g. FIG. 2C).
V. Kits
[0088] In one embodiment the above-described device for
administration of mPMMA is included in a kit. In one embodiment,
the kit contains (a) powdered mPMMA precursor material, (b) the
canula trocar assembly, (c) the inner canula (30), catheter (40),
and or more barrier forming materials to faun a barrier (50) when
inflated, to form the mPMMA injection device and (d) instructions
for use thereof. Preferably the kit also contains a first syringe
(60) to inflate the barrier forming material(s) and, optionally, a
second syringe for delivering the mPMMA. More preferably the kit
also contains a plunger to administer the mPMMA to the desired
site.
[0089] In another embodiment, the kit contains (a) the canula
trocar assembly, (b) the inner canula (30), catheter (40), and the
one or more barrier forming materials to form a barrier (50) when
inflated, to form the mPMMA injection device, (c) instructions for
use thereof, and (d) a pre-filled syringe which contains a suitable
volume of the injectable mPMMA to form the desired bone cement.
Preferably the kit also contains a first syringe (60) to inflate
the barrier forming material(s). More preferably the kit also
contains a plunger.
[0090] The kit may ensure that the above-describe device is a
single-use device and protect patients from the potential adverse
consequences occasioned by multiple use, which include disease
transmission, or material stress and instability, or decreased or
unpredictable performance.
[0091] The kit may include at least one wrap, which is peripherally
sealed by heat or the like, to enclose the above-listed components
of the kit and prevent contact with the outside environment. One
end of the inner wrap, preferably includes a conventional peal-away
seal, to provide quick access to the above-listed components of the
kit upon instance of use, which preferably occurs in a sterile
environment, such as within an operating room.
[0092] Preferably at least one portion of the wrap, e.g. a top
sheet, is made of transparent plastic film, such as polyethylene or
MYLAR.RTM. material, to allow visual identification of the contents
of the kit. Preferably at least one portion of the wrap, e.g. a
bottom sheet, is made from a material that is permeable to EtO
sterilization gas, e.g., TYVEC.RTM. plastic material (available
from DuPont).
[0093] The sterile kit preferably contains a label or insert, which
includes the statement "For Single Patient Use Only" (or comparable
language) to affirmatively caution against reuse of the contents of
the kit. The label also preferably instructs the physician or user
to dispose of the entire contents of the kit upon use in accordance
with applicable biological waste procedures.
[0094] The presence of the contents packaged in the kit verifies to
the physician or user that device is sterile and has not be
subjected to prior use.
VI. Methods of Using Materials and/or Device
[0095] I. Delivery of Injectable mPMMA
[0096] A. Cleaning the Intervertebral Space
[0097] In the first step, the intervertebral space is cleaned using
standard methods. In this step the system contains a canula/trocar
assembly (26). The canula/trocar assembly is advanced into the
intervertebral space via an oblique posterior approach (also
referred to as the "discogram approach").
[0098] In a posterior lateral interbody fusion, the canula/trocar
assembly (26) is inserted percutaneously into the patient,
typically via a posterior-lateral approach, to gain access to the
disc space using an extra-pedicular approach (see FIG. 8).
[0099] In a lateral interbody fusion, a mini-open technique may be
used. In this embodiment, the canula/trocar assembly is advanced
into the intervertebral space via a lateral transpsoas
approach.
[0100] Once the desired site in the disc space is reached, the
inner trocar (25) is removed, leaving the outer canula (20) in
place, which provides canula access to the intervertebral disc
space.
[0101] Then the intervertebral disc material is evacuated using
standard procedures and the effacing vertebral endplates are
prepared for fusion by scraping the cartilaginous disc attachments
to the bone. Any suitable technique for performing the discectomy
may be used. For example, instruments that fit through the outer
canula and that can curette and aspirate within the disc space can
be inserted into the canula to curette and aspirate within the disc
space. Examples of suitable instruments for removing the
intervertebral disc material include, but are not limited to,
HydroCision.RTM.'s instruments (e.g. HydroCision.RTM.'s
HydroSurgery system, such as SpineJet.RTM.), which use a high
pressure, pulsatile means for evacuating the disc, and nitinol
brushes, etc.
[0102] B. Assembly of the Device for Delivering mPMMA
[0103] Upon completion of the endplate preparation, the barrier
forming materials, preferably deflated or collapsed balloons (52
and 54), are advanced through the outer canula (20) into the
intervertebral space by pushing the inner canula (30) into and
through the outer canula (20) (see FIG. 2A). The inner canula (30)
is pushed through the outer canula until the proximal end (42) of
the first delivery portion (36) and the proximal end (32) of the
second delivery portion (38) are beyond the proximal end (12) of
the outer canula (20).
[0104] After the barrier forming materials, preferably deflated or
collapsed balloons (52 and 54), reach the desired site, the barrier
forming materials are inflated, such as by depressing the syringe
device. In the preferred embodiment, the syringe contains a normal
saline solution, preferably containing a radio-opaque material,
which is injected into the one or more, and preferably two,
balloons to the desired fill level. The barrier forming materials,
preferably balloons (52 and 54), are inflated to a sufficient
height to restore the intervertebral height and alignment in both
the coronal and sagittal planes. Thus, the barrier forming
materials can be inflated to restore lumbar lordosis. The barrier
forming materials form a barrier (50) that is suitable for
retaining the mPMMA cement in the desired site, thereby preventing
cement extravasation.
[0105] In a lateral interbody fusion, the shape of the resulting
barrier is a hollow rectangle and side view of the barrier
generally corresponds with the shape of the side view of the
implant illustrated in FIG. 3A.
[0106] The desired fill level and location of the barrier (50) is
determined by intraoperative fluoroscopic imaging. Typically the
location of the barrier is confirmed, and adjusted, if necessary by
the surgeon, prior to delivery of the injectable mPMMA. The fill
level of the barrier forming materials can also be increased, or
decreased, if necessary, prior to delivery of the injectable mPMMA.
In a posterior lateral interbody fusion, the balloons are filled
with a sufficient amount of fluid to restore the intervertebral
disc height and sagittal balance (see FIG. 2C). In a lateral
interbody fusion, the balloons are filled with a sufficient amount
of fluid to restore the anatomic reduction of the disc height and
sagittal and coronal balance.
[0107] C. Delivery of Injectable Material
[0108] After the barrier is formed via inflation of the barrier
forming materials, and preferably after its location, shape and
size are confirmed, the injectable mPMMA can be delivered
percutaneously into the intervertebral space guided by fluoroscopy
(intraoperative x-ray).
[0109] The opening (39) at the proximal end (32) of the second
delivery portion (38) of the inner canula (30) is located in the
hollow portion (46) of the barrier (50), and the injectable mPMMA
is forced out of the second syringe and through the inner canula
(30) by depressing the second syringe. Typically, the injectable
mPMMA is forced out of the inner canula (30) by pushing a plunger
(not shown in figures) through the second delivery portion (38) the
inner canula (30). The plunger is in telescoping relation to the
second delivery portion (38) of the inner canula and removable
therefrom. The mPMMA is pushed out of the second delivery portion
(38) of the inner canula and into the area within the
intervertebral space that corresponds with the hollow portion (46)
of the barrier. Thus, the injected mPMMA is surrounded by the
barrier (50), which prevents cement extravasation.
[0110] The placement of the mPMMA is verified radiographically
using intraoperative fluoroscopy. In the preferred embodiment, the
amount of contrast agent in the mPMMA is different than the amount
of contrast agent in the saline to facilitate distinguishing the
mPMMA from the barrier (50) and thereby determining the location of
the mPMMA. Preferably the mPMMA has a greater concentration of
contrast agent than the concentration of contrast agent in the
saline. This difference in concentrations of contrast agents allows
the surgeon to distinguish the barrier from the mPMMA using
fluoroscopic imaging.
[0111] D. Curing of mPMMA to form Cement
[0112] Following delivery of a suitable amount of injectable mPMMA
to the desired site, the mPMMA is cured. In one embodiment, the
curing occurs by merely waiting a sufficient period of time,
preferably greater than 10 minutes following mixing the powder MMA
with the liquid to form the injectable mPMMA.
[0113] In another preferred embodiment, the mPMMA is exposed to UV
light for a sufficient period of time to cure the mPMMA, typically
a few seconds or less, preferably for about one second. In this
embodiment, the plunger is removed from the second delivery portion
(38) of the inner canula (30) after the mPMMA is delivered to the
desired site. Then a UV light source (not shown in figures) is
passed down the second delivery portion (38) of the inner canula
until it reaches the proximal end (32) of the second delivery
portion (38) and is located proximal to the mPMMA material in the
hollow portion (46) of the barrier. Alternatively, the plunger may
contain a UV light source at its proximal end, which is located
inside the proximal end (32) of the second delivery portion (38),
or a UV light source may be located at the distal end (34) of the
second delivery portion (38) of the inner canula.
[0114] After the mPMMA is cured, the barrier (50) is deflated by
aspirating the fluid via the syringe. The inner canula (30) along
with the one or more deflated barrier forming materials are
withdrawn and removed from the distal end (24) of the outer canula
(20). Finally, the outer catheter (20) is removed from the
patient.
[0115] 1. Delivery of Implantable mPMMA
[0116] Implantable mPMMA materials, such as prefabricated interbody
grafts may be implanted into the intervertebral space in need of
treatment via open surgical procedures using the traditional
anterior, posterior or lateral surgical approaches. Typical
surgical approaches include posterior approaches such as the
transforaminal lumbar interbody fusion (TLIF) and posterior lateral
interbody fusion (PLIF). Alternatively, an anterior approach may be
used, such as the anterior lumbar interbody fusion (ALIF). Finally,
the lateral transpsoas approach may be used to place a lateral
intervertebral graft.
[0117] After the intervertebral space has been cleaned as described
above with respect to the injectable mPMMA material, the
implantable mPMMA material can be implanted using a standard open
or mini-open approach.
[0118] The placement of the prefabricated implantable mPMMA is
verified by direct visualization by the surgeon.
[0119] The prefabricated implants contain cured mPMMA. The implant
may be formed into a variety of shapes. These implants are porous,
with a trabecular network of channels that allows fluids to flow
through easily (e.g., blood or BMP). The mPMMA may then be able to
bind to BMP or calcium hydroxyapetite or calcium phosphate prior to
implantation. In the case of BMP, the implant can be bathed in a
solution of BMP at the time of surgery prior to implantation.
[0120] Typically, a variety of different shapes and sizes of each
graft are stocked for use in the operating room. Trial size
implants are used by the surgeon to determine the final size and
shape to implant intraoperatively.
[0121] A Treatment of the Thoracic Spine Using Implantable
mPMMA
[0122] The device described herein may be used in a lateral,
mini-open approach to treat not only the lumbar spine, but also the
thoracic spine
[0123] The surgical approach for this use is a lateral
mini-thoracotomy, which is used to access the thoracic spine. A
retractor system which fixes to the operating table is used to
protect the lung parenchyma and major vessels (inferior vena cava
and thoracic aorta). Examples of this existing technology are
NuVasive XLIF, Medtronic DLIF or Synthes Oracle instrumentation
sets.
[0124] After the discectomy is performed using traditional
techniques, templating of the final implant is performed using any
of various existing technologies noted above.
[0125] The final mPMMA implant is tamped across the intervertebral
disc space using anterior-posterior and lateral fluoroscopic
imaging to guide the placement. These implants are similar in shape
to the implants illustrated in FIGS. 6A and 6B for the anterior
lumbar intervertebral fusion (ALIF), however the end of the shape
of the implant is parallel rather than lordotic. Further typical
sizes for these implants are: from 6 to 14 min in height, from 30
to 50 mm in length.
[0126] The mPMMA prefabricated implants would exhibit the same
properties as those described for the lumbar and cervical
spine.
[0127] B. Treatment of the Cervical Spine Using Implantable
mPMMA
[0128] The implantable mPMMA can be implanted in a patient's neck
by using the standard Smith Robinson approach for the access to the
cervical spine. Preferably the implant also contains a radio-opaque
material to allow for fluoroscopic imaging.
[0129] Upon gaining access to the appropriate treatment level of
the cervical spine, the standard techniques for performing a
discectomy and osteophyte and disc decompression of the spinal cord
and neural foraminal can be performed prior to implanting the
prefabricated mPMMA graft.
[0130] Trial sizing is performed to determine the appropriate
implant size prior to selecting the implant. Implant sizes range
from 5 to 8 mm in height, 10 to 13 mm in depth, to 8 to 12 mm in
width in lordotic configuration to restore or maintain the normal
lordotic sagittal alignment of the cervical spine.
[0131] Implants are shaped to match the typical endplate shapes of
the adjacent vertebrae to the treatment disc level. The appropriate
sized and shaped implant is then tamped into position under direct
visualization and can be imaged fluoroscopically to verify
positioning.
[0132] Unless defined otherwise, all technical and scientific terms
used herein have the same meanings as commonly understood by one of
skill in the art to which the disclosed invention belongs.
Publications cited herein and the materials for which they are
cited are specifically incorporated by reference.
[0133] Those skilled in the art will recognize, or be able to
ascertain using no more than routine experimentation, many
equivalents to the specific embodiments of the invention described
herein. Such equivalents are intended to be encompassed by the
following claims.
* * * * *