U.S. patent application number 13/650390 was filed with the patent office on 2013-02-07 for system and method for minimally invasive posterior fixation.
This patent application is currently assigned to WARSAW ORTHOPEDIC, INC. The applicant listed for this patent is Warsaw Orthopedic, Inc. Invention is credited to Michael R. Henson, Thanh V. Nguyen, To V. Pham, Samuel M. Shaolian, George P> Tietelbaum.
Application Number | 20130035726 13/650390 |
Document ID | / |
Family ID | 42561184 |
Filed Date | 2013-02-07 |
United States Patent
Application |
20130035726 |
Kind Code |
A1 |
Nguyen; Thanh V. ; et
al. |
February 7, 2013 |
SYSTEM AND METHOD FOR MINIMALLY INVASIVE POSTERIOR FIXATION
Abstract
The present invention relates generally to systems and methods
for aligning and implanting orthopedic fixation or stabilization
implants within the body. In one embodiment, the system includes at
least two bone anchors, at least one of which is provided with an
angularly adjustable connector. In one aspect, the system also
includes at least one linkage rod, for linking two or more bone
anchors through their respective adjustable connectors. The bone
anchors and the linkage rod may be locked into place to form a
spinal fusion or fixation prosthesis. An alignment tool is
provided, for guiding a guidewire through one or more
connectors.
Inventors: |
Nguyen; Thanh V.; (Irvine,
CA) ; Shaolian; Samuel M.; (Newsport Beach, CA)
; Tietelbaum; George P>; (Santa Monica, CA) ;
Henson; Michael R.; (Coto De Caza, CA) ; Pham; To
V.; (Trabuco Canyon, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Warsaw Orthopedic, Inc; |
Warsaw |
IN |
US |
|
|
Assignee: |
WARSAW ORTHOPEDIC, INC
Warsaw
IN
|
Family ID: |
42561184 |
Appl. No.: |
13/650390 |
Filed: |
October 12, 2012 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12328914 |
Dec 5, 2008 |
8317838 |
|
|
13650390 |
|
|
|
|
Current U.S.
Class: |
606/278 ;
606/86A |
Current CPC
Class: |
A61B 17/7005 20130101;
A61B 17/1757 20130101; A61B 17/864 20130101; A61B 17/7019 20130101;
A61B 17/7089 20130101; A61B 17/702 20130101; A61B 17/861 20130101;
A61B 17/3472 20130101; A61B 17/7086 20130101; A61B 2017/90
20130101; A61B 17/7082 20130101; A61B 17/7001 20130101; A61B
17/1615 20130101; A61B 17/8897 20130101; A61B 17/7011 20130101;
A61B 17/7083 20130101; A61B 17/8861 20130101; A61B 17/1671
20130101; A61B 17/704 20130101; A61B 17/1642 20130101; A61B 17/3468
20130101; A61B 17/7004 20130101 |
Class at
Publication: |
606/278 ;
606/86.A |
International
Class: |
A61B 17/70 20060101
A61B017/70; A61B 17/90 20060101 A61B017/90 |
Claims
1. A prosthesis assembly for minimally invasive posterior fixation,
comprising: a curved rod, having a proximal end and a distal end,
and releasable coupling on the proximal end; and a bone anchor
provided with an adjustable connector, said adjustable connector
including a lock to securely engage said rod at any of a variety of
angular orientations between the rod and the bone anchor.
2. The prosthesis assembly of claim 1 further comprising a second
bone anchor having a connector adapted to securely engage said
rod.
3. The prosthesis assembly of claim 1, wherein the bone anchor
comprises a head and a rotatable connector disposed within said
head, said rotatable connector adapted to securely engage said
rod.
4. A prosthesis for minimally invasive posterior fixation,
comprising: a bone anchor having a head; a transverse portal
extending through said head along an axis transverse to a central
axis of said bone anchor; a rod extending through said transverse
portal; a rotating connector with an aperture seated in a groove
within said head; said aperture adapted to securely engage said
rod; and a locking cap which secures said rotating connector
against said groove and said rod within said aperture.
5. The prosthesis of claim 4, wherein said rotating connector
further comprises indentations on its exterior adapted to cooperate
with complementary projections within said head to limit the
rotation of said rotating connector.
6. The prosthesis of claim 4, wherein said rotating connector
further comprises at least one compression gap.
7. The prosthesis of claim 4, wherein said rod is adapted to be
detachably secured to an insertion tool used to insert said rod
into said aperture.
8. A guide wire introducer for inserting a guide wire through a
transverse portal of a bone anchor, comprising: an adapter aligned
with a central axis of said bone anchor; a handle attached at a
pivot to said adapter; and an access needle on said handle adapted
for insertion through said transverse portal of said bone
anchor.
9. The guide wire apparatus of claim 8 further comprising an
obturator.
10. The guide wire apparatus of claim 8 further comprising a guide
wire capture device.
11. The guide wire apparatus of claim 10 wherein said guide wire
capture device further comprises a retractable conical funnel.
12-16. (canceled)
17. A guide wire insertion device to insert a guide wire through a
portal of a bone anchor, comprising: A central arm adapted to
engage said bone anchor; A radial arm attached to said central arm
at a pivot; A hollow access needle secured to said radial arm;
Wherein said radial arm pivots on said pivot to move said access
needle through said port of said bone anchor.
18. The guide wire insertion device of claim 17, further comprising
a guide wire capture device.
19. The guide wire insertion device of claim 18 wherein said guide
wire capture device further comprises a conical receiving end which
comprises one or more partial conical segments.
20-39. (canceled)
Description
RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C.
.sctn.119(e) to U.S. Provisional Application No. 60/465,902 filed
on Apr. 25, 2003, the disclosure of which is incorporated by
reference in its entirety herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to medical devices
and, more particularly, to systems for aligning and implanting
orthopedic fixation or stabilization implants within the body. In
one application, the present invention relates to minimally
invasive procedures and devices for implanting posterior
instrumentation.
[0004] 2. Description of the Related Art
[0005] The human vertebrae and associated connective elements are
subject to a variety of diseases and conditions which cause pain
and disability. Among these diseases and conditions are
spondylosis, spondylolisthesis, vertebral instability, spinal
stenosis and degenerated, herniated, or degenerated and herniated
intervertebral discs. Additionally, the vertebrae and associated
connective elements are subject to injuries, including fractures
and torn ligaments and surgical manipulations, including
laminectomies.
[0006] The pain and disability related to these diseases,
conditions, injuries and manipulations often result from the
displacement of all or part of a vertebra from the remainder of the
vertebral column. A variety of methods have been developed to
restore the displaced vertebrae or portions of displaced vertebrae
to their normal position and to fix them within the vertebral
column. For example, open reduction with screw fixation is one
currently used method. The surgical procedure of attaching two or
more parts of a bone with pins, screws, rods and plates requires an
incision into the tissue surrounding the bone and the drilling of
one or more holes through the bone parts to be joined. Due to the
significant variation in bone size, configuration, and load
requirements, a wide variety of bone fixation devices have been
developed in the prior art. In general, the current standard of
care relies upon a variety of metal wires, screws, rods, plates and
clamps to stabilize the bone fragments during the healing or fusing
process. These methods, however, are associated with a variety of
disadvantages, such as morbidity, high costs, lengthy in-patient
hospital stays and the pain associated with open procedures.
[0007] Therefore, devices and methods are needed for repositioning
and fixing displaced vertebrae or portions of displaced vertebrae
which cause less pain and potential complications. Preferably, the
devices are implantable through a minimally invasive procedure.
SUMMARY OF THE INVENTION
[0008] In accordance with one aspect of the present invention, a
system is provided for the minimally invasive implantation of
posterior fixation hardware. The system generally includes at least
two bone anchors, at least one of which is provided with an
adjustable connector. In many clinical situations, all of the bone
anchors used in the system may be provided with adjustable
connectors. The system may also include a driver for inserting the
bone anchor into a bone and locking the adjustable connector. The
system also includes at least one linkage rod, for linking two or
More bone anchors through their respective adjustable connectors.
In one embodiment, an insertion tool is provided for the insertion
of the linkage rod. The bone anchors and the linkage rod may be
fixed to each other by the locking of the adjustable connectors on
the bone anchors, to subcutaneously form a prosthesis.
[0009] In accordance with another aspect of the present invention,
the system additionally includes a guidance apparatus for the
minimally invasive implantation of posterior fixation hardware. In
one embodiment, the guidance apparatus includes a central support
arm adapted to engage a bone anchor. A radial arm is pivotably
attached to the central arm. A hollow access needle is secured to
the radial arm. The radial arm is pivotable with respect to the
central arm, to allow the hollow access needle to travel along an
arcuate path, for guiding a guidewire through a tissue tract and
into and through at least one adjustable connector on a bone anchor
(or bone screw). The hollow access needle may removably carry an
obturator, to facilitate percutaneous advancement. The hollow
needle may additionally removably carry a distal guidewire capture
device, for capturing a proximally advancing guidewire
subcutaneously within the hollow access needle. The guidewire
capture device may comprise a radially enlargeable structure such
as a conical funnel, for deflecting an approaching guidewire into
the lumen of the hollow access needle.
[0010] In another aspect of the present invention, a method is
provided for the minimally invasive implantation of posterior
fixation hardware. In one embodiment, the method comprises the
insertion of a first bone anchor, having a first adjustable
connector, into a first vertebral body. A second bone anchor,
having a second adjustable connector, is inserted into a second
vertebral body. The first and second vertebral bodies may be
adjacent to each other, or separated by one or more other vertebral
body or bodies. A linkage rod is inserted through the adjustable
connectors of both bone anchors. The adjustable connector of each
bone anchor is then locked, fixing the position of the adjustable
connector within the bone anchor, and securing the linkage rod
within the adjustable connector, to form a prosthesis.
[0011] In accordance with another embodiment of the present
invention, the method further comprises the insertion of another
bone anchor with an adjustable connector into another vertebral
body. This latter vertebral body may be adjacent to either or both
of the first and second vertebral bodies, or separated from both
the first and second vertebral bodies. The linkage rod is inserted
through the adjustable connectors of all of the bone anchors to
form the prosthesis.
[0012] In accordance with another embodiment of the present
invention, the method additionally includes the placement of one or
more guide wires. A guide wire may be inserted into a bone to
define a path for the insertion of a bone anchor. Another guide
wire may be threaded through the adjustable connectors of two or
more bone anchors, to guide the insertion of the linkage rod. The
guide wire may be placed using the guidance apparatus described
above.
[0013] In any of the foregoing systems and methods, the guide wire
may be replaced or supplemented by a flexible guide tube. In such
implementations of the invention, the bone anchor and/or the
linkage rod may be advanced through the interior of the guide
tube.
[0014] Further features and advantages of the present invention
will become apparent to those skilled in the art in view of the
detailed description of preferred embodiments which follows, when
considered together with the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is an overview of a system for minimally invasive
posterior spinal fixation according to one embodiment of the
present invention.
[0016] FIG. 2 is an exploded view of the bone anchor and the driver
of FIG. 1.
[0017] FIG. 3A is an enlarged view of the circled area in FIG.
2.
[0018] FIG. 3B illustrates an angularly adjustable connector with
rotation limits according to another embodiment.
[0019] FIG. 3C illustrates a connector, a locking cap and its
complementary inner adapter according to yet another
embodiment.
[0020] FIGS. 3D-3F illustrate the connector illustrated in FIG. 3C
in further detail.
[0021] FIG. 3G is a cross-sectional view of an angularly adjustable
connector with rotation limits positioned within a head of a hone
anchor according to another embodiment.
[0022] FIG. 4 is another view of the system for minimally invasive
posterior spinal fixation illustrated in FIG. 1, with the linkage
rod detached from its insertion tool.
[0023] FIG. 5 is an enlarged view of the circled area in FIG.
4.
[0024] FIG. 6 is another view of the system for minimally invasive
posterior spinal fixation illustrated in FIG. 4.
[0025] FIGS. 7-12 illustrate the use of positioning tools to
position a guide wire into a vertebral body.
[0026] FIGS. 13-14 illustrate the use of a dilation balloon
catheter to dilate a tissue tract.
[0027] FIGS. 15-20 illustrate the positioning of a sheath adjacent
to a vertebral body.
[0028] FIGS. 21-23 illustrate a drill used to create an opening in
a vertebral body to receive a bone anchor.
[0029] FIGS. 24-25 illustrate advancing a bone anchor over the wire
towards a vertebral body.
[0030] FIGS. 26-27 illustrate a bone anchor and the driver used to
insert the bone anchor into a vertebral body.
[0031] FIGS. 28-31 illustrate the use of the driver to insert a
bone anchor into a vertebral body.
[0032] FIG. 32 illustrates two bone anchors positioned in two
adjacent vertebral bodies.
[0033] FIG. 33 illustrates an alignment device for positioning a
guidewire though a bone anchor in accordance with one aspect of the
present invention.
[0034] FIG. 34 illustrates a flexible obturator for positioning
within the arcuate arm of the alignment device.
[0035] FIG. 35 illustrates a first alignment device coupled to
first bone anchor, and a second alignment device coupled to a
second bone anchor.
[0036] FIGS. 36 and 37 illustrate a guidewire capture device, for
positioning within the arcuate arm on an alignment device.
[0037] FIG. 38 illustrates the first and second alignment devices,
with a guidewire advancing from the first alignment device towards
the capture device carried by the second alignment device.
[0038] FIG. 39 is an illustration as in FIG. 38, after the
guidewire has entered the guidewire capture device and traversed
the curved arm on the second alignment device.
[0039] FIG. 40 is a side elevational view of a linkage rod,
decoupled from an insertion tool, both over a guidewire.
[0040] FIG. 41 is a side elevational perspective view of a
guidewire positioned through two adjacent bone anchors, and a
linkage rod being advanced along the guidewire by an insertion
tool.
[0041] FIG. 42 is an illustration as in FIG. 41, with the linkage
rod positioned within the first and second bone anchors.
[0042] FIG. 43 is an illustration as in FIG. 42, with a driver in
position to lock the first bone anchor to the linkage rod.
[0043] FIG. 44 is an illustration as in FIG. 43, with a portion of
the driver tool proximally retracted.
[0044] FIG. 45 is an illustration as in FIG. 44, with the driver
tool retracted, the first and second bone anchors locked onto the
linkage rod, and the insertion tool decoupled from the linkage
rod.
[0045] FIG. 46 is an illustration as in FIG. 45, with the insertion
tool and the guidewire removed from the linkage rod, illustrating a
formed in place one level posterior fusion device in accordance
with the present invention.
[0046] FIG. 47 is an illustration as in FIG. 46, showing a two
level fusion or fixation device, percutaneously assembled in
accordance with the present invention.
[0047] FIG. 48 is a side elevational schematic view of an alternate
linkage rod in accordance with the present invention.
[0048] FIG. 49 is an enlarged exploded view as in FIG. 3A, showing
the proximal end of a bone anchor adapted for use with the linkage
rod of FIG. 48.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0049] Although the application of the present invention will be
disclosed primarily in the context of a spinal fixation procedure,
the systems and methods disclosed herein are intended for use in a
wide variety of medical applications where the minimally invasive
implantation of an attachment, bulking, brace, support, fixation or
other prosthesis may be desirable.
[0050] One advantage of the prosthesis formation described in the
various embodiments of the present invention is the ability to
access a treatment site through minimally invasive pathways, while
allowing the formation of a relatively larger prosthesis at the
treatment site. In one embodiment, various components of a
prosthesis are inserted into a patient through minimally invasive
pathways, then joined to form a single prosthesis. This is
facilitated by the angularly adjustable connectors between the
various components, which provide leeway or angular adjustability
as the components are joined. Afterwards, the junctions between the
various components may be locked to fix or set the prosthesis in a
desired configuration.
[0051] A corollary advantage of several embodiments is the ability
to unlock and adjust one or more junctions between components of
the prosthesis, to set the prosthesis in other desirable
configurations during or even after its implantation and formation.
The prosthesis may thus be adjusted in subsequent procedures.
[0052] The systems and methods for spinal fixation according to
various embodiments of the present invention minimize procedure
morbidity by avoiding open surgical cutdowns or other invasive
access procedures. The basic percutaneous access, bone screw
construction and implantation methods, and methods and structures
for percutaneously positioning a fixation rod across bone screws,
all of which are useful in the practice of the present invention,
are disclosed in U.S. patent application Ser. No. 09/747,066,
entitled Percutaneous Vertebral Fusion System, to Teitelbaum, filed
Dec. 21, 2000; U.S. patent application Ser. No. 09/943,636 to
Shaolian et al., entitled Formable Orthopedic Fixation System,
filed Aug. 29, 2001; U.S. patent application Ser. No. 09/976,459 to
Teitelbaum et al., entitled Formable Orthopedic Fixation System
with Cross-Linking, filed Oct. 10, 2001; and U.S. patent
application Ser. No. 10/161,554 to Shaolian et al., entitled Formed
in Place Fixation System with Thermal Acceleration, filed May 31,
2002; the disclosures of all of which arc hereby incorporated in
their entireties by reference herein.
[0053] An overview of a system for minimally invasive posterior
spinal fixation according to one embodiment of the present
invention is provided in FIG. 1. The system includes at least two
and optionally three or four or more bone anchors 100 and a linkage
rod 200. In FIG. 1, the bone anchors are shown connected by the
linkage rod 200. The system also includes a driver 150, shown
engaging one of the bone anchors 100, and an insertion tool 250,
shown connected to the linkage rod 200. Although the present
invention will be described primarily in the context of a single
linkage rod connected to two bone anchors, the normal fusion
application will involve the implantation of two linkage rods, each
carried by two or more bone anchors, bilaterally symmetrically
mounted on the spine as is well understood in the art.
[0054] FIG. 2 shows an exploded view of the bone anchor 100 and the
driver 150. The bone anchor 100 is provided with threads 102 by
which it is screwed into a vertebral body. A connector 104 and a
locking cap 106 are disposed within the head 108 of the bone anchor
100.
[0055] The driver 150 comprises an outer adapter 152 concentrically
arranged around an inner adapter 154. Either adapter may be freely
rotated with respect to the other. The outer adapter 152 is adapted
to engage the head 108, to screw the bone anchor 100 into a bone.
The inner adapter 154 is adapted to engage the locking cap 106, to
tighten the connector 104 within the head 108. In one embodiment,
the hexagonal proximal end 156 of the outer adapter 152 allows
torque to be applied to the outer adapter 152 by means of a wrench,
a spanner or another tool. Similarly, the hexagonal proximal end
158 of the inner adapter 154 allows torque to be applied to the
inner adapter 154.
[0056] Releasable, rotational engagement between the driver and the
bone anchor may be accomplished in any of a variety of ways. In the
illustrated embodiment, the distal end the inner adapter 154 is
provided with at least one surface for cooperating with a
complimentary surface on the proximal end of the bone anchor 100,
for transmitting torque from the inner adapter 154 to the bone
anchor 100, to enable transmission of torque from the inner adapter
154 to locking cap 106. Similarly, the distal end of the outer
adapter 152 is provided with at least one surface for cooperating
with a complimentary surface on the proximal end of the bone anchor
100, for transmitted torque from the outer adapter 152 to the bone
anchor 100 to enable credible engagement between the bone anchor
100 and the vertebral body.
[0057] In one embodiment, the bone anchor 100, its connector 104,
its locking cap 106, and the inner adapter 154 are all provided
with a central axial lumen through which a guide wire 190 may
pass.
[0058] FIG. 3A is an enlarged view of the circled area in FIG. 2,
showing the proximal head 108 of the bone anchor 100 and the distal
ends of the outer adapter 152 and the inner adapter 154. The
connector 104 and the locking cap 106 are disposed within the head
108. In one embodiment, the connector 104 is spherical with an
aperture 110 extending therethrough, and a gap 112 in its
circumference, such that it is approximately C-shaped when viewed
along the central axis of the aperture 110. The aperture 110 is
adapted for the insertion of a linkage rod (not shown), and has a
diameter slightly larger than that of the linkage rod. One skilled
in the art will understand that the connector 104 can be provided
in a variety of suitable shapes.
[0059] In one embodiment, the connector 104 is seated on a race or
groove 114 within the head 108. The groove 114 is preferably
provided with a complementary surface to the spherical exterior
surface of the connector 104. The connector 104 may rotate on any
axis within the head 108 of the bone anchor (or bone screw) 100. A
locking cap 106 may be threaded into the head 108 to lock the
connector 104 against the linkage rod 200, by compressing the
groove 114, fixing the connector 104 within the head 108. The
bottom of the locking cap 106 may be provided with a concave
surface (not shown) which is complementary to the spherical
exterior surface of the connector 104.
[0060] A transverse portal 116 extends through the head 108 along
an axis approximately perpendicular to the central axis of the bone
anchor 100. While the aperture 110 of, the connector 104 and the
transverse portal 116 of the head 108 are illustrated as circular,
they may be of different shapes in other embodiments, depending
upon the cross sectional shape of the fixation rod (e.g. oval,
elliptical, rectangular, square, etc.). The diameter of the
transverse portal 116 is generally smaller than the outside
diameter of the uncompressed connector 104 but greater than the
inside diameter of the aperture 110. Before the locking cap 106 is
tightened, the connector 104 may rotate on any axis within the head
108 to accommodate different entrance angles for the fixation rod.
Thus the central axis of the aperture 110 and the central axis of
the transverse portal 116 may be coaxial or angularly offset.
[0061] In one embodiment, the threading of the locking cap 106 into
the head 108 compresses the connector 104, decreasing the width of
the gap 112 and reducing the cross sectional area of the aperture
110. This secures a linkage rod (not shown) extending through the
transverse portal 116 of the bone anchor 100 within the aperture
110. The tightening of the locking cap 106 into the head 108 also
fixes the rotational position of the connector 104 within the head
108.
[0062] FIG. 3B illustrates an alternate connector 104'. Similar to
the connector 104 described above, the connector 104' is provided
with an aperture 110' having a longitudinal axis and a gap 112'.
The spherical exterior surface of the connector 104' is provided
with one or two or three or more surface structures such as
projections or indentations 111. The indentations 111 receive
complementary surface structures such as projections provided
within the head 108 of the bone anchor 100 to limit the degree of
rotation of the connector 104' within the head 108. For example,
FIG. 3G illustrates an exemplary embodiment wherein the
complementary surface structure comprises a pin 101 that may be
laser welded or otherwise coupled to or integrally formed with the
screw head 108. As described above, the pin 101 interacts with the
indentation 111 to limit the degree of rotation of the connector
104' within the head 108. In one specific embodiment, the connector
104' is limited to about 30 degrees of rotation on any axis within
the head 108, from the longitudinal axis through the transverse
portal 116. In other embodiments, the connector 104' may be limited
to a range of up to about 60 degrees of rotation from the
longitudinal axis. In one embodiment, the connector 104' is limited
to no more than about 5 degrees or about 10 degrees of rotation on
any axis from the longitudinal axis.
[0063] In general, the rotation of the connector 104' is limited
such that the aperture will always be exposed through transverse
portal 116 to the linkage rod 200. As can be seen, for example, in
FIG. 4, below, the linkage rod 200 may be provided with a tapered
distal end 201. The tapered distal end 201 may be machined or
molded integrally with the linkage rod 200, or may be separately
formed and attached to the linkage rod 200. In one implementation,
the tapered end 201 may be a polymeric component such as nylon,
HDPE, PEBAX or other materials known in the art. The tapered tip
201 facilitates advance of the linkage rod 200 through aperture
110, by causing the connector 104 to pivot about its center of
rotation into alignment for receiving the linkage rod 200. In this
manner, the connector 104 will self align with the linkage rod 200
to accommodate any of a wide variety of angular relationships that
may be found in vivo.
[0064] FIG. 3C is similar to FIG. 3A above, and illustrates an
inner adapter 154' and a locking cap 106' according to another
embodiment. In one embodiment, the inner adapter 154' is provided
with a Torx distal end 158' which is adapted to engage a
complementary Torx opening 120' at the top of the locking cap 106'.
Any of a variety of complementary surface structures may be used,
as will be understood in the art in view of the disclosure
herein.
[0065] FIG. 3C illustrates a connector 104'' according to another
embodiment. Similar to the connectors 104 and 104' described above,
the connector 104'' is provided with an aperture 110'' and one or
more compressible gaps 112''. The gaps 112'' are provided with a
compressible material which compresses when the locking cap 106'
tightens the connector 104'' against the groove 114 within the head
108. Compressible material, including any of a variety of
compressible polymeric materials known in the medical device arts
can be used according to several embodiments of the present
invention. One skilled in the art will appreciate that other
suitable flexible or compressible materials may also be used. In
addition, any of a variety of metal (stainless steel, titanium,
etc.) connectors 104 may be configured such that the aperture 110
is moveable from a first, large cross-section, for receiving a
linkage rod 200 therethrough, to a second, reduced cross section
for locking the linkage rod 200 in place. This may be accomplished
by providing opposing components forming the side wall of the
connector 104 with any of a variety of interlocking structures such
as ramp and pawl ratchet structures, or sliding fit structures
which permit a reduction in the diameter in the aperture 110 under
compressive force from the locking cap 106.
[0066] In an alternate embodiment, portions or all of the connector
104 comprise a compressible media such as an open cell foam, closed
cell foam or solid compressible material. Structures comprising
polyethylene, PEEK, nylon, and other polymers known in the medical
arts may be utilized, depending upon the construction and desired
compressibility. In general, the combination of material and the
structure of the connector 104 is sufficient to allow angular
adjustment of the longitudinal axis of the aperture 110, to
accommodate various entrance angles of the linkage rod 200. After
the linkage rod 200 has been positioned within the aperture 110,
rotational and/or axial movement of a locking element such as
locking cap 106 functions to both prevent axial movement of the
linkage rod 200 within the aperture 110, as well as prevent further
angular adjustment of the longitudinal axis of the aperture 110
with respect to the longitudinal axis of the bone anchor 100.
[0067] FIGS. 3D-3F illustrate the connector 104'', the aperture
110'', the gaps 112'', and a compressible or foldable membrane or
link 115 in greater detail. FIG. 3D is an isometric view of the
connector 104''. FIG. 3E is a front plan view of the connector
104'' viewed along the central axis of the aperture 110''. FIG. 3F
is the corresponding side plan view. In the embodiment illustrated
in FIGS. 3D-3F, the compressible link is formed by grinding, laser
etching, molding or otherwise forming a recess such as a V-shaped
channel 113 that leaves a thin link 115 which folds flat when the
connector 104'' is compressed. One of ordinary skill in the art
will understand that compressible materials and structures can be
provided in a variety of suitable shapes and forms.
[0068] In one embodiment, the apertures 110' and 110'' have a
tendency to return to their original diameters even after the
connectors 104 and 104', respectively, are compressed by the
locking cap 106 against the groove 114 within the head 108. This
tendency results from the resiliency of the metal, alloy or other
material used to make the connectors 104 and 104'. The use of
compressible material, such as V-shaped channels 113 in the gaps
112'' of the connector 104'', reduces or eliminates this tendency
and may allow a linkage rod (not shown) to be more firmly secured
within the aperture 110''. One skilled in the art will understand
that the connectors 104 and 104' can be made from lower resiliency
materials which can also reduce or eliminate the tendency of
apertures 110' and 110'' to return to their original diameters.
[0069] As discussed above with reference to FIG. 2, in one
embodiment, the outer adapter 152 is adapted to engage the head
108, and the inner adapter 154 is adapted to engage the locking cap
106. In the illustrated embodiment, projections 156 on the distal
end of the outer adapter 152 are adapted to engage complementary
projections 118 on the head 108 of the bone anchor 100. The
hexagonal distal end 158 of the inner adapter 154 is adapted to
engage a complementary hexagonal opening 120 at the top of the
locking cap 106.
[0070] Although specific interlocking relationships between the
driver 150 and the bone anchor 100 are illustrated herein, the
present inventors contemplate a variety of modifications. For
example, the male-female relationship between the driver and the
implant may be reversed, for either or both of the inner adaptor
154 and outer adapter 152. In addition, each of the inner adapter
154 and outer adapter 152 is provided with a surface structure for
enabling rotational engagement with a corresponding component on
the implant. Although this may be conveniently executed using
corresponding hexagonal male and female components, any of a
variety of alternative structures may be utilized in which a first
surface on the inner adapter 154 or outer adapter 152 cooperates
with a second, complementary surface on the corresponding aspect of
the bone anchor 100, for allowing rotational engagement, followed
by axial decoupling.
[0071] In FIG. 4, the linkage rod 200 is shown positioned within
two adjacent bone anchors 100, and released from the insertion tool
250. The insertion tool 250 is provided for the insertion of the
linkage rod 200 into the bone anchors 100. The insertion tool 250
comprises an arm 252 and a handle 254. In the illustrated
embodiment, the arm 252 is curved to facilitate insertion of the
linkage rod 200 into the bone anchors 100 within a patient along a
curved tissue tract which passes through the aperture 110 of at
least each of a first bone anchor and a second bone anchor. A
central control line 256 (shown mostly in phantom) such as a torque
transmission tube, rod or cable extends through an axial lumen of
the insertion tool 250, and terminates at a control such as a knob
258 at the proximal end of the insertion tool 250. A screw (not
shown) threaded into a, tunnel 260 extending along a radius of the
knob 258 may be used to secure the control line 256 within the knob
258. The control line 256 is provided with a threaded distal tip
262. Rotating the knob 258 thus rotates the control line 256 and
its threaded distal tip 262 to engage or disengage the linkage rod
200.
[0072] In one embodiment, both the linkage rod 200 and the control
line 256 are provided with a central axial lumen for the passage
over a guide wire.
[0073] FIG. 5 is an enlarged view of the circled area in FIG. 4,
showing the distal end of the outer adapter 152, the bone anchor
100, the linkage rod 200, and the distal end of the arm 252 of the
insertion tool. The linkage rod 200 is shown fixed within the head
108 of the bone anchor 100.
[0074] The linkage rod 200 is provided with a hexagonal proximal
end 202 adapted to engage a complementary hexagonal socket (not
shown) in the distal end of the arm 252 of the insertion tool. In
some embodiments, alternative complementary surface structures may
be provided on the linkage rod 200 and the arm 252 to rotationally
fix their orientation with respect to one another. In the
illustrated embodiment, the hexagonal proximal end 202 is provided
with a dimple 204 adapted to engage a complementary nub (not shown)
within the hexagonal socket (not shown) in the distal end of the
arm 252 of the insertion tool. The dimple 204 and nub (not shown)
fix the axial orientation of the linkage rod 200 with respect to
the arm 252. The threaded distal tip 262 of the control line 256
may be threaded into a complementary threaded hole 206 in the
hexagonal proximal end 202 of the linkage rod 200, enabling the
linkage rod 200 to be detachably secured to the arm 252 of the
insertion tool. The threaded distal tip 262 may be threaded into
the threaded hole 206 by rotating the knob (not shown) at the
proximal end of the insertion tool. Unthreading the threaded distal
tip 262 from the threaded hole 206 allows the linkage rod 200 to be
released from the insertion tool 250.
[0075] In one embodiment, the outer adapter 152 is provided with an
opening 160 extending along a diameter for fluoroscopic or other
visualization of the rotational orientation of the outer adapter
152, to align the portal 116 of the bone anchor 100 engaged by the
outer adapter 152. Towards this end, the axis of the opening 160 is
preferably arranged at a right angle to the axis of the portal 116
as shown in FIG. 5. To visualize the axial position of the outer
adapter 152 and the bone anchor 100, the inner adapter 154 may be
temporarily retracted so that it does not block the opening 160. In
another embodiment a translucent marker may be installed in opening
160 for fluoroscopic or other visualization of the outer adapter
152.
[0076] Alternatively, any of a variety of other indicium of the
rotational orientation of the bone anchor 100 may be provided. For
example, the complementary surface structures between the proximal
end of the bone anchor 100 and the distal end of the insertion tool
250 may be configured to only allow coupling between the two
components in a predetermined rotational orientation. In this
construction, visual indicia may be provided on a portion of the
insertion tool 250 (e.g. "T" handle, painted or etched markings or
other indicium) which remains external to the patient, to allow
direct visual observation of the rotational orientation of the
longitudinal axis of the transverse portal 116.
[0077] FIG. 6 illustrates the described system from another angle.
The knob and its attached central cable have been removed for
clarity. The hexagonal socket 264 adapted to engage the hexagonal
proximal end 202 of the linkage rod 200, as described above, is
shown. The nub 266 adapted to engage the dimple (not shown) on the
hexagonal proximal end 202 of the linkage rod 200 is also
shown.
[0078] In several embodiments, the components of the bone anchor,
the linkage rod, the driver, and the arm of the insertion tool may
be made of titanium, stainless steel or any other suitable metals,
alloys, or material. The handle of the insertion tool is preferably
made of a suitable non-slip material. The selection of these
materials for the manufacture of the components and devices
described in the above embodiments would be known by those skilled
in the art.
[0079] Methods for the minimally invasive implantation of posterior
fixation hardware according to embodiments of the present invention
are disclosed in the context of a spinal fixation procedure with
reference to FIGS. 7-45. Additional details concerning the method
are disclosed in the copending patent applications incorporated by
reference previously herein. Although the methods and instruments
of the present invention can be utilized in an open surgical
procedure, the present invention is optimized in the context of a
percutaneous or minimally invasive approach. Thus, the method steps
which follow and those disclosed in the copending patent
applications incorporated by reference herein are intended for use
in a trans tissue approach. However, to simplify the illustrations,
the soft tissue adjacent the treatment site is not illustrated in
the drawings discussed below.
[0080] In FIGS. 7 and 8, a trocar 300 is inserted through a tissue
tract and into a vertebral body 310. The trocar 300 comprises a
sharp-tipped rod (not shown) attached to a proximal or top
half-handle 302. The sharp-tipped rod is arranged concentrically
within a cannula 304, which is attached to the bottom half-handle
306 of the trocar 300. The top half-handle 302 and the bottom
half-handle 306 of the trocar 300 are screwed together for initial
use, as shown in FIGS. 7-8. The trocar 300 is inserted through the
skin, muscle and other tissues of the patient into the vertebral
body 310.
[0081] The tip 308 of the sharp-tipped rod is visible in FIG.
16.
[0082] FIG. 9 shows the bottom half-handle 306 with the attached
cannula 304 embedded in the vertebral body 310. The top half-handle
(not shown) has been unscrewed and set aside from the bottom
half-handle 306. In FIG. 10, a guide wire 312 is inserted into the
vertebral body 310 via the bottom half-handle 306 and the cannula
304.
[0083] In FIG. 11, the bottom half-handle 306 and the cannula 304
are removed from the vertebral body 310. Preferably, the guide wire
312 remains in place in the vertebral body 310.
[0084] FIG. 12 shows the guide wire 312 in the vertebral body 310
after the bottom half-handle 306 and the cannula 304 are
removed.
[0085] FIGS. 13-14 show one embodiment of the invention in which an
inflatable tissue expander for enlarging the tissue tract is used.
In FIG. 13, a balloon catheter 314 carrying a balloon 316 is
advanced over the guide wire 312 towards the vertebral body 310. In
FIG. 14, the balloon 316 is inflated to dilate the tissues adjacent
the access pathway to the vertebral body 310. This provides an
enlarged path for the insertion of a sheath as described below.
[0086] In FIG. 15, a guide tube 322 is advanced over the guide wire
312 into the vertebral body 310. As shown in FIG. 16, in one
embodiment, the guide tube 322 may be approximately the same
diameter as the cannula 304 of the trocar 300, allowing the guide
tube 322 to be inserted into the opening in the vertebral body 310
created earlier by the trocar 300. The guide tube 322 acts as a
stable rail over which a tapered dilation cylinder 324 may be
advanced against the vertebral body 310.
[0087] In FIGS. 16-17, a tapered dilation cylinder 324 is advanced
over the guide tube 322 against the vertebral body 310. In one
embodiment, the tapered dilation cylinder 324 may be approximately
the same diameter as the inflated dilation balloon 316 discussed
above with reference to FIGS. 13-14. The tapered dilation cylinder
324 is used to occupy the path created by the dilation balloon, and
facilitates the insertion of a sheath. In an alternate sequence,
the dilation cylinder 324 is provided without a tapered distal end,
and is distally advanced into position directly over the inflatable
balloon.
[0088] In FIGS. 18-20, a sheath 320 is advanced over the tapered
dilation cylinder 324 against the vertebral body 310. The sheath
320 occupies the path created by the dilation balloon. Afterwards,
the guide tube 322 and the tapered dilation cylinder 324 are
removed. As shown in FIG. 20, the guide wire 312 preferably remains
in the vertebral body 310 after the placement of the sheath
320.
[0089] In FIGS. 21-23, a drill 330 having a rotatable distal tip
332 is advanced over the guide wire 312 and through the sheath 320.
The drill 330 drills an opening (not shown) in the vertebral body
310 adapted for the insertion of a bone anchor 100. Afterwards, the
drill 330 is removed. In FIGS. 24-25, the bone anchor 100 is
advanced over the guide wire 312 and through the sheath 320 towards
the vertebral body 310.
[0090] In FIGS. 24 and 25, a bone anchor 100 is advanced over the
wire 312 and through the sheath 320 into engagement with the
vertebral body 310. Although the insertion tool 250 is not
illustrated, the bone anchor 100 may be coupled to the insertion
tool 250 prior to the step of advancing the bone anchor 100 into
contact with the vertebral body 310.
[0091] FIGS. 26 and 27 show the outer adapter 152 and the inner
adapter 154 of the driver 150, as well as a bone anchor 100, with
the connector 104 and the locking cap 106 disposed within the head
108 of the bone anchor 100. The interrelation of these components
have been described in detail above with reference to FIGS. 2 and
3A. The outer adapter 152 illustrated in FIGS. 26-28 additionally
comprises a pivot hole 153 which extend through a diameter of the
outer adapter 152. The pivot hole 153 is adapted for the attachment
of a guide wire insertion device 400 described in further detail
below. In FIG. 28, these components are shown arranged over a guide
wire 190.
[0092] In FIG. 28, the driver 150 (comprising the outer adapter 152
and the inner adapter 154) is advanced over the guide wire 312
until the driver 150 engages the bone anchor 100. In FIGS. 29 and
30, torque is applied to the outer adapter 152 to screw the bone
anchor 100 into the vertebral body 310. In FIG. 31, the driver 150
is removed, leaving the bone anchor 100 in place, with the
longitudinal axis of the portal 116 aligned approximately parallel
with the longitudinal axis of the spine. The sheath 320, discussed
above with reference to FIGS. 18-25, while not shown in the steps
discussed with reference to FIGS. 28-31, may nonetheless be used to
shield the driver from adjacent tissue in these steps, as will be
understood by those skilled in the art.
[0093] In FIG. 32, a second bone anchor 340 has been inserted into
another vertebral body 350. While bone anchors 100 and 340 are
shown inserted into adjacent vertebral bodies 310 and 350,
respectively, the system and methods for minimally invasive spinal
fixation according to the embodiments of the present invention are
also applicable to nonadjacent vertebral bodies. For example, a
first bone anchor may be positioned in a first vertebral body as
has been described above. A second bone anchor may be positioned in
a second vertebral body, spaced apart from the first vertebral body
by one or more intervening third vertebral bodies. The first and
second bone anchors may thereafter be connected by the implantation
of a linkage rod 200. Alternatively, a third bone anchor may be
positioned in a third vertebral body, positioned in between the
first and second vertebral bodies to produce, for example, a three
level fusion system as will be discussed.
[0094] FIG. 33 shows an overview of the guide wire insertion device
400 according to one embodiment of the invention. The guide wire
insertion device comprises a handle 410 and a hollow access needle
450. The handle 410 is detachably joined to the outer adapter 152
of the driver 150. The handle 410 is forked at its proximal end
412. Each fork is provided with a pivot pin 414, which engages the
pivot hole 153 (FIG. 28) of the outer adapter 152. The forked
proximal end 412 of the handle 410 may be spread slightly to allow
the pivot pins 414 to engage the pivot hole 153. The handle 410
swings on its pivot pins 414 at the pivot hole 153 of the outer
adapter 152 of the driver 150 to insert the access needle 450
through the transverse portal 116 of the bone anchor 100.
[0095] A hollow access needle 450 is attached to the distal end 416
of the handle 410. In one embodiment, the access needle 450 is
disposed within an opening 418 at the distal end 416 of the handle
410. A screw (not shown) may be threaded through a screw hole 420
at the distal end 416 of the handle 410 to tighten the access
needle 450 within the opening 418. The lengthwise position of the
access needle 450 within the opening 418 is therefore adjustable to
allow the access needle 450 to be aimed through the transverse
portal 116 of the bone anchor 100. In one embodiment, the access
needle 450 may be aimed such that it passes through the transverse
portal 116 at a point lower (towards the threads 102 in FIG. 2)
than the center of the transverse portal 116 because obstructions
encountered during the in vivo insertion of the access needle 450
may deflect the needle 450 towards the inside of its curvature and
the center of the transverse portal 116.
[0096] In several embodiments, the sharp, tapered distal end 452 of
the access needle 450 terminates at an opening 454. In one
embodiment, the access needle 450 is provided with threaded
proximal end 456, the purpose of which is described in further
detail below.
[0097] FIG. 34 illustrates a flexible obturator 500 of the guide
wire insertion device 400 according to one embodiment. The
obturator 500 comprises a tubing 502, a threaded cap 504 on its
proximal end and a plug 506 on its distal end. The tubing 502 is
sized such that it fits snugly within the hollow access needle 450
and occupies the length of its lumen. The cap 504 can be made with
a threaded luer connector which may be tightened onto the threaded
proximal end 456 of the access needle 450. The plug 506 may be
formed from an adhesive, for example, Loctite 3104, etc. The
obturator 500 occupies the lumen of the access needle 450, and
minimizes the collection of tissue or other matter within the
access needle 450 as it is advanced through the patient.
[0098] FIG. 35 shows a first guide wire insertion device 400 joined
to a first outer adapter 152 engaging a first bone anchor 100 and a
second guide wire insertion device 400' joined to the outer adapter
152' engaging a second bone anchor 340. In one embodiment, both
handles 410 and 410' are pivoted with respect to outer adapters 152
and 152' to advance access needles 450 and 450' through the
patient's tissues and towards the transverse portals 116 of bone
anchors 100 and 340, respectively. FIG. 35 also shows an obturator
500 according to one embodiment being inserted into the access
needle 450 of the guide wire insertion device 400 as described
above with reference to FIG. 34. Preferably, the obturator 500 is
inserted into the access needle 450 and threaded onto its threaded
proximal end 456 before the access needle 450 is inserted into the
patient. Likewise, another obturator 500 may be inserted into the
access needle 450'.
[0099] In one embodiment of the present invention, the guide wire
insertion device 400 additionally comprises a guide wire snare or
capture device 530, illustrated in FIG. 36. The guide wire capture
device 530 comprises an inner tubing 532 located coaxially within
an outer tubing 534. The inner tubing 532 is provided with an inner
half-cone 536 and the outer tubing 534 is provided with an outer
half cone 538. The inner half-cone 536 may be furled and retracted
within the outer tubing 534. Likewise, the outer half-cone 536 may
be furled to ease its insertion into and navigation through the
lumen of the hollow access needle 450. Inner half-cone 536 may be
rotationally oriented with respect to outer half-cone 538 to form
the conical funnel 540 of the guide wire capture device 530, as
illustrated in FIG. 37. When a guide wire contacts the conical
funnel 540 of the guide wire capture device 530, the guide wire is
directed into the lumen 542 of the inner tubing 532. The guide wire
capture device 530 also additionally comprises a handle 544 in the
illustrated embodiment.
[0100] In FIG. 38, the access needle 450 has been advanced through
the transverse portal 116 of bone anchor 100, and access needle
450' has been advanced through the transverse portal 116 of bone
anchor 340. The guide wire capture device 530 is inserted through
the lumen of the access needle 450, and its conical funnel 540 is
deployed. A guide wire 368 is inserted through the lumen of the
access needle 450' and advanced towards the conical funnel 540 of
the guide wire capture device 530. When the guide wire 368 contacts
the conical funnel 540, the guide wire 368 is directed into the
lumen 542 of the inner tubing 532 of the guide wire capture device
530.
[0101] In FIG. 39, the guide wire 368 is advanced through the lumen
542 of the inner tubing 532 until it extends past the handle 544 of
the guide wire capture device 530 Various methods of inserting
guide wires are known in the art and the invention is not limited
to the methods disclosed herein. Instead, any method of inserting a
guide wire known to those skilled in the art may be used in
accordance with the present invention. Following placement of the
guide wire 368, the first insertion device 400 and second insertion
device 400' may be removed.
[0102] A flexible or curved bone drill (not shown) may be advanced
along the guide wire 368 to clear a path between the transverse
portals 116 of bone anchors 100 and 340. In one embodiment, the
bone drill arm carrying the drill bit is provided with a certain
degree of flexibility to allow it to travel along the arcuate
course of the guide wire 368. In another embodiment, the curvature
the bone drill arm carrying the drill bit is matched to the
curvature of the linkage rod 200 to ensure that the path cleared
between transverse portals 116 of bone anchors 100 and 340 fits the
linkage rod 200. The bone drill is removed from the guide wire 368
after a path has been cleared between transverse portals 116 of
bone anchors 100 and 340.
[0103] In FIG. 40, a linkage rod 200 and its insertion tool 250 are
shown arranged over the guide wire 368. The linkage rod 200 and
insertion tool 250 are described above with reference to FIGS. 4-6.
The linkage rod 200 and insertion tool 250 in the embodiment
illustrated in FIG. 40 are provided with slightly different
indexing features than the linkage rod and insertion tool described
with reference to FIGS. 4-6. Referring again to FIG. 40, the
linkage rod 200 is provided with one or more bumps 220 on its
hexagonal proximal end 202. The bumps 220 are complementary with
one or more holes 280 at the distal end of the insertion tool 250.
In FIG. 40, the linkage rod 200 is detached from the insertion tool
250. The attachment of the linkage rod 200 to the insertion tool
250 is described above with reference to FIGS. 4-6.
[0104] In FIG. 41, the insertion tool 250 is used to advance the
linkage rod 200 over the guide wire 368 towards the bone anchors
100 and 340. While the linkage rod 200 is inserted from a rostral
or sacral approach (tail-to-head) in the illustrated embodiment, it
may also be inserted from a caudal approach (head-to-tail) in
another embodiment.
[0105] In FIG. 42, the linkage rod 200 is inserted through the
respective connectors 104 within bone anchors 100 and 340. The
connector 104 within the bone anchor 100 is described above with
reference to FIGS. 2-3. In FIGS. 43-44, the inner adapter 154 of
the driver 150 is used to tighten the locking cap 106 within the
bone anchor 340, fixing the linkage rod 200 within the bone anchor
340, as described above with reference to FIGS. 2-3. The outer
adapter 152 of the driver 150 engages the head of bone anchor 340
to prevent it from rotating as the locking cap is tightened. The
engagement between the bone anchor 340 and the driver 150 is
described above with reference to FIGS. 1-3 in the context of bone
anchor 100.
[0106] In FIG. 44, the driver 150 (comprising the outer adapter 152
and the inner adapter 154) is withdrawn from the bone anchor 340.
The locking cap 106 in the bone anchor 100 is similarly tightened,
fixing the linkage rod 200 within the bone anchor 100.
[0107] In FIG. 45, the insertion tool 250 is released from the
linkage rod 200. The attachment and detachment of the linkage rod
200 to and from the insertion tool 250 is discussed above with
reference to FIGS. 4-6. Afterwards, the driver 150, the sheath 320
and the guide wire 368 are removed from the patient.
[0108] FIG. 46 illustrates the percutaneously assembled in place
prosthesis resulting from the procedure described above, comprising
the bone anchors 100, 340 and the linkage rod 200.
[0109] FIG. 47 illustrates a three level prosthesis comprising an
additional bone anchor inserted into an additional adjacent
vertebral body, to provide a three level spinal fusion.
[0110] Referring to FIGS. 48 and 49, there is illustrated an
alternate implementation of the invention. FIG. 48 illustrates a
side elevational view of a modified linkage rod 200. Linkage rod
200 in FIG. 48 may be the same general dimensions and configuration
as the linkage rods disclosed previously herein, except as
described below. In all of the linkage rods disclosed herein, the
linkage rod 200 comprises an elongate body 401 extending between a
proximal end 402 and a distal end 404. The length of the body 401
in a device intended for use in a human adult one level lumbar or
lumbar-sacral fusion, will generally be in the range from about 30
mm to about 90 mm. A linkage rod 200 intended for a two level
fusion in the same environment will generally have a length within
the range of from about 50 mm to about 110 mm.
[0111] In an embodiment of the body 401 having a circular cross
sectional configuration, the diameter of the body 401 will
generally be in the range of from about 3 mm to about 8 mm. In one
embodiment, the diameter of the body 401 in a two level fusion
device is about 6.35 mm. In general, the cross sectional area of
the body 401, which may be expressed as a diameter in a circular
cross sectional implementation, may be varied depending upon the
desired structural integrity of the finished implant.
[0112] The distal end 404 of the body 401 may be provided with a
distal opening 408 to a central guidewire lumen, not illustrated.
The distal end 404 may also be provided with tapered tip 406 as has
been previously discussed. In general, the tapered tip 406 may
facilitate navigation through the tissue tract, as well as
introduction of the body 401 into the bone anchor. Tapered tip 406
may be integrally formed with the body 401, or attached thereto in
a subsequent manufacturing step.
[0113] The body 401 is generally provided with a preformed curve,
such that it forms a portion of an arc as illustrated. In certain
implementations of the invention, the arc has an approximately
constant radius of curvature along the length the body 401. The
radius of curvature of body 401 is generally in excess of about 19
cm, and, in many embodiments, within the range of from about 8 cm
to about 30 cm. In one implementation of the invention, intended
for a two level fusion, the overall length of the body 401 is about
65 mm, the diameter is about 6.35 mm, and the radius of curvature
is about 19 cm.
[0114] The radius of curvature of the body 401 may be equal or
approximately the same as the radius of curvature of the hollow
access needle 450 in the guidewire insertion device 400 discussed
previously. Thus, the radius may be approximately equal to the
distance between the access needle 450 and the pivot point 414,
which is also equal to the effective lever arm length of the handle
410. This facilitates introduction of the linkage rod 200 along the
same curved tissue tract used by or created by the access needle
450.
[0115] The linkage rod 200 illustrated in FIG. 48, unlike the
embodiments previously illustrated herein, includes a distinct
distal locking surface 410 formed by a discontinuity in the outer
profile of the body 401. In the illustrated embodiment the distal
locking surface 410 is in the form of an increase in the cross
sectional area of the body 401, such as a spherical or curved
enlargement of the profile of the body 401. This distal locking
surface 410 is adapted to cooperate with a modified bone anchor,
illustrated in FIG. 49.
[0116] FIG. 49 is an enlarged, explored view of the proximal end of
the bone anchor and distal end of a driver tool as illustrated in
FIG. 3A, except that the connector 104 has been omitted from the
embodiment illustrated in FIG. 49. Instead, the distal locking
surface 410 is adapted for insertion through the transverse portal
116 and positioning within the proximal head 108. The locking cap
106 may be threadably distally advanced into the head 108, to
compress against the distal locking surface 410 and lock the bone
anchor with respect to the linkage rod throughout any of a variety
of angular orientations, as had been discussed previously. For this
purpose, the distal wall of the chamber within the head 108 may be
provided with a complimentary curved surface for cooperating with
the distal locking surface 410. Similarly, the distal surface on
the locking cap 106 may be concave in the distal direction, to
increase the surface area of contact between the locking cap 106
and the distal locking surface 410.
[0117] A similar locking configuration may be used in connection
with the proximal bone anchor, and the proximal locking surface
412. Proximal locking surface 412 is carried by an axially moveable
tubular collar 414. In the illustrated embodiment, the collar 414
comprises a generally tubular body axially movably carried by the
body 401 of the linkage rod 200. The proximal locking surface 412
comprises a spherical, semi-spherical, curved or other enlargement
in the cross-sectional area collar 414, to provide a locking
surface which may be useful throughout a variety of angular
orientations as has described. One or two or three or four more
axially extending slots 416 may be provided on the proximal lock,
to facilitate compression of the lock from a slideable orientation
to a locked orientation in which it is compressed against the body
401. In the illustrated embodiment, two or more axially extending
slots extend in a proximal direction from the distal end of the
lock.
[0118] In use, the linkage rod 200 is advanced distally along a
guidewire, through a tube, or otherwise through the first and
second bone anchors. With the distal locking surface 410 positioned
within the proximal head 108 of the distal bone anchor, the locking
cap 106 of the distal bone anchor is tightened to lock the linkage
rod 200 with respect the distal bone anchor. The proximal lock is
thereafter axially distally advanced along the insertion tool
and/or linkage rod 200, until the proximal locking surface 412 is
positioned within the head 108 of the proximal bone anchor. The
locking cap 106 of the proximal bone anchor is tightened, to lock
the proximal locking surface 412 against the body 401.
[0119] The proximal lock may be distally advanced along the
insertion tool and/or linkage rod 200 in any of a variety of
manners, such as by distally advancing a pusher sleeve which is
axially movably carried on the insertion tool.
[0120] In one embodiment, the transverse portal 116 of the proximal
bone anchor is provided with a proximal opening having a first
diameter and distal opening having a second, smaller diameter. The
outside diameter of proximal locking surface 412 is dimensioned
relative to the portal 116 such that it can pass through the
proximal opening on the transverse portal 116 but cannot pass
distally through the distal opening of the transverse portal 116.
In this manner, the clinician can perceive tactile feedback once
the proximal lock has been distally advanced into position within
the head 108. This same construction can be utilized on the distal
bone anchor as well, such that distal advancement of the distal
locking surface 410 may be accomplished until the positive stop is
felt by the clinician as the distal locking surface 410 is seated
within the head 108. The driver tool can be provided with indicium
of the rotational position of the bone anchor.
[0121] In all of the foregoing embodiments, the insertion tool may
be provided with a curved distal region, having a radius of
curvature which approximates the radius of curvature of the linkage
rod, described above. Thus, in one embodiment both the linkage rod
200 and the distal portion of the insertion tool are provided with
a curve having a radius of approximately 12 cm. This further
facilitates introduction of the linkage rod and insertion tool
along a curved tissue tract, while minimizing trauma to surrounding
tissue, as the linkage rod 200 is navigated through the first and
second bone anchors.
[0122] The foregoing construction also allows the percutaneous
access site for the introduction of the linkage rod 200 to be
predetermined distance from the longitudinal axis of the driver
150. For example, in one implementation of the guidance system, the
radius of curvature of the curved needle 450 is approximately 9 cm.
This enables the percutaneous access site to be approximately 8
centimeters from the percutaneous entry site for the driver 150.
The transdermal access site for the linkage rod is preferably no
more than about one radius away from the driver 150. This allows
minimization of the length of the tissue tract, and thus minimizes
the access induced trauma to surrounding tissue.
[0123] Not all of the steps described above are critical to the
minimally invasive implantation of posterior fixation hardware.
Accordingly, some of the described steps may be omitted or
performed in an order different from that disclosed. Further,
additional steps may be contemplated by those skilled in the art in
view of the disclosure herein, without departing from the scope of
the present invention.
[0124] The present inventors contemplate the interchangeability of
and recombination of various structural and method elements in the
foregoing description. For example, the guidewire may be positioned
through portals of adjacent bone anchors utilizing either the
procedures disclosed in the copending patent applications
previously incorporated by reference herein. Alternatively, the
guidewire may be positioned utilizing the pivotable guidance system
disclosed herein. As a further alternative, a tubular sleeve may be
advanced over the guidewire and through the portals on bone anchors
100, with the guidewire thereafter removed. The linkage rod 200 may
thereafter be advanced through the tubular sleeve.
[0125] The linkage rod 200 may be advanced utilizing the manual
insertion tool 250, as disclosed herein. Alternatively, the linkage
rod 200 may be releasably connected to the distal end of a curved
pivotable arm 450, using releasable connection structures disclosed
elsewhere herein. In this manner, the pivotable insertion system
such as that illustrated in FIG. 33 can be utilized to insert the
linkage rod 200 through one or more apertures 116 in one or more
bone anchors 100.
[0126] The various materials, methods and techniques described
above provide a number of ways to carry out the invention. Of
course, it is to be understood that not necessarily all objectives
or advantages described may be achieved in accordance with any
particular embodiment described herein. Thus, for example, those
skilled in the art will recognize that the components of the system
may be made and the methods may be performed in a manner that
achieves or optimizes one advantage or group of advantages as
taught herein without necessarily achieving other objectives or
advantages as may be taught or suggested herein.
[0127] Although the present invention has been described in terms
of certain preferred embodiments, other embodiments of the
invention including variations in dimensions, configuration and
materials will be apparent to those of skill in the art in view of
the disclosure herein. In addition, all features discussed in
connection with any one embodiment herein can be readily adapted
for use in other embodiments herein. The use of different terms or
reference numerals for similar features in different embodiments
does not imply differences other than those which may be expressly
set forth. Accordingly, the present invention is intended to be
described solely by reference to the appended claims, and not
limited to the preferred embodiments disclosed herein.
* * * * *