Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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EXPANDABLE SPINAL 1NTERBODY FUSION DEVICE
FIELD OF THE INVENTION
The subject invention relates generally to the field of spinal implants and
more
particularly to an expandable spinal interbody fusion device.
BACKGROUND OF THE INVENTION
Spinal implants such as spinal 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.
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. Patent No. 6,595,998 entitled "Tissue Distraction Device",
which issued on
July 22, 2003 (the '998 Patent), U.S. Patent No. 7,931,688 entitled
"Expandable Interbody
Fusion Device", which issued on April 26, 2011 (the '688 Patent), and U.S.
Patent No.
7,967,867 entitled "Expandable Interbody Fusion Device", which issued on June
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.
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An 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. One approach addressing this issue is described in commonly
assigned
U.S. Patent Number 8,828,019, entitled "Inserter for Expanding an Expandable
Interbody
Fusion Device", issued on September 9, 2014 ("the '019 Patent").
Accordingly, there is a need for an improved expandable interbody fusion
device and
inserter to expand and insert such a device, including the capability to
determine when proper
expansion of the device has been achieved and no further inserts may be
introduced.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved spinal interbody
fusion device
and to introduce inserts therein after the implant has been expanded. A
further object is to
provide an inserter that has the capability of allowing a surgeon to determine
that suitable
expansion has been reached and no additional inserts may be inserted.
DESCRIPTION OF THE FIGURES
FIG. la is a top perspective of an apparatus including an inserter releasably
attached
to an expandable spinal interbody fusion device in accordance with an
embodiment of the
present invention, the expandable interbody fusion device being unexpanded.
FIG. lb is a side elevation view of the apparatus of FIG. la.
FIG. 1 c is a top plan view of the apparatus of FIG. la.
FIG. 2 is an enlarged view of the distal portion of the apparatus as circled
in FIG. lc.
FIG. 3a is top perspective view of the unexpanded fusion device of FIG. la.
FIG. 3b is top perspective view of the fusion device of FIG. 3 after being
expanded.
FIG. 4 is an exploded top perspective view of the expanded device of FIG. 3b.
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FIG. 5a is a side elevation view of the expanded device of FIG. 3b.
FIG. 5b is a sectional view of the device of FIG. 5a as seen along viewing
lines B-B
of FIG. 5a.
FIG. 5c is a sectional view of the device of FIG. 5a as seen along viewing
lines C-C
of FIG. 5a.
FIG. 6a is a top perspective view of an insert used in the expandable spinal
interbody
fusion device of FIG. 3a.
FIG. 6b is a top plan view of the insert of FIG. 6a.
FIG. 6c is a longitudinal cross-sectional view of the insert as seen along
viewing lines
VI-VI of FIG. 6b.
FIG. 6d is a bottom plan view of the insert of FIG. 6a.
FIG. 6e is a distal end elevation view of the insert of FIG. 6a.
FIG. 7a is a top perspective view of an elevator used in the expandable spinal
interbody fusion device of FIG. 3a.
FIG. 7b is a top plan view of the elevator of FIG. 7a.
FIG. 7c is a longitudinal cross-sectional view of the elevator as seen along
viewing
lines VII-VII of FIG. 7b.
FIG. 7d is a bottom plan view of the elevator of FIG. 7a.
FIG. 7e is a distal end elevation view of the elevator of FIG. 7a.
FIG. 8 is an exploded top perspective view of the track and components of the
inserter
of FIG. la, including the translatable lifting platform and translatable
driver.
FIG. 8a is an enlarged view of the distal portion of the inserter track and
components
as circled in FIG. 8.
FIG. 9 is a cross-sectional view of the inserter and device of FIG. la as seen
along
viewing lines IX-IX of FIG. lc.
FIG. 9a is an enlarged view of the encircled portion A of FIG. 9.
FIG. 9b is an enlarged view of the encircled portion B of FIG. 9.
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FIG. 10a is a cross-sectional view of the distal end of the inserter and
device as seen
along viewing lines A-A of FIG. 2 with the expandable device unexpanded.
FIG. 10b is a cross-sectional view of the distal end of the inserter and
device as seen
along viewing lines B-B of FIG. 2 with the expandable device unexpanded.
FIG. 11 is a top partial perspective view of the distal end of the lifting
platform and
the elevator of the expandable device in the position depicted in FIGS. 10a
and 10b.
FIG. 12 is a cross-sectional view of the lifting platform and elevator as seen
along
viewing lines XII-XII of FIG. 11.
FIGS. 13a and 13b are views similar to FIGS. 10a and 10b with the lifting
platform
having been distally moved to a position lifting the elevator and expanding
the expandable
device and a first insert partially entering the expanded device.
FIG. 14 is a view similar to FIG. 10a showing the first insert inserted into
the
expanded expandable device.
FIGS. 15a and 15b are views similar to FIGS. 13a and 13b with the lifting
platform
having been moved distally to a position lifting the elevator and the first
insert to further
expand the expandable device with a second insert partially entering the
expanded device.
FIGS. 16a and 16b are views of the expandable device expanded as shown in the
views of FIGS. 15a and 15b with the second insert having been further distally
moved to a
position moving the elevator away from the first insert and creating a space
for the insertion
of the second insert.
FIG. 17 is a view similar to the view of FIG. 14 showing the first and second
inserts
inserted into the expanded expandable device.
FIG. 18 is a cross-sectional view as seen along the viewing lines XVIII-XVIII
of FIG.
17.
FIG. 19 is a proximal perspective view of the expanded spinal interbody fusion
device
with a guide pin releas ably connected thereto subsequent to the inserter
having been detached
from the guide pin with inserts not being shown for clarity.
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FIG. 20 is a top perspective of an apparatus including an inserter releasably
attached
to an expandable spinal interbody fusion device in accordance with a further
embodiment of
the present invention with the inserter being modular.
DESCRIPTION OF THE EMBODIMENTS
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.
Turning now to FIGS. la-c, 2, 3a-b and 4, an apparatus 1 for use in spinal
interbody
fusion is shown. Apparatus 1 comprises an expandable spinal interbody fusion
device 10 and
an inserter 100. The inserter 100 is an instrument used for inserting the
device 10 into an
intradiscal space between opposing vertebral bodies of a spine, expanding the
device in situ
and for inserting inserts into the expanded device 100. The expandable
interbody fusion
device 10 includes a first element, such as superior endplate 12, a second
element, such as
inferior endplate 14, at least one insert 16 and expansion structure including
an elevator 18,
as will be detailed hereinbelow. The height, H, across the superior and
inferior endplates 12,
14 in the unexpanded condition as illustrated in FIG. lb is less than the
normal anatomic
height of a typical intradiscal space. The invention contemplates expanding
the interbody
fusion device 10 by the inserter 100 from an unexpanded condition as shown in
FIG. 3a to the
expanded height as shown in FIG. 3b to ultimately restore the normal anatomic
height of the
disc space and thereafter inserting one or more inserts, such as inserts 16,
as will be
described, to form a stack of inserts 16 between the expanded superior
endplate 12 and
inferior endplate 14. In the particular arrangement being described, fusion
device 10 is
configured and sized for implantation into the spine from the posterior
approach. In the
unexpanded state as shown in FIG. 3a, device 10 has a length of approximately
25mm, a
width of approximately 1 Omm, and an unexpanded height H of approximately 7mm.
Fusion
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device 10 may also be configured and sized for implantation into the spine
using
posteriolateral, anterior or lateral approaches, as will be described.
The superior endplate 12 as shown in FIGS. 3a-b and 18 is elongate and
comprises a
hub 20 having pair of side surfaces 22 and 24 extending longitudinally on each
side of the
hub 20 and a pair of end surfaces 26 and 28 extending respectively at the
proximal rear end
and the distal front end of the superior endplate 12. The hub 20 is sized and
configured to fit
within a cavity 48 of the inferior endplate 14 for telescoping movement
therewithin, as will
be described. The lower surface 30 of the hub 20 (FIG. 18) is generally flat
and planar.
Suitable friction or crush ribs may be provided between the hub 20 and cavity
48 of inferior
endplate 14 at inner surface 44a to temporarily hold the superior and inferior
endplates 12, 14
together in the direction of expansion as the device 10 is introduced into the
intradiscal space
to be distracted.
With continued reference to FIGS. 3a-b and 18, the superior endplate 12
includes a
graft chamber defined by an opening 38 extending through the upper outer
surface 12a and
the lower surface 30. In accordance with one arrangement, the superior
endplate 12 is
formed of a biocompatible polymer such as polyethylethylketone (PEEK). PEEK is
used in
fusion applications for its combination of strength, biocompatibility, and
elasticity which is
similar to human bone. Other composites may include derivatives of PEEK such
as carbon
fiber reinforced PEEK and PEKK, respectively. In a particular aspect, the
superior endplate
12 may further include an upper endcap that defines the outer surface 12a. The
endcap may
be a separate plate formed of material for the promotion of bone growth, such
as titanium,
and may be attached to the endplate 12 with suitable conventional techniques.
As an
alternative, the upper surface 12a may be defined by a coating of a suitable
layer of bone
growth promotion material, such as titanium, which may be deposited by
conventional
techniques.
The inferior endplate 14 of the interbody fusion device 10 as shown in FIGS.
3a-b
and 18 is elongate and comprises a pair of opposing spaced apart sidewalls 40
and 42
extending along the longitudinal direction and projecting upwardly from the
lower outer
surface 14a. A pair of spaced apart end walls 44 and 46 extend laterally
across the device 10
and project upwardly from outer surface 14a. Rear end wall 44 is disposed at
the rear or
proximal end of the device 10 and front end wall 46 is disposed at the front
or distal end of
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the device 10. The side walls 40, 42 together with rear end wall 44 and front
end wall 46
form an open, upwardly facing fully bounded interior cavity 48 as shown in
FIGS. 3a and 4.
The interior cavity 48 is sized and configured to receive the superior
endplate 12 including
the hub 20 in relatively close fit between the side walls 40 and 42 and the
end walls 44 and 46
of the inferior endplate 14 in a non-expanded condition as shown in FIGS. la-
b. The hub 20
of superior endplate 12, as well as the entire stack of inserts 16, remains
fully contained
within the inferior endplate 14 during telescoping expansion of the device 10
as shown in
FIGS. 18 and 19, contributing to the torsional strength of the expanded device
10.
The inferior plate 14 as shown in FIGS. 4 and 19 includes a lower inner
support
surface 54 on which elevator 18 is supported. Inner surface 54 defines the
bottom surface of
the cavity 48. Inferior endplate 14 further defines a fully bounded insert
channel 50
extending through the rear end wall 44 in communication with interior cavity
48 and through
which one or more inserts 16 are introduced. The height of channel 50 as
measured vertically
from inner surface 54 is slightly greater than the combined thicknesses of
insert 16 and
elevator 18. With insert 16 being slidably received through channel 50 on top
of elevator 18,
as will be described, only one insert 16 may be introduced at a time. As
device 10 is
expanded and further inserts 16 are sequentially introduced, all inserts 16
lying above the
lowermost insert 16, which would be situated on top of elevator 18, will be
prevented from
backing out of the device 10 by the interior surface 44a of rear end wall 44
(FIG. 4). The rear
end wall 44 further defines a threaded connection opening 56 (FIG. 10a) for
threaded
releasable receipt of a guide pin 108 for use in the introduction of inserts
16 and in the
delivery of bone graft material into the device 10, as will also be described.
Rear end wall 44
may also additionally include a pair of bilateral openings, such as holes 58,
adjacent the
sidewalls 40 and 42 for use in releas ably attaching the inserter 100 to the
device 10 for the
establishment of a rigid connection to the device 10 for insertion into the
intradiscal space.
Elevator 18 is supported on inner surface 54 of inferior endplate 14 with the
lateral
width of elevator 18 being dimensioned for relatively close sliding fit
between opposite
interior surfaces 40a and 42a of side walls 40 and 42, as shown in FIGS. Sc
and 18. As such,
lateral movement of elevator 18 in directions transverse to the direction of
expansion is
substantially constrained. In addition, inferior endplate 14 includes a rail
14b projecting
inwardly from each interior surface 40a and 42a and upwardly from lower inner
surface 54
toward superior endplate 12. The upward projection of each rail 14b from inner
surface 54 is
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slightly greater than twice the thickness of elevator 18. Rails14b slidably
project into recesses
310 extending into the base 305 of elevator 18 at each lateral side. Rails14b
substantially
constrain movement of elevator 18 in the axial direction while the clearance
in recesses 310
allows free movement of elevator 18 in the direction of expansion along rails
14b as shown
by the arrow 130 in FIG. 10a. As such, elevator 18 is captively supported
within inferior
endplate 14 and is independently movable along the direction of expansion
toward and away
from each of the superior endplate 12 and the inferior endplate 14.
As shown particularly in FIGS. 4, 5a-b and 18, the inferior endplate 14
includes a
graft chamber defined by an opening 60 extending through the lower outer
surface 14a and
the lower inner surface 54 in communication with cavity 48. In accordance with
one
arrangement, the inferior endplate 14 is formed of a material different from
the material of
the superior endplate 12. In this aspect, the inferior endplate 14 may be
formed of a
biocompatible metal, such as titanium, for its strength properties. Titanium
is chosen for
strength, biocompatibility, processing capability, and fluoroscopic imaging
properties
(radiolucency). Other alternative materials include cobalt chrome, stainless
steel (both
stronger than titanium but much less radiolucent), or biocompatible ceramics
such as silicon
nitride or zirconia, which are radiolucent. Titanium and silicon nitride have
demonstrated
good apposition to bone and superiority to PEEK. In this regard where inferior
endplate 14 is
formed of titanium, the lower outer surface 14a would provide for the
promotion of bone
growth. Lower outer surface 14a may also, however, be coated with a suitable
layer of bone
growth promotion material, such as titanium, and deposited in a conventional
manner so as to
match the roughness/porosity of the superior endplate outer surface 12a.
Where inferior endplate 14 is formed of titanium or other suitable metal that
is
radiopaque, windows 62 may be formed through sidewalls 40 and 42 as shown in
FIGS. 3a-b
and 19 so as to allow visual observation of bony through growth by suitable
imaging
techniques, such as fluoroscopy. Details of a related interbody fusion device
are described in
commonly assigned U.S. Patent Number 8,900,312 entitled "Expandable lnterbody
Fusion
Device with Graft Chambers" ("the '312 Patent").
Details of insert 16 are shown in FIGS. 6a-e. The insert 16 comprises an
elongate and
generally flat body 200 having an upper surface 202 and a lower surface 204,
both of which
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are generally planar and substantially parallel so that the inserts 16 can
form a stable stack
within the interbody fusion device 10 upon expansion. Insert 16 includes a
trailing rear
proximal end 206 and a leading front distal end 208. The body 200 is formed to
have a
generally U-shaped, horseshoe configuration, with a pair of spaced opposing
arms 212 and
214 projecting rearwardly from a base 205 and defining a rearwardly facing
generally U-
shaped opening 216 extending through the rear end 206 and through upper
surface 202 and
lower surface 204. The lateral width of body 200 between side surfaces 212a
and 214a is
dimensioned for a relatively close sliding fit between interior surfaces 40a
and 42a of side
walls 40 and 42 of inferior endplate 14, as shown in FIG. 5b. Such close
dimensioning
reduces the potential of lateral movement of insert 16 during insert
introduction and within
cavity 48 of inferior endplate 14. A surface 218 between the upper surface 202
and the lower
surface 204 at the base 205 of opening 216 defines a pushing surface 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 10 through the
insert openings
216 and into the openings 38 and 60 extending through the superior endplate 12
and the
inferior endplate 14, respectively. A pair of inclined surfaces 208a extends
upwardly from
and communicating with lower surface 204 on each lateral side the insert 16
adjacent the
front distal end 208.
The insert 16 includes a feature for interlocking engagement with elevator 18
in a
complementary cooperative connection. Distal front end 208 of insert body 200
includes
therein a latching receptacle 220 defined by a pair of spaced opposing arms
222a and 222b
for receipt therein of a flexible latch 318 (FIG. 7a-e) on elevator 18, as
will be described.
Arms 222a and 222b include inwardly projecting locking surfaces 224a and 224b
respectively for cooperative locking engagement with elevator latch 318.
Unlike the inserts
described in the '312 Patent, the inserts 16 described herein do not function
to assist in the
separation of superior endplate 12 and inferior endplate 14 or any subsequent
inserts 16
inserted into interbody fusion device 16, as that lifting function is provided
herein by inserter
100 in conjunction with elevator 18. It is contemplated that the inserts 16
described herein be
formed of a biocompatible material that is sufficiently rigid to form a solid
stack as the
successive inserts are inserted into the device. Thus, in one specific
embodiment, the inserts
16 are formed of PEEK or a carbon-fiber reinforced PEEK, or similar polymeric
material.
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Turning now to FIGS. 7a-e, details of the elevator 18 are shown. The elevator
18
comprises an elongate and generally flat body 300 having an upper surface 302
and a lower
surface 304, both of which are generally planar and substantially parallel.
The elevator 18
has a thickness between upper surface 302 and lower surface 304 that is
slightly greater than
the thickness of insert 16. As such, when as noted below the thickness of an
insert 16 is, for
example, 1.0 mm, the thickness of elevator 18 may be 1.03 mm. Elevator 18
includes a
trailing rear proximal end 306 and a leading front distal end 308. The
elevator body 300 is
formed to have a generally U-shaped, horseshoe configuration similar to the
configuration of
insert 16. Elevator body 300 includes a pair of spaced opposing arms 312 and
314 projecting
rearwardly from a base 305 and defining a rearwardly facing generally U-shaped
opening 316
extending through the rear end 306 and through upper surface 302 and lower
surface 304.
Base 305 has a rearwardly facing surface 305a that communicates with opening
316. The
opening 316 at the rear end of elevator 18 is provided to allow bone graft
material introduced
into the device 10 to flow through the insert openings 216 of inserts 16 and
into the openings
38 and 60 extending through the superior endplate 12 and the inferior endplate
14,
respectively. The rear proximal end 306 includes an inclined surface 312a and
314a,
respectively at the free end of each arm 312 and 314 extending downwardly from
and
communicating with the upper surface 302. The rear proximal end 306 further
includes an
inclined lifting surface 312b and 314b, respectively at the free end of each
arm 312 and 314
extending upwardly from and communicating with the lower surface 304. The
front distal
end 308 includes adjacent base surface 305a an inclined lifting surface 308a
extending
upwardly from and communicating with lower surface 304. The inclined lifting
surfaces
312b, 314b and 308a are angled in the same direction with approximately equal
angles. The
lifting surfaces 312b, 314b and 308a define inclined ramps with multiple
points of contact for
cooperative contact with complementary surfaces of an expansion component on
the inserter
100 for lifting elevator 18, as will be described. Inclined surface 308a is
generally centrally
located along the elongate axis of elevator, while surfaces 312b and 314b are
spaced
bilaterally. Thus, lifting surfaces 308a, 312b and 314b define three
triangulated points of
contact. Elevator has a recess 310 extending into the elevator base 305 at
each lateral side
thereof. Recesses 310 are sized to receive rails 14b on the interior surfaces
of inferior
endplate 14, as described. In one specific embodiment, the elevator 18 is
formed of titanium
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alloy, type 2, which may be anodized for lubricity. Other materials, such as
PEEK, may also
be used as the material for elevator 18.
Distal front end of elevator body 300 includes a flexible latch 318 projecting
upwardly from upper surface 302. Latch 318 comprises a pair of spaced opposing
flexible
arms 320a and 320b that are configured to flex toward each other. Flexible
arms 320a and
320b include outwardly directed locking surfaces 322a and 322b respectively,
for cooperative
receipt within receptacle 220 of each insert 16, as shown in FIG. 5b. Upon
receipt of latch
318 into receptacle 220, locking surfaces 224a and 224b resiliently engage
locking surfaces
322a and 322b, respectively. Latch 318 projects above the upper surface 302
and a height
slightly greater than the thickness of an insert 16. The lateral width of
elevator body 300
between the side surfaces 312c and 314c, respectively of arms 312 and 314 is
dimensioned
for a relatively close sliding fit as noted hereinabove between interior
surfaces 40a and 42a of
inferior endplate 14, as shown in FIG. Sc.
Turning again now to FIGS. la-c and FIGS. 8 and 8a, details of the inserter
100 are
described. Inserter 100 is elongate having a distal end 100a and at a proximal
end 100b a
frame 101. A trigger actuator 102 to effect expansion of device 10 and
insertion of inserts 16
into device 10 after expansion includes a frame 101 at the proximal end 100b
of inserter. A
plurality of inserts 16 are movably supported in a linear array on an elongate
track 104 for
individual successive insertion into device 10. Track 104 supports at least
one insert 16 and
may, for example, support an array of five inserts 16, although fewer or more
inserts 16 may
be supported as desired.
The distal end 100a is shown in exploded detail in FIGS. 8 and 8a. The
inserter 100
includes elongate track 104 and an outer elongate track cover 106, the cover
106 being
substantially rigidly joined to track 104. Track 104 is configured as a closed
channel and is
supported within outer track cover 106. Cover 106 is fixedly secured to frame
101, although
in a particular arrangement as will be described, cover 106 may be removably
attached to
frame 101. An elongate guide pin 108 is supported within an opening 110
extending
lengthwise through the cover 106. The distal end 108a of the guide pin 108 is
threaded for
releasable threaded engagement into opening 56 in the proximal rear end wall
44 of the
inferior endplate 14. The proximal end of guide pin 108 is provided with a
threaded knob
112 for compressing and releas ably attaching the cover 106, and thereby the
track 104 to the
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device 10. The track cover 106, in one arrangement, includes a pair of
opposing pins 114 that
engage corresponding holes 58 in rear wall 44 of inferior endplate 14 (FIG.
19) to assist in
rigidly securing the inserter 100 to the device 10. It should be appreciated
that other
securement structure may be used to releasably attach the inserter 100 to the
device 10. Track
104, in one embodiment, is formed of stamped stainless steel and cover 106 is
an extruded
aluminum alloy. Stainless steel or strong reinforced plastic could also be
used for cover 106.
The track 104 at the distal end 100a of the inserter 100 supports an expansion
component defined by an axially translatable lifting platform 116 movably
supported on track
104 for relative axial movement thereto to cooperatively slidably contact
elevator 18 for
expanding the device 10. The lifting platform 116 is elongate and generally
flat having an
upper surface 118 and a lower surface 120, both of which are generally planar
and
substantially parallel (FIG. 18). The lifting platform 116 has a thickness
between upper
surface 118 and lower surface 120 that is dimensioned to be the same as the
thickness of
elevator 18, i.e., slightly greater than the thickness of an insert 16.
Lifting platform 116 is
supported by the inserter 100 for reciprocating axial movement in projecting
and retracting
directions. The proximal end of the lifting platform 116d is coupled to the
trigger actuator
102 to effect such projecting and retracting directions, as will be described.
Lifting platform 116 projects slidably axially outwardly from track 104 and
includes
at its free distal end an inclined lifting surface 116a extending downwardly
from and
communicating with upper surface 118. At a location spaced proximally of
lifting surface
116a, lifting platform further includes a pair of laterally spaced inclined
surfaces 116b and
116c. The inclined lifting surfaces 116a, 116b and 116c are angled in the same
direction with
angles approximately equal to the angles respectively of inclined lifting
surfaces 312b, 314b
and 308a of elevator body 300. Inclined surfaces 116a, 116b and 116c define
inclined ramps
with multiple complementary points of contact for cooperative contact with
elevator 18.
Inclined surface 116a is generally centrally located along the elongate axis
of lifting platform
116, while surfaces 116b and 116c are spaced bilaterally. Thus, lifting
surfaces 116a, 116b
and 116c define three triangulated points of contact that are located and
spaced to
cooperatively contact lifting surfaces 308a, 312b, and 314b, respectively
during movement of
lifting platform 116 in the projecting direction. Lifting platform 116,
particularly inclined
surfaces 116a, 116b and 116c, may be coated or otherwise include a suitable
lubricant to
facilitate sliding contact with elevator 18 for expansion of device 10. Where
lifting platform
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116 is made of stainless steel, for example, such lubricant may include a
molybdenum
disulfide (M0S2) material.
Still referring to FIGS. 8 and 8a, inserter 100 further supports at its distal
end 100a a
driver 124 for axial translational movement within track 104. The proximal end
124a (FIG.
8) of driver 124 is coupled to trigger actuator 102 to effect translational
movement of the
driver 124, as will be described. The distal end of driver 124 comprises a
pushing surface
124b sized and configured to enter into the opening 216 of an insert body 200
to engage
pushing surface 218 and push the insert 16 from track 104 into the device 10
upon axial distal
movement of driver 124. Furthermore, driver 124 includes an upper surface 124c
on which
inserts 16 are movably supported in a linear array. Also included as shown in
FIG. 8 is an
indexing member 125 that cooperates with driver 124 to distally incrementally
move inserts
16 in the projecting direction to be positioned for individual contact with
driver pushing
surface 124b while preventing retrograde movement of inserts 16 as they are
positioned.
With further reference still to FIG. 8a, inserter 100 comprises a flexible
graft shield
128 projecting distally from inner track 104. Graft shield 128 is supported at
one end 128a in
a cantilevered manner with an opposite end 128b being unsupported and free to
flex. Graft
shield 128 is elongate and generally flat and is sized and configured to
substantially block
communication between the opening 38 through the superior endplate 12 and
inserts 16
slidably inserted into device 10. As will be described, graft shield 128 is
configured to extend
into device 10 through channel 50 between the superior endplate 12 and the
expansion
structure adjacent the lower surface 30 of the superior endplate 12.
Turning now to FIGS. 9 and 9a-b, the details of the trigger actuator 102 of
the inserter
100 and its operating mechanism and function are described. Trigger actuator
102 comprises
a pair of hand grips 132 and 134 biased apart by an extension spring 136. Hand
grip 132 is
fixedly secured to frame 101 of inserter 100. Hand grip 134 is pivotally
connected to frame
101 at pivot point 138 and is movable toward hand grip 132 against the bias of
extension
spring 136 by manual pressure. Hand grip 134 has gear teeth 140 that interface
with a gear
rack 146 slidably coupled to the frame 101. The gear mechanism is sized to
provide the
appropriate translation of the gear rack 146 in the projecting direction as
trigger actuator 102
is actuated. Also slidably coupled to the frame 101are a driving slide 150
that is configured
for relative and joint movement with driver 124, and a lifting slide 154 that
is configured for
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joint movement with lifting platform 116. Gear rack 146 includes a lower
surface 146a
defining a tooth pattern, an upper surface 146b defining a pushing surface
146d, a ramp
surface 146e, and a distal end 146c. Distal end 146c includes a pawl 148
configured for
limited rotation about pivot point 148a, the distal end of pawl 148 being
biased toward the
driving slide 150 by a compression spring 152. Prior to actuation of trigger
102 the pawl 148
is constrained from rotation about pivot point 148a by the lower surface 150a
of driving slide
150. Upon a first actuation of trigger 102, and therefor translation of the
gear rack 146 in the
projecting direction, the pawl 148, under bias of compression spring 152,
slides along lower
surface 150a. When sufficient translation of gear rack 146 has occurred such
that the pawl
148 has passed the distal end of driving slide 150, pawl 148 rotates
counterclockwise as
viewed in FIG. 9a about pivot point 148a to a position limited by contact with
upper surface
146f of gear rack 146.
Pawl 148 includes a pushing surface 148b sized to engage pushing surface 154a
at
proximal end of lifting slide 154. Further actuation of the trigger 102
promotes contact of
pushing surfaces 148b and 154a and therefor movement of the lifting slide 154
and lifting
platform 116 in the projecting direction causing expansion of the device 10.
Lifting slide 154 further includes a proximal elongate tethering portion 154b
with
pushing surface 154c sized to engage pushing surface 150b at proximal end of
driving slide
150. Upon translation of lifting slide 154 in the projecting direction,
pushing surface 154c
engages pushing surface 150b for joint translation therebetween.
Driving slide 150 further includes an upper boss feature 156 defining pushing
surfaces
156a and 156b sized to fit within slot a 124d (FIG. 8) of driver 124. Slot
124d comprises
complementary axially spaced apart pushing surfaces 124e and 124f,
respectively. The
length of slot 124d is sized such that translation of driving slide 150 during
first actuation of
trigger 102 does not induce contact between pushing surfaces 156b and 124f and
therefore
does not impart translation of driver 124.
Driving slide 150 further includes a pawl 158 configured for limited rotation
about
pivot point 158a, the proximal end of pawl being biased toward the gear rack
146 by bilateral
torsion springs (not shown). Prior to actuation of trigger 102 the pawl 148 is
constrained
from rotation about pivot point 158a by a ledge surface 160 rigidly coupled to
frame 101.
Upon translation of the driving slide 150 in the projecting direction, the
pawl 158, under bias
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of the torsion springs, slides along upper ledge surface 160. When sufficient
translation of
driving slide 150 has occurred such that the pawl 158 has passed the distal
end of ledge
surface 160, pawl 158 rotates counterclockwise as viewed in FIG. 9a about
pivot point 158a
to a position limited by contact with lower surface 150c of driving slide 150.
Such
translation is configured to be slightly longer than the translation required
by the lifting
platform 116 to achieve full expansion of device 10 such that rotation of pawl
158 will not
occur in the absence of full expansion of device 10. Further, rigidly coupled
to pawl 158 for
rotation therewith are bilateral flags 162 positioned in slots 163 in frame
101(FIG. la), the
flags 162 projecting laterally outwardly of both sides of frame 101. Upon
joint rotation of
pawl 158 and flags 162 the user is visually alerted to the position of the
driving slide 150 and
lifting slide 154 thereby indicating to the user that full expansion of device
10 has been
achieved and that no further inserts can be introduced.
Pawl 158 further comprises a pushing surface 158b sized to engage pushing
surface
146d of gear rack 146 and a ramp surface 158c sized to engage ramp surface
146e of gear
rack 146. After full actuation and a complete stroke of trigger 102 and
release of grip
pressure, the gear rack 146 and hand grips 132/134 are returned under the bias
of the
extension spring136. During retraction of the gear rack 146, cooperative ramp
surfaces 146e
and 158c collide inducing pawl 158 to rotate clockwise thereby allowing
passage of the gear
rack 146. Upon sufficient translation of the gear rack 146 in the retracting
direction such that
the ramp surface 146e has passed the proximal edge of ramp 158c, pawl 158
rotates
counterclockwise about pivot point 158a back to a position limited by contact
with lower
surface 150c of driving slide 150.
It should be appreciated that upon completion of first actuation of trigger
102 and
completion of the first stroke, lifting platform 116 remains projected
maintaining the
expanded state of device 10 and that driving slide 150 remains in a partially
projected state
due to tether 154b of lifting slide 154. It should also be noted that pawl 158
remains in a
rotated state limited by contact with driving slide 150 while pawl 148 is
returned to its
original collapsed state limited by lower surface 150a of driving slide 150.
Upon a second actuation of trigger 102 gear rack 146 translates again in the
projecting direction such that pushing surface146d contacts pushing surface
158b of pawl 158
causing joint translation of gear rack146 and driving slide 150. Upon further
actuation,
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pushing surface 156b of driving slide 150 contacts pushing surface 124f of
driver 124 causing
joint translation therebetween, thereby engaging pushing surface 218 of insert
16 and pushing
the insert 16 from track 104 into the device 10 during completion of the
second stroke of
trigger actuator 102.
For the purpose of returning the track lifting platform 116 to its original
position in
the retracting direction a cam 164 and gear 166 are provided. The gear 166
interfaces with a
second gear rack 154d rigidly connected to the lower surface of lifting slide
154. The cam
164 is coupled to gear 166 for opposite rotation therebetween and is
positioned to contact a
notch 170 (FIG. 8a) in the driver 124 after an insert 16 has been partially
inserted into the
device 10. Further trigger actuation returns the lifting platform 116 to its
original position
while the driver further inserts the insert 16. When full trigger actuation is
achieved, the gear
rack 146 and hand grips 132/134 are returned under the bias of the extension
spring136. To
reset the position of driving slide 150 manually, the user pulls up on
bilateral tabs 162b
rigidly coupled to flags 162 thereby imparting rotation of pawl 158 and
translation of driving
slide 150 in the retracting direction. Due to the rotated state of flags 162
and pawl 158, driver
slide 150 can be returned to its original retracted position with pawl 158
rotation limited by
ledge 160 surface. A two way ratchet mechanism 168 prevents unwanted motion of
driving
slide 150 in the wrong direction. In the event full expansion of device 10 is
achieved and the
surgeon prefers to abort the procedure without further introduction of an
insert 16, hex fitting
174 (FIG. la) coupled to gear 166 may be actuated by a hex wrench or other
suitable tool.
Rotation of fitting 174 rotates gear 166 which directly translates lifting
slide 154 and hence
lifting platform 116 proximally to release the expansion of device 10 with no
insert 16
introduced.
It should now be understood how the trigger actuator 102 operates to expand
device
10 and introduce one or more inserts 16. During the first stroke, only lifting
platform 116 is
translated in the projecting direction to cause expansion of device 10. Driver
124 remains
stationary during the entire first stroke. After the hand grips 132/ 134 are
returned to the
starting position under the bias of extension spring 136 upon completion of
the first stroke,
lifting platform 116 remains stationary in the projecting position maintaining
the expanded
state of device 10 as hand grips 132/134 return. During the second stroke of
trigger actuator
102, driver 124 is translated in the projecting direction while the lifting
platform 116 is
initially stationary in the projecting direction. When driver 124 has inserted
an insert 16
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partially into the expanded device 10 continued operation of trigger actuator
102 retracts
lifting platform 116 in the retracting direction. As lifting platform 116
retracts, driver 124
continues to advance in the projecting direction to push insert 16 fully into
position upon
completion of the second stroke.
Thus, for the particular device being described for insertion into the
intradiscal space
in the posterior approach, expansion of device 10 is achieved during the first
stroke of trigger
actuator 102 and full insertion of an insert 16 during completion the second
stroke. For
longer devices, such as those insertable from the lateral approach, the
mechanism of inserter
100 may be adjusted such that the longer device is expanded in a first stroke,
the inserts 16
inserted partially into the expanded device during a second stroke, and fully
inserted in the
third stroke. It should thus be appreciated by those skilled in the art that
the number of
strokes employed for expansion of device 10 and insertion of an insert 16 into
the expanded
device 10 may be varied by suitable adjustment of the operating mechanism of
trigger
actuator 102. Such adjustment may include, for example, varying the number of
pushing
surfaces 146d that are provided on gear rack 146 for engagement with pawl 158.
Turning now to FIGS. 10a-b and 11-12 the assembly of the device 10 and the
inserter
100 is described. The superior endplate 12 and the inferior endplate 14 are
assembled in an
unexpanded condition to the inserter 100 with the superior endplate 12
residing fully within
cavity 48 of inferior endplate 14. In such condition elevator 18 is captively
retained between
superior endplate 12 and inferior endplate 14 as described above and shown in
FIG. Sc for
independent movement along the direction of expansion 130. The inserter 100 is
releasably
attached to the device 10 upon threaded engagement of the guide pin 108 into
threaded
opening 56 in the proximal rear end wall 44 of the inferior endplate 14. Graft
shield 128
extends into device 10 through channel 50 between the superior endplate 12 and
the elevator
18 adjacent the lower surface 30 of the superior endplate 12. With the
inserter 100 fixed to
the device 10, lifting platform 116 and driver 124 are axially translatable
relative to the
device 10 in the projecting and retracting directions. In this unexpanded
condition, there are
no inserts 16 in the device 10. In the arrangement being described, there are
five inserts 16
supported in a linear array on track 104.
In the position illustrated in FIGS. 10a-b and 11-12 lifting platform 116 is
in a
retracted position relative to device 10 and elevator 18. Insert 16, as seen
in FIG. 10a, is
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disposed on track 104 exteriorly of and ready for insertion into device 10. In
this position the
lower surface 120 of lifting platform 116 is situated on lower inner surface
54 of inferior
endplate 14. Likewise lower surface 304 of elevator 18 is supported by lower
inner surface
54 of inferior endplate 14. As such, lifting platform 116 and elevator 18 are
on substantially
the same plane, with the upper surface 118 of lifting platform 116 being
substantially
coplanar with the upper surface 302 of elevator 18. With the inserter 100
attached to the
device 10, elevator 18 is fixed in the axial direction relative to axial
movement of lifting
platform 116.
In the condition shown in FIGS. 10a-b, apparatus 1 comprising unexpanded
device 10
releasably attached to inserter 100 is ready for use in inserting device 10
into an intradiscal
space between two opposing vertebral bodies. Prior to insertion, opening 38
through superior
endplate 12 may be pre-packed with a suitable bone graft material for the
promotion of fusion
through device 10 to the opposing vertebral bodies. Graft shield 128 extends
into device 10
through channel 50 between the superior endplate 12 and the elevator 18
adjacent the lower
surface 30 of the superior endplate 12 defining a pocket for receipt of the
graft material. The
free end 128b of graft shield 128 rests unattached on an interior ledge 12b of
superior
endplate 12 adjacent the distal end thereof. Opening 38 is therefore open
adjacent outer
surface 12a of superior endplate 12 and closed by graft shield 128 adjacent
lower surface 30.
As such, graft shield 128 provides a barrier between the graft material and
the elevator 18 and
inserts 16 inserted into device 10 during expansion. Pre-packing of bone graft
material in
opening 38 on graft shield 128 advantageously allows for less introduction of
graft material
in situ and provides more assurance that sufficient graft material will be
contained throughout
device 10 and into openings 38 and 60 through superior endplate 12 and
inferior endplates 14
and in a stress-loaded condition against opposing vertebral bodies. In
addition, graft shield
128 provides a barrier substantially preventing graft material within opening
38 from being
disturbed during expansion and by substantially blocking graft material from
interfering with
the expansion of device 10 or with the slidable insertion of inserts 16 which
may be impeded
by graft material on the sliding interfacing surfaces.
At this point in the surgical procedure, inserter 100 is used to insert
unexpanded
device 10 into the intradiscal space. Device 10 may be implanted as explained
hereinabove
into the spine posteriorly or posteriolaterally, either bilaterally or
unilaterally, or in an
anterior or lateral approach depending upon the surgical indication and the
surgeons
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preference. Once device 10 is inserted in the intradiscal space in a suitable
location, actuator
102 as described hereinabove is then operated in a first actuation. Initially
during the first
stroke lifting platform 116 is translated axially while driver 124 remains
stationary. Lifting
platform 116 is moved from the retracted position of FIGS.10a-b to a
projecting direction
whereby lifting platform 116 is moved further into device 10. During movement
in the
projecting direction, lifting surfaces 116a, 116b and 116c of lifting platform
116 contact
cooperative lifting surfaces 308a, 312b, and 314b, respectively of elevator
18. The
cooperative engagement causes elevator 18 to move in the direction of
expansion away from
lower inner surface 54 of inferior endplate 14 and toward superior endplate
12. The upper
surface 302 of elevator 18 contacts lower surface 30 of superior endplate 12
and elevator 18
slidably moves in the direction of expansion along rails 14b toward superior
endplate 12 and
away from inferior endplate 14 as shown in FIGS. 13a-b, thereby expanding
device 10.
When complete expansion of device 10 is achieved the first stroke of trigger
actuator
102 is completed and hand grips 132/134 are returned to the original starting
position, as
described above. Trigger actuator 102 is then operated in a second actuation
to start a second
stroke. As the second stroke commences, lifting platform 116 remains
stationary holding
device 10 in the expanded condition while axial translation of driver 124
begins. Continued
operation of actuator 102 pushes insert 16 distally so that the distal front
end 208 moves
freely into expanded device 10 through channel 50 until the distal front end
208 of insert 16
is partially inserted into expanded device 10 between superior endplate 12 and
inferior
endplate 14 adjacent the proximal end of device 10, as illustrated in FIGS.
13a-b.
With insert 16 partially inserted in device10, continued operation of the
actuator 102
during the second stroke causes lifting platform 116 to move proximally
thereby moving
lifting platform 116 in a retracting direction. With distal front end 208 of
insert 16
supporting superior endplate 12, continued proximal movement of lifting
platform 116 causes
lifting surfaces 116a, 116b and 116c of lifting platform 116 to sufficiently
disengage
cooperative lifting surfaces 308a, 312b, and 314b, respectively of elevator 18
to allow
elevator 18 to move away in the direction of expansion from superior endplate
12 and toward
inferior endplate 14 along rails 14b and return to the position of elevator 18
shown in FIGS.
10a-b. As elevator 18 returns to the position whereby the lower surface 120 of
lifting
platform 116 is situated on lower inner surface 54 of inferior endplate 14, a
space like the
space 64 as described hereinbelow with reference to FIG. 16b, is created
between lower
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surface 30 of superior endplate 12 and upper surface 302 of elevator 18. Such
space between
the superior endplate 12 and the elevator 18 is slightly greater than the
thickness of an insert
16 and is in direct communication with lower surface 30 of superior endplate
12 and upper
surface 302 of elevator 18. During completion of the second stroke of actuator
102 driver
124 continues to move axially distally slidably pushing insert 16 fully into
such space of
expanded device 10, as shown in FIG. 14, with lower surface 204 of insert 16
facing and
being in slidable contact with upper surface 302 of elevator 18. Driver 124 is
retracted
proximally to the original position shown in FIGS. 10a-b when the hand grip
134 of actuator
102 is released.
During insertion of insert 16 into device 10, receptacle 220 described
hereinabove at
the distal end 208 of insert 16 cooperatively receives complementary flexible
latch 318 on the
upper surface 302 of elevator 18 such that locking surfaces 224a, 224b and
322a, 322b
resiliently interlock, as shown in FIG. 5b. Such interlocking substantially
resists any back out
of the insert 16 through channel 50 as driver 124 is withdrawn away from
insert 16 in the
retracted position. In the event device 10 is further expanded, as described
hereinbelow, the
initial insert 16 is moved upwardly with superior endplate 12 by elevator 18.
As elevator 18
then returns downwardly toward inferior endplate 14 as will be explained,
latch 318 is
separated from receptacle 220 as space 64 is created. With the initial insert
16 moved
upwardly, it is situated above channel 50 and held captive by the interior
surfaces of inferior
endplate 14, including interior surface 44a of rear end wall 44. It should be
appreciated that
while insert 16 is held in position within device 10 by interlocking of
receptacle 220 and latch
318, other structure to resist back out movement of insert 16 may be provided,
such as
interlocking structure between insert 16 and one or more interior surfaces of
the inferior
endplate 14, or interlocking structure between adjacent inserts 16. Upon
completion of
insertion of insert 16, opening 216 of insert 16 is at least partially aligned
with opening 316
of elevator 18, opening 38 of superior endplate 12 and opening 60 of inferior
endplate 14.
Once inserter 100 is removed from the expanded device upon completion of the
surgical
procedure, insert opening 216, elevator opening 316 and graft chambers 38 and
60,
respectively, will all be in at least partial alignment and communication with
each other.
In the event the surgeon determines that additional inserts 16 are required in
order to
provide proper correction of the height of the intradiscal space, actuator 102
may be operated
to insert one or more additional inserts 16 in the same manner as described
with respect to the
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insertion of first insert 16. FIGS.15a-b show device 10 with one insert 16
having been
inserted and a second insert 16 partially introduced after device 10 has been
further expanded
during a first stroke of actuator 102 by elevator 18 upon lifting by the
lifting platform 116 in
the same process as described with respect to FIGS. 13a-b. As the second
insert 16 enters the
further expanded device 10 during the second stroke, lifting platform 116 is
pulled
proximally in a retracting direction, sufficiently disengaging lifting
surfaces 116a, 116b and
116c of lifting platform 116 from cooperative lifting surfaces 308a, 312b, and
314b,
respectively of elevator 18 to allow elevator 18 to freely return to inner
surface 54 of inferior
endplate 14. However, in the event elevator 18 fails to fully or partially
return to such
position, during pushing of second insert 16 into device 10 by driver 124, the
inclined
surfaces 208a adjacent the front distal end 208 of second insert 16 contacts
inclined surfaces
312a and 314a, respectively at the upper free end of each arm 312 and 314 of
elevator 18, as
shown in FIGS. 16a-b, to urge elevator 18 toward and against lower surface 54
of the inferior
endplate 14 creating a space 64 between lower surface 204 of the first insert
16 and upper
surface 302 of elevator 18. Alternatively, or in addition, a suitable biasing
element may be
included to normally urge elevator 18 toward inner surface 54 of inferior
endplate 14. Inferior
endplate 14 may be formed to include a lip 46a on the front end wall 46
adjacent the distal
end of cavity 48 to contain a spring 107 which would serve as the biasing
element, as shown,
for example, in FIG. 15a. It should be understood that the features urging
elevator 18 toward
lower inner surface 54 of inferior endplate 14 function during the insertion
of first insert 16 as
well as with all subsequently inserted inserts 16.
Continued operation of actuator 102 during the second stroke will continue to
move
second insert 16 until fully inserted shown in FIG. 17. During insertion of
second insert 16
into device 10, the resilient interlocking features of receptacle 220
described hereinabove of
the second insert 16 cooperatively interlock with the complementary
interlocking features of
flexible latch 318 on the distal end of elevator 18. Upon completion of
insertion of second
insert 16, opening 216 of insert 16 is at least partially aligned with opening
216 of the first
insert, opening 38 of superior endplate 12 and opening 60 of inferior endplate
14, all of which
will be in communication upon removal of inserter 100. The second insert 16 is
the
lowermost insert and resides on upper surface 302 of elevator 18 directly
below and in
contact with first insert 16, as shown in FIGS. 17 and 18. Driver 124 is then
again retracted
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proximally to the original position shown n FIGS. 10a-b when the hand grip 134
of actuator
102 is released.
When the intradiscal space has been expanded to its maximum anatomic extent as
the
spine reaches ligamentotaxis and the device 10 cannot be further expanded, the
surgeon will
be able to determine such condition by tactile feedback. Insertion of an
insert 16 into device
can only be achieved after elevator 18 reaches its ultimate movement in the
direction of
expansion toward superior endplate 12. As such, failure to compress hand grips
132/134 in a
manner to complete the first stroke of actuator 102 will allow the surgeon to
recognize that
ligamentotaxis has been reached and the proper intradiscal height has been
restored.
10 Inasmuch as the insertion of an insert 16 follows the expansion of
device 10 upon full
movement of elevator 18 in the direction of expansion toward inferior endplate
14,
incomplete insertion of an insert 16 may be avoided. An indication that full
expansion of
device 10 has been reached may also be determined visually as described
hereinabove by
observation that flags 162 on actuator 102 have rotated relative to frame 101.
The surgeon
would then terminate the procedure by actuating hex fitting 174, as described
hereinabove.
Inserter 100 would then be removed from the expanded device 10 by rotatably
removing
knob 112 from the proximal end of guide pin 108. As shown in FIG. 19, the
guide pin 108
may remain releasably connected to expanded device 10 to serve as a locator
for subsequent
attachment to an apparatus containing suitable bone graft to assist in the
delivery of such
material into channel 50 of inferior endplate 14 through which inserts 16 were
inserted. As
such, upon removal of inserter 100 from expanded device 10, a substantially
unobstructed
path exists from channel 50 though opening 316 of elevator 18 and openings 216
of inserts 16
and into openings 38 and 60 extending through the superior endplate 12 and the
inferior
endplate 14, respectively, to allow bone graft material introduced into
expanded device 10
through channel 50 to flow fully through device 10.
In accordance with certain specific applications of device 10 for posterior
implantation as described hereinabove, the overall length of the device 10 as
defined by the
length of the inferior endplate 14 is about 25 mm. The width of the device 10
is
approximately 10 mm. The height of the unexpanded device 10 of FIGS. la-c with
the
superior endplate 12 fully nested within the inferior endplate 14 is
approximately 7 mm.
With the introduction of five inserts 16, each of which has a thickness of
approximately 1.0
mm, the height of device 10 may be expanded from an unexpanded height of
approximately 7
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mm to an expanded height of approximately 12 mm. It should be appreciated that
these
dimensions are only illustrative and the number of inserts 16 as well as the
dimensions of
device 10 may vary depending upon the particular surgery and application. For
example,
device 10 for posterior implantation may have an initial unexpanded height in
the range of
approximately 7-10 mm, a width in the range of approximately 10-14 mm, and a
length in the
range of approximately 20-35 mm, with up to eight inserts 16 for the taller
sizes. For
implementing such posterior-size devices 10, trigger actuator 102 may have an
operating
mechanism as described herein for expanding device 10 in a first stroke and
fully inserting an
insert 16 in a second stroke.
For certain applications of device 10 that may be implanted from a lateral
approach,
device 10 may have an unexpanded height in the range of approximately 8-10 mm,
a width in
the range of approximately 14-26 mm, and a length in the range of
approximately 35-60 mm.
To implant such devices 10 from the lateral approach, trigger actuator 102 may
have an
operating mechanism adjusted to expand device 10 in a first stroke, partially
insert an insert
16 in a second stroke, and fully insert an insert 16 in a third stroke.
Channel 50, extending through the rear end wall 44, is sized and configured to
facilitate the introduction of a suitable bone graft material by a graft
delivery apparatus that
may use guide pin 108 as a locator, as shown in FIG. 19. Such a graft delivery
apparatus may
have an entry tip sized and configured for entry into channel 50. In a
particular arrangement,
it may be desirable to increase the entry opening to further ease the delivery
of graft material.
In such instance, a portion of rear end wall 44 may be notched out to form a
channel portion
50a of increased height directly below threaded opening 56. Channel portion
50a situated
below threading opening 56 would direct the entry flow of bone graft material
into the center
of expanded device 10. Channel portion 50a may be suitably configured to
cooperatively
receive the entry tip of the graft delivery apparatus, with such channel
portion 50a being
rectangular, square or arcuate. In the example of device 10 for posterior
applications, channel
portion 50a may be particularly configured to be square. Where such device 10
has an initial
unexpanded height of 7 mm and a width of 10 mm, channel portion 50a may have a
width of
3 mm and a height of 3 mm as measured vertically from inner surface 54. In the
example of
device 10 for lateral applications, channel portion 50a may be particularly
configured to be
generally rectangular. Where such device 10 has an initial unexpanded height
of 8 mm and a
width of 16 mm, channel portion 50a may have a height of 3 mm as measured
vertically from
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inner surface 54, and a width of 6 mm. For purposes of delivering bone graft
material in the
form of autograft, it is desirable that the minimum dimension of channel
portion 50a, or any
portion of channel 50 used as an entry port for such autograft material be no
less than about 2
mm. It should be appreciated, however, that depending upon the viscosity of
bone graft
material to be delivered, such minimum dimension may vary.
Turning now to FIG. 20, an alternative inserter 400 embodying a modular
construction is described. Inserter 400 comprises an actuator 402 and a
releasable cartridge
404. Actuator 402 includes a pair of hand grips 407 and 408 that are biased
apart by an
extension spring in the same manner as in trigger actuator 102 described
hereinabove.
Actuator 402 includes a frame 410 housing an operating mechanism 411
substantially the
same as the operating mechanism of trigger actuator 102. Grip 407 is fixedly
secured to
frame 410 while grip 408 is pivotally connected to frame 410 by a pivot pin
412. Frame 410
supports a rotatable flag 414 that is coupled to the operating mechanism 411
as in trigger
actuator 102. Frame 410 includes a pair of spring-loaded flexible latches 416
projecting
upwardly from an interface surface 410a adjacent the proximal end 410b of
frame 410.
Adjacent the distal end 410c of frame 410 a support surface 410d is provided.
Actuator 402
in a particular embodiment is reusable. Frame 410, as well as frame 101, and
hand grips 407,
408, as well as hand grips 132, 134 are all formed of stainless steel in a
particular
arrangement, although other materials, such as aluminum alloys and plastics
may also be
used.
Cartridge 404 comprises a track 406 contained within an outer cover 418
similar to
track 104 and cover 106 of trigger actuator 102. Cartridge 404 likewise houses
a translatable
lifting platform, a translatable driver and an indexing member (all not shown)
that are
constructed the same as lifting platform 116, driver 124 and indexing member
125 of trigger
actuator 102, and that function in the same manner. A support 420 comparable
to support 172
is secured to the bottom of cover 418. Cartridge 404 supports a plurality of
inserts 16 in a
linear array for insertion into the expandable device 10. Cooperative latching
structure is
provided at the bottom surface of cover 418 for releasable engagement with
latches 416 of
actuator 402. In a particular embodiment, cartridge 404 is disposable.
Cartridge 404 is releasably attached to frame 410 by initially engaging
support 420
with support surface 410d on frame 410 and then rotating cartridge down toward
proximal
24
CA 02941054 2016-10-14
end 410b until latches 416 releasably attach to the cooperative latching
structure at the
bottom of cartridge 404. Upon attachment of cartridge 404 with actuator 402,
components of
operating mechanism 411 interface with the driver and the lifting mechanism
within track
406 in a manner comparable to actuator 102, including the receipt of boss
feature 422 (the
same as boss feature 156) into a slot that is the same as slot 124d of driver
124. Cartridge 404
may be released from actuator 402 by actuation of release levers 424 supported
by frame 410
on both sides thereof and movably coupled to latches 416. In all other
respects, modular
inserter 400 operates the same as trigger actuator 102 described hereinabove.
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, an inserter with a graft shield,
such as shield 128,
may be used with expandable spinal interbody fusion devices having an
expansion structure
without an elevator 18 as described hereinabove. For example, an inserter with
a graft shield
128 may be used with the expandable interbody fusion device shown and
described in the
'312 Patent referenced hereinabove wherein the device is expanded upon
introduction of a
series of wafers. Shield 128 may be used similarly as described herein to
provide a barrier
between a graft opening through one of the endplates, such as the superior
endplate, and the
wafers. Such a barrier would substantially prevent bone graft material pre-
packed into such
opening from interfering with sliding receipt of such wafers during insertion
and expansion
of the device. In addition, it should also be appreciated that actuators other
than trigger
actuators, such as with threaded rotary mechanisms, may be used with the
inserter 100
described herein.
