U.S. patent application number 13/799792 was filed with the patent office on 2014-09-18 for inserter for expanding an expandable interbody fusion device.
This patent application is currently assigned to SPINE WAVE, INC.. The applicant listed for this patent is SPINE WAVE, INC.. Invention is credited to Nicola Cullinan, Scott McLean, Spanky Allen Raymond.
Application Number | 20140277479 13/799792 |
Document ID | / |
Family ID | 51455113 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140277479 |
Kind Code |
A1 |
Raymond; Spanky Allen ; et
al. |
September 18, 2014 |
INSERTER FOR EXPANDING AN EXPANDABLE INTERBODY FUSION DEVICE
Abstract
An elongate inserter has a distal end releasably connected to an
expandable interbody fusion device and a proximal end including a
trigger actuator. The interbody fusion device comprises a superior
endplate and an inferior endplate that are movable in an expansion
direction relative to each other in the intradiscal space. The
inserter includes a lifting platform and an elevator that define
cooperatively engaging ramps and ramps surfaces that upon operation
of the trigger actuator cause the superior and inferior endplates
to move relatively away from each other. A driver is supported by
the inserter for pushing an insert into the expanded device between
the superior and inferior endplates.
Inventors: |
Raymond; Spanky Allen;
(Uniontown, OH) ; McLean; Scott; (Waterbury,
CT) ; Cullinan; Nicola; (Bethel, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SPINE WAVE, INC. |
Shelton |
CT |
US |
|
|
Assignee: |
SPINE WAVE, INC.
Shelton
CT
|
Family ID: |
51455113 |
Appl. No.: |
13/799792 |
Filed: |
March 13, 2013 |
Current U.S.
Class: |
623/17.16 |
Current CPC
Class: |
A61F 2/4611 20130101;
A61F 2/442 20130101; A61F 2/447 20130101; A61F 2/4603 20130101;
A61F 2002/30556 20130101; A61F 2/4455 20130101 |
Class at
Publication: |
623/17.16 |
International
Class: |
A61F 2/46 20060101
A61F002/46 |
Claims
1. An inserter for expanding an expandable spinal interbody fusion
device and inserting an insert therewithin, said device including a
superior endplate having an outer surface configured to contact a
first vertebral body of a spine and an inferior endplate movable
relative to said superior endplate in an expansion direction, said
inferior endplate having an outer surface configured to contact a
second opposing vertebral body of said spine, comprising: an
elongate barrel having a distal end and a proximal end, said distal
end being releasably attachable to said device and comprising a
trigger actuator at said proximal end, said barrel including at
said distal end a lifting platform for engaging said superior
endplate and an elevator for engaging said inferior endplate, said
lifting platform being movable translationally relative to said
elevator in a direction transverse to the direction of expansion of
said device to cause during such translational movement said
lifting platform to move away from said elevator in the direction
of expansion and thereby lift said lifting platform relative to
said inferior endplate and expand said device, one of said lifting
platform and said elevator being operably coupled to said trigger
actuator to cause said translational movement upon operation of
said trigger actuator, and said barrel movably supporting at least
one insert insertable upon operation of said trigger actuator into
said device between said superior endplate and said inferior
endplate after expansion of said device, said barrel supporting a
driver coupled to said trigger actuator for translational movement
relative to one of said lifting platform and said elevator, said
driver having a distal end defining a pushing surface for
engagement with a cooperative pushing surface on said insert.
2. The inserter of claim 1, wherein said lifting platform and said
elevator comprise cooperating ramps that upon relative translation
of said lifting platform and said elevator cause said ramps to
cooperatively engage and move said lifting platform and said
elevator relatively away from each other in the direction of
expansion.
3. The inserter of claim 2, wherein said lifting platform is
coupled to said trigger actuator for translational movement and
said elevator is attached to said barrel in a fixed position.
4. The inserter of claim 3, wherein said driver is coupled to said
trigger actuator for translational movement relative to said
elevator.
5. The inserter of claim 4, wherein said lifting platform includes
an upper surface for supporting said insert and a lower opposing
surface defining said cooperating ramps.
6. The inserter of claim 5, wherein said driver and said lifting
platform are coupled to said trigger actuator to move independently
upon operation of said trigger actuator.
7. The inserter of claim 6, wherein said driver and said lifting
platform are coupled to said trigger actuator to move independently
of each other upon operation of a single stroke of said trigger
actuator.
8. The inserter of claim 7, wherein said lifting platform is
coupled to said trigger actuator to move before movement of said
driver and cause said superior endplate to lift relative to said
inferior endplate.
9. The inserter of claim 8, wherein said lifting platform is
coupled to said trigger actuator to hold the position of said
superior endplate in a lifted position relative to said inferior
endplate during operation of said trigger actuator while said
driver is moved during such operation to push said insert at least
partially between said superior endplate and said inferior
endplate.
10. The inserter of claim 9, wherein said lifting platform is
coupled to said trigger actuator to retract said lifting platform
towards said elevator after said insert is positioned at least
partially between said superior endplate and said inferior
endplate, said driver being coupled to said trigger actuator to
advance said insert thereafter substantially fully between said
superior endplate and said inferior endplate.
11. The inserter of claim 10, wherein said lifting movement of said
lifting platform relative to said elevator, said translational
movement of said driver insert for pushing said insert into said
device and said retraction movement of said lifting platform
towards said elevator are effected in a single operational stroke
of said trigger actuator.
12. The inserter of claim 11, wherein said trigger actuator
comprises a linkage mechanism that substantially prevents
translational movement of said driver until the lifting movement of
said lifting platform is completed.
13. The inserter of claim 12, wherein said barrel movably supports
a further insert insertable upon operation of said trigger actuator
between said at least first insert and said inferior endplate.
14. An apparatus for use in spinal interbody fusion, comprising: an
expandable interbody fusion device including an inferior endplate
having an outer surface configured to contact a vertebral body of
the spine, a superior endplate having an outer surface configured
to contact an opposing vertebral body of said spine, said inferior
endplate and said superior endplate being movable relative to each
other in a direction of expansion, said device including at least
one insert insertable into said device between said inferior
endplate and said superior endplate upon expansion of said device;
and an elongate inserter having a distal end and a proximal end,
said distal end of said inserter being releasably attached to said
device, said inserter including an actuator at said proximal end,
said inserter comprising a lifting platform operably coupled to
said actuator for engaging and lifting one of said superior
endplate and an insert within said device, and a driver operably
coupled to said actuator to insert said at least one insert into
said device, said inserter including an elongate track linearly
supporting a plurality of inserts for sequential insertion into
said device one below the other.
15. The apparatus of claim 14, wherein said inserter comprises an
elevator at said distal end, said elevator having an upper surface
and a lower surface, said lower surface being in engagement with an
interior surface of said inferior endplate.
16. The apparatus of claim 15, wherein said lifting platform has a
lower surface, the lower surface of said lifting platform and the
upper surface of said elevator comprising cooperatively engaging
ramps.
17. The apparatus of claim 16, wherein said elevator is disposed in
a fixed position relative to said inferior endplate and said
lifting platform is coupled to said actuator for translational
movement relative to said elevator upon operation of said actuator
to cause said ramps to cooperatively engage and thereby move said
lifting platform and said elevator relatively away from each other
in the direction of expansion.
18. The apparatus of claim 14, wherein said actuator comprises a
trigger actuator including a handle and a bar linkage mechanism
pivotally coupled thereto.
19. The apparatus of claim 14, wherein said apparatus further
comprises a guide pin releasably connected to said device and
detachably connected to said inserter.
20. The apparatus of claim 14, wherein said at least one insert
comprises a locking structure to interlock said at least one insert
to said superior endplate upon insertion into said device.
21. The apparatus of claim 20, wherein said at least one insert
comprises a locking structure to interlock said at least one insert
to a subsequent insert inserted below said at least one insert.
22-25. (canceled)
26. A method of expanding an expandable spinal interbody fusion
implant, in situ, said device including an inferior endplate having
an outer surface configured to contact a vertebral body of the
spine, a superior endplate having an outer surface configured to
contact an opposing vertebral body of said spine, said inferior
endplate and said superior endplate being movable relative to each
other in a direction of expansion, comprising the steps of:
releasably attaching a distal end of an inserter to said device,
said inserter including an actuator at a proximal end thereof;
initially operating said actuator to cause said inferior endplate
and said superior endplate to move relative to each other in a
direction of expansion to expand said device; and inserting a first
insert movably supported by said inserter into said device after
expansion of said device between said inferior endplate and said
superior endplate; and then further operating said actuator to
cause said superior endplate and said first insert to move jointly
relative to said inferior endplate to further expand said device,
and after said further expansion sequentially inserting a second
insert movably supported by said inserter directly between said
first insert and said inferior endplate.
27. The method of claim 26, wherein said first insert and said
second inserts are supported linearly by said inserter immediately
adjacent each other, and wherein after said device is expanded in
the initial operating step said first insert is inserted directly
between said superior endplate and said inferior endplate.
28. The method of claim 27, further including the step of
determining whether said expanded device is capable of receiving a
further insert prior to insertion of said further insert between
said inferior endplate and said superior endplate.
29. The method of claim 28, wherein said determining step is
effected by tactile feedback through said actuator.
30. The method of claim 29, wherein said actuator comprises a
trigger actuator including a handle and a linkage mechanism, and
wherein the expansion of said device and the insertion of said at
least one insert into said expanded device is effected in a single
operational stroke of said trigger actuator.
31. A method of expanding an expandable spinal interbody fusion
implant, in situ, said device including an inferior endplate having
an outer surface configured to contact a vertebral body of the
spine, a superior endplate having an outer surface configured to
contact an opposing vertebral body of said spine, said inferior
endplate and said superior endplate being movable relative to each
other in a direction of expansion, comprising the steps of:
releasably attaching a distal end of an inserter to said device,
said inserter including an actuator at a proximal end thereof and
an elongate track therebetween supporting a plurality of inserts,
each insert having a thickness in the direction of expansion;
operating said actuator for the individual insertion of said
plurality of inserts, during said operation causing the inferior
endplate and the superior endplate to move apart relative to each
other in the direction of expansion independently of the insertion
of each insert and creating for each insert an incremental space in
the expanded device of dimension not less than the thickness of an
insert; and sequentially individually inserting said plurality of
inserts into a respectively created incremental space.
32. The method of claim 31, wherein a first incremental space is
created directly between said inferior endplate and said superior
endplate for the insertion of a first insert.
33. The method of claim 32, wherein a second incremental space is
created directly between said inferior endplate and said first
insert for the insertion of a second insert, said first insert and
said superior endplate having been moved jointly relative to said
inferior endplate upon the operation of said actuator.
34. The method of claim 33, further including the step of
determining whether said expanded device is capable of receiving a
third insert prior to insertion of said third insert between said
inferior endplate and said second insert as determined by tactile
feedback through said actuator.
Description
FIELD OF THE INVENTION
[0001] The subject invention relates generally to the field of
spinal implants and more particularly to an inserter for expanding
an expandable interbody fusion device and inserting an insert
therewithin.
BACKGROUND OF THE INVENTION
[0002] Spinal implants such as interbody fusion devices are used to
treat degenerative disc disease and other damages or defects in the
spinal disc between adjacent vertebrae. The disc may be herniated
or suffering from a variety of degenerative conditions, such that
the anatomical function of the spinal disc is disrupted. Most
prevalent surgical treatment for these conditions is to fuse the
two vertebrae surrounding the affected disc. In most cases, the
entire disc will be removed, except for a portion of the annulus,
by way of a discectomy procedure. A spinal fusion device is then
introduced into the intradiscal space and suitable bone graft or
bone substitute material is placed substantially in and/or adjacent
the device in order to promote fusion between two adjacent
vertebrae.
[0003] Certain spinal devices for achieving fusion are also
expandable so as to correct disc height between the adjacent
vertebrae. Examples of expandable interbody fusion devices are
described in U.S. Pat. No. 6,595,998 entitled "Tissue Distraction
Device", which issued on Jul. 22, 2003 (the '998 patent), U.S. Pat.
No. 7,931,688 entitled "Expandable Interbody Fusion Device", which
issued on Apr. 26, 2011 (the '688 patent), and U.S. Pat. No.
7,967,867 entitled "Expandable Interbody Fusion Device", which
issued on Jun. 28, 2011 (the '867 patent). The '998 patent, the
'688 patent and the '867 patent each discloses sequentially
introducing in situ a series of elongate inserts referred to as
wafers in a percutaneous approach to incrementally distract
opposing vertebral bodies to stabilize the spine and correct spinal
height, the wafers including features that allow adjacent wafers to
interlock in multiple degrees of freedom. The '998 patent, the '688
patent and the '867 patent are assigned to the same assignee as the
present invention, the disclosures of these patents being
incorporated herein by reference in their entirety.
[0004] One issue that has arisen regarding such interbody fusion
devices that use inserts or wafers to incrementally expand such
devices is the determination of when full expansion has been
achieved as a result of ligamentotaxis and no further inserts may
be inserted. It is therefore desirable for a surgeon to know when a
sufficient number of inserts has been introduced to stabilize the
spine and correct spinal height and whether any additional inserts
may be introduced.
[0005] Accordingly, there is a need for a method and instrument to
expand an expandable interbody fusion device and introduce inserts
therein and to determine when proper expansion of the device has
been achieved and no further inserts may be introduced.
SUMMARY OF THE INVENTION
[0006] It is an object of the invention to provide an inserter for
expanding an expandable spinal implant, such as an interbody fusion
device and to introduce inserts therein after the implant has been
expanded. It is a further object of the invention to also provide a
method whereby full expansion of the expandable device may be
determined in a manner such that a user may ascertain that no
additional inserts may be inserted.
DESCRIPTION OF THE FIGURES
[0007] FIG. 1 is a top perspective of an inserter in accordance
with one embodiment of the present invention releasably attached to
and expandable interbody fusion device, shown unexpanded.
[0008] FIG. 2 is an exploded perspective view of the distal end of
the inserter of FIG. 1.
[0009] FIG. 3 is an enlarged view of the exploded portion of FIG.
2.
[0010] FIG. 4 is a longitudinal cross-sectional view of the
inserter of FIG. 1.
[0011] FIG. 5 is a top perspective view of an insert used in an
expandable spinal interbody fusion device of the subject
invention.
[0012] FIG. 6 is a bottom perspective view of the insert of FIG.
5.
[0013] FIG. 7 is a partial perspective cross sectional view of the
inserter of FIG. 1 releasably attached to an expandable interbody
fusion device with a first insert of FIG. 5 having been inserted
therein.
[0014] FIG. 8a is a partial side perspective view of the inserter
and expandable interbody fusion device bottom of FIG. 7 showing a
second insert entering the interbody fusion device at the proximal
end and below the first insert.
[0015] FIG. 8b is an enlarged view of a portion of FIG. 8a showing
the relative positions of the first and second inserts.
[0016] FIG. 9 is a partial side perspective view of the inserter
and expandable interbody fusion device of FIG. 8a showing the
second insert fully inserted into the interbody fusion device.
[0017] FIG. 10 is a proximal perspective view of an expanded spinal
interbody fusion device with a guide pin releasably connected
thereto subsequent to the inserter having been the detached from
the guide pin with inserts not being shown for clarity.
DESCRIPTION OF THE EMBODIMENTS
[0018] For the purposes of promoting and understanding of the
principles of the invention, reference will now be made to the
embodiments illustrated in the drawings and described in the
following written specification. It is understood that no
limitation to the scope of the invention is thereby intended. It is
further understood that the present invention includes any
alterations and modifications to the illustrated embodiments and
includes further applications of the principles of the invention as
would normally occur to one skilled in the art to which this
invention pertains.
[0019] Turning now to FIGS. 1-3, inserter 10 is shown for use in
expanding in situ a spinal implant, such as an interbody fusion
device 100, and for inserting inserts into the expanded device 100.
The expandable interbody fusion device 100 includes a first
element, such as superior endplate 112 and a second element, such
as inferior endplate 114, as shown in FIGS. 2-3. The height across
the superior and inferior endplates 112, 114 in the unexpanded
condition as illustrated in FIG. 1 is less than the normal anatomic
height of a typical intradiscal space. The invention contemplates
expanding the interbody fusion device 100 by the inserter 10 to
ultimately restore the normal anatomic height of the disc space and
thereafter inserting a series of inserts, such as interlocking
inserts 200, as will be described, to form a stack of inserts 200
between the expanded superior and inferior endplates.
[0020] The superior endplate 112 is elongate and comprises a hub
116 that is sized and configured to fit within a cavity 118 of the
inferior endplate 114 for telescoping movement therewithin upon
expansion. The lower surface 120 of the hub 116 includes a shaped
configuration defined by insert mating features 122 (see FIG. 7)
that are substantially identical to the mating features on the
lower surface of each insert 200, as will be described. The
superior endplate 112 includes a graft chamber defined by an
opening 124 extending therethrough and inferior endplate 114
includes a graft chamber defined by an opening 126 extending
therethrough for receipt of a suitable bone filler or bone graft to
promote fusion between opposing vertebral bodies of a spine.
Further details of interbody fusion device 100 are described in
commonly assigned U.S. patent application Ser. No. 13/795,054
entitled "Expandable Interbody Fusion Device with Graft Chambers",
filed on Mar. 12, 2013 ("the '054 Application") and incorporated
herein by reference.
[0021] Details of the interlocking insert 200 are shown in FIGS.
5-6. The insert 100 is elongate and has an upper surface 202 and a
lower surface 204, both of which are generally planar so that the
inserts can form a stable stack within the interbody fusion device
10 upon expansion. Insert 200 includes a trailing rear end 206 and
a leading front end 208. The rear end 206 is formed substantially
in the form of a horseshoe, with a pair of spaced opposing arms 212
and 214 defining an open rearward facing generally U-shaped opening
216. The surface 218 between the upper surface 202 and the lower
surface 204 at the base of opening 216 defines a pushing surface
218 for receipt of a driver of inserter 10, as will be described.
The opening 216 at the rear end of each insert 200 is provided to
allow bone graft material to flow into the device 100 through the
insert openings 216 and into the openings 124 and 126 extending
through the superior endplate 112 and the inferior endplate 114,
respectively. The rear end 206 includes a flat surface 212a and
214a, respectively at the free end of each arm 212 and 214 and a
flat surface 208a on the leading front end 208 of the insert
200.
[0022] The insert 200 includes several features for interlocking
engagement to the hub 116 and to adjacent inserts 100 in a
complementary interlocking mating interface. One particular feature
includes a series of locking elements defined by resiliently
deflectable prongs 220 that project outwardly above the upper
surface 202 of the insert 200 in the direction of expansion of
device 100. A complementary series of locking surfaces 222 are
defined in the lower surface 204 of the insert 200 for resilient
engagement with the prongs 220 as wafers are inserted into device
100 to form a stack. The lower surface 204 of each insert 200 as
shown in FIGS. 5 and 6 also defines a T-slot configuration 224 for
mating with a T-bar configuration 226 on the upper surface 202 of a
successive insert 100. In the illustrated arrangement, there are
two prongs 220 extending generally linearly and substantially
centrally along the elongate longitudinal direction adjacent the
front end 208 of insert 200. The structure and function of insert
200 and the prongs 220 and locking surfaces 222 are more fully
described in the '054 Application. However, unlike wafers 100
described in the '054 Application, the inserts 200 described herein
do not function to assist in the separation of superior endplate
112 and inferior endplate 114 or any subsequent inserts 200
inserted into interbody fusion device 100 as that lifting and
function is provided by inserter 10.
[0023] Turning again now to FIGS. 1-3, details of the inserter 10
are described. Inserter 10 comprises an elongate barrel 12 having a
distal end 12a and a proximal end 12b. A trigger actuator 14 to
effect expansion of device 100 and insertion of inserts 200 into
device 100 after expansion is provided at the proximal end 12b of
barrel 12. A cartridge 15 supported by barrel 12 on the underside
thereof contains a plurality of inserts 200 to provide a supply of
inserts 204 inserting into device 100 by inserter 10.
[0024] The distal end 12a is shown in exploded detail in FIGS. 2-3.
The barrel 12 includes a lower track 16 and an upper track cover
18. An elongate guide pin 20 is supported by barrel 12, the distal
end 20a of the guide pin 20 being threaded for releasable threaded
engagement into a suitable threaded opening in the proximal end of
the inferior endplate 114. The proximal end 20b of guide pin 20 is
provided with a threaded knob 22 for compressing the barrel 12 and
thereby the inserter to the device 100. The track cover 18, in one
arrangement, includes a pair of opposing tabs 18a that engage
corresponding notches 128 at the proximal end of the inferior
endplate 114 to assist in rigidly securing the barrel 12 to the
device 100. It should be appreciated that other securement
structure may be used to releasably attach the barrel 12 and
thereby inserter 10 to the device 100.
[0025] The distal end 12a of barrel 12 supports a lifting platform
24 and an elevator 26. The lifting platform 24 is coupled at its
proximal end 24a by a boss 24b or other suitable projection to a
lifting platform link 28. The boss 24b is suitably received and
retained in opening 28a at the distal end of link 28. The lifting
platform 24 is axially translatable relative to elevator 26 upon
axial translational movement of link 28 which is coupled to an
actuator, such as trigger actuator 14 at its proximal end, as will
be described. Link 28 is supported by track 16 for translational
movement within a track channel 16a extending axially along track
16. Inserts 200 or movably supported in a linear array on link 28
within the channel 16a. It should be appreciated that actuators
other than trigger actuators may be used with the inserter 10
described herein.
[0026] Elevator 26 comprises a proximal end 26a and a distal
projecting end 26b. The proximal end 26a is suitably affixed to the
track 16 and, in the particular arrangement being described,
remains in a fixed position relative to lifting platform 24 and
inferior endplate 114 as lifting platform is translationally moved.
The proximal end 26a defines a channel 26c for receipt of the
proximal end 24a of lifting platform 24. The lifting platform 24
and elevator 26 may in one arrangement be a disposable component
and replaced by a new unused lifting platform 24 and elevator 26
for subsequent procedures.
[0027] The distal projecting end 26b of elevator 26 includes a
lower substantially flat surface 26c and an upper surface 26d,
generally parallel to lower surface 26c. Projecting end 26b is
configured to extend within inferior endplate 114 with lower
surface 26c supported by an interior surface 114a (see FIG. 7).
Upper surface 26d is formed to have a series of axially extending
ramp surfaces 26e extending therewithin, three such ramp surfaces
26e being illustrated. Lifting platform 24 includes at its distal
end 24b an upper substantially flat surface 24c and a lower surface
24d, generally parallel to upper surface 24c. Upper surface 24c is
configured to engage and support surface 205 at the underside of
insert 200 (see FIG. 6) as well as the lower surface 120 of
superior endplate 112 which has mating features 122 that are
substantially identical to the mating features on the lower surface
of each insert 200. Lower surface 24d is formed to have a series of
axially extending ramps 24e, three of which are shown. Ramps 24e
projecting downwardly from lifting platform 24 and ramp surfaces
26e extending within elevator 26 are configured to have suitably
inclined surfaces such that upon axial translational movement of
lifting platform 24 relative to elevator 26 ramps 24e engage ramp
surfaces 26e to cause lifting platform 24 to move upwardly and
separate from elevator 26.
[0028] Lifting platform link 28 includes thereon an upper surface
28a on which the inserts 200 are movably supported in a linear
array. Link 28 includes a spring element 28b having an inclined
surface for engaging an insert 200 and moving such insert upwardly
into an insertion position from track 16 during axial transit along
link 28. A pair of cantilevered spring projections 28d and 28e may
be spaced axially along link 20 in a manner to substantially
prevent retrograde movement of inserts 200 along link 28.
[0029] Barrel 12 further supports a driver 30 for axial
translational movement within the barrel 12. The proximal end of
driver 30 is coupled to trigger actuator 14 to effect translational
movement of the driver, as will be described. The distal end of
driver 30 comprises a pushing surface 30a sized and configured to
enter into the opening 216 of an insert 200 to engage pushing
surface 218 and push the insert 200 into the device 100 upon axial
distal movement of driver 30.
[0030] Turning now to FIG. 4, the details of the trigger actuator
14 of the inserter 10 and its function are described. Trigger
actuator 14 comprises a bar linkage mechanism 31 comprising a first
bar 32 and a second bar 34. The lower end of each bar 32 and 34 is
pivotally connected to a handle 36 by a pivot pin 38. Pin 38 slides
within a cam track 40 supported on handle 36. The upper end of bar
32 is pivotally connected to the proximal end of driver 38 pivot
pin 42. The upper end of bar 34 is pivotally connected to the
proximal end 12b of barrel 12 by a pivot pin 44. Handle 36 is
pivotally connected to barrel 12 by a pivot pin 46. A curved cam
member 48 is attached at its lower end 48a to handle 36 with upper
end 48b extending though barrel 12. Cam member 48 upon squeezing
movement of the handle 36 toward barrel 12 engages a cam following
surface 50 on barrel 12 to initially pull lifting platform link
proximally. The bar linkage mechanism 31 of the trigger actuator 14
is structured to move lifting platform link 28 and driver 30
independently of each other and with suitable time delays between
such movements based on the configuration of the cam track 40. The
driver 30 is returned to its original starting position when the
handle 36 is released. Thus, during a single stroke operation of
trigger actuator 14 the lifting platform 24 is lifted relative to
elevator 26, driver 30 pushes an insert 200 into the device 100,
lifting platform 24 is retracted relatively toward elevator 26 and
finally driver 30 is retracted from device 100. Such single stroke
of operation is initiated when handle 36 is in the starting
position of FIG. 4 and is completed when handled 36 is released and
returns to its starting position.
[0031] Turning now to FIGS. 7-9 the use of inserter 10 to expand
the device 100 and insert one or more inserts 200 to form an
interlock stack is further described. FIG. 7 illustrates a
condition of the expansion of device 100 wherein a first insert 200
has been positioned between superior endplate 112 and inferior
endplate 114 with prongs 220 suitably interlockingly engaging the
mating features 122 at the lower surface of hub 116. It should be
understood that to insert the first insert 200 the inserter 10 and
the method described herein were similarly employed. A subsequent
insert 200a is shown on spring element 28b with the insert 200a
having been lifted by spring element 28b into an insertion position
from channel 16a of track 16 during axial advancement distally by
driver 30. In this condition the ramps 24e of lifting platform 24
are not deployed relative to ramp surfaces 26e of elevator 26.
Upper surface 24c of lifting platform 24 is in contact with and
supports the underside surface 205 of insert 200.
[0032] Upon operation of trigger actuator 14, lifting platform link
28 is translated proximally causing ramps 24e to engage and ride
upwardly along ramp surfaces 26e of elevator 26 thereby causing
during such translational movement the lifting platform 24 to move
upwardly and away from elevator 26. Such movement lifts insert 200
together with interlocked superior endplate 112 in the direction of
expansion an incremental distance slightly greater than the
thickness of insert 200a. With the bar linkage mechanism 31 of
trigger actuator 14 configured to temporarily hold this position
for a certain period of time, continued operation of trigger
actuator 14 moves pusher 30 distally until the pushing surface 30a
of driver 30 causes the front end 208a of subsequent insert 200a to
enter device 100 between lower surface 204 of a previously inserted
insert 200 and inferior ledge 114b of the inferior endplate 114, as
shown in FIGS. 8a and 8b. At a point when front end 208a has
entered a certain distance, D, continued operation of trigger
actuator 14 causes lifting platform link 28 to translate distally
causing ramps 24e to slide downwardly along ramp surfaces 26e
thereby retracting lifting platform 24 toward elevator 26. Further
operation of trigger actuator 14 causes driver 30 to move axially
distally pushing insert 200a fully into device 100 with little
further resistance until the prongs 220 engage locking surfaces
222. As illustrated in FIG. 9, once insert 200a is completely
inserted prongs 220 suitably interlock with locking surfaces 222 of
previously inserted insert 200. When handle 36 is released the
driver 30 is drawn proximally a sufficient distance within barrel
12 to be positioned to receive another insert 200b supported within
track channel 16a, if necessary. For illustrative purposes, wherein
inserts 200 and 200a each have a length of approximately 25 mm in
the thickness of approximately 1 mm, distance D may be a minimum of
approximately 2-3 mm.
[0033] It should be appreciated that upon when operation of trigger
actuator 14 lifting platform 24 is incapable of physically reaching
the desired elevation (which is approximately slightly greater than
the thickness of an insert 200 and determined by the bar linkage
mechanism 31), further operation of the trigger actuator 14 during
any given stroke will be substantially prevented. Such resistance
will provide tactile feedback to the surgeon who will recognize
that the device 100 has been expanded to its maximum anatomic
extent as the spine has reached ligamentotaxis. The surgeon would
then terminate the insert insertion procedure releasing handle 36,
and then removing the inserter 10 from the expanded device 100 by
rotatably removing knob 22 from the proximal end of guide pin 20.
As shown in FIG. 10, the guide pin 20 may remain releasably
connected to expanded device 100 to serve as a locator for
subsequent attachment to an apparatus containing suitable bone
growth material to assist in the delivery of such material into a
channel 114c of inferior endplate 114 through which inserts 200
were inserted.
[0034] Having described the inserter 10 and the method of expanding
an interbody fusion device 100 and inserting thereinto one or more
inserts 200 with reference to device 100 wherein a first insert 200
has been positioned between superior endplate 112 and inferior
endplate 114, it should be appreciated that the inserter 10 and
method may also be used to introduce insert 200 initially between
superior endplate 112 and inferior endplate 114.
[0035] While the invention has been illustrated and described in
detail in the drawings and foregoing description, the same should
be considered as illustrative and not restrictive in character. It
is understood that only the preferred embodiments have been
presented and that all changes, modifications and further
applications that come within the spirit of the invention are
desired to be protected. For instance, while the lifting platform
24 has been described herein as being movable axially relative to a
fixed elevator 26, it should be appreciated that lifting platform
24 may be held in a fixed axial position while the elevator 26 is
moved axially relative thereto. Also, while the illustrated
embodiments have been directed particularly to interbody fusion of
the spine, the expandable devices and inserts disclosed herein may
be used in other applications that require distraction of tissue
surfaces, such as, for example, vertebral compression fracture
treatments. Modifications in size may be necessary depending upon
the body space being distracted.
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