U.S. patent application number 14/336728 was filed with the patent office on 2014-11-06 for minimally invasive spinal stabilization system.
The applicant listed for this patent is Industrial Technology Research Institute. Invention is credited to Chang-Jung Chiang, Shih-Jui Han, Huang-Chien Liang, Chun-Jen Liao, Fon-Yih Tsuang, Yang-Hwei Tsuang.
Application Number | 20140330314 14/336728 |
Document ID | / |
Family ID | 47354285 |
Filed Date | 2014-11-06 |
United States Patent
Application |
20140330314 |
Kind Code |
A1 |
Tsuang; Yang-Hwei ; et
al. |
November 6, 2014 |
MINIMALLY INVASIVE SPINAL STABILIZATION SYSTEM
Abstract
A spinal fixation assembly including a pedicle rod and pedicle
screws which secure the pedicle rod to the spine. Each pedicle
screw includes a head configured to receive a portion of the
pedicle rod, and a threaded portion extending from a first end of
the head and configured to engage a vertebra. The pedicle rod is
secured to the head by a fastener. The head includes a breakaway
region that defines a location in which at least a first portion of
the head can be easily separated from the remainder of the head
upon application of sufficient force to the first portion.
Inventors: |
Tsuang; Yang-Hwei; (Taipei
City, TW) ; Liao; Chun-Jen; (Taipei City, TW)
; Liang; Huang-Chien; (Hsinchu City, TW) ; Han;
Shih-Jui; (Taichung City, TW) ; Tsuang; Fon-Yih;
(Taipei City, TW) ; Chiang; Chang-Jung; (Changhua
County, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Industrial Technology Research Institute |
Hsinchu |
|
TW |
|
|
Family ID: |
47354285 |
Appl. No.: |
14/336728 |
Filed: |
July 21, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13161686 |
Jun 16, 2011 |
8784424 |
|
|
14336728 |
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Current U.S.
Class: |
606/267 |
Current CPC
Class: |
A61B 2090/037 20160201;
A61B 17/7002 20130101; A61B 17/7085 20130101; A61B 17/7091
20130101; A61B 17/7032 20130101; A61B 17/8863 20130101; A61B
17/7089 20130101; A61B 17/1671 20130101; A61B 17/1757 20130101 |
Class at
Publication: |
606/267 |
International
Class: |
A61B 17/70 20060101
A61B017/70 |
Claims
1. A minimally invasive spinal fixation assembly configured to
provide relative fixation of a series of vertebrae, comprising: a
pedicle rod; pedicle screws, each screw including a head configured
to receive a portion of the pedicle rod, the head having a first
end and an open second end opposed to the first end, the head being
generally tubular and formed of a single piece having a first
opening that extends from the open second end along an axial
direction of the head to a location adjacent to, and spaced apart
from, the first end, and a second opening on an opposed side of the
head relative to the first opening, the second opening extending
from the open second end along an axial direction of the head to a
location adjacent to and spaced apart from the first end, the first
and second openings being diametrically aligned so as to form a
transverse through channel through the head, and a threaded portion
extending from the first end of the head and configured to engage
one of the vertebrae, a fastener including external threads
configured to engage corresponding threads formed on an inner
surface of the head; and a cap configured to engage the open second
end of the head, wherein the pedicle rod is a hollow tube and is
secured to the head by the fastener, and the head includes a
breakaway region between the first end and the open second end, the
breakaway region including a portion of the head that is formed to
be relatively structurally weak compared to the remaining portions
of the head so as to define a location in which at least a first
portion of the head can be easily separated from the remainder of
the head upon application of sufficient force to the first portion
of the head.
2. The minimally invasive spinal fixation assembly of claim 1,
wherein the pedicle rod is configured to engage a suture.
3. The minimally invasive spinal fixation assembly of claim 1,
wherein the cap includes a hollow cylindrical body having an open
end dimensioned to receive therein the open second end of the head,
and an opposed end, the opposed end including a central cap
opening, wherein the open end includes an interior surface having
an annular protrusion, and the head includes a circumferential
groove adjacent to the open second end configured to engage the
annular protrusion whereby the cap can be releasably secured to the
open second end of the head.
4. The minimally invasive spinal fixation assembly of claim 3,
further comprising a U-shaped pedicle screw stabilizer including a
grip portion; an annular base extending from one side of the grip
portion and having a diameter substantially equal to the diameter
of the head; and a pair of legs extending from one side of the
annular base, the legs configured to conform to the shape of, and
be received within, the respective first and second openings of the
head.
5. The minimally invasive spinal fixation assembly of claim 4,
wherein the central cap opening is configured to receive
therethrough the legs of the U-shaped pedicle screw stabilizer.
6. The minimally invasive spinal fixation assembly of claim 5,
wherein a portion of the edge of the cap corresponding to the
central cap opening is formed having a shape that conforms to a
cross sectional shape of a leg.
7. The minimally invasive spinal fixation assembly of claim 1,
further comprising a pedicle screw breaking device configured to be
received within an interior space of the head and to facilitate
separation of the open second end of the head from the first end of
the head along a prescribed circumferential breakaway line provided
on the head between the first end and the open second end of the
head.
8. The minimally invasive spinal fixation assembly of claim 1,
further comprising a suture guide assembly including a suture
leader configured to retain a suture, and a guide tool including
pivotably-joined first and second arms, the first arm terminating
at a first end in a male suture guide, the second arm terminating
at a first end in a female suture guide, wherein the male and
female suture guides are configured to permit the suture leader to
be passed from the male suture guide to the female suture guide
upon movement of the first and second arms between an open position
in which the male and female suture guides are spaced apart and a
closed position in which the male and female suture guides are
adjacent.
9. The minimally invasive spinal fixation assembly of claim 8,
wherein the suture leader comprises a tip shaped to facilitate
insertion into the female suture guide, and an opening formed
adjacent to the tip.
10. The minimally invasive spinal fixation assembly of claim 8,
wherein the first and second arms are configured to be received
within the hollow interior space of the head and pass through the
first and the second opening.
11. The minimally invasive spinal fixation assembly of claim 1,
wherein the series of vertebrae includes at least two
vertebrae.
12. The minimally invasive spinal fixation assembly of claim 1,
wherein the spinal fixation assembly is configured to be
implemented via non-continuous wound sites having a length
generally corresponding to a cross sectional dimension of the
head.
13. A pedicle screw for use in spinal fixation, comprising: a head
including a first end, an open second end opposed to the first end;
a threaded body extending from the first end; and a removable cap
configured to close the head second end for stabilizing the open
second end, the removable cap being a hollow cylinder having a
sidewall including a transverse through channel, wherein the head
is tubular, and is formed of a single piece having a first opening
that extends from the open second end along an axial direction of
the head to a location adjacent to, and spaced apart from, the
first end, and a second opening on an opposed side of the head
relative to the first opening, the second opening extending from
the open second end along an axial direction of the head to a
location adjacent to and spaced apart from the first end, the first
and second openings being diametrically aligned so as to form a
transverse through channel through the head, the head having a
breakaway region located between the first end and the open second
end, the breakaway region including a portion of the head that is
formed to be relatively structurally weak compared to the remaining
portions of the head so as to define a location in which at least a
portion of the open second end can be easily separated from the
head upon application of sufficient force to the open second
end.
14. The pedicle screw of claim 13, wherein the distance between the
first end and the open second end of the head is in a range from 40
mm to 120 mm.
15. The pedicle screw of claim 13, wherein the distance between the
first end and the open second end of the head is in a range from 50
mm to 80 mm.
16. The pedicle screw of claim 13, wherein the portion of the head
that is formed to be relatively structurally weak includes a
circumferential groove, the circumferential groove configured to
provide a prescribed breakaway line along which at least a portion
of the open second end can be easily separated from the head
17. The pedicle screw of claim 13, wherein the force is a twisting
force about a longitudinal axis of the head.
18. The pedicle screw of claim 13, wherein the head includes a
circumferential groove adjacent to the open second end configured
to engage a corresponding annular lip provided on an interior
surface of the removable cap.
19. The pedicle screw of claim 13, wherein the first end of the
head is configured to permit poly-axial rotation of the threaded
body relative to the head.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 13/161,686, filed on Jun. 16, 2011. The content of the prior
application is hereby incorporated by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] Each year 13 million people see a doctor for chronic back
pain, which is estimated to cause 2.4 million Americans to be
chronically disabled. About 25 percent of people who have back pain
have a herniated disk. In the US, about 450 cases of herniated disk
per 100,000 require surgery such as a discectomy.
[0003] Referring to FIG. 1, a discectomy (FIG. 1(a)) is performed
when the intervertebral disc 8 has herniated or torn and has not
responded to a more conservative treatment. When a surgeon performs
a discectomy, it is usually performed through an incision in the
patient's back at a location corresponding to the problem area of
the spine 2. Muscles and ligaments are moved aside to expose the
offending disc 8. The surgeon then uses a variety of surgical
instruments to first separate the vertebrae 4 sandwiching the disc
8, and then remove the disc 8 completely. After a discectomy is
performed, the spinal column at the operation site is separated to
approximate the height of the removed disc (FIG. 1b), and then an
artificial disk may be placed in the separation. Spinal fixation
devices (FIG. 1(c)) are used to stabilize and/or align the spine 2
during the healing process following such procedures. In some
cases, clinicians fill the separation with the implantation of
autologous bone to achieve fusion (fusion is illustrated in FIG.
1(d)) to restore stability of the spine 2. Alternatively,
discectomy may be followed by spinal fusion, or other procedure
that may be deemed necessary to strengthen and straighten the
spinal canal.
[0004] Although a discectomy is frequently performed using
minimally invasive devices and procedures, it is still challenging
to provide the minimally invasive spine stabilization that is
required following this and other spinal procedures. Improved
minimally invasive spinal fixation devices and methods are required
to minimizing patient risk, trauma, recovery time, and to reduce
the overall costs of such procedures.
SUMMARY OF THE INVENTION
[0005] In some aspects, a minimally invasive spinal fixation
assembly is provided. The minimally invasive spinal fixation
assembly is configured to provide relative fixation of a series of
vertebrae, and includes a pedicle rod and pedicle screws, each
screw including a head configured to receive a portion of the
pedicle rod, and a threaded portion extending from a first end of
the head and configured to engage one of the vertebrae. The
assembly further includes a fastener including external threads
configured to engage corresponding threads formed on an inner
surface of the head. The pedicle rod is secured to the head by the
fastener, and the head includes a breakaway region. The breakaway
region includes a portion of the head that is formed to be
relatively structurally weak compared to the remaining portions of
the head so as to define a location in which at least a first
portion of the head can be easily separated from the remainder of
the head upon application of sufficient force to the first
portion.
[0006] The minimally invasive spinal fixation assembly may include
one or more of the following features: The pedicle rod is
configured to engage a suture. The pedicle rod is a hollow tube.
Each pedicle screw includes the first end, and an open second end
opposed to the first end. The head is generally tubular, and is
formed of a single piece having a first opening that extends from
the second end along an axial direction of the head to a location
adjacent to, and spaced apart from, the first end, and a second
opening on an opposed side of the body relative to the first
opening, the second opening extending from the second end along an
axial direction of the body to a location adjacent to and spaced
apart from the first end. The first and second openings are
diametrically aligned so as to form a transverse through channel
through the head. A cap may be included that is configured to
engage the second end of the pedicle screw head. The cap includes a
hollow cylindrical body having an open end dimensioned to receive
therein a second end of the head, and an opposed end, the opposed
end including a central cap opening. The first end of the cap
includes an interior surface having an annular protrusion, and the
head includes a circumferential groove adjacent to the second end
configured to engage the annular protrusion whereby the cap can be
releasably secured to the second end of the head.
[0007] The minimally invasive spinal fixation assembly may include
one or more of the following additional features: A U-shaped
pedicle screw stabilizer may be included. The stabilizer includes a
grip portion, an annular base extending from one side of the grip
portion and having a diameter substantially equal to the diameter
of the head, and a pair of legs extending from one side of the
annular base, the legs configured to conform to the shape of, and
be received within, the respective first and second openings of the
of the head. A cap may be included that is configured to close the
second end of the pedicle screw head and including a cap opening
through which the legs of pedicle screw stabilizer can be received.
A portion of the edge of the cap corresponding to the cap opening
is formed having a shape that conforms to a cross sectional shape
of a leg. The minimally invasive spinal fixation assembly further
includes a pedicle screw breaking device configured to be received
within an interior space of the pedicle screw head and facilitate
separation of the second end of the head from the first end of the
head along a prescribed circumferential breakaway line provided on
the head between the first and second ends of the head.
[0008] The minimally invasive spinal fixation assembly may include
one or more of the following additional features: A suture guide
assembly may be included. The suture guide assembly includes a
suture leader configured to retain a suture, and a guide tool
including pivotably-joined first and second arms. The first arm
terminates at a first end in a male suture guide, and the second
arm terminates at a first end in a female suture guide. The male
and female suture guides are configured to permit the suture leader
to be passed from the male suture guide to the female suture guide
upon movement of the first and second arms between an open position
in which the male and female suture guides are spaced apart and a
closed position in which the male and female suture guides are
adjacent. The suture leader comprises a tip shaped to facilitate
insertion into the female suture guide, and an opening formed
adjacent to the tip. The first and second arms are configured to be
received within the hollow interior space of the pedicle screw head
and pass through the first and second openings. The series of
vertebrae includes at least two vertebrae. The spinal fixation
assembly is configured to be implemented via non-continuous wound
sites having a length generally corresponding to a cross sectional
dimension of the head.
[0009] In some aspects, a pedicle screw for use in spinal fixation
is provided. The pedicle screw includes a head including a first
end, and an open second end opposed to the first end, and a
threaded body extending from the first end. The head is tubular,
and is formed of a single piece having a first opening that extends
from the second end along an axial direction of the head to a
location adjacent to, and spaced apart from, the first end, and a
second opening on an opposed side of the body relative to the first
opening, the second opening extending from the second end along an
axial direction of the body to a location adjacent to and spaced
apart from the first end. The first and second openings are
diametrically aligned so as to form a transverse through channel
through the head.
[0010] The pedicle screw may include one or more of the following
features: The distance between first and second ends of the head is
in a range from 40 mm to 120 mm. The distance between first and
second ends of the head is in a range from 50 mm to 80 mm. The head
includes breakaway region located between the first and second
ends, the breakaway region including a portion of the head that is
formed to be relatively structurally weak compared to the remaining
portions of the head so as to define a location in which at least a
portion of the second end can be easily separated from the head
upon application of sufficient force to the second end. The
breakaway region includes a circumferential groove positioned
between the first end and a midpoint between the first and second
ends, the circumferential groove configured to provide a prescribed
breakaway line along which at least a portion of the second end can
be easily separated from the head upon application of sufficient
force to the second end. The force is a twisting force about a
longitudinal axis of the head. The pedicle screw further includes a
removable cap configured to close the head second end, wherein the
head includes a circumferential groove adjacent to the second end
configured to engage a corresponding annular lip provided on an
interior surface of the cap. The first end of the head is
configured to permit poly-axial rotation of the threaded body
relative to the head.
[0011] In some aspects, a suture guide assembly is provided. The
suture guide assembly includes a suture leader configured to retain
a suture, and a guide tool including pivotably-joined first and
second arms. The first arm terminates at a first end in a male
suture guide, and the second arm terminates at a first end in a
female suture guide. The male and female suture guides are
configured to permit the suture leader to be passed from the male
suture guide to the female suture guide upon movement of the first
and second arms between an open position in which the male and
female suture guides are spaced apart and a closed position in
which the male and female suture guides are adjacent.
[0012] The suture guide assembly may include one or more of the
following features: The suture leader includes a conical tip, and
an eye protruding from the conical tip. The male suture guide
includes a cylindrical stem configured to releasably engage the
suture leader eye, and the female suture guide includes cylindrical
shell configured to releasably engage the suture leader conical
tip, and the guide tool is configured so as to support the male and
female suture guides so that the conical tip at least partially
received within the shell when the guide tool is in the closed
position. The shell includes a first shell opening through which
the suture leader is inserted into the shell, and a second shell
opening through which the suture leader is withdrawn from the
shell. The second shell opening has a shape that generally conforms
to the shape of the suture leader. The first shell opening has a
dimension that is smaller than the dimension of the widest portion
of the suture leader. The suture leader includes a conical tip, and
when the guide tool is moved from the open position to the closed
position, the conical tip of the suture leader is driven through
the first shell opening, and is prevented from being retracted from
the shell via the first shell opening. The first and second arms
are angled. The arm angle is between 90-180 degrees.
[0013] In some aspects, a minimally invasive method for achieving
spinal stabilization is provided. The method includes the following
method steps: Implanting a pedicle screw into each vertebra of a
portion of the spine to be stabilized, each pedicle screw implanted
through a unique incision. Subcutaneously threading a suture
through a corresponding passage provided in each pedicle screw.
Withdrawing a leading end of the suture from the body through an
access incision. Subcutaneously threading a hollow pedicle rod
through the passage of each pedicle screw by passing the pedicle
rod along the suture through the access incision into the body and
through each respective passage such that the pedicle rod spans all
implanted pedicle screws. Securing the pedicle rod relative to each
pedicle screw.
[0014] The method may include one or more of the following
additional steps and/or features: At least two pedicle screws are
implanted. The implanting step includes providing an incision
through the skin overlying the vertebra, where the incision length
generally corresponds to the outer diameter of the pedicle screw;
forming a hole in the pedicle; inserting a Kirshner pin at the
desired implantation location; dilating soft tissues in the
vicinity of the Kirshner pin; implant the pedicle screw in the hole
of the vertebra by passing it along the Kirshner pin and screwing
the pedicle screw into the hole in the vertebra; and removing the
Kirshner pin from the incision, leaving the pedicle screw in place.
The step of threading a suture includes linking the pedicles screws
by subcutaneously threading a suture through each respective
pedicle screw head. The step of linking the pedicle screws includes
the following: passing a suture through the interior space of the
pedicel screw head from a second end of the pedicle screw head to a
first end of the screw head along a longitudinal axis of the
pedicle screw head, the first end being closer to the spine than
the second end; guiding the suture from the first end of the
pedicle screw in a direction generally parallel to a longitudinal
axis of the spine to the first end of an adjacent pedicle screw;
withdrawing the suture from the adjacent pedicle screw head; and
repeating the passing and guiding steps for the adjacent pedicle
screw and any remaining pedicle screws. Prior to the step of
threading a hollow pedicle rod, the following step is performed:
adjusting the curvature of the rod ex vivo and prior to insertion
into the body by bending the rod to correspond to the curvature of
a line defined by upper surfaces of the implanted pedicle screws.
The securing step further comprises engaging exterior threads of a
set screw with corresponding threads provided on an interior
surface of the pedicle screw such that the pedicle rod is retained
between the set screw and the surface the pedicle screw. The
pedicle screw includes a head including a first end, and a second
end opposed to the first end, a threaded body extending from the
first end, and an annular breakaway region located between the
first and second ends. The breakaway region includes a portion of
the head that is formed to be relatively structurally weak compared
to the remaining portions of the head so as to define a location in
which at least a portion of the second end can be easily separated
from the head upon application of sufficient force to the second
end. The securing step further comprises engaging exterior threads
of a set screw with corresponding threads provided on an interior
surface of the pedicle screw head such that the pedicle rod is
retained on the interior surface of the pedicle screw head at a
location between the first end and the breakaway region. The method
further comprises the steps of removing a portion of the pedicle
screw by applying a force to the portion such that the portion
breaks away from the remainder of the pedicle screw along a
predetermined breakaway line. The force is a twisting force or a
compressive force. The hollow pedicle rod is at least 10 cm in
length, and is inserted into the body through the access incision
of up to about 1 cm in length. Each pedicle screw is implanted
through a unique incision of up to about 1 cm in length.
[0015] The minimally invasive spinal fixation device described
herein can be implanted through a series of small incisions of
about 1 cm or less along the region of the spine to be supported.
Advantageously, this device avoids several drawbacks associated
with many conventional spinal fixation devices. In particular, the
minimally invasive spinal fixation device described herein does not
need a large incision of 10 cm or more through which a spinal
fixation cage can be implanted. As a result, patient risks of blood
loss, infection, and/ or tissue damage which can lead to lower back
weakness can be avoided. In addition, recovery time and negative
side effects are minimized.
[0016] The spinal fixation device includes pedicle screws that
secure a pedicle rod to the respective vertebra within the region
of the spine to be stabilized. Each pedicle screw includes a
U-shaped head and a threaded portion that extends from one end of
the head. The head is formed of an elongated single body having a
circumferentially-extending, annular breakaway region. In fact, the
pedicle screw head has a sufficient length to protrude upward out
of the incision so as to permit manipulation during implantation,
and after implantation is complete, the excess length of the
pedicle screw head can be broken off along the pre-defined
breakaway region. Since the pedicle screw head is manufactured as a
single body, no preassembly of the screw head is required prior to
implantation as is required in some conventional pedicle screws,
and there is no risk of malfunction or loss of small components
into the wound site during implantation. Due to the fact that the
pedicle screw head includes the breakaway region, removal of the
excess portions of the head after implementation is a very simple
and quick procedure.
[0017] The method of implanting the spinal fixation device employs
a novel method of threading a suture through a series of implanted
pedicle screws, and then using the suture to link the pedicle
screws using a pedicle rod. This method is advantageous since it
can be accomplished performed subcutaneously and submuscularly via
minimal incisions. Moreover, the disclosed method permits a larger
region of the spine to be fixed than some known minimally invasive
spinal fixation methods. For example, the method permits a series
of four or more adjacent vertebra to be fixed.
[0018] Modes for carrying out the present invention are explained
below by reference to an embodiment of the present invention shown
in the attached drawings. The above-mentioned object, other
objects, characteristics and advantages of the present invention
will become apparent from the detailed description of the
embodiment of the invention presented below in conjunction with the
attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The invention description below refers to the accompanying
drawings, of which:
[0020] FIG. 1(a)-1(d) illustrate procedures for repairing a
herniated disk;
[0021] FIG. 2 is a perspective view of a minimally invasive spinal
fixation system implanted on a series of four adjacent
vertebrae;
[0022] FIG. 3 is a side view of a pedicle rod used in the spinal
fixation system of FIG. 2;
[0023] FIG. 4 is is an exploded perspective view of a pedicle screw
assembly including a pedicle screw as used in the spinal fixation
system of FIG. 2, a cap and a stabilizer tool;
[0024] FIG. 4a is a cross-sectional view of the pedicle screw
assembly of FIG. 4, as seen across line 4a-4a;
[0025] FIG. 5 is a perspective view of a fastener used in the
spinal fixation system of FIG. 2;
[0026] FIG. 6a is an exploded view of a breaking tool used during
implantation of the spinal fixation system of FIG. 2;
[0027] FIG. 6b is an enlarged view of the portion of the breaking
tool marked as 6b in FIG. 6a;
[0028] FIG. 6c illustrates the breaking tool in use separating the
pedicle head into two portions;
[0029] FIG. 7 is a perspective view of a guide tool assembly;
[0030] FIG. 8(a)-8(e) are alternative embodiments of a male suture
guide of the guide tool assembly of FIG. 7;
[0031] FIG. 9(a)-9(d) are alternative embodiments of a female
suture guide of the guide tool assembly of FIG. 7;
[0032] FIG. 10 is a side view of an awl used during implantation of
the spinal fixation system of FIG. 2;
[0033] FIG. 11 is a detail view of the tip of the awl of FIG.
10;
[0034] FIGS. 12-14 illustrate use of the awl to form a pedicle
screw hole and facilitate insertion of a Kirshner pin into a
vertebra;
[0035] FIG. 15 illustrates dilation of soft tissues in the vicinity
of the Kirshner pin;
[0036] FIG. 16 illustrates that the Kirshner pin remains in place
after completion of dilation and removal of the dilation tubes;
[0037] FIG. 17 illustrates insertion of the pedicle screw into the
body over the Kirshner pin;
[0038] FIGS. 18-19 illustrate implantation of the pedicle screw in
the vertebra;
[0039] FIG. 20 illustrates repeating the pedicle screw implantation
steps for several adjacent vertebrae;
[0040] FIG. 21 illustrates using a device to align the pedicle
screw heads;
[0041] FIGS. 22-29 illustrate using the guide tool assembly to
thread a suture subcutaneously and submuscularly between respective
first ends of the implanted pedicle screw heads;
[0042] FIGS. 30-31 illustrate using the exposed ends of the pedicle
screws as a template for preshaping the pedicle screw rod to the
shape of the spine prior to implantation;
[0043] FIG. 32 illustrates threading the pedicle rod over the
suture and across the respective implanted pedicle screw heads;
[0044] FIG. 33 illustrates assembling a cap and stabilizer on the
pedicle screw head;
[0045] FIG. 34 illustrates insertion of a fastener through the cap
and stabilizer to secure the pedicle rod to the pedicle screw;
[0046] FIG. 35 illustrates repeating the step shown in FIG. 34 for
each pedicle screw;
[0047] FIGS. 36-37 illustrate using the breaking tool to break off
a dorsal portion of each pedicle screw head;
[0048] FIG. 38 illustrates the implanted spinal fixation system;
and
[0049] FIG. 39 is a perspective view of another embodiment of a
guide tool assembly.
DETAILED DESCRIPTION THE INVENTION
[0050] Referring to FIG. 2, a minimally invasive spinal fixation
system 20 used to stabilize a region of the spine 2 includes a
fixation rod 200 of sufficient length to extend across the
vertebrae 4 to be stabilized, pedicle screws 300 for anchoring the
fixation rod 200 to each corresponding vertebra 4, and a fastener
500 on each pedicle screw 300 to secure the pedicle rod 200 to the
pedicle screw 300. Each pedicle screw 300 is implanted in the
pedicle 6 of the corresponding vertebra 4 through a small skin
incision having a length generally corresponding to a cross
sectional dimension of the pedicle screw 300. In the illustrated
embodiment, for example, the incision has a length of 1 cm or less,
and the rod 200 is assembled with the pedicle screws 300 through a
separate skin incision of 1 cm or less, as discussed further
below.
[0051] Referring to FIG. 3, the fixation rod 200 is a structure
that is configured to engage a suture, where a suture is defined
herein as an elongated strand or fiber such as a thread or wire. In
the illustrated embodiment, the fixation rod 200 is a hollow tube,
including a first end 212, a second end 214 that is opposed to the
first end 212, and an interior passageway 210 that extends between
the first end 212 and the second end 214. In this embodiment, the
fixation rod 200 can receive a suture within the passageway
210.
[0052] The rod 200 is relatively long compared to its
cross-sectional dimension. For example, in the illustrated
embodiment, the rod 200 is cylindrical, and it has a diameter of
5.5 mm and an axial length that corresponds to the overall length
of the region of the spine 2 to be stabilized. For example, to
stabilize two adjacent vertebrae 4, the rod has a length of
approximately 60.0 mm. To stabilize a series of four adjacent
vertebrae 4, the rod has a length of approximately 150.0 mm. The
rod 200 is formed of an implantable material, and is formed of a
material of sufficient strength and stiffness to provide spinal
stabilization, while also being sufficiently malleable to permit
shaping of the rod curvature. For example, the rod 200 may be
formed of a titanium alloy such as Ti6Al4V.
[0053] Referring to FIG. 4, a polyaxial pedicle screw 300 is used
to anchor the pedicle rod 200 to each corresponding vertebra 4.
Each pedicle screw 300 is dimensioned to be inserted through a skin
incision of 1 cm or less and screwed into the pedicle of the
corresponding vertebra 4, which lies below the skin and underlying
muscle at a depth of about 5 cm for an average male. Toward this
end, each pedicle screw 300 includes an elongated head 302 and a
threaded tip 304.
[0054] The head 302 is generally tubular, and is formed of a single
piece. The head 302 includes a closed first end 306, and an open
second end 308 that is opposed to the first end 306. The head 302
is provided with a first axially-extending opening 310 that extends
from the second end 308 to a location adjacent to, and spaced apart
from, the first end 306. The head 302 is also provided with a
second axially-extending opening 312 on an opposed side of the head
302 relative to the first opening 310. Mirroring the first opening
310, the second opening 312 extends from the second end 308 to a
location adjacent to and spaced apart from the first end 306. The
first and second openings 310, 312 are diametrically aligned so as
to form a transverse through channel 316 through the head 302. As a
result, the head 302 is generally U shaped.
[0055] The head 302 is long in an axial direction relative to its
cross sectional dimension. For example, in the illustrated
embodiment, the distance d1 between the first end 306 and the
second end 308 is in a range from 4 cm to 12 cm, whereas it has a
diameter of about 1 cm. In other embodiments, the distance d1 may
be in a range of 5 cm to 8 cm.
[0056] The head 302 is provided with an annular breakaway region
318 that is located between the first end 306 and the second end
308. In the illustrated embodiment, the breakaway region 318 is
located between the first end 306 and a midpoint P between the
first and second ends 306, 308, or more specifically, at a location
about midway between the point P and the first end 306. As a
result, the head 302 is partitioned into two portions by the
breakaway region 318. A ventral portion 322 that extends between
the first end 306 and the breakaway region 318; and a dorsal
portion 324 that extends between the breakaway region 318 and the
second end 308. The breakaway region 318 is a region of the head
302 that is formed to be relatively structurally weak compared to
the remainder of the head 302 so as to define a circumferential
line along which the dorsal portion 324 can be easily separated
from the ventral portion 322 upon application of sufficient force
to the dorsal portion 324. In the illustrated embodiment, the
breakaway region 318 is a circumferentially-extending V-shaped
groove 320. In some embodiments, the spinal fixation system 20 may
include a screw breaking tool 800, described further below, that is
configured to provide a twisting force about a longitudinal axis of
the head 302 and thereby selectively separate the dorsal portion
324 from the ventral portion 322 at the groove 320. It will be
appreciated that although a bending force could also be applied to
the dorsal portion 324 to achieve separation, use of a twisting
force will be less damaging to surrounding tissues than a bending
force.
[0057] The interior surface of the ventral portion 322 is provided
with threads 326 configured to engage corresponding threads 508
provided on an outer surface 506 of a fastener 500, described
further below. In addition, a retention groove 332 is formed in the
outer surface of the head 302 at a location adjacent the second end
308. The retention groove 332 is dimensioned and positioned so as
to receive and retain a corresponding annular ridge 610 formed on
an inner surface of a screw cap 600, described further below.
[0058] The threaded tip 304 of the pedicle screw 300 extends
outward from the first end 306 of the head 302. More specifically,
the threaded tip 304 includes a base 342 that is supported within
the first end 306 of the head 302, and a shank 344 that extends
from the base. The first end 306 of the head 302 is configured to
permit three dimensional rotation of the threaded tip 304 relative
to the head 302. The shank 344 has outer threads and terminates at
an apex 346. In addition, the threaded tip 304 includes an axial
through hole 350 that opens at the base 342, extends through the
shank 344 and opens the apex 346.
[0059] Referring to FIG. 5, the fastener 500 is a cylindrical
member having external threads 508 formed on an outer surface 506.
The threads 508 are configured to engage corresponding threads 326
formed on an inner surface of the ventral portion 322 of the
pedicle screw head 302. In the illustrated embodiment, the fastener
500 is a set screw having a first end 502 that is configured to
receive a driving tool. For example, the end 502 includes a
hexagonal-shaped socket 510 suited for receiving a hex wrench, or
the shaped tip 892 of an actuator tool 850 (described below). In
use, the fastener 500 is secured to the ventral portion 322 of the
pedicle screw head 302 so as to retain the position of the fixation
rod 200 relative to the pedicle screw 300.
[0060] Referring again to FIG. 4, the spinal fixation system 20
further includes a removable screw cap 600 that is shaped and
dimensioned to be secured to the pedicle screw head second end 308,
to support and stabilize the head second end 308, and to serve as a
guide to direct a stabilizer tool 700 (described below) during
insertion of the stabilizer tool 700 into the hollow interior of
the pedicle screw 300 (described below). The screw cap 600 is a
hollow cylinder having an open first end 602, a closed second end
604 opposed to the first end 602, and a sidewall 606 extending
between the first end 602 and the second end 604. The open first
end 602 is dimensioned to receive the second end 308 of the pedicle
screw head 302 therein.
[0061] The screw cap sidewall 606 is provided with a first
axially-extending cap opening 612 that extends from the first end
602 to a location adjacent to, and spaced apart from, the second
end 604. The screw cap sidewall 606 is also provided with a second
axially-extending cap opening 614 on an opposed side of the
sidewall 606 relative to the first cap opening 612. Mirroring the
first cap opening 612, the second cap opening 614 extends from the
first end 602 to a location adjacent to and spaced apart from the
second end 604. The first and second cap openings 612, 614 are
diametrically aligned so as to form a transverse through channel
616 through the screw cap 600. When the screw cap 600 is disposed
on the second end 308 of the pedicle screw head 302, the screw cap
transverse through channel 616 can be aligned with the pedicle
screw through channel 316.
[0062] The screw cap 600 includes an inwardly-protruding annular
ridge 610 formed on an interior surface of the sidewall 606 that is
sized and positioned to permit engagement with the cap retention
groove 332 formed on the pedicle screw second end 608. The
protruding ridge 610 extends about the inner circumference of the
sidewall, and cooperates with the retention groove 332 to maintain
the screw cap 600 on the pedicle screw second end 308.
[0063] In addition, the second end 604 of the screw cap 600
includes a central opening 618. The central opening 618 has an
irregular shape, including a generally circular central portion 622
and an elongated portion 624 positioned along each opposed side of,
and intersecting, the central portion 622. In the illustrated
embodiment, the central portion 622 is shaped and dimensioned to
permit passage of surgical tools through the screw cap 600 and into
the interior space of the pedicle screw head 302. In addition, the
elongated portions 624 are shaped and dimensioned to receive leg
portions 712 of the stabilizer tool 700 when the stabilizer tool
700 is inserted into the hollow interior of the pedicle screw 300
(described below). It should be noted that the elongated portions
624 of the central opening 618 are located along a periphery of the
second end 604 so as to overlie respective first and second cap
openings 612, 614. This configuration ensures that the leg portions
712 of the stabilizer tool 700 are aligned with respective first
and second openings 310, 312 of the pedicle screw head 302 after
assembly of the pedicle screw 300, cap 600 and stabilizer tool 700,
as discussed further below.
[0064] The spinal fixation system 20 further includes the
stabilizer tool 700 which is a hollow cylinder including an open
first end 702, a closed second end 704 opposed to the first end
702, and a sidewall 706 extending between the first end 702 and the
second end 704. The sidewall 706 is formed having an outer diameter
that corresponds to that of the pedicle screw head 302 and
diametrically opposed openings 708, 710 that extend axially from
the first end 702 to a location adjacent the second end 704. The
openings 708, 710 provide the sidewall 706 with a generally
U-shape, including leg portions 712 that are joined by an annular
base portion 714. A grip portion 716 is disposed between the base
portion 714 and the second end 704 that has a larger outer diameter
than the base portion 714, and includes surface features such as
axially-extending grooves 718 to improve gripability. In addition,
the second end 704 includes a central opening (not shown in FIG. 4)
through which tools can be inserted.
[0065] When the stabilizer tool 700 is assembled with the cap 600
and pedicle screw 300, the leg portions 712 reside within the
openings 310, 312 of the pedicle screw head 302 (see FIG. 4a). The
stabilizer tool 700 is used to position the pedicle rod 200 within
the interior space of the pedicle screw head 302 during
implantation of the spinal fixation system 20. In addition, the
stabilizer tool 700 is used to maintain the position of the pedicle
rod 200 while the fastener 500 is used to secure the pedicle rod
200 to the ventral portion 322 of the pedicle screw head 302, and
to reinforce the dorsal portion 324 during separation of the dorsal
portion 324 from the ventral portion 322 after implantation, as
discussed further below.
[0066] Referring to FIGS. 6a-6c, the spinal fixation system 20
further includes the screw breaking tool 800 that is configured to
be received within the interior space of the pedicle screw head 302
and is used to remove the dorsal portion 324 of the pedicle screw
head 302 once the pedicle screw ventral portion 322 and pedicle rod
200 are correctly positioned and mutually fixed. The screw breaking
tool is 800 includes a sleeve 820 and a T-shaped actuator 850
shaped and dimensioned to be received within the sleeve 820 (FIG.
6a). The sleeve 820 is a hollow cylinder that includes an open
first end 802, a second end 804 opposed to the first end 802, and a
sidewall 806 extending between the first end 802 and the second end
804. A pair of slots 814 (only one slot 814 is shown) extend from
the first end 802 toward a mid portion of the sleeve 820. The slots
814 divided the first end 802 into two end portions 802a, 802b. A
grip region 810 is provided on the second end 804 that has a larger
outer diameter than the sidewall 806, and includes surface features
such as axially-extending grooves 818 to improve gripability. In
addition, the second end 804 includes a central opening 812 through
which tools, including the actuator 850, can be inserted. The axial
length of sleeve 820 is greater than that of an assembly of the
pedicle screw 300, cap 600 and stabilizer tool 700.
[0067] The actuator 850 includes a shank 854 having a first end 856
and a second end 858. A handle 852 is fixed to the second end 858,
giving the actuator its T-shape. The shank first end 856 includes a
flared portion 890, and a shaped portion 892 that extends coaxially
from the flared portion 890 (FIG. 6b). The shaped portion 892 has
an outer cross sectional dimension that is less than that of the
flared portion 890 and shank 854, and includes surface features
that enable it to engage the socket 510 of the fastener 500. For
example, in the illustrated embodiment, the shaped portion 892 is
hexagonal in cross-sectional shape so as to engage the hexagonal
socket 510 of the fastener 500. The flared portion 890 has an outer
dimension that is greater than that of the sleeve sidewall 806 and
the diameter of the interior space of the pedicle screw head 302.
When the actuator 850 is assembled within the sleeve 820 with the
flared portion 890 protruding beyond the sleeve first end 802, the
sleeve 820 can be inserted into the screw head 302, for example to
secure the fastener 500 to the screw head 302. By drawing the
actuator 850 upward so that at least a portion of the flared
portion 890 is disposed within first end of the sleeve 820, the
flared portion 890 causes the two end portions 802a, 802b to
slightly separate. By this action, the outer wall of the sleeve 820
is compressed against the inner wall of the pedicle screw head
dorsal portion 324. Due to frictional engagement of the sleeve 820
with the pedicle screw head 302, by rotating the actuator 850 about
its longitudinal axis, a twisting force is applied to the dorsal
portion 324 of the screw head 302. Upon application of sufficient
force, the dorsal portion 324 of the screw head 302 can be
separated from the ventral portion 322 along the breakaway line 318
(FIG. 6c).
[0068] Referring to FIG. 7, a suture guide assembly 900 is used to
implant the pedicle rod 200 within each respective pedicle screw
head 302, as discussed further below. The suture guide assembly 900
includes a guide tool 980 having a pair of elongated arms 982, 984
that are joined via a pivot pin 986 at a location between
respective arm first ends 988 and respective arm second ends 990.
The first end 988 of each arm 982, 984 is formed into a finger loop
992 to permit manual actuation of the tool, and the second end 990
of each arm 982, 984 is configured to hold a suture guide 940, 960.
During actuation, the arms 982, 984 of the guide tool 980 move in a
scissoring motion about the pin 986.
[0069] The first and second arms 982, 984 of the guide tool 980 are
each dimensioned to be received within the hollow interior space of
the pedicle screw head 302 and to extend along the axial length of
the pedicle screw head 302. Moreover, the guide tool 980 operates
in a scissoring motion in which the first arm 982 and the second
arm 984 move between an open position (shown in FIGS. 7 and 22-23)
in which the second ends 990 of the arms 982, 984 are spaced apart
a first distance, and a closed position in which the second ends
990 of the arms 982, 984 are spaced apart a second distance (shown
in FIG. 24), the first distance being greater than the second
distance. The first and second arms 982, 984 are dimensioned to
pass through the pedicle screw head first and second openings 310,
312 when the guide tool 980 is actuated while the guide tool 980 is
inserted in a pedicle screw 300, as discussed further below. In
some embodiments, the first and second arms 982', 984' can be
angled. For example, the arms 982', 984' may be angled midway
between the pivot pin 986' and the arms second ends 990', so that
the second ends 990' lie out of a plane defined by the finger loops
992' (FIG. 39). The arm angle may be in a range between 90-180
degrees.
[0070] The suture guide assembly 900 also includes a leader 920
that retains an end of a suture 1216 (not shown in FIG. 7), a male
suture guide 940 mounted on the first arm 982 of the guide tool
980, and a female suture guide 960 mounted on the second arm 984 of
the guide tool 980.
[0071] Referring to FIG. 7, detail A, the leader 920 includes a
conical tip 922 having an apex 926. In addition, the leader 920
includes an eyelet 924 protruding from the tip 922 on a side 928
opposite to the apex 926. The diameter of the eyelet 924 is small
relative to the diameter of the side 928. In use, a suture 1216 is
secured to the leader 920 using the eyelet 924, as discussed
further below.
[0072] The male suture guide 940 includes a base 946 that is
received in and supported by the second end 990 of the guide tool
arm 982, and a cylindrical stem 942 extending from an axial end of
the base 946. The stem 942 is configured to releasably engage the
leader eyelet 924. In particular, the stem 942 includes an axially
extending opening 948 dimensioned to receive the eyelet 924 in a
press fit manner. The stem 942 also includes a transverse opening
950 that extends through a diameter of the stem 942 in a direction
transverse to the axial opening 948 and intersects the axial
opening 948. Thus, when the eyelet 924 of the leader 920 is
received within the axial opening 948 with a suture 1216 attached
thereto, the suture 1216 passes freely along the transverse opening
950 without binding and a portion of the suture 1216 drapes outward
from the transverse opening 950.
[0073] Referring to FIG. 7, detail B, the female suture guide 960
includes a base 968 that is received in and supported by the second
end 990 of the guide tool arm 984, and a hollow cylindrical shell
962 extending from an axial end of the base 968. The shell 962 is
configured to receive the leader 920 from the male suture guide
940, and to releasably retain the conical tip 922 therein. In
particular, the shell 962 includes a first shell opening 966
through which the conical tip 922 of the leader 920 is inserted
into the hollow interior of the shell 962, and a second shell
opening 964 through which the leader 920 is withdrawn from the
shell 962. The first shell opening 966 is located on an axial end
of the shell 962, is generally circular in shape and has a
dimension that is smaller than the dimension of the leader side
928. The second shell opening 964 is located on a sidewall of the
shell 926, and has a shape that generally conforms to the size and
shape of the tip 922 of the leader 920. In the illustrated
embodiment, the second shell opening 964 includes a triangularly
shaped portion through which the leader 920, including the conical
tip 922, can be withdrawn from the shell 962.
[0074] In use, the suture leader is supported on a first arm 982 of
the guide tool 980, and particular is retained in the axial opening
948 of the stem 942 of the male suture guide 940. The male suture
guide 940 is configured to support the leader 920, and to transfer
the leader 920 to the female suture guide 960 upon movement of the
first arm 982 and the second arm 984 to the guide tool closed
position. In the closed position, the male suture guide 940 and
female suture guide 960 are touching or nearly touching. As a
result, the leader 920, which is disposed on a side of the male
suture guide 940 that faces the female suture guide 960, is pressed
into the female suture guide 960. In particular, as the guide tool
980 moves to the closed position, the tip 922 is inserted, apex 926
first, into the first shell opening 966. Although the first shell
opening 966 is small relative to the outer dimensions of the leader
end 928, the shell 962 is formed to be relatively structurally weak
so that the tip 922 of the leader 920 can pass through the first
shell opening 966. Due to the size differences between the first
shell opening 966 and the tip side 928, the leader 920 is prevented
from being withdrawn from the shell 962 through the first opening
966. The leader 920, housed within the shell 962 of the female
suture guide 960, is now retained on the second end 990 of the
second arm 984 of the guide tool 980, and moves with the second arm
984 when the guide tool 980 is opened. Thus, by using the guide
tool 980, a suture 1216 can be secured to the first arm 982 by
attaching a leader 920 to the male suture guide 940, and the suture
1216 can then passed to the second arm 984 via the female suture
guide 960 through a simple operation of the guide tool 980. Since
the guide tool arms 982, 984 are configured to fit within the
pedicle screw heads 302, and because the pedicle screw heads 302
each include axially-elongated side openings 310, 312, a suture
1216 can be passed subcutaneously and submuscularly between
adjacent pedicle screws 300 after implantation of the pedicle
screws 300 in the spine. This feature is important to the method of
using the system 20, as discussed further below.
[0075] Referring to FIGS. 8(a)-8(e), some examples of alternative
embodiment male suture guides 1340 are illustrated. For example, in
FIG. 8(a), the male suture guide 1340a may be formed integrally
with the suture leader, and includes a base 1346a that is
configured to be supported on the second end of the guide tool arm
982, the base 1346a including an opening 1342a to which a suture
can be secured. The male suture guide 1340a also includes a conical
tip 1322a to facilitate insertion into the corresponding opening of
the female suture guide 960. FIGS. 8(b) to 8(e) illustrate
additional alternative embodiments of the male suture guide, where
like reference numbers refer to like structures. In these
alternative embodiments, it can be seen that the base 1346 can be
formed having a larger outer diameter than the tip 1322 (FIG. 8(b))
or formed having a non-cylindrical shape (FIGS. 8(b), 8(d), 8(e)).
In addition, the tip 1322 is not limited to having a conical shape
(FIGS. 8(b), 8(c), 8(d)).
[0076] Referring to FIGS. 9(a)-9(d), examples of alternative
embodiment female suture guides 1360 are illustrated. For example,
in FIG. 9(a), the female suture guide 1360a includes a base 1362a
that is configured to be supported on the second end of the guide
tool arm 984. In this example, the base 1362a also serves as the
shell portion and includes a first shell opening 1366a through
which the leader tip 922, 1322 is inserted into the hollow interior
of the base 1362a, and a second shell opening 1364a through which
the leader 920 is withdrawn from the base 1362a. FIGS. 9(b) to 9(d)
illustrate additional alternative embodiments of the female suture
guide 1360, where like reference numbers refer to like structures.
In these alternative embodiments, it can be seen that the first
shell opening 1366 and second shell opening 1364 may be formed
having different shapes (FIGS. 9(b), 9(c), 9(d)), for example to
compliment a corresponding structure of the male suture guide
and/or facilitate insertion and/or extraction of the leader from
the female suture guide 1360.
[0077] Referring to FIGS. 10 and 11, an awl 1400 is used to prepare
each vertebra for implantation, as described further below. The awl
1400 includes an elongated shaft 1402 that terminates at one end in
a handle 1420 and at the other end with a cutting tip 1408. The
cutting tip 1408 has a drill portion 1416 on a leading end thereof,
and a tap portion 1414 disposed between the drill portion 1416 and
the shank 1402. In addition, an axially extending through hole 1418
that extends from the handle 1420 to the cutting tip 1408 is
dimensioned to receive a Kirshner pin 1200.
[0078] Referring to FIGS. 12-39, an example of a minimally invasive
method for achieving spinal stabilization using spinal fixation
system 20 will now be described.
[0079] In Step 1, a pedicle screw 300 is implanted into each
vertebra 4 of a portion of the spine 2 to be stabilized (FIGS.
12-20). Implantation of pedicle screws 300 includes the following:
[0080] Step 1a. Provide an incision through the skin 10 overlying
the vertebra 4. In general, the incision length corresponds to the
outer diameter of the pedicle screw 300, and may be slightly less
due to the pliability of skin. In the illustrated embodiment, the
pedicle screw 300 is approximately 1 cm in diameter, whereby an
incision of at most 1 cm is required to accommodate pedicle screw
300. [0081] Step 1b. Referring to FIG. 12, prepare the vertebra 4
to receive the pedicle screw 300 by forming a threaded hole in the
pedicle 6. An awl 1400 (described in co-pending U.S. application
Ser. Nos. 13/161,705 and 13/161,698 and incorporated by reference
herein) is inserted into the incision and is used to locate the
pedicle and form the threaded hole therein. Correct positioning is
verified using an imaging device such as a C-arm or fluoroscope.
[0082] Step 1c. Referring to FIG. 13, insert a Kirshner pin 1200
through the axial passageway 1418 of the awl and into the vertebra
4 at the desired implantation location. [0083] Step 1d. Referring
to FIG. 14, removal the awl 1400, leaving the pin 1200 in place.
[0084] Step 1e. Referring to FIGS. 15-16, insert a series of
dilation cannulas 1202, 1204 into the incision over the pin 1200,
starting with a relatively small-diameter cannula 1202, and each
successive cannula having a slightly larger outer diameter.
Although only two cannulas 1202, 1204 are shown, six to eight
cannulas may be used in order to dilate the skin 10, muscle and
other soft tissues in the vicinity of the pin 1200 and create space
for insertion of the pedicle screw 300 into the body (FIG. 15). The
pin 1200 is used to stabilize and direct each respective dilation
cannula 1202, 1204 during dilation. After dilation is completed,
the dilation cannulas 1202, 1204 are withdrawn, leaving the pin
1200 in place (FIG. 16). [0085] Step 1f. Referring to FIGS. 17-18,
implant the pedicle screw 300 in the pre-threaded drill hole of the
vertebra 4 by passing it along the pin 1200. Specifically, the
pedicle screw 300 is loaded onto the pin 1200 so that the pin 1200
is received within the shank axial through hole 350 and the
interior space of the pedicle screw head 302. The pin 1200 serves
to stabilize and direct the pedicle screw shank 344 so that the
threads 348 on the shank 344 engage with and are screwed onto the
drill hole threads. In the illustrated embodiment, a driving tool
is used to rotate the pedicle screw 300, screwing the pedicle screw
into the hole in the vertebra 4. As seen in the figure, when the
shank 344 is fully screwed into the vertebra 4, a portion of
pedicle screw head 302 protrudes through the incision outwardly
relative to the skin 10. [0086] Step 1g. Referring to FIG. 19,
remove driving tool and pin 1200 from the incision, leaving the
pedicle screw 300 in place. [0087] Step 1h. Referring to FIG. 20,
repeat the previous pedicle screw 300 implantation steps 1a-1g for
each vertebra 4 to be stabilized. In the illustrated embodiment,
four vertebrae 4 are to be stabilized, whereby a pedicle screw 300
is implanted in each of the four vertebrae 4 (300a, 300b, 300c,
300d).
[0088] Referring to FIG. 21, Step 2 includes aligning the
respective pedicle screw heads 302 using an alignment tool 1214 so
that the longitudinal axes of the screws 300 are parallel to each
other and vertically aligned. In FIG. 21, a reference frame is
defined in which an x axis corresponds generally to a longitudinal
axis of the spine 2 and is oriented horizontally, and a y axis
transverse to the x axis is oriented vertically and corresponds to
an anterior-posterior direction of the spine 2. In step 2, the
respective pedicle screw heads 302 are aligned so that the first
and second pedicle screw openings 310, 312 open along the x axis,
and thus the respective pedicle screw transverse openings 318 are
aligned with the x axis.
[0089] Step 3 includes linking the pedicles screws 300 by
subcutaneously threading a suture 1216 through the respective
pedicle screw heads 302. Linking the pedicle screws 300 includes
the following: [0090] Step 3a. Referring to FIGS. 22-23, use the
suture guide tool 980 to insert a suture 1216 into the cranial-most
pedicle screw 300a such that the suture leading end passes through
the interior space of the pedicel screw head 302 from the second
end 308 of the head to the first end 306 (e.g., along the y axis).
[0091] Step. 3b. Referring to FIGS. 24-25, actuate the guide tool
980 to guide the suture 1216 from the first end 306 of the
cranial-most pedicle screw 300a to the first end 306 of the
adjacent pedicle screw 300b along the x axis and generally parallel
to the longitudinal axis of the spine 2. In particular, the suture
1216 is transferred between adjacent pedicle screws 300a, 300b by
actuating the guide tool 980 from an open position to a closed
position, whereby the leader 920 is transferred from the male
suture guide 940 to the female suture guide 960 (FIG. 24). The
suture 1216 is then moved to the adjacent pedicle screw 300b by
actuating the suture guide to an open position (FIG. 25). [0092]
Step 3c. Referring to FIG. 26, the suture guide tool 980 is
withdrawn from the pedicle screw heads 302a, 302b, with the suture
1216 now linking the cranial-most pedicle screw 300a and the
adjacent pedicle screw 302b. At this time, the leader 920 is
transferred back to the male suture guide 940, in preparation for
repeating steps 3a and 3b for pedicle screws 300b and 300c. [0093]
Step 3d. Referring to FIG. 27, Steps 3a-c are repeated until the
first end 306 of each pedicle screw 300a, 300b, 300c, 300d is
serially linked subcutaneously and submuscularly via the suture
1216. Although the linking step is described as proceeding from the
cranial-most pedicle screw 300a to the caudal-most pedicle screw
300d, the method is not limited to this. For example, the method
can include proceeding from caudal-most to cranial-most pedicle
screw 300.
[0094] Step 4 includes withdrawing the suture leading end 1216a
from the body through a small access incision (1 cm or less)
located caudally with respect to the caudal-most pedicle screw
300d. Withdrawing the suture includes the following: [0095] Step
4a. Referring to FIGS. 28-29, a compass tool 1218 is provided that
facilitates withdrawal of the suture 1216 from the body. The
compass tool 1218 includes a base leg 1220 configured to hold the
suture leader 920 and a curved pivoting leg 1222 configured to
receive the suture leader 920, and to pivot relative to the base
leg 1220 about a pivot axis at one end of the base leg 1220. As
seen in FIG. 28, the base leg 1220 holds the suture leader 920
adjacent the pedicle screw 300d. In subsequent actions, the base
leg 1220 is inserted into the caudal-most pedicle screw 300d, and
the pivoting leg 1222 is rotated (clockwise in the figure) relative
to the base leg 1220 so as to pass through the access incision. As
a result, the suture leader 920 is moved from an end of the base
leg 1220 to an end of the pivoting leg 1222 in a manner similar to
that used within the suture guide assembly 900. The pivoting leg
1222 is then rotated (counterclockwise in the figure) relative to
the base leg 1220 to withdraw the suture 1200 from the access
incision (FIG. 29).
[0096] Referring to FIGS. 30 and 31, Step 5 includes providing a
pedicle rod 200. In particular, the pedicle rod 200 must be
provided in a length that is at least sufficient for the rod to
simultaneously span all implanted pedicle screws 300a-300d. In some
embodiments, the respective protruding second ends 308 of the
pedicle screws 300 may be used as a template to cut a length of rod
stock to the desired length (FIG. 30). In addition, the pedicle rod
200 is preformed to have a curvature (shown as a dashed line)
corresponding to the curvature of the spine 2. In particular, the
curvature of the pedicle rod 200 is adjusted ex vivo and prior to
insertion into the body by bending the rod 200 to correspond to the
curvature of a line defined by the upper surfaces of the second
ends 308 of the implanted pedicle screws 300 (FIG. 31).
[0097] Referring to FIG. 32, Step 6 includes subcutaneously and
submuscularly threading the sized- and shaped-pedicle rod 200 onto
the suture 1216 by passing the suture 1216 through hollow interior
passageway 210 of the pedicle rod 200.
[0098] Step 7 includes passing the pedicle rod 200 along the suture
1216 into the body and through each respective pedicle screw head
302 such that the pedicle rod 200 resides in the transverse passage
316 adjacent the first end 306 of each respective pedicle screw
head 302.
[0099] Step 8 includes removing the suture 1216 from the body,
leaving the pedicle rod 200 in position within the series of
pedicle screws 300.
[0100] Step 9 includes securing the pedicle rod 200 to each pedicle
screw 300. The following steps are used to secure the pedicle rod
200 to a pedicle screw: [0101] Step 9a. Referring to FIG. 33,
stabilize the pedicle rod 200 with respect to the pedicle screw 300
by securing the cap 600 to the pedicle screw head second end 308,
and then inserting the stabilizer tool 700 through the cap and onto
the pedicle screw head 302. When assembled, the stabilizer tool
legs 712 securely seat the pedicle screw rod 200 within the
interior space of the pedicle screw head 302 at the lowermost
aspect of the first and second openings 310, 312, and maintain the
rod 200 in that position during the subsequent step (9b). [0102]
Step 9b. Referring to FIG. 34, secure the pedicle rod 200 relative
to the pedicle screw 300 by using the actuator 850 to drive the set
screw 500 into the pedicle screw head 302 such that the exterior
threads 508 of the set screw 500 engage with corresponding threads
326 provided on the interior surface of the first end 306 of the
pedicle screw head 302. As a result, the pedicle rod 200 is
retained between the set screw 500 and first end 306 of the pedicle
screw 300. [0103] Step 9c. Referring to FIG. 35, repeat steps 9a
and 9b until the pedicle rod 200 is secured to each pedicle screw
300a-300d.
[0104] Step 10 includes removing the pedicle screw head dorsal
portion 324 from the remainder of the head 302 of each pedicle
screw. The removing step includes the following: [0105] Step 10a.
Referring to FIGS. 36-38, apply a twisting force to the dorsal
portion 324 using the breaking tool 800 such that the dorsal
portion 324 breaks away from the first end of the pedicle screw
along the annular breakaway region 318, and withdrawing the
separated dorsal portion 324 from the body.
[0106] Step 11 includes closure of all minimal incisions.
[0107] A selected illustrative embodiment of the invention is
described above in some detail. It should be understood that only
structures considered necessary for clarifying the present
invention have been described herein. Other conventional
structures, and those of ancillary and auxiliary components of the
system, are assumed to be known and understood by those skilled in
the art. Moreover, while a working example of the present invention
has been described above, the present invention is not limited to
the working example described above, but various design alterations
may be carried out without departing from the present invention as
set forth in the claims.
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