U.S. patent application number 11/941764 was filed with the patent office on 2009-05-21 for steerable vertebroplasty system.
Invention is credited to Jan R. Lau, Y. King Liu, Michael T. Lyster, Judson E. Threlkeld.
Application Number | 20090131886 11/941764 |
Document ID | / |
Family ID | 46331824 |
Filed Date | 2009-05-21 |
United States Patent
Application |
20090131886 |
Kind Code |
A1 |
Liu; Y. King ; et
al. |
May 21, 2009 |
STEERABLE VERTEBROPLASTY SYSTEM
Abstract
Methods and devices for augmenting bone, such as in performing
vertebroplasty are disclosed. A bone cement injection needle is
provided, having a laterally deflectable distal end. Systems are
also disclosed, including the steerable injection needle,
introducer and stylet. The system may additionally include a cement
delivery gun, one-time use disposable cement cartridges and a
cement mixing chamber. Methods are also disclosed.
Inventors: |
Liu; Y. King; (Petaluma,
CA) ; Lau; Jan R.; (Windsor, CA) ; Threlkeld;
Judson E.; (Camas, WA) ; Lyster; Michael T.;
(Riverwoods, IL) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
46331824 |
Appl. No.: |
11/941764 |
Filed: |
November 16, 2007 |
Current U.S.
Class: |
604/272 ;
604/264; 606/191; 606/92 |
Current CPC
Class: |
A61M 25/0054 20130101;
A61M 2025/0092 20130101; A61M 25/007 20130101; A61B 2017/00557
20130101; A61M 25/0138 20130101; A61M 2025/009 20130101; A61M
25/0152 20130101; A61B 17/8811 20130101; A61B 17/8827 20130101;
A61M 25/0136 20130101; A61M 5/19 20130101; A61M 25/0147
20130101 |
Class at
Publication: |
604/272 ; 606/92;
604/264; 606/191 |
International
Class: |
A61M 5/32 20060101
A61M005/32; A61B 17/58 20060101 A61B017/58; A61M 5/00 20060101
A61M005/00; A61M 29/00 20060101 A61M029/00 |
Claims
1. A steerable vertebroplasty device, comprising: an elongate,
tubular body, having a proximal end, a distal end, and a central
lumen extending therethrough; a deflectable zone on the distal end
of the tubular body, deflectable through an angular range; a handle
on the proximal end of the tubular body; and a deflection control
on the handle; wherein the handle and deflection control are
configured for single hand operation.
2. A steerable vertebroplasty device as in claim 1, wherein the
deflection control comprises a rotatable element.
3. A steerable vertebroplasty device as in claim 1, wherein the
distal end comprises a distally facing exit port in communication
with the central lumen.
4. A steerable vertebroplasty device as in claim 1, wherein the
distal end comprises a laterally facing exit port in communication
with the central lumen.
5. A steerable vertebroplasty device as in claim 1, further
comprising an actuator extending axially between the deflection
control and the deflectable zone.
6. A steerable vertebroplasty device as in claim 5, wherein the
actuator comprises an axially moveable element.
7. A steerable vertebroplasty device as in claim 1, further
comprising a port on the proximal end of the vertebroplasty device,
in communication with the central lumen.
8. A steerable vertebroplasty device as in claim 7, wherein the
deflectable zone is deflectable within a plane, and the port
resides in the same plane.
9. A steerable vertebroplasty device as in claim 1, wherein the
tubular body comprises a proximal zone and a distal, deflectable
zone separated by a transition, and the transition is at least
about 15% of the length of the tubular body from the distal
end.
10. A system for performing vertebroplasty, comprising: a steerable
injection needle with a proximal portion, elongate shaft, and a
distal portion, the distal portion movable from a first
substantially straight configuration to a second configuration not
substantially coaxial with the proximal portion; and a cement
dispensing pump comprising a first cartridge housing configured to
house a cartridge containing two separate bone cement components;
and a mixing nozzle for mixing the first bone cement component and
second bone cement component material into a bone cement
composite.
11. The system of claim 10, further comprising a stylet for
creating an access pathway in a pedicle.
12. The system of claim 10, further comprising an introducer
cannula.
13. The system of claim 10, further comprising the first bone
cement component, wherein the first bone cement component comprises
MMA.
14. The system of claim 13, further comprising the second bone
cement component, wherein the second bone cement component
comprises from about 25% to about 35% by weight of bone
particles.
15. The system of claim 13, further comprising the second bone
cement material, wherein the second bone cement material comprises
at least about 35% weight percent of bone particles.
16. The system of claim 10, wherein the steerable injection needle
comprises an input port for receiving bone cement from the cement
dispensing pump.
17. The system of claim 16, wherein the input port comprises a Luer
lock.
18. The system of claim 10, wherein the steerable injection needle
comprises an adjustment control configured to adjust the curvature
of the distal end.
19. The system of claim 10, wherein the steerable injection needle
comprises an end cap on the distal end of the needle.
20. The system of claim 10, wherein the steerable injection needle
comprises a pull wire operably connected to the distal end of the
needle.
21. The system of claim 10, wherein the steerable injection needle
comprises a filter operably connected to a distal opening of the
needle.
22. The system of claim 10, wherein the distal portion of the
steerable injection needle has a working length of at least about
20% of the total working length of the needle.
23. The system of claim 10, wherein the steerable injection needle
comprises a spring coil.
24. A closed vertebroplasty bone cement injection system,
comprising: a cartridge containing at least a first chamber and a
second chamber; a first bone cement component in the first chamber
and a second bone cement component in the second chamber; a mixing
chamber, for mixing the first and second bone cement components; an
elongate injection needle, for directing bone cement into a
treatment site in the spine; and a closed flow path for directing
the first and second bone cement components from the first and
second chambers, through the mixing chamber, through the injection
needle and into the spine at the treatment site.
25. A closed vertebroplasty bone cement injection system as in
claim 24, wherein the cartridge is releaseably connected to the
flow path.
26. A closed vertebroplasty bone cement injection system as in
claim 24, wherein the mixing chamber is releaseably connected to
the flow path.
27. A closed vertebroplasty bone cement injection system as in
claim 24, wherein the injection needle is releaseably connected to
the flow path.
28. A closed vertebroplasty bone cement injection system as in
claim 24, wherein the injection needle has a deflectable distal
end.
Description
[0001] The present invention relates to bone augmentation devices
and procedures. In particular, the present invention relates to
steerable injection devices and systems for introducing
conventional or novel bone cement formulations such as in
performing vertebroplasty.
BACKGROUND OF THE INVENTION
[0002] According to the National Osteoporosis Foundation ten
million Americans have osteoporosis, and an estimated 34 million
with low bone mass are at risk of developing osteoporosis
(http://www.nof.org/osteoporosis/diseasefacts.htm). Called the
"silent disease," OSP develops slowly over a number of years
without symptoms. Eighty percent of those affected are women,
particularly petite Caucasian and Asian women, although older men
and women of all races and ethnicities are at significant risk.
[0003] In the United States, 700,000 people are diagnosed with
vertebral compression fractures as a result of OSP each year.
Morbidity associated with vertebral fractures includes severe back
pain, loss of height and deformity, all of which negatively affect
quality of life.
[0004] Once microfracture of the vertebra begins, there is little
the clinician can do except palliative medical treatment using
analgesics, bed rest and/or restriction of activity. With time, the
microfractures widen at one level and without surgical
intervention, the fractures cascade downward with increasing
kyphosis or "hunching" of the back. Once a mechanical lesion
develops, surgery is the only option. Vertebroplasty or kyphoplasty
are the primary minimally-invasive surgical procedures performed
for the treatment of compression-wedge fractures due to OSP.
[0005] Vertebroplasty stabilizes the collapsed vertebra by
injecting polymethylmethacrylate (PMMA) or a substantially
equivalent bone cement into cancellous bone space of the vertebrae.
Besides providing structural support to the vertebra, the
exothermic reaction of PMMA polymerization is said to kill off the
nociceptors or pain receptors in the bone, although no proof of
this hypothesis has been provided in the literature. This procedure
is typically performed as an outpatient procedure and requires only
a short-acting local or general anesthetic. Once the surgical area
of the spine is anesthetized, the physician inserts one or two
needles through small skin incisions into either the pedicle
(uni-transpedicular) or the pedicles of the vertebral body i.e.,
bi-transpedicular. PMMA is injected through the needle and into the
cancellous-bone space of the vertebra.
[0006] Kyphoplasty mirrors the vertebroplasty procedure but has the
additional step of inserting and expanding a nylon balloon in the
interior of the vertebral body. Expansion of the balloon under
pressure reduces the compression fracture and creates a cavity.
After withdrawal of the balloon, PMMA is injected into the cavity
to stabilize the reduction. The kyphoplasty procedure may restore
the vertebral body height. Kyphoplasty is an in-patient surgery
that requires hospitalization and a general anesthetic. Kyphon Inc.
claims over 275,000 spinal fractures have been treated using their
PMMA derivative and their "balloon" kyphoplasty procedure worldwide
(Sunnyvale, Calif., Sep. 5, 2006, (PR NEWSWIRE) Kyphon study
2006).
[0007] Bone cement for both vertebroplasty and kyphoplasty
procedures currently employ variations of standard PMMA in a powder
and a methyl methacrylate monomer liquid. When the powder and
liquid monomer are mixed, an exothermic polymerization takes place
resulting in the formation of a "dough-like" material, which is
then inserted into the cancellous bone space. The dough, when
hardened, becomes either the reinforcing structure or the grout
between the bone and prosthesis.
[0008] The average clinical in vivo life of the PMMA grout is
approximately 10 years due to corrosion fatigue of either the
bone-cement/prosthesis and/or the bone cement/bone interfaces.
Jasty et al. (1991) showed that in cemented total hip replacements:
"Fractures in the cement mantle itself were found on cut sections
around all prostheses which had been in use for over three years."
Jasty et al. also noted: "In general, specimens less than 10 years
in situ showed small incomplete fractures while the specimens in
place more than 10 years all showed large complete cement mantle
fractures."
[0009] When an implant fails, a revision becomes mandatory. After
removal of the cement and hardware, a cemented arthroplasty can be
repeated if enough cancellous bone matrix exists to grip the new
PMMA. Alternatively, cement-less prosthesis can be installed. Such
a revision, however, can only be applied to total joint replacement
failures. For vertebroplasty and/or kyphoplasty, a classical screw
and plate internal fixation with autograft fusion is necessary.
[0010] Despite advances in the foregoing procedures, there remains
a need for improved bone cement delivery systems which enable rapid
and controllable deployment of bone cement for the treatment of
conditions such as vertebral compression fractures.
SUMMARY OF THE INVENTION
[0011] According to one embodiment of the present invention,
disclosed is a steerable vertebroplasty device, including an
elongate tubular body having a proximal end, a distal end, and a
central lumen extending therethrough; a deflectable zone on the
distal end of the tubular body, deflectable through an angular
range; a handle on the proximal end of the tubular body; and a
deflection control on the handle. The handle and deflection control
are configured for single hand operation. The deflection control
can include a rotatable element. The distal end can include a
distally facing exit port in communication with the central lumen,
or a laterally facing exit port in some embodiments. The device can
also include an actuator extending axially between the deflection
control and the deflectable zone. The actuator can be an axially
moveable element. The device can also include a port on the
proximal end of the vertebroplasty device, in communication with
the central lumen. The deflectable zone can be deflectable within a
plane, and the port can reside in the same plane. In some
embodiments, the tubular body includes a proximal zone and a
distal, deflectable zone separated by a transition, and the
transition can be at least about 15% of the length of the tubular
body from the distal end.
[0012] Also disclosed herein is a method of treating a vertebral
body. The method includes the steps of introducing a tubular
injector having a longitudinal axis through cortical bone and into
cancellous bone of a vertebral body; deflecting a distal section of
the injector angularly with respect to the longitudinal axis; and
introducing media through the injector and into the vertebral
body.
[0013] In another embodiment, disclosed is a system for performing
vertebroplasty. The system includes a steerable injection needle, a
cement dispensing pump, and a mixing nozzle. The steerable
injection needle has a proximal portion, elongate shaft, and a
distal portion, the distal portion movable from a first
substantially straight configuration to a second configuration not
substantially coaxial with the proximal portion. The cement
dispensing pump can include a first cartridge housing configured to
house a cartridge containing two separate bone cement components.
The mixing nozzle is present for mixing the first bone cement
component and second bone cement component material into a bone
cement composite. In some embodiments, the system also includes a
stylet for creating an access pathway in a pedicle. The system can
also include an introducer cannula. The first and/or second bone
cement component can also be present in the system. The first bone
cement component can include MMA. The second bone cement component
can include from about 25% to about 35% by weight of bone
particles, or at least about 35% weight percent of bone particles
in other embodiments. The steerable injection needle can also
include an input port for receiving bone cement from the cement
dispensing pump. The input port can include a Luer lock. The
steerable injection needle can include an adjustment control
configured to adjust the curvature of the distal end. In some
embodiments, the steerable injection needle includes an end cap on
the distal end of the needle. The steerable injection needle can
include a pull wire operably connected to the distal end of the
needle. In other embodiments, the steerable injection needle
includes a filter operably connected to a distal opening of the
needle. The distal portion of the steerable needle can have a
working length of at least about 20% of the total working length of
the needle. The steerable injection needle may also include a
spring coil.
[0014] Also disclosed herein is a method of treating a bone,
including the steps of creating a pedicular access channel in a
pedicle to access the interior of a vertebral body; inserting an
introducer cannula into the pedicle; inserting a steerable
injection needle through the introducer cannula into the interior
of a vertebral body, the steerable injection needle having a
proximal end and a distal end, the distal end having a first
configuration substantially coaxial with a long axis of the
proximal end; deflecting the distal end of the steerable injection
needle to a second configuration that is not substantially coaxial
with the long axis of the proximal end; and flowing bone cement
through the steerable injection needle into the interior of the
vertebral body. In some embodiments, the second configuration of
the distal end of the steerable injection needle includes a curved
portion. In some embodiments, deflecting the distal end of the
steerable injection needle is accomplished by exerting tension on a
pull wire operably connected to the distal end. In some
embodiments, deflecting the distal end of the steerable injection
needle is accomplished by withdrawing a sheath at least partially
covering the distal end. The method can also include the steps of:
providing a cement dispensing pump with a cartridge containing a
first bone cement material and a second bone cement material out of
contact with the first bone cement material, and a mixing nozzle;
flowing the first bone cement material and the second bone cement
material into the mixing nozzle, creating a bone cement; and
flowing the bone cement into an input port of the steerable
injection needle. Flowing bone cement through the steerable
injection needle into the interior of the vertebral body can
include releasing a first bone cement within the interior of the
vertebral body. The bone cement can have at least 35% particles by
weight in some embodiments. In some embodiments, flowing bone
cement through the steerable injection needle into the interior of
the vertebral body additionally includes releasing a second bone
cement within the first bone cement, where the second bone cement
includes less than about 35% particles by weight.
[0015] Also disclosed herein is a closed vertebroplasty bone cement
injection system, that includes a cartridge containing at least a
first chamber and a second chamber; a first bone cement component
in the first chamber and a second bone cement component in the
second chamber; a mixing chamber, for mixing the first and second
bone cement components; an elongate injection needle, for directing
bone cement into a treatment site in the spine; and a closed flow
path for directing the first and second bone cement components from
the first and second chambers, through the mixing chamber, through
the injection needle and into the spine at the treatment site. The
cartridge, mixing chamber, and/or injection needle can be
releaseably connected to the flow path. The injection needle can
have a deflectable distal end.
[0016] Also disclosed herein is a method of injecting bone cement
into a treatment site in a bone, including the steps of: providing
a first chamber having a first bone cement component, and a second
chamber having a second bone cement component, the first and second
bone cement components formulated to form a hardenable bone cement
following mixing; providing a mixing chamber for mixing the first
and second bone cement components; providing an elongate, tubular
injection needle; connecting the first and second bone cement
chambers, the mixing chamber and the injection needle into a closed
flow path; and expressing first and second bone cement components
through the mixing chamber, through the injection needle and into
the site. The first and the second chambers can be contained in a
single cartridge.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a perspective view of a steerable injection needle
in accordance with one aspect of the present invention.
[0018] FIG. 2 is a perspective view of an introducer in accordance
with one aspect of the present invention.
[0019] FIG. 3 is a perspective view of a stylet in accordance with
one aspect of the present invention.
[0020] FIG. 4 is a side elevational view of the steerable injection
needle moveably coaxially disposed within the introducer, in a
substantially linear configuration.
[0021] FIG. 5 is a side elevational view of the assembly of FIG. 4,
showing the steerable injection needle in a curved
configuration.
[0022] FIG. 6 is a side elevational schematic view of another
steerable injection needle in accordance with the present
invention.
[0023] FIG. 7A is a schematic view of a distal portion of the
steerable needle of FIG. 6, shown in a linear configuration.
[0024] FIG. 7B is a schematic view as in FIG. 7A, following
proximal retraction of a pull wire to laterally deflect the distal
end.
[0025] FIG. 8 is a schematic view of a distal portion of a
steerable needle, having a side port.
[0026] FIG. 9A is a schematic view of a distal portion of a
steerable needle, positioned within an outer sheath.
[0027] FIG. 9B is an illustration as in FIG. 9A, with the distal
sheath partially proximally retracted.
[0028] FIG. 9C is an illustration as in FIG. 9B, with the outer
sheath proximally retracted a sufficient distance to fully expose
the deflection zone.
[0029] FIGS. 10A-10C illustrate various aspects of an alternative
deflectable needle in accordance with the present invention.
[0030] FIGS. 11A-11C illustrate various views of a further
embodiment of a deflectable needle in accordance with the present
invention.
[0031] FIGS. 12A-12C illustrate a distal section of a deflectable
needle, comprising a helically wound coil structure.
[0032] FIG. 13 is a partially exploded schematic view of a cement
gun, dual chamber cement cartridge and mixing chamber for use with
the present invention.
[0033] FIG. 14 is a schematic view of an alternate two-part
dispensing system for the cement of the present invention.
[0034] FIGS. 15A and 15B are schematic views of a bone cement
delivery system in accordance with the present invention.
[0035] FIGS. 16A through 16F show stages in the method of
accomplishing vertebroplasty in accordance with present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0036] The present invention provides improved delivery systems for
delivery of a bone cement or bone cement composite for the
treatment of vertebral compression fractures due to osteoporosis
(OSP), osteo-trauma, and benign or malignant lesions such as
metastatic cancers and myeloma, and associated access and
deployment tools and procedures.
[0037] The primary materials in the preferred bone cement composite
are methyl methacrylate and inorganic cancellous and/or cortical
bone chips or particles. Suitable inorganic bone chips or particles
are sold by Allosource, Osteotech and LifeNet (K053098); all have
been cleared for marketing by FDA The preferred bone cement also
may contain the additives: barium sulfate for radio-opacity,
benzoyl peroxide as an initiator, N,N-dimethyl-p-toluidine as a
promoter and hydroquinone as a stabilizer. Other details of bone
cements and systems are disclosed in U.S. patent application Ser.
No. 11/626,336, filed Jan. 23, 2007, the disclosure of which is
hereby incorporated in its entirety herein by reference.
[0038] One preferred bone cement implant procedure involves a
two-step injection process with two different concentrations of the
bone particle impregnated cement. To facilitate the implant
procedure the bone cement materials are packaged in separate
cartridges containing specific bone cement and inorganic bone
particle concentrations for each step. Tables 1 and 2, infra, list
one example of the respective contents and concentrations in
Cartridges 1A and 1B for the first injection step, and Cartridges
2A and 2B for the second injection step.
[0039] The bone cement delivery system generally includes at least
three main components: 1) stylet; 2) introducer cannula; and 3)
steerable injection needle. See FIGS. 1-3. Packaged with the system
or packaged separately is a cement dispensing pump. The complete
system also preferably includes at least one cement cartridge
having at least two chambers therein, and a spiral mixing
nozzle.
[0040] The stylet is used to perforate a hole into the pedicle of
the vertebra to gain access to the interior of the vertebral
body.
[0041] The introducer cannula is used for bone access and as a
guide for the steerable injection needle. The introducer cannula is
sized to allow physicians to perform vertebroplasty or kyphoplasty
on vertebrae with small pedicles such as the thoracic vertebra T5
as well as larger vertebrae. In addition, this system is designed
for uni-transpedicular access and/or bi-pedicular access.
[0042] Once bone access has been achieved, the steerable injection
needle can be inserted through the introducer cannula into the
vertebra. The entire interior vertebral body may be accessed using
the steerable injection needle. The distal end of the needle can be
manually shaped to any desired radius within the product
specifications. The radius is adjusted by means of a knob on the
proximal end of the device.
[0043] The hand-held cement dispensing pump may be attached to the
steerable injection needle by a slip-ring luer fitting. The
pre-filled 2-chambered cartridges (1A and 1B, and 2A and 2B) are
loaded into the dispensing pump. As the handle of the dispensing
pump is squeezed, each piston pushes the cartridge material into
the spiral mixing tube. The materials are mixed in the spiral
mixing nozzle prior to entering the steerable injection needle. The
ratio of diameters of the cartridge chambers determines the mixing
ratio for achieving the desired viscosity. One particular
non-limiting example of an exemplary system is described below.
Delivery System Component Specifications
[0044] Stylet [0045] Diameter 0.110''.+-.0.010'' [0046] Length
5.25''.+-.0.125'' [0047] 304 stainless steel and/or ABS
materials
[0048] Introducer Cannula [0049] Cannula profile 10 gauge (0.134'')
[0050] Cannula length 4.9''.+-.0.125 (124 mm) [0051] Cannula
internal diameter 0.120''.+-.0.002'' [0052] 304 stainless steel
and/or ABS materials
[0053] Steerable Injection Needle [0054] Needle profile 12 gauge
(0.109'') with a 0.077'' (1.96 mm) lumen [0055] Needle working
length 7.0''.+-.0.125''(178 mm) [0056] 2.25''.+-.0.125'' adjustable
section on distal tip [0057] 0.688''.+-.0.125'' Minimum needle
radius to .infin. (straight) [0058] Luer fitting for connection to
dispensing gun [0059] 304 stainless steel and ABS Hub
[0060] Cement Dispensing Pump and Spiral Mixing Nozzle [0061]
Manual dispensing of cement [0062] Approximately 10:1 by volume
mixing ratio cartridges [0063] Liquid-Liquid Cartridge 9 mL.+-.0.5
mL [0064] Real-time mixing through screw nozzle [0065] Luer fitting
for connection to steerable injection needle [0066] Mixing tube
length 2.0''.+-.0.100'' [0067] Mixing tube inside diameter
0.187''.+-.0.025'' [0068] 1000 psi HP (high pressure) Extension
Tubing [0069] Volume per ratchet 0.5 mL+0.25/-0.0 mL
[0070] The bone cement implant procedures described herein use
established vertebroplasty and kyphoplasty surgical procedures to
stabilize the collapsed vertebra by injecting bone cement into
cancellous bone.
[0071] The preferred procedure is designed for uni-transpedicular
access and may be accomplished under either a local anesthetic or
short-duration general anesthetic. Once the area of the spine is
anesthetized, an incision is made and the stylet is used to
perforate the vertebral pedicle and gain access to the interior of
the vertebral body. The introducer cannula is then inserted and
acts as a guide for the steerable injection needle.
[0072] Injection of the preferred bone cement involves a two-step
procedure. The pre-filled Cartridges 1A and 1B are loaded into the
dispensing pump. As the dispensing pump handle is squeezed, each
piston pushes material into the spiral mixing tube. The diameter of
each chamber may be utilized to determine the mixing ratio for
achieving the desired viscosity.
[0073] The first step involves injecting a small quantity of PMMA
with more than about 35%, e.g., 60% inorganic bone particles, onto
the outer periphery of the cancellous bone matrix, i.e., next to
the inner wall of the cortical bone of the vertebral body. The
cement composite is designed to harden relatively quickly, forming
a firm but still pliable shell. This shell is intended to prevent
bone marrow/PMMA content from being ejected through any venules or
micro-fractures in the vertebral body wall. The second step of the
procedure involves a second injection of PMMA with an approximately
30% inorganic bone particles to stabilize the remainder of the
weakened, compressed cancellous bone.
[0074] Alternatively, the steerable needle disclosed herein and
discussed in greater detail below, can be used in conventional
vertebroplasty procedures, using a single step bone cement
injection.
[0075] Injection control for the first and second steps is provided
by a 2 mm ID flexible injection needle, which is coupled to the
hand operated bone cement injection pump. The 60% (>35%) and 30%
ratio of inorganic bone particle to PMMA concentrations may be
controlled by the pre-filled cartridge sets 1A and 1B, and 2A and
2B. At all times, the amount of the injectate is under the direct
control of the surgeon or intervention radiologist and visualized
by fluoroscopy. The introducer cannula is slowly withdrawn from the
cancellous space as the second injection of bone cement begins to
harden, thus preventing bone marrow/PMMA content from exiting the
vertebral body. The procedure concludes with closure of the
surgical incision with bone filler. In vitro and in vivo studies
have shown that the 60% (>35%) bone-particle impregnated bone
cement hardens in 2-3 minutes and 30% bone-particle impregnated
bone cement hardens between 4 to 10 minutes.
[0076] Details of the system components will be discussed
below.
[0077] There is provided in accordance with the present invention a
steerable injection device that can be used to introduce any of a
variety of materials or devices for diagnostic or therapeutic
purposes. In one embodiment, the system is used to inject bone
cement, e.g., PMMA or any of the bone cement compositions disclosed
elsewhere herein. The injection system most preferably includes a
tubular body with a steerable (i.e., deflectable) distal portion
for introducing bone cement into various locations displaced
laterally from the longitudinal axis of the device within a
vertebral body during a vertebroplasty procedure.
[0078] Referring to FIG. 1, there is illustrated a side perspective
view of a steerable injection needle 10 in accordance with one
aspect of the present invention. The steerable injection needle 10
comprises an elongate tubular body 12 having a proximal end 14 and
a distal end 16. The proximal end 14 is provided with a handle or
manifold 18, adapted to remain outside of the patient and enable
introduction and/or aspiration of bone cement or other media, and
control of the distal end as will be described herein. In general,
manifold 18 is provided with at least one injection port 20, which
is in fluid communication with a central lumen (not illustrated)
extending through tubular body 12 to at least one distal exit port
22.
[0079] The manifold 18 is additionally provided with a control 26
such as a rotatable knob, slider, or other moveable control, for
controllably deflecting a deflection zone 24 on the distal end 16
of the tubular body 12. As is described elsewhere herein, the
deflection zone 24 may be advanced from a relatively linear
configuration as illustrated in FIG. 1 to a deflected configuration
throughout an angular range of motion.
[0080] Referring to FIG. 2, there is illustrated an elongate
tubular introducer 30, having a proximal end 32, a distal end 34
and an elongate tubular body 36 extending therebetween. A central
lumen 38 (not shown) extends between a proximal access port 40 and
a distal access port 42.
[0081] The central lumen 38 has an inside diameter which is adapted
to slideably axially receive the steerable injection needle 10
therethrough. This enables placement of the distal end 34 adjacent
a treatment site within the body, to establish an access pathway
from outside of the body to the treatment site. As will be
appreciated by those of skill in the art, the introducer 30 enables
procedures deep within the body such as within the spine, through a
minimally invasive and/or percutaneous access. The steerable
injection needle 10 and/or other procedure tools may be introduced
into port 40, through lumen 38 and out of port 42 to reach the
treatment site.
[0082] The proximal end 32 of introducer 30 may be provided with a
handle 44 for manipulation during the procedure. Handle 44 may be
configured in any of a variety of ways, such as having a frame 46
with at least a first aperture 48 and a second aperture 50 to
facilitate grasping by the clinician.
[0083] Referring to FIG. 3, there is illustrated a perspective view
of stylet 60. Stylet 60 comprises a proximal end 62, a distal end
64 and an elongate body 66 extending therebetween. The proximal end
62 may be provided with a stop 68 such as a grasping block,
manifold or other structure, to facilitate manipulation by the
clinician. In the illustrated embodiment, the block 68 is
configured to nest within a recess 70 on the proximal end of the
introducer 30.
[0084] As will be appreciated by those of skill in the art, the
stylet 60 has an outside diameter which is adapted to coaxially
slide within the central lumen on introducer 30. When block 68 is
nested within recess 70, a distal end 64 of stylet 60 is exposed
beyond the distal end 34 of introducer 30. The distal end 64 of
stylet 60 may be provided with a pointed tip 72, such as for
anchoring into the surface of a bone.
[0085] Referring to FIG. 4, there is illustrated a side elevational
view of an assembly in accordance with the present invention in
which a steerable injection needle 10 is coaxially positioned
within an introducer 30. The introducer 30 is axially moveably
carried on the steerable injection needle 10. In the illustration
of FIG. 4, the introducer 30 is illustrated in a distal position
such that it covers at least a portion of the deflection zone 24 on
injection needle 10.
[0086] FIG. 5 illustrates an assembly as in FIG. 4, in which the
introducer 30 has been proximally retracted along the injection
needle 10 to fully expose the deflection zone 24 on injection
needle 10. In addition, the control 26 has been manipulated to
deflect the deflection zone 24 through an angle of approximately
90.degree.. Additional details of the steerable needle will be
discussed below.
[0087] FIG. 6 illustrates a schematic perspective view of an
alternate steerable vertebroplasty injector, according to one
embodiment of the invention. The steerable injector 700 includes a
body or shaft portion 702 that is preferably elongate and tubular,
input port 704, adjustment control 706, and handle portion 708. The
elongate shaft 702 preferably has a first proximal portion 710 and
a second distal portion 712 which merge at a transition point 714.
Shaft 702 may be made of stainless steel, such as 304 stainless
steel, Nitinol, Elgiloy, or other appropriate material.
Alternatively, the tubular body 702 may be extruded from any of a
variety of polymers well known in the catheter arts, such as PEEK,
PEBAX, nylon and various polyethylenes. Extruded tubular bodies 702
may be reinforced using metal or polymeric spiral wrapping or
braided wall patterns, as is known in the art.
[0088] The shaft 702 defines at least one lumen therethrough that
is preferably configured to carry a flowable bone cement prior to
hardening. Proximal portion 710 of shaft 702 is preferably
relatively rigid, having sufficient column strength to push through
cancellous bone. Distal portion 712 of shaft 702 is preferably
flexible and/or deflectable and reversibly actuatable between a
relatively straight configuration and one or more deflected
configurations or curved configurations as illustrated, for
example, in FIG. 5, as will be described in greater detail below.
The distal portion 712 of shaft 702 may include a plurality of
transverse slots 718 that extend partially circumferentially around
the distal portion 712 of the shaft 702 to provide a plurality of
flexion joints to facilitate bending.
[0089] Input port 704 may be provided with a Luer lock connector
although a wide variety of other connector configurations, e.g.,
hose barb or slip fit connectors can also be used. Lumen 705 of
input port 704 is fluidly connected to central lumen 720 of shaft
702 such that material can flow from a source, through input port
704 into central lumen 720 of the shaft 702 and out the open distal
end or out of a side opening on distal portion 712. Input port 704
is preferably at least about 20 gauge and may be at least about 18,
16, 14, or 12 gauge or larger in diameter.
[0090] Input port 704 advantageously allows for releasable
connection of the steerable injection device 700 to a source of
hardenable media, such as a bone cement mixing device described
herein. In some embodiments, a plurality of input ports 704, such
as 2, 3, 4, or more ports are present, for example, for irrigation,
aspiration, introduction of medication, hardenable media
precursors, hardenable media components, catalysts or as a port for
other tools, such as a light source, cautery, cutting tool,
visualization devices, or the like. A first and second input port
may be provided, for simultaneous introduction of first and second
bone cement components such as from a dual chamber syringe or other
dispenser. A mixing chamber may be provided within the injection
device 700, such as within the proximal handle, or within the
tubular shaft 702
[0091] A variety of adjustment controls 706 may be used with the
steerable injection system, for actuating the curvature of the
distal portion 712 of the shaft 702. Preferably, the adjustment
control 706 advantageously allows for one-handed operation by a
physician. In one embodiment, the adjustment control 706 is a
rotatable member, such as a thumb wheel or dial. The dial can be
operably connected to a proximal end of an axially movable actuator
such as pull wire 724. See FIG. 7A. When the dial is rotated in a
first direction, a proximally directed tension force is exerted on
the pull wire 724, actively changing the curvature of the distal
portion 712 of the shaft 702 as desired. The degree of deflection
can be observed fluoroscopically, and/or by printed or other
indicium associated with the control 706. Alternative controls
include rotatable knobs, slider switches, compression grips,
triggers such as on a gun grip handle, or other depending upon the
desired functionality.
[0092] In some embodiments, the adjustment control 706 allows for
continuous adjustment of the curvature of the distal portion 712 of
shaft 702 throughout a working range. In other embodiments, the
adjustment control is configured for discontinuous (i.e., stepwise)
adjustment, e.g., via a ratcheting mechanism, preset slots,
deflecting stops, a rack and pinion system with stops, ratcheting
band (adjustable zip-tie), adjustable cam, or a rotating dial of
spring loaded stops. In still other embodiments, the adjustment
control 706 may include an automated mechanism, such as a motor or
hydraulic system to facilitate adjustment.
[0093] The adjustment control may be configured to allow deflection
of the distal portion 712 through a range of angular deviations
from 0 degrees (i.e., linear) to at least about 15.degree., and
often at least about 25.degree., 35.degree., 60.degree.,
90.degree., 120.degree., 150.degree., or more degrees from
linear.
[0094] In some embodiments, the length X of the flexible distal
portion 712 of shaft 702 is at least about 10%, in some embodiments
at least about 15%, 25%, 35%, 45%, or more of the length Y of the
entire shaft 702 for optimal delivery of bone cement into a
vertebral body. One of ordinary skill in the art will recognize
that the ratio of lengths X:Y can vary depending on desired
clinical application. In some embodiments, the maximum working
length of needle 702 is no more than about 15'', 10'', 8'', 7'',
6'', or less depending upon the target and access pathway. In one
embodiment, when the working length of needle 702 is no more than
about 8'', the adjustable distal portion 712 of shaft has a length
of at least about 1'' and preferably at least about 1.5'' or
2''.
[0095] FIGS. 7A-B are schematic perspective views of a distal
portion of shaft 702 of a steerable vertebroplasty injector,
according to one embodiment of the invention. Shown is the
preferably rigid proximal portion 710 and deflectable distal
portion 712. The distal portion 712 of shaft 702 includes a
plurality of transverse slots 718 that extend partially
circumferentially around the distal portion 712 of the shaft 702,
leaving a relatively axially non-compressible spine 719 in the form
of the unslotted portion of the tubular wall.
[0096] In some embodiments, the slots 718 can be machined or laser
cut out of the tube stock that becomes shaft 702, and each slot may
have a linear, chevron or other shape. In other embodiments, the
distal portion 712 of shaft 702 may be created from an elongate
coil rather than a continuous tube.
[0097] Slots 718 provide small compression hinge joints to assist
in the reversible deflection of distal portion 712 of shaft 702
between a relatively straightened configuration and one or more
curved configurations. One of ordinary skill in the art will
appreciate that adjusting the size, shape, and/or spacing of the
slots 718 can impart various constraints on the radius of curvature
and/or limits of deflection for a selected portion of the distal
portion 712 of shaft 702. For example, the distal portion 712 of
shaft 702 may be configured to assume a second, fully deflected
shape with a relatively constant radius of curvature throughout its
length. In other embodiments, the distal portion 712 may assume a
progressive curve shape with a variable radius of curvature which
may, for example, have a decreasing radius distally. In some
embodiments, the distal portion may be laterally displaced through
an arc having a radius of at least about 0.5'', 0.75'', 1.0'',
1.25'', or 1.5'' minimum radius (fully deflected) to .infin.
(straight) to optimize delivery of bone cement within a vertebral
body. Wall patterns and deflection systems for bendable slotted
tubes are disclosed, for example, in U.S. Pat. Nos. 5,378,234 or
5,480,382 to Hammerslag et al., the disclosures of which are
incorporated in its entirety by reference herein.
[0098] Still referring to FIGS. 7A-B, a pull wire 724 resides
within the lumen 720 of shaft 702. The distal end 722 of the pull
wire 724 is preferably operably attached, such as by adhesive,
welding, soldering, crimping or the like, to an inner side wall of
the distal portion 712 of the shaft 702. Preferably, the attachment
point will be approximately 180.degree. offset from the center of
the axially extending spine 719. Proximal portion of pull wire 724
is preferably operably attached to adjustment control 706. The
adjustment control 706 may be configured to provide an axial
pulling force in the proximal direction toward the proximal end of
pull wire 724. This in turn exerts a proximal traction on the
distal portion 712 of shaft 702 operably attached to distal end 722
of pull wire 724. The slotted side of the tubular body shortens
under compression, while the spine side 719 retains its axial
length causing the distal portion 712 of shaft 702 to assume a
relatively curved or deflected configuration. In some embodiments,
a plurality of pull wires, such as two, three, four, or more pull
wires 724 may be present within the lumen 720 with distal points of
attachment spaced axially apart to allow the distal portion 712 of
shaft 702 to move through compound bending curves depending on the
desired bending characteristic. Distal axial advance of the
actuator will cause a deflection in an opposite direction, by
increasing the width of the slots 718.
[0099] A distal opening 728 is provided on shaft 702 in
communication with central lumen 720 to permit expression of
material, such as bone cement, from the injector 700. Some
embodiments may include a filter such as mesh 812. Mesh structure
812 can advantageously control cement output by controlling bubbles
and/or preventing undesired large or unwieldy aggregations of bone
cement from being released at one location and thus promote a more
even distribution of bone cement within the vertebral body. The
mesh 812 may be created by a laser-cut crisscrossing pattern within
distal end as shown, or can alternatively be separately formed and
adhered, welded, or soldered on to the distal opening 728.
Referring to FIG. 8, the distal shaft portion 712 may also include
an end cap 730 or other structure for occluding central lumen 720,
and a distal opening 728 on the sidewall of shaft 702.
[0100] In some embodiments, the distal shaft 712 can generate a
lateral force of at least about 0.125 pounds, 0.25 pounds, 0.5
pounds, 1 pound, 1.5 pounds, 2 pounds, 3 pounds, 4 pounds, 5
pounds, 6 pounds, 7 pounds, 8 pounds, 9 pounds, 10 pounds, or more
by activating control 706. This can be advantageous to ensure that
the distal portion 712 is sufficiently navigable laterally through
cancellous bone to distribute cement to the desired locations. In
some embodiments, the distal shaft 712 can generate a lateral force
of at least about 0.125 pounds but no more than about 10 pounds; at
least about 0.25 pounds but no more than about 7 pounds; or at
least about 0.5 pounds but no more than about 5 pounds.
[0101] In some embodiments, the distal portion 712 of shaft 702 (or
end cap 730) has visible indicia, such as, for example, a marker
visible via one or more imaging techniques such as fluoroscopy,
ultrasound, CT, or MRI.
[0102] FIGS. 9A-C illustrate in schematic cross-section another
embodiment of a distal portion 734 of a steerable injection device
740. The tubular shaft 736 can include a distal portion 734 made of
or containing, for example, a shape memory material that is biased
into an arc when in an unconstrained configuration. Some materials
that can be used for the distal curved portion 734 include Nitinol,
Elgiloy, stainless steel, or a shape memory polymer. A proximal
portion 732 of the shaft 736 is preferably relatively straight as
shown. Also shown is end cap 730, distal lateral opening 728 and
mesh 812.
[0103] The distal curved portion 734 may be configured to be
axially movably received within an outer tubular sheath 738. The
sheath 738 is preferably configured to have sufficient rigidity and
radial strength to maintain the curved distal portion 734 of shaft
732 in a relatively straightened configuration while the outer
tubular sheath 738 coaxially covers the curved distal portion 734.
Sheath 738 can be made of, for example, a metal such as stainless
steel or various polymers known in the catheter arts. Axial
proximal withdrawal of the sheath 738 with respect to tubular shaft
736 will expose an unconstrained portion of the shape memory distal
end 734 which will revert to its unstressed arcuate configuration.
Retraction of the sheath 738 may be accomplished by manual
retraction by an operator at the proximal end, retraction of a pull
wire attached to a distal portion of the sheath 738, or other ways
as known in the art. The straightening function of the outer sheath
738 may alternatively be accomplished using an internal stiffening
wire, which is axially movably positionable within a lumen
extending through the tubular shaft 736. The length, specific
curvature, and other details of the distal end may be as described
elsewhere herein.
[0104] In another embodiment, as shown in FIGS. 10A-C, tubular
shaft 802 of a steerable vertebroplasty injector may be generally
substantially straight throughout its length in its unstressed
state, or have a laterally biased distal end. A distally facing or
side facing opening 810 is provided for the release of a material,
such as bone cement. In this embodiment, introducer 800 includes an
elongate tubular body 801 with a lumen 805 therethrough configured
to receive the tubular shaft (also referred to as a needle) 802.
Introducer 800 can be made of any appropriate material, such as,
stainless steel and others disclosed elsewhere herein. Needle 802
may be made of a shape memory material, such as nitinol, with
superelastic properties, and has an outside diameter within the
range of between about 1 to about 3 mm, about 1.5-2.5 mm, or about
2.1 mm in some embodiments.
[0105] Introducer 800 includes a needle-redirecting element 804
such as an inclined surface near its distal end. Needle-redirecting
element 804 can be, for example, a laser-cut tang or a plug having
a proximal surface configured such that when needle 802 is advanced
distally into introducer 800 and comes in contact with the
needle-redirecting element 804, a distal portion 814 of needle 802
is redirected out an exit port 806 of introducer 800 at an angle
808, while proximal portion 816 of needle 802 remains in a
relatively straightened configuration, as shown in FIG. 10B. Bone
cement can then be ejected from distal opening 810 on the end or
side of needle 802 within bone 1000. Distal opening 810 may be
present at the distal tip of the needle 802 (coaxial with the long
axis of the needle 802) or alternatively located on a distal radial
wall of needle 802 as shown in FIG. 10C. In some embodiments, the
angle 808 is at least about 15 degrees and may be at least about
30, 45, 60, 90, 105 degrees or more with respect to the long axis
of the introducer 800.
[0106] The illustrated embodiment of FIGS. 10A-C and other
embodiments disclosed herein are steerable through multiple degrees
of freedom to distribute bone cement to any area within a vertebral
body. For example, the introducer 800 and needle 802 can both
rotate about their longitudinal axes with respect to each other,
and needle 802 can move coaxially with respect to the introducer
800, allowing an operator to actuate the injection system three
dimensionally. The distal portion 814 of needle 802 can be
deflected to a position that is angularly displaced from the long
axis of proximal portion 816 of needle without requiring a discrete
curved distal needle portion as shown in other embodiments
herein.
[0107] FIGS. 11A-C illustrate another embodiment of a steerable
vertebroplasty injector. FIG. 11A schematically shows handle
portion 708, adjustment control 706, and elongate needle shaft 702,
including proximal portion 710, distal portion 712, and transition
point 714. FIG. 11B is a vertical cross-section through line A-A of
FIG. 11A, and shows adjustment control 706 operably connected to
pull wire 724 such as through a threaded engagement. Also shown is
input port 704, and proximal portion 710 and distal portion 712 of
needle shaft 702. FIG. 11C illustrates a cross-sectional view of
distal portion 712 of shaft 702. The distal end 722 of pull wire
724 is attached at an attachment point 723 to the distal portion
712 of shaft 702. Proximal retraction on pullwire 724 will collapse
transverse slots 718 and deflect the injector as has been
discussed. Also shown is an inner tubular sleeve 705, which can be
advantageous to facilitate negotiation of objects or media such as
bone cement, through the central lumen of the needle shaft 702.
[0108] The interior sleeve 705 is preferably in the form of a
continuous, tubular flexible material, such as nylon or
polyethylene. In an embodiment in which the needle 702 has an
outside diameter of 0.095 inches (0.093 inch coil with a 0.001 inch
thick outer sleeve) and an inside diameter of 0.077 inches, the
interior tubular sleeve 705 may have an exterior diameter in the
area of about 0.074 inches and an interior diameter in the area of
about 0.069 inches. The use of this thin walled tube 705 on the
inside of the needle shaft 702 is particularly useful for guiding a
fiber through the needle shaft 702. The interior tube 705 described
above is additionally preferably fluid-tight, and can be used to
either protect the implements transmitted therethrough from
moisture, or can be used to transmit bone cement through the
steerable needle.
[0109] In some embodiments, an outer tubular coating or sleeve (not
shown) is provided for surrounding the steerable needle shaft at
least partially throughout the distal end of the needle. The outer
tubular sleeve may be provided in accordance with techniques known
in the art and, in one embodiment, is a thin wall polyester (e.g.,
ABS) heat shrink tubing such as that available from Advanced
Polymers, Inc. in Salem, N.H. Such heat shrink tubings have a wall
thickness of as little as about 0.0002 inches and tube diameter as
little as about 0.010 inches. The outer tubular sleeve enhances the
structural integrity of the needle, and also provides a fluid seal
and improved lubricity at the distal end over embodiments with
distal joints 718. Furthermore, the outer tubular sleeve tends to
prevent the device from collapsing under a proximal force on a pull
wire. The sleeve also improves pushability of the tubular members,
and improves torque transmission.
[0110] In other embodiments, instead of a slotted tube, the needle
shaft of a vertebroplasty injection system may include a metal or
polymeric coil. Steerable helical coil-type devices are described,
for example, in U.S. Pat. Nos. 5,378,234 or 5,480,382 to Hammerslag
et al., which are both incorporated by reference herein in their
entirety. As shown in FIGS. 12A-C, steerable sheath 1010 includes
an elongate tubular body 1012 which is laterally flexible at least
in the distal steering region thereof. Tubular body 1012 generally
includes a spring coil portion 1014 as known in the art. Spring
coil 1014 may additionally be coupled to a proximal hypodermic
needle tubing section. Spring coil 1014 defines a central elongate
lumen 1016 for guiding materials, such as bone cement axially
through the sheath and out a distal opening 728. In some
embodiments, an end cap 730 may be provided. End cap 730 may be
preferably additionally provided with one or more axially extending
support structures such as annular flange 1024 which extends in a
proximal direction through central lumen 1016 to securely anchor
end cap 730. Axial flange 1024 and radial flange 1022 can be
mounting surfaces for attachment of a deflection wire 1026 and pull
ribbon 724 as will be discussed.
[0111] Portion of spring coil 1014 which extends around axial
flange 1024 is relatively inflexible. Thus, the axial length of
flange 1024 can be varied to affect the deflected profile of the
steerable sheath 1010. A deflection wire 1026 or other column
support enhancing element is preferably secured with respect to a
relatively noncompressible portion of tubular body 1012 at a
proximal point 1028 and extends distally to a distal point of
attachment 1030 to provide column strength. The distal point of
attachment may secure the deflection wire 1026 to either or both of
the spring coil 1014 and end cap 730. Deflection wire 1026 bends
upon axial displacement of pull wire 724, with proximal point of
attachment 1028 functioning as a fulcrum or platform.
[0112] Proximal attachment 1028 may be a solder, braze or weld
joint, as is known in the art, with any excess on the radial
outside surface of the tubular body 1012 being trimmed or polished
to minimize rough edges. Distal point of attachment 1030 is
similarly provided by any of a variety of conventional securing
techniques which is appropriate for the construction materials of
the steerable sheath 1010.
[0113] The length of the space between the proximal point of
attachment 1028 and distal point of attachment 1030 affects the
radius of the curve of the deflection wire 1026 and hence of the
region 712, as will be appreciated by one of skill in the art. The
deflection wire 1026 will tend to remain positioned along the
exterior circumference of the curve during deflection by axial
compression of the steerable sheath 1010. Since the circumference
in a given steerable sheath 1010 will be a fixed distance, the
radius of the curve during deflection will differ, depending upon
the degree of deflection achieved.
[0114] Deflection at distal steering region 712 of steerable sheath
1010 is accomplished by providing a pull wire 724. Pull wire 724 is
preferably secured at a distal point of attachment 1036 and extends
proximally to the control end of the steerable sheath 1010. Axial
displacement of the pull wire 724 will tend to pivot the steering
region 712 of the tubular body 1012 around proximal point of
attachment 1028, as shown in FIG. 12B. Preferably, lateral
displacement of steering region 712 is accomplished by axial
proximal displacement of pull wire 724.
[0115] Pull wire 724 is rotationally offset from deflection wire
1026 by at least about 90.degree.. Preferably, pull wire 724 is
rotationally offset from deflection wire 1026 by about 180.degree.,
as illustrated in FIGS. 12A-B and cross-sectional view FIG. 12C.
Among other advantages of this configuration, opposing placement of
deflection wire 1026 and pull wire 1035 tends to maintain central
lumen 1016 open while the steering region 712 is laterally
deflected in response to proximal displacement of pull wire 724.
This tends to optimize the flowability of bone cement through the
central lumen.
[0116] In another embodiment, an interior tubular sleeve (not
illustrated) is additionally provided to facilitate flow of media
through central lumen 1016 as described elsewhere in the
application. In some embodiments, a heat-shrink outer tubular
sleeve as described elsewhere in the application is also provided
to enhance the structural integrity of the sheath, provide a fluid
seal, as well as improve lubricity.
[0117] In one embodiment, the steerable injection needle (also
referred to as the injection shaft) has an outside diameter of
between about 8 to 24 gauge, more preferably between about 10 to 18
gauge, e.g., 12 gauge, 13 gauge (0.095'' or 2.41 mm), 14 gauge, 15
gauge, or 16 gauge. In some embodiments, the inside diameter
(luminal diameter) of the injection needle is between about 9 to 26
gauge, more preferably between about 11 to 19 gauge, e.g., 13
gauge, 14 gauge, 15 gauge, 16 gauge, or 17 gauge. In some
embodiments, the inside diameter of the injection needle is no more
than about 4 gauge, 3 gauge, 2 gauge, or 1 gauge smaller than the
outside diameter of the injection needle.
[0118] The inside luminal diameter of all of the embodiments
disclosed herein is preferably optimized to allow a minimal
exterior delivery profile while maximizing the amount of bone
cement that can be carried by the needle. In one embodiment, the
outside diameter of the injection needle is 13 gauge (0.095'' or
2.41 mm) with a 0.077'' (1.96 mm) lumen. In some embodiments, the
percentage of the inside diameter with respect to the outside
diameter of the injection needle is at least about 60%, 65%, 70%,
75%, 80%, 85%, or more.
[0119] The steerable injection systems described above are
preferably used in conjunction with a mixing and dispensing pump
for use with a multi-component cement. In some embodiments, a
cement dispensing pump is a hand-held device having an interface
such as a tray or chamber for receiving one or more cartridges. In
one embodiment, the pump is configured to removably receive a
double-barreled cartridge for simultaneously dispensing first and
second bone cement components. The system additionally includes a
mixing chamber, for mixing the components sufficiently and
reproducibly to fully automate the mixing and dispensing process
within a closed system.
[0120] Bone cement components have conventionally been mixed, such
as by hand, e.g., in mixing bowls in the operating room, which can
be a time-consuming and unelegant process. Use of a mixing device
such as a double-barreled dispensing pump as disclosed herein is
highly advantageous in reducing bone cement preparation time,
ensuring that premature cement curing does not occur (i.e., the
components are mixed immediately prior to delivery into the body),
and ensuring adequate mixing of components.
[0121] Two separate chambers contain respective materials to be
mixed in a specific ratio. Manual dispensing (e.g., rotating a knob
or squeezing a handle) forces both materials into a mixing nozzle,
which may be a spiral mixing chamber within or in communication
with a nozzle. In the spiral mixing nozzle, all or substantially
all mixing preferably occurs prior to the bone cement entering the
steerable injection needle and, subsequently, into the vertebra.
The cement dispensing hand pump may be attached to the steerable
injection needle permanently, or removably via a connector, such as
slip-ring Luer fittings. A wide range of dispensing pumps can be
modified for use with the present invention, including dispensing
pumps described in, for example, U.S. Pat. Nos. 5,184,757,
5,535,922, 6,484,904, and Patent Publication No. 2007/0114248, all
of which are incorporated by reference in their entirety.
[0122] FIG. 13 illustrates an exploded perspective view of a
double-barreled cement dispensing pump, which may be used to
practice the present invention. FIG. 13 shows a dispenser gun 976
having a cartridge tray 977 affixed to an actuator 978, for
ejecting the compounds contained in a removable, disposable,
two-chamber, two-component cartridge 910. The actuator 978 can be
any of a variety of mechanisms known in the art, such as found in a
caulking gun having either a friction or ratchet advance mechanism.
The degree of advancement of the actuator mechanism is controlled
by turning a rotatable control such as a wheel or knob (not shown)
or by squeezing handles 979, 980, one or both of which moves
relative to the other in a conventional manner. In addition to
purely mechanical advance mechanisms, the dispensing pump can also
be used with a hydraulic, compressed air or electromagnetic advance
mechanism. The ejector gun 976 may have at least one actuator rod
981 and may have a piston rod 982, 983 for each cylinder 912, 914,
respectively.
[0123] The actuator rod 981 and piston rods 982, 983 may be linked
at a proximal end such as by a bridge 984 to which a pull knob 985
is attached, such that all rods 981, 982, 983 move simultaneously
as an assembly. A piston plate 986 is attached to piston rod 983 at
the distal end thereof proximate to the cartridge tray 977. A
second piston plate 987 (illustrated as larger than first plate
986) is affixed to the distal end of piston rod 982 and optionally
actuator rod 981. In this manner, the ejector gun 976 can be
utilized with cartridges having cylinders 912, 914 of the same or
different diameters. As depicted in FIG. 13, the cylinders 912, 914
are the same diameter but they could be of different diameters for
the purpose of dispensing reactive compounds in other than a 1:1
ratio. In that instance, the larger of the cylinders 912, 914 can
be positioned proximate the larger piston plate 987, with the
smaller of the cylinders 912, 914 positioned proximate piston plate
986. The pistons 986, 987 could have the same dimensions in other
embodiments.
[0124] The tray 977 is held to the actuator portion 978 by a
plurality of fasteners 989, or by welding, gluing, integral molding
or other conventional means. Distal to the actuator 978, the tray
has an end plate 990 with a cartridge docking cutout 991 for
slideably receiving and embracing the cartridge 910 at the base of
the outlet 922.
[0125] A cartridge support 997 may extend up from the bottom of the
tray 977 and engage the cartridge to retain alignment with the
motion of the piston plates 986, 987 to maximize the transfer of
force from piston plates 986, 987 to expel the compound from the
cartridge 910.
[0126] The present disclosure is directed primarily to a cartridge
embodiment having two cylindrical chambers. This permits expression
of media from the chambers using a plunger arrangement such as a
common syringe. However, any of a wide variety of chamber
configurations and structures for expressing media from the chamber
may be utilized.
[0127] Currently favored bone cement compositions are normally
stored as two separate components or precursors, for mixing at the
clinical site shortly prior to implantation. As has been described
above, mixing of the bone cement components has traditionally been
accomplished manually, such as by expressing the components into a
mixing bowl in or near the operating room. In accordance with the
present invention, the bone cement components may be transmitted
from their storage and/or shipping containers, into a mixing
chamber, and into the patient, all within a closed system. For this
purpose, the system of the present invention includes at least one
mixing chamber positioned in the flow path between the bone cement
component container and the distal opening on the bone cement
injection needle. This permits uniform and automated or
semi-automated mixing of the bone cement precursors, within a
closed system, and thus not exposing any of the components or the
mixing process at the clinical site.
[0128] Thus, the mixing chamber may be formed as a part of the
cartridge, may be positioned downstream from the cartridge, such as
in-between the cartridge and the proximal manifold on the injection
needle, or within the proximal manifold on the injection needle or
the injection needle itself, depending upon the desired performance
of the device. The mixing chamber may be a discrete component which
may be removably or permanently coupled in series flow
communication with the other components of the invention, or may be
integrally formed within any of the foregoing components.
[0129] In general, the mixing chamber includes an influent flow
path for accommodating at least two bone cement components. The
first and second incoming flow path are combined, and mixing
structures for facilitating mixing of the components are provided.
This may include any of a variety of structures, such as a helical
flow path, baffles and or additional turbulence inducing
structures.
[0130] In the embodiment illustrated in FIG. 13, a discrete mixing
device 994 includes a proximal connector 997 in fluid flow
communication with a distal aperture 996 through a mixing chamber
995. Mixing chamber 995 may include any of a variety of turbulence
inducing structures as has been discussed.
[0131] The cement mixing gun, cartridge and mixing chamber are
illustrated in FIG. 13 in a highly schematic form to assist in
understanding the invention. However, as will be appreciated by
those of skill in the art, the cement mixing and dispensing systems
in accordance with the present invention may be constructed in any
of wide variety of forms which may differ significantly in
appearance from that illustrated in FIG. 13.
[0132] After cement is mixed in mixing nozzle 994, the cement is
preferably immediately or eventually directed into the input port
704 of a steerable delivery device, either directly, such as via a
Luer lock connector, or through a bridging tubing set.
[0133] Cement dispensing pump 976 is preferably configured to
accommodate cartridges of appropriate volume for the formation of
the amount of bone cement likely to be needed in a single level or
a two level vertebroplasty. In some embodiments, cartridges have a
volume sufficient to produce a unit volume of mixed bone cement
between about 25-200 cc, preferably between 25-100 cc, and in one
implementation about 50 cc.
[0134] FIG. 14 illustrates schematically another, simplified
embodiment of a bone cement mixing dispenser. Shown are first
syringe 1102 and second syringe 1104 filled with first and second
bone cement precursor materials respectively (e.g., the contents of
cartridges 1A and 1B, or 2A and 2B, respectively and described
below). First 1102 and second 1104 syringes may be integrally
molded together or coupled together, e.g., by an adhesive and share
a common plunger top 1106 such that contents of syringes 1102 and
1104 may be dispensed approximately in a 1:1 or other preset ratio.
Applying an axially distally directed force to plunger top 1106
either by hand or by a dispensing device will result in stopper
1108 portions of the plunger to advance distally thereby expressing
contents of first 1102 and second 1104 syringes out through nozzles
1110, 1112 and into Y-connector tubing 114 into mixing nozzle 995,
and thereafter into the input port 704 of a steerable delivery
device.
[0135] In some embodiments, a bone cement composite is packaged in
two separate chambers contained in a single cartridge. This may be
useful, for example, for delivering conventional two part PMMA
formulations in an otherwise conventional vertebroplasty or
kyphoplasty procedure.
[0136] In other embodiments, the system is adapted for delivering a
bone cement composite in which the final construct comprises a mass
of hardened cement having a particulate content with a non uniform
spatial distribution. In this embodiment, a total of three or four
chambers will normally be used which may conveniently be
distributed into two chambers each in two cartridges.
[0137] Tables 1-2 below depict the contents and concentrations of
one exemplary embodiment of bone cement precursors. Chambers 1A and
1B contain precursors for a first cement composition for
distribution around the periphery of the formed in place vertebral
body implant with a higher particle concentration to promote
osteoinduction, as discussed previously in the application.
Chambers 2A and 2B contain precursors for a second cement
composition for expression more centrally within the implanted mass
within the vertebral body, for stability and crack arresting, as
discussed previously in the application.
[0138] One of ordinary skill in the art will recognize that a wide
variety of chamber or cartridge configurations, and bone cements,
can be used with the present injection system. For example, in one
embodiment, a first cartridge includes pre-polymerized PMMA and a
polymerization catalyst, while a second cartridge includes a liquid
monomer of MMA as is common with some conventional bone cement
formulations.
[0139] In some embodiments, the contents of two cartridges can be
combined into a single cartridge having multiple (e.g., four)
chambers. Chambers may be separated by a frangible membrane (e.g.,
1A and 2A in a first cartridge and 1B and 2B in a second cartridge,
each component separated by the frangible membrane or other
pierceable or removable barrier). In other embodiments, contents of
the below cartridges can be manually pre-mixed and loaded into the
input port of the injection system without the use of a cement
mixing dispenser.
TABLE-US-00001 TABLE 1 Chamber 1A Methyl methacrylate (balance)
Hydroquinone (~75 ppm) (stabilizer) N,N-dimethyl-p-toluidine
(~0.9%) (catalyst Sterile bone for polymerization) particles
(.gtoreq.35 wt. %) Barium sulfate (~20 wt. %) (radio-opacifier)
Chamber 1B Benzoyl peroxide (~2%) (activator for Physiological
saline or polymerization) poppy seed oil (balance)
TABLE-US-00002 TABLE 2 Chamber 2A Methyl methacrylate (balance)
Hydroquinone (~75 ppm) (stabilizer) N,N-dimethyl-p-toluidine
(~0.9%) (catalyst Sterile bone particles for polymerization) (~30
wt. %) Barium sulfate (~20 wt. %) (radio-opacifier) Chamber 2B
Benzoyl peroxide (~2%) (activator for Physiological saline or
polymerization) poppy seed oil (balance)
[0140] As illustrated in FIGS. 15A-B, in one embodiment, a system
or kit for implanting bone cement includes at least some of the
following components: a stylet configured to perforate a hole into
the pedicle of the vertebral body; an introducer cannula 800 for
providing an access pathway to the treatment site, a steerable
injection needle 700 to deliver bone cement to a desired location,
and, a cement dispensing pump 910 preferably configured to
accommodate one or two or more dual chamber cartridges 1200 as well
as a mixing nozzle 995.
[0141] The stylet may have a diameter of between about 0.030'' to
0.300'', 0.050'' to about 0.200'' and preferably about 0.100'' in
some embodiments. The introducer cannula 800 is between about 8-14
gauge, preferably between about 10-12 gauge, more preferably 11
gauge in some embodiments. The introducer cannula 800, which may be
made of any appropriate material, such as stainless steel (e.g.,
304 stainless steel) may have a maximum working length of no more
than about 12'', 8'', or 6'' in some embodiments. One or two or
more bone cement cartridges, each having one or two or more
chambers, may also be provided. Various other details of the
components have been described above in the application.
[0142] One embodiment of a method for delivering bone cement into a
vertebral body is now described, and illustrated in FIGS. 16A-F.
The method involves the general concept of vertebroplasty and
kyphoplasty in which a collapsed or weakened vertebra is stabilized
by injecting bone cement into cancellous bone.
[0143] The cement implantation procedure is designed for
uni-transpedicular access and generally requires either a local
anesthetic or short-duration general anesthetic for minimally
invasive surgery. Once the area of the spine is anesthetized, as
shown in FIGS. 16A-B, the physician inserts a stylet 1302 to
perforate a lumen 1304 into the pedicle wall 1300 of the vertebra
1308 to gain access to the interior of the vertebral body 1310. As
illustrated in FIG. 16C, the introducer cannula 800 is then
inserted through the lumen 1304 for bone access as well as acting
as the guide for the steerable injection needle 700. The introducer
cannula 800 is sized to allow physicians to perform vertebroplasty
or kyphoplasty on vertebrae with small pedicles 1300 such as the
thoracic vertebra (e.g., T5) as well as larger vertebrae. In
addition, this system and method is advantageously designed to
allow uni-transpedicular access as opposed to bi-pedicular access,
resulting in a less invasive surgical procedure.
[0144] Once bone access has been achieved, as shown in FIG. 16C the
steerable injection needle 700 such as any of the devices described
above can be inserted through the introducer cannula 800 and into
the vertebra 1308. The entire interior 1310 of the target vertebral
body may be accessed using the steerable injection needle 800. The
distal end 712 of the needle 700 can be laterally deflected,
rotated, and/or proximally retracted or distally advanced to
position the bone cement effluent port at any desired site as
previously described in the application. The radius can be adjusted
by means of an adjustment control, such as a knob on the proximal
end of the device as previously described.
[0145] The actual injection procedure may utilize either one or two
basic steps. In a one step procedure, a homogenous bone cement is
introduced as is done in conventional vertebroplasty. The first
step in the two step injection involves injection of a small
quantity of PMMA with more than about 35%, e.g., 60% particles such
as inorganic bone particles onto the periphery of the treatment
site, i.e., next to the cortical bone of the vertebral body as
shown in FIG. 16D. This first cement composite 1312 begins to
harden rather quickly, forming a firm but still pliable shell,
which is intended to minimize or prevent any bone marrow/PMMA
content from being ejected through any venules or micro-fractures
in the vertebral body wall. The second step in the procedure
involves an injection of a bolus of a second formulation of PMMA
with a smaller concentration such as approximately 30% inorganic
bone particles (second cement composite 1314) to stabilize the
remainder of the weakened, compressed cancellous bone, as
illustrated in FIG. 16E.
[0146] Injection control for the first and second steps is provided
by an approximately 2 mm inside diameter flexible introducer
cannula 800 coupled to a bone cement injection pump (not shown)
that is preferably hand-operated. Two separate cartridges
containing respective bone cement and inorganic bone particle
concentrations that are mixed in the 60% and 30% ratios are
utilized to control inorganic bone particle to PMMA concentrations.
The amount of the injectate is under the direct control of the
surgeon or interventional radiologist by fluoroscopic observation.
The introducer cannula 800 is slowly withdrawn from the cancellous
space as the bolus begins to harden, thus preventing bone
marrow/PMMA content from exiting the vertebral body 1308. The
procedure concludes with the surgical incision being closed, for
example, with bone void filler 1306 as shown in FIG. 16F. Both the
high and low bone cement particle concentration cement composites
1312, 1314 harden after several minutes. In vitro and in vivo
studies have shown that the 60% bone-particle impregnated bone
cement hardens in 2-3 minutes and 30% bone-particle impregnated
bone cement hardens between 4 to 10 minutes.
[0147] The aforementioned bone cement implant procedure process
eliminates the need for the external mixing of PMMA powder with MMA
monomer. This mixing process sometimes entraps air in the dough,
thus creating porosity in the hardened PMMA in the cancellous bone
area. These pores weaken the PMMA. Direct mixing and hardening of
the PMMA using an implant procedure such as the above eliminates
this porosity since no air is entrapped in the injectate. This,
too, eliminates further weakening, loosening, or migration of the
PMMA.
[0148] While described herein primarily in the context of
vertebroplasty, one of ordinary skill in the art will appreciate
that the disclosed injection system can be used or modified in a
wide range of clinical applications, such as, for example, other
orthopedic applications such as kyphoplasty, treatment of any other
bones, pulmonary, cardiovascular, gastrointestinal, gynecological,
or genitourinary applications. While this invention has been
particularly shown and described with references to embodiments
thereof, it will be understood by those skilled in the art that
various changes in form and details may be made therein without
departing from the scope of the invention. For all of the
embodiments described above, the steps of the methods need not be
performed sequentially and the individual components of the devices
may be combined permanently or be designed for removable attachment
at the clinical site.
* * * * *
References