U.S. patent application number 17/328713 was filed with the patent office on 2021-09-09 for polyaxial bone anchor with compound articulation and pop-on shank.
The applicant listed for this patent is NuVasive, Inc.. Invention is credited to Roger P. Jackson, James L. Surber.
Application Number | 20210275230 17/328713 |
Document ID | / |
Family ID | 1000005600843 |
Filed Date | 2021-09-09 |
United States Patent
Application |
20210275230 |
Kind Code |
A1 |
Jackson; Roger P. ; et
al. |
September 9, 2021 |
POLYAXIAL BONE ANCHOR WITH COMPOUND ARTICULATION AND POP-ON
SHANK
Abstract
A polyaxial bone screw assembly includes a threaded shank body
having an integral shank head receivable in a one-piece receiver
having an upper channel for receiving a longitudinal connecting
member and a lower cavity cooperating with a lower opening. A
compression insert (some with an independent tool lock, lock and
release feature and/or friction fit feature) and a split retaining
ring articulatable with respect to both the shank head and the
receiver (prior to locking) cooperate with the receiver to provide
for pop- or snap-on assembly of the shank with the receiver either
prior to or after implantation of the shank into a vertebra.
Inventors: |
Jackson; Roger P.; (Prairie
Village, KS) ; Surber; James L.; (Kansas City,
KS) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NuVasive, Inc. |
San Diego |
CA |
US |
|
|
Family ID: |
1000005600843 |
Appl. No.: |
17/328713 |
Filed: |
May 24, 2021 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
16223598 |
Dec 18, 2018 |
|
|
|
17328713 |
|
|
|
|
13385997 |
Mar 20, 2012 |
10194951 |
|
|
16223598 |
|
|
|
|
13373289 |
Nov 9, 2011 |
9907574 |
|
|
13385997 |
|
|
|
|
12924802 |
Oct 5, 2010 |
8556938 |
|
|
13385997 |
|
|
|
|
12072354 |
Feb 26, 2008 |
10076361 |
|
|
13385997 |
|
|
|
|
11126965 |
May 10, 2005 |
7476239 |
|
|
12072354 |
|
|
|
|
12008067 |
Jan 8, 2008 |
7901437 |
|
|
11126965 |
|
|
|
|
61465812 |
Mar 24, 2011 |
|
|
|
61456649 |
Nov 10, 2010 |
|
|
|
61460234 |
Dec 29, 2010 |
|
|
|
61278240 |
Oct 5, 2009 |
|
|
|
61336911 |
Jan 28, 2010 |
|
|
|
61343737 |
May 3, 2010 |
|
|
|
61395564 |
May 14, 2010 |
|
|
|
61395752 |
May 17, 2010 |
|
|
|
61396390 |
May 26, 2010 |
|
|
|
61398807 |
Jul 1, 2010 |
|
|
|
61400504 |
Jul 29, 2010 |
|
|
|
61402959 |
Sep 8, 2010 |
|
|
|
61403696 |
Sep 20, 2010 |
|
|
|
61403915 |
Sep 23, 2010 |
|
|
|
60905472 |
Mar 7, 2007 |
|
|
|
60897723 |
Jan 26, 2007 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 17/7037 20130101;
A61B 17/7032 20130101; A61B 17/864 20130101 |
International
Class: |
A61B 17/70 20060101
A61B017/70 |
Claims
1. In a bone anchor, the improvement comprising: a) a shank having
a body for fixation to a bone and an integral upper portion having
a substantially spherical surface; b) a receiver having a top
portion and a base with a lower opening, the receiver top portion
defining a first open channel, the base having a curved surface
partially defining a cavity, the channel communicating with the
cavity and the lower opening; c) at least one insert disposed
within the receiver, the insert having a second open channel and a
concave surface operatively frictionally mating and locking with
the shank first spherical surface; d) a resilient open retainer
captured within the cavity and expandable in the cavity about at
least a portion of the shank, the open retainer having an inner
surface for unlocked slidable, articulatable engagement with the
shank and an outer surface for unlocked slidable articulatable
engagement with the receiver curved surface; and e) wherein
expansion-only operative locking engagement occurs between the
shank upper portion and the retainer and between the retainer and
the receiver.
2. The improvement of claim 1 wherein the receiver curved surface
has a first radius and the retainer outer surface has a second
radius, the first radius being substantially equal to the second
radius.
3. The improvement of claim 1 wherein the retainer inner surface
has a first radius and the shank substantially spherical surface
has a second radius, the first radius being substantially equal to
the second radius.
4. The improvement of claim 1 wherein at least one of the insert
arms has an outer surface engaging the receiver top portion.
5. The improvement of claim 4 wherein the receiver top portion has
at least one surface crimped inwardly against at least one of the
insert arms.
6. The improvement of claim 1 wherein the insert is top loaded into
the receiver and then rotated into a position above the retainer
with the second channel aligned with the first channel.
7. The improvement of claim 1 wherein the receiver top portion has
a first pair of opposed tool receiving through apertures formed
therein and the insert has a second pair of opposed tool receiving
apertures in alignment with the first pair of apertures, the first
pair of apertures sized and shaped to provide tool access to the
insert, each of the second pair of opposed tool receiving apertures
having a tool receiving surface sized and shaped to allow a tool to
press the insert downwardly into temporary locking engagement with
the shank.
8. The improvement of claim 7, wherein the receiver top portion has
at least one sloping surface communicating with each of the first
pair of apertures, each sloping surface sized and shaped for
aligning a tool with the respective insert tool receiving
surface.
9. The improvement of claim 8 wherein the receiver top portion at
least one sloping surface is a first sloping surface and the insert
has a second sloping surface substantially aligned with the first
sloping surface, the second sloping surface being adjacent to and
oriented at an obtuse angle with respect to one of the insert tool
receiving surfaces.
10. The improvement of claim 1 wherein the retainer has a top
surface and a slit.
11. The improvement of claim 10 wherein the slit is disposed at an
obtuse angle with respect to the top surface.
12. The improvement of claim 10 wherein the retainer top surface is
planar.
13. The improvement of claim 1 wherein the insert is spaced from
the retainer in all angular orientations of the shank with respect
to the receiver.
14. In a bone anchor, the improvement comprising: a) a shank having
a body for fixation to a bone and an integral head having at least
one curved surface; b) a receiver having a top portion and a base,
the receiver top portion defining an open channel, the base having
a first surface partially defining a cavity, the channel
communicating with the cavity, the receiver having at least one
tool receiving through aperture; c) at least one insert disposed
within the receiver, the insert sized and shaped to directly engage
with the shank head curved surface and to cooperate with lock and
release tools that extend through the receiver tool receiving
aperture for pressing the insert downwardly against the shank head
into one of non-floppy sliding engagement and temporary locking
engagement with the shank head; and d) a resilient open retainer
captured within the cavity and expandable within the cavity about
at least a portion of the shank head, the retainer having a first
polyaxial articulation with the shank head and a second polyaxial
articulation with the receiver when in an unlocked position, and
wherein expansion-only locking engagement occurs between the shank
head and the retainer and between the retainer and the receiver
when in a locked position.
15. The improvement of claim 14 wherein the at least one tool
receiving aperture is a pair of opposed tool receiving apertures
and the insert has a pair of opposed recessed tool receiving
surfaces formed in outer walls thereof, the recessed tool receiving
surfaces being accessible through the receiver tool receiving
apertures.
16. The improvement of claim 14 wherein the receiver has a first
tool receiving sloping surface adjacent the through aperture and
the insert has a second tool receiving surface generally aligned
with the first tool receiving sloping surface.
17. The improvement of claim 16 wherein the insert tool receiving
surface forms a v-shaped recess.
18. In a bone anchor, the improvement comprising: a) a shank having
a body for fixation to a bone and an integral head having a first
spherical surface; b) a receiver having a top portion and a base,
the receiver top portion having first and second opposed arms
defining an open channel, the base having a lower opening and a
second spherical surface partially defining a base cavity, the
channel communicating with the cavity and the lower opening, each
receiver arm having a tool receiving sloping surface and a through
aperture; c) at least one top loaded insert disposed within the
receiver, the insert having a third spherical surface sized and
shaped to directly engage with the shank head first spherical
surface, the insert having third and fourth opposed arms, each arm
having a recessed surface aligned with one of the receiver sloping
surfaces and sized and shaped for receiving lock and release tools
that extend through the receiver tool receiving apertures for
pressing the insert downwardly into engagement with the shank head;
and d) a resilient open retainer captured within the cavity and
expandable within the cavity about at least a portion of the shank
head first spherical surface, the retainer having a first polyaxial
articulation with the shank head first spherical surface and a
second polyaxial articulation with the receiver second spherical
surface when in an unlocked position, and wherein the retainer is
in expansion-only locking engagement between the shank head and the
receiver when the shank is in a locked position with respect to the
receiver.
19. The improvement of claim 18 wherein the retainer has a fourth
spherical surface and a fifth spherical surface, the fourth
spherical surface engaging the shank first spherical surface and
the fifth spherical surface engaging the receiver second spherical
surface.
20. The improvement of claim 18, wherein the insert is top loaded
into the receiver.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Prov. Pat. App.
Ser. No. 61/465,812, filed Mar. 24, 2011 and incorporated by
reference herein. This application is also a continuation-in-part
of U.S. patent application Ser. No. 13/373,289 filed Nov. 9, 2011
that claims the benefit of U.S. Prov. Pat. App. Ser. No. 61/456,649
filed Nov. 10, 2010 and U.S. Prov. Pat. App. Ser. No. 61/460,234
filed Dec. 29, 2010, all of which are incorporated by reference
herein. This application is also a continuation-in-part of U.S.
patent application Ser. No. 12/924,802 filed Oct. 5, 2010 that
claims the benefit of the following U.S. Prov. Pat. App. Ser. Nos.
61/278,240, filed Oct. 5, 2009; 61/336,911, filed Jan. 28, 2010;
61/343,737 filed May 3, 2010; 61/395,564 filed May 14,2010;
61/395,752 filed May 17, 2010; 61/396,390 filed May 26, 2010;
61/398,807 filed Jul. 1, 2010; 61/400,504 filed Jul. 28, 2010;
61/402,959 filed Sep. 8, 2010; 61/403,696 filed Sep. 20, 2010; and
61/403,915 filed Sep. 23, 2010, all of which are incorporated by
reference herein. This application is also a continuation-in-part
of U.S. patent application Ser. No. 12/072,354 filed Feb. 26, 2008
that claims the benefit of U.S. Prov. Pat. App. Ser. No. 60/905,472
filed Mar. 7, 2007 and is a continuation-in-part of U.S. patent
application Ser. No. 11/126,965 filed May 10, 2005, now U.S. Pat.
No. 7,476,239 and is a continuation-in-part of U.S. patent
application Ser. No. 12/008,067 filed Jan. 8, 2008, now U.S. Pat.
No. 7,901,437, that claims the benefit of U.S. Prov. App. Ser. No.
60/897,723 filed Jan. 26, 2007, all of which are incorporated by
reference herein.
BACKGROUND OF THE INVENTION
[0002] The present invention is directed to polyaxial bone screws
for use in bone surgery, particularly spinal surgery and
particularly to such screws with compression or pressure inserts
and expansion-only split retainers to snap over, capture and retain
the bone screw shank head in the receiver member assembly and later
fix the bone screw shank with respect to the receiver assembly.
[0003] Bone screws are utilized in many types of spinal surgery in
order to secure various implants to vertebrae along the spinal
column for the purpose of stabilizing and/or adjusting spinal
alignment. Although both closed-ended and open-ended bone screws
are known, open-ended screws are particularly well suited for
connections to rods and connector arms, because such rods or arms
do not need to be passed through a closed bore, but rather can be
laid or urged into an open channel within a receiver or head of
such a screw. Generally, the screws must be inserted into the bone
as an integral unit along with the head, or as a preassembled unit
in the form of a shank and pivotal receiver, such as a polyaxial
bone screw assembly.
[0004] Typical open-ended bone screws include a threaded shank with
a pair of parallel projecting branches or arms which form a yoke
with a U-shaped slot or channel to receive a rod. Hooks and other
types of connectors, as are used in spinal fixation techniques, may
also include similar open ends for receiving rods or portions of
other fixation and stabilization structure.
[0005] A common approach for providing vertebral column support is
to implant bone screws into certain bones which then in turn
support a longitudinal structure such as a rod, or are supported by
such a rod. Bone screws of this type may have a fixed head or
receiver relative to a shank thereof, or may be of a polyaxial
screw nature. In the fixed bone screws, the rod receiver head
cannot be moved relative to the shank and the rod must be favorably
positioned in order for it to be placed within the receiver head.
This is sometimes very difficult or impossible to do. Therefore,
polyaxial bone screws are commonly preferred. Also, it is often
desirable to insert the bone screw shank separate from the receiver
or head due to its bulk which can get in the way of what the
surgeon needs to do. Such screws that allow for this capability are
sometimes referred to as modular polyaxial screws.
[0006] With specific reference to modular snap-on or pop-on
polyaxial pedicle screw systems having shank receiver assemblies,
the prior art has shown and taught the concept of the receiver and
certain retainer parts forming an assembly wherein a contractile
locking engagement between the parts is created to fix the shank
head with respect to the receiver and retainer. The receiver and
shank head retainer assemblies in the prior art have included a
slotted contractile retainer ring and/or a lower pressure slotted
insert with an expansion and contraction collet-type of structure
having contractile locking engagement for the shank head due to
direct contact between the retainer and/or the collet structure
with the receiver resulting in contraction of the slotted retainer
ring and/or the collet-type structure of the insert against the
shank head. The receiver and slotted insert have generally included
tapered locking engagement surfaces.
[0007] The prior art for modular polyaxial screw assemblies has
also shown and taught that the contact surfaces on the outside of
the slotted collet and/or retainer and the inside of the receiver,
in addition to being tapered, can be conical, radiused, spherical,
curvate, multi-curvate, rounded, as well as other configurations to
create a contractile type of locking engagement for the shank head
with respect to the receiver.
[0008] In addition, the prior art for modular polyaxial screw
assemblies has shown and taught that the shank head can both enter
and escape from a collet-like structure on the insert or from the
retainer when the insert or retainer is in the up position and
within an expansion recess or chamber of the receiver. This is the
case unless the slotted insert and/or the slotted retainer are
blocked from being able to be pushed back up into receiver bore or
cavity, or unless the screw assemblies are otherwise uniquely
configured to prevent this from happening.
SUMMARY OF THE INVENTION
[0009] The present invention differentiates from the prior art by
not allowing the receiver to be removed from the shank head once
the parts are snapped-on and connected. This is true even if the
retainer can go back up into the expansion chamber. This approach
or design has been found to be more secure and to provide more
resistance to pull-out forces compared to the prior art for modular
polyaxial screw designs. Collect-like structures extending
downwardly from lower pressure inserts, when used in modular
polyaxial screw designs, as shown in the prior art, have been found
to be somewhat weak with respect to pull-out forces encountered
during some spinal reduction procedures. The present invention is
designed to solve these problems.
[0010] The present invention also differentiates from the prior art
by providing an expansion-only split or open retainer ring that is
ultimately positioned in sliding, pivoting relation with the shank
and positioned substantially below the shank head hemisphere in the
receiver and can be a stronger, more substantial structure to
resist larger pull-out forces on the assembly. Furthermore, the
slitted or slotted retainer ring is also ultimately in sliding,
pivoting relation with an inner surface of the receiver. The
expansion only retainer has been found to be stronger and more
secure when compared to that of the prior art which uses some type
of contractile locking engagement between the parts, as described
above; and, again, once assembled it cannot be disassembled.
[0011] Thus, a polyaxial bone screw assembly according to the
invention includes a shank having an integral upper portion
illustrated as a spherical head and a body for fixation to a bone;
a separate receiver defining an upper open channel, a central bore,
a lower cavity and a lower opening; a compression insert; and a
resilient expansion-only split retainer for capturing the shank
head in the receiver lower cavity, the retainer being slidingly
engageable with both the shank head and a surface defining the
receiver cavity. Thus, a first polyaxial articulation is formed by
the shank head and the retainer and a second polyaxial articulation
is formed by the retainer and the receiver making a compound
articulation. In the illustrated embodiment, the shank upper
portion or head is convex, more specifically, spherical, and the
retainer has an inner concave surface, also illustrated as
spherical, in slidable, pivoting and rotational relation thereto.
The retainer also has an outer convex surface, illustrated as
spherical, and the receiver has an inner concave surface,
illustrated as spherical, in slidable, pivoting and rotational
relation thereto. Thus, cooperation between the retainer and the
shank head at one side thereof and the receiver at the other side
thereof allows for multiple or, again, compound articulation of the
shank with respect to the receiver.
[0012] It is foreseen in some embodiments when assembled with the
receiver, retainer and insert, but prior to locking, that the shank
head can be frictionally engaged with, but still movable in a
non-floppy manner with respect to the insert to allow for movement
of the shank to a desired position or angular orientation of the
shank with respect to the receiver. For example, this could be done
with a tool. The insert operatively engages the shank head and is
spaced from the retainer by the shank head. The shank can be
finally locked into a fixed position relative to the receiver by
frictional engagement between a portion of the insert due to a
downward force placed on the compression insert by a temporary
locking tool or by a closure top pressing on a rod, or other
longitudinal connecting member, captured within the receiver bore
and channel. In the illustrated embodiments, retainers and inserts
are downloaded into the receiver, but uploaded retainer embodiments
are also foreseen. The shank head can be positioned into the
receiver lower cavity at the lower opening thereof prior to or
after insertion of the shank into bone. It is also foreseen that
some compression inserts may include a lock and release feature for
independent locking of the polyaxial mechanism so the screw can be
used like a fixed monoaxial screw. In some embodiments the shank
can be cannulated for minimally invasive surgery applications. The
lower pressure insert and/or the retainer are both devoid of any
type of receiver-retainer contractile locking engagements with
respect to the shank head, and the receiver is devoid of any
spring-tab like members.
[0013] Again, a pre-assembled receiver, compression insert and
split retainer may be "pushed-on", "snapped-on" or "popped-on" to
the shank head prior to or after implantation of the shank into a
vertebra. Such a "snapping on" procedure includes the steps of
uploading the shank head into the receiver lower opening, the shank
head pressing against the base of the split retainer ring and
expanding the resilient retainer out into an expansion portion or
chamber of the receiver cavity followed by an elastic return of the
retainer back to an original or near nominal shape thereof after
the hemisphere of the shank head or upper portion passes through
the ring-like retainer. In such neutral or original shape, the
retainer is slidable with respect to both a lower portion of the
shank head and an inner surface defining the receiver cavity, the
illustrated retainer, shank and receiver surfaces being
substantially spherical, with the retainer having an inner
partially spherical surface and an outer partially spherical
surface. However, it is foreseen that other surface configurations
or combinations may be utilized. In the illustrated embodiment, the
ultimate locking of the shank between the compression insert and
the retainer is the result of a locking expansion-type of contact
between the shank head and the split retainer and an expansion-type
of non-tapered locking engagement between the retainer ring and a
lower portion of the receiver cavity. The retainer can expand more
in an upper portion of the receiver cavity to allow the shank head
to pass through, but has restricted expansion to retain the shank
head when the retainer is against the lower receiver surfaces
defining the receiver cavity. The shank head is forced down against
the retainer during final locking. It is foreseen that in some
embodiments, when the polyaxial mechanism is locked, the insert
could be forced or wedged against surfaces of the receiver
resulting in an interference, non-contractile locking engagement,
allowing for adjustment or removal of the rod or other connecting
member without loss of a desired angular relationship between the
shank and the receiver. This type of independent, non-contractile
locking feature would allow the polyaxial screw to function like a
fixed monoaxial screw, which could be very helpful in some
applications.
[0014] The compression or pressure insert (a lock and release
embodiment or a non-locking embodiment) may also be configured to
be independently locked (permanently or temporarily) by a tool or
instrument, thereby allowing the pop-on polyaxial screw to be
distracted, compressed and/or rotated along and around the rod to
provide for improved spinal correction techniques. Such a tool
engages the pop-on receiver from the sides and then engages the
insert to force or wedge the insert down into a locked position on
the shank within the receiver. With the tool still in place and the
correction maintained, the rod is then locked within the receiver
channel by a closure top followed by removal of the tool. This
process may involve multiple screws all being manipulated
simultaneously with multiple tools to achieve the desired
correction.
[0015] Objects of the invention further include providing apparatus
and methods that are easy to use and especially adapted for the
intended use thereof and wherein the tools are comparatively
inexpensive to produce. Other objects and advantages of this
invention will become apparent from the following description taken
in conjunction with the accompanying drawings wherein are set
forth, by way of illustration and example, certain embodiments of
this invention.
[0016] The drawings constitute a part of this specification and
include exemplary embodiments of the present invention and
illustrate various objects and features thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is an exploded perspective view of a polyaxial bone
screw assembly according to the present invention including a
shank, a receiver, a retainer in the form of an open ring
articulatable with respect to both the shank and the receiver and a
crown compression insert, further shown with a portion of a
longitudinal connecting member in the form of a rod and a closure
top.
[0018] FIG. 2 is an enlarged top plan view of the shank of FIG.
1.
[0019] FIG. 3 is reduced cross-sectional view taken along the line
3-3 of FIG. 2.
[0020] FIG. 4 is an enlarged perspective view of the receiver of
FIG. 1.
[0021] FIG. 5 is a side elevational view of the receiver of FIG.
4.
[0022] FIG. 6 is a top plan view of the receiver of FIG. 4.
[0023] FIG. 7 is a bottom plan view of the receiver of FIG. 4.
[0024] FIG. 8 is an enlarged cross-sectional view taken along the
line 8-8 of FIG. 6.
[0025] FIG. 9 is an enlarged cross-sectional view taken along the
line 9-9 of FIG. 6.
[0026] FIG. 10 is an enlarged and partial perspective view of a
portion of the receiver of FIG. 4 with portions broken away to show
the detail thereof.
[0027] FIG. 11 is an enlarged perspective view of the retainer of
FIG. 1.
[0028] FIG. 12 is a reduced top plan view of the retainer of FIG.
11.
[0029] FIG. 13 is a bottom plan view of the retainer of FIG.
12.
[0030] FIG. 14 is a front elevational view of the retainer of FIG.
12.
[0031] FIG. 15 is a cross-sectional view taken along the line 15-15
of FIG. 12.
[0032] FIG. 16 is an enlarged perspective view of the insert of
FIG. 1.
[0033] FIG. 17 is a side elevational view of the insert of FIG.
16.
[0034] FIG. 18 is a front elevational view of the insert of FIG.
16.
[0035] FIG. 19 is a bottom plan view of the insert of FIG. 16.
[0036] FIG. 20 is a top plan view of the insert of FIG. 16.
[0037] FIG. 21 is an enlarged cross-sectional view taken along the
line 21-21 of FIG. 20.
[0038] FIG. 22 is an enlarged cross-sectional view taken along the
line 22-22 of FIG. 20.
[0039] FIG. 23 is an enlarged front elevational view of the
retainer and receiver of FIG. 1 with portions of the receiver
broken away to show the detail thereof and further showing in
phantom an intermediate position of the retainer while being
downloaded into the receiver.
[0040] FIG. 24 is a front elevational view with portions broken
away, similar to FIG. 23, further showing the insert of FIG. 1 in
enlarged side elevation, with an early stage of assembly of the
insert being shown in phantom.
[0041] FIG. 25 is a front elevational view with portions broken
away, similar to FIG. 24, showing the insert rotated within the
receiver during an assembly stage subsequent to that shown in FIG.
24.
[0042] FIG. 26 is an enlarged perspective view with portions broken
away of the assembly shown in FIG. 25 and further showing a
subsequent step of crimping a portion of the receiver against the
insert.
[0043] FIG. 27 is a reduced side elevational view of the assembly
shown in FIG. 26.
[0044] FIG. 28 is a front elevational view with portions broken
away, similar to FIG. 25 and shown with the crimping of FIGS. 26
and 27.
[0045] FIG. 29 is a reduced front elevational view with portions
broken away, similar to FIG. 28 and further showing an alternative
assembly stage with the shank of FIG. 1 shown in partial front
elevation in which the shank is first implanted in a vertebra,
shown in phantom, followed by assembly with the receiver, retainer
and insert.
[0046] FIG. 30 is an enlarged and partial front elevational view
with portions broken away, similar to FIG. 28 showing the shank
(not implanted in a vertebra) in a stage of assembly with the
retainer, the retainer being pushed up into engagement with the
insert.
[0047] FIG. 31 is an enlarged partial front elevational view with
portions broken away, similar to FIG. 30, and having further
portions broken away showing the retainer in an expanded state
about an upper portion of the shank.
[0048] FIG. 32 is a partial front elevational view with portions
broken away, similar to FIG. 31, and showing a subsequent step of
the retainer being returned to a neutral state capturing the shank
within the receiver.
[0049] FIG. 33 is a partial front elevational view with portions
broken away, similar to FIG. 32, the shank upper portion and
retainer being pulled downwardly into the receiver.
[0050] FIG. 34 is a partial front elevational view with portions
broken away, similar to FIG. 33 showing a subsequent step of
lowering the insert into engagement with the shank.
[0051] FIG. 35 is a partial front elevational view of the assembly
as shown in FIG. 34 with further portions broken away to show the
detail thereof.
[0052] FIG. 36 is a partial front elevational view of the assembly
of FIG. 35, further showing the shank being articulated at an angle
with respect to the receiver.
[0053] FIG. 37 is a partial front elevational view of the assembly
of FIG. 35, further showing the shank and the retainer being
articulated at an angle with respect to the receiver.
[0054] FIG. 38 is a reduced perspective view of the assembly of
FIG. 35 further shown in engagement with the rod and closure of
FIG. 1 and with portions broken away to show the detail
thereof.
DETAILED DESCRIPTION OF THE INVENTION
[0055] As required, detailed embodiments of the present invention
are disclosed herein; however, it is to be understood that the
disclosed embodiments are merely exemplary of the invention, which
may be embodied in various forms. Therefore, specific structural
and functional details disclosed herein are not to be interpreted
as limiting, but merely as a basis for the claims and as a
representative basis for teaching one skilled in the art to
variously employ the present invention in virtually any
appropriately detailed structure. It is also noted that any
reference to the words top, bottom, up and down, and the like, in
this application refers to the alignment shown in the various
drawings, as well as the normal connotations applied to such
devices, and is not intended to restrict positioning of the bone
attachment structures in actual use.
[0056] With reference to FIGS. 1-38 the reference number 1
generally represents a polyaxial bone screw apparatus or assembly
according to the present invention. The assembly 1 includes a shank
4, that further includes a body 6 integral with an upwardly
extending upper portion or head-like capture structure 8; a
receiver 10; a retainer structure illustrated as a resilient open,
articulatable ring 12, and a compression or pressure insert 14. The
receiver 10, retainer 12 and compression insert 14 are initially
assembled and may be further assembled with the shank 4 either
prior or subsequent to implantation of the shank body 6 into a
vertebra 17, as will be described in greater detail below. FIGS. 1
and 38 further show a closure structure 18 for capturing a
longitudinal connecting member, for example, a rod 21 which in turn
engages the compression insert 14 that presses against the shank
upper portion 8 into fixed frictional contact with the retainer 12,
so as to capture, and fix the longitudinal connecting member 21
within the receiver 10 and thus fix the member 21 relative to the
vertebra 17. The receiver 10 and the shank 4 cooperate in such a
manner that the receiver 10 and the shank 4 can be secured at any
of a plurality of angles, articulations or rotational alignments
relative to one another and within a selected range of angles both
from side to side and from front to rear, to enable flexible or
articulated engagement of the receiver 10 with the shank 4 until
both are locked or fixed relative to each other near the end of an
implantation procedure. The illustrated rod 21 is hard, stiff,
non-elastic and cylindrical, having an outer cylindrical surface
22. It is foreseen that in other embodiments, the rod 21 may be
elastic, deformable and/or of a different cross-sectional geometry.
In such cases, the closure top could deform the rod and press
directly on the insert 14.
[0057] The shank 4, best illustrated in FIGS. 1-3, is elongate,
with the shank body 6 having a helically wound bone implantable
thread 24 (single or dual lead thread form) extending from near a
neck 26 located adjacent to the upper portion or head 8, to a tip
28 of the body 6 and extending radially outwardly therefrom. During
use, the body 6 utilizing the thread 24 for gripping and
advancement is implanted into the vertebra 17 (e.g., see FIG. 29)
leading with the tip 28 and driven down into the vertebra with an
installation or driving tool (not shown), so as to be implanted in
the vertebra to a location at or near the neck 26, as more fully
described in the paragraphs below. The shank 4 has an elongate axis
of rotation generally identified by the reference letter A.
[0058] The neck 26 extends axially upward from the shank body 6.
The neck 26 may be of the same or is typically of a slightly
reduced radius as compared to an adjacent upper end or top 32 of
the body 6 where the thread 24 terminates. Further extending
axially and outwardly from the neck 26 is the shank upper portion
or head 8 that provides a connective or capture apparatus disposed
at a distance from the upper end 32 and thus at a distance from the
vertebra 17 when the body 6 is implanted in such vertebra.
[0059] The shank upper portion 8 is configured for a pivotable
connection between the shank 4 and the retainer 12 and receiver 10
prior to fixing of the shank 4 in a desired position with respect
to the receiver 10. The shank upper portion 8 has an outer, convex
and substantially spherical surface 34 that extends outwardly and
upwardly from the neck 26 and terminates at a substantially planar
top or rim surface 38. The spherical surface 34 has an outer radius
configured for frictional, sliding cooperation with a concave
surface of the compression insert 14, as well as ultimate
frictional engagement with the insert as will be discussed more
fully in the paragraphs below. The top surface 38 is substantially
perpendicular to the axis A. The spherical surface 34 shown in the
present embodiment is substantially smooth, but in some embodiments
may include a roughening or other surface treatment and is sized
and shaped for cooperation and ultimate frictional engagement with
the compression insert 14 as well as ultimate frictional engagement
with the retainer 12. The shank spherical surface 34 is locked into
place exclusively by the insert 14 and the retainer 12 and not by
inner surfaces defining the receiver cavity, the shank being held
in spaced relation with the receiver by the retainer 12.
[0060] A counter sunk substantially planar base 45 partially
defines an internal drive feature or imprint 46. The illustrated
internal drive feature 46 is an aperture formed in the top surface
38 and has a star shape designed to receive a driving tool (not
shown) of an Allen wrench type, into the aperture for rotating and
driving the bone screw shank 4. It is foreseen that such an
internal tool engagement structure may take a variety of
tool-engaging forms and may include one or more apertures of
various shapes, such as a hex shape, a pair of spaced apart
apertures or a multi-lobular or star-shaped aperture, such as those
sold under the trademark TORX, or the like. The seat or base
surface 45 of the drive feature 46 is disposed substantially
perpendicular to the axis A with the drive feature 46 otherwise
being coaxial with the axis A. The drive seat 45 may include
beveled or stepped surfaces that may further enhance gripping with
the driving tool. In operation, a driving tool (not shown) is
received in the internal drive feature 46, being seated at the base
45 and engaging the plurality of faces of the drive feature 46 for
both driving and rotating the shank body 6 into the vertebra 17,
either before the shank 4 is attached to the receiver 10 or after
the shank 4 is attached to the receiver 10, with the shank body 6
being driven into the vertebra 17 with the driving tool extending
into the receiver 10.
[0061] The shank 4 shown in the drawings is cannulated, having a
small central bore 50 extending an entire length of the shank 4
along the axis A. The bore 50 is defined by an inner cylindrical
wall of the shank 4 and has a circular opening at the shank tip 28
and an upper opening communicating with the external drive 46 at
the driving seat 45. The bore 50 is coaxial with the threaded body
6 and the upper portion 8. The bore 50 provides a passage through
the shank 4 interior for a length of wire (not shown) inserted into
the vertebra 17 prior to the insertion of the shank body 6, the
wire providing a guide for insertion of the shank body 6 into the
vertebra 17.
[0062] To provide a biologically active interface with the bone,
the threaded shank body 6 may be coated, perforated, made porous or
otherwise treated. The treatment may include, but is not limited to
a plasma spray coating or other type of coating of a metal or, for
example, a calcium phosphate; or a roughening, perforation or
indentation in the shank surface, such as by sputtering, sand
blasting or acid etching, that allows for bony ingrowth or
ongrowth. Certain metal coatings act as a scaffold for bone
ingrowth. Bio-ceramic calcium phosphate coatings include, but are
not limited to: alpha-tri-calcium phosphate and beta-tri-calcium
phosphate (Ca.sub.3(PO.sub.4).sub.2, tetra-calcium phosphate
(Ca.sub.4P.sub.2O.sub.9), amorphous calcium phosphate and
hydroxyapatite (Ca.sub.10(PO.sub.4).sub.6(OH).sub.2). Coating with
hydroxyapatite, for example, is desirable as hydroxyapatite is
chemically similar to bone with respect to mineral content and has
been identified as being bioactive and thus not only supportive of
bone ingrowth, but actively taking part in bone bonding.
[0063] With particular reference to FIGS. 1 and 4-10, the receiver
10 has a generally U-shaped appearance with partially discontinuous
and partially planar and cylindrical inner and outer profiles. The
receiver 10 has an axis of rotation B that is shown in FIG. 1 as
being aligned with and the same as the axis of rotation A of the
shank 4, such orientation being desirable, but not required during
assembly of the receiver 10 with the shank 4 (see, e.g., FIG. 29
showing the receiver 10 being "popped on" to a shank 4 that is
implanted in a vertebra 17 and disposed at an angle with respect to
the receiver). After the receiver 10 is pivotally attached to the
shank 4, either before or after the shank 4 is implanted in a
vertebra 17, the axis B is typically disposed at an angle with
respect to the axis A, as shown, for example, in FIGS. 36 and
37.
[0064] The receiver 10 includes a partially curved or cylindrical
and partially planar and diverging base 60 defining a bore or inner
cavity, generally 61, the base 60 being integral with a pair of
opposed upstanding arms 62 forming a cradle and defining a channel
64 between the arms 62 with an upper opening, generally 66, and a
U-shaped lower channel portion or seat 68, the channel 64 having a
width for operably snugly receiving the rod 21 or portion of
another longitudinal connector between the arms 62; the channel 64
communicating with the base cavity 61. Outer front and rear opposed
substantially planar arm surfaces 69 define an outer perimeter of
the channel 64 at the arms 62 and about the channel seat 68.
[0065] Each of the arms 62 has an interior surface, generally 70,
that includes various inner cylindrical profiles, an upper one of
which is a partial helically wound guide and advancement structure
72 located adjacent top surfaces 73 of each of the arms 62. In the
illustrated embodiment, the guide and advancement structure 72 is a
partial helically wound interlocking flangeform configured to mate
under rotation with a similar structure on the closure structure
18, as described more fully below. However, it is foreseen that for
certain embodiments of the invention, the guide and advancement
structure 72 could alternatively be a square-shaped thread, a
buttress thread, a reverse angle thread or other thread-like or
non-thread-like helically wound discontinuous advancement
structures, for operably guiding under rotation and advancing the
closure structure 18 downward between the arms 62, as well as
eventual torquing when the closure structure 18 abuts against the
rod 21 or other longitudinal connecting member. It is foreseen that
the arms could have break-off extensions.
[0066] An opposed pair of rounded off triangular or delta-shaped
tool receiving and engaging apertures, generally 74, each having a
through bore formed by an upper arched surface 75 and a
substantially planar bottom surface 75', are formed on outer
surfaces 76 of the arms 62. Each through bore surface 75 and 75'
extends through the arm inner surface 70. The apertures 74 with
through bore portions 75 and 75' are sized and shaped for receiving
locking, unlocking and other manipulation tools and may aid in
receiving and downloading the retainer ring 12 during top loading
of the retainer 12 into the receiver 10. Each aperture 74 further
includes a sloping tool alignment surface 77 that generally
surrounds the arched bore portion 75 and does not extend completely
through the respective arm 62, the sloping surfaces 77 terminating
at a substantially planar thin wall 78, the wall 78 defining the
bore portion 75 and disposed at an angle to the wall 78. Each wall
78 further includes a further recessed crimping portion or area 79
that is also partially formed in one of the sloping surfaces 77. As
will be described in greater detail below, during an assembly
stage, each of the four crimping portions 79 is pressed or crimped
into the insert 14 to aid in retaining the insert 14 in alignment
with the receiver and prohibit rotation of the retainer with
respect to the receiver, but to allow for movement of the retainer
up and down along the receiver axis B. In a preferred embodiment,
such up and down movement is possible only through the application
of some upward or downward force, allowing for the insert to be
placed in an out-of-the-way location during insertion of the shank
head 8 through the retainer 12 and then later, for a non-floppy
frictional engagement between the insert 14 and the shank upper
portion 8 during intermediate assembly and/or implantation steps
and positions prior to locking the shank into place between the
insert 14 and the retainer 12. In other embodiments of the
invention, other walls or surfaces defining the aperture 74 or
other material defining other apertures or grooves may be inwardly
crimped. It is noted that the illustrated receiver 10 is an
integral structure and devoid of any spring tabs or collet-like
structures. Alternatively, in some embodiments, spring tabs or
other movable structure may be included on the receiver 10 or the
insert 14 for retaining the insert 14 in a desired position, with
regard to rotation and axial movement (along the axis A) with
respect to the receiver 10. Preferably the insert and/or receiver
are configured with structure for blocking rotation of the insert
with respect to the receiver, but allowing some up and down
movement of the insert with respect to the receiver during the
assembly and implant procedure.
[0067] Formed in each surface 77 and also partially in each arm
surface 76 and located opposite the planar surface 75' is another
tool receiving recess 80 having a somewhat rectangular profile. A
further recess 81 is located directly above the recess 80, the
recess 81 being formed in each arm surface 76 and located between
the aperture 74 and the arm top surface 73. Each recess 81 has a
substantially rectangular profile with a base surface 82 that does
not extend all the way through the respective arm 61 and further
includes an upper curved portion 83 having a half-circular profile.
Four V-shaped grooves 84 are formed in each of the arm surfaces 76
at each of the front and rear planar surfaces 69, each groove 84
running from the respective top surface 73 to a location midway
along the receiver arm on either side of the aperture 74. Some or
all of the apertures or grooves 74, 81 and 84 may be used for
holding the receiver 10 during assembly with the insert 14, the
retainer 12 and the shank 4; during the implantation of the shank
body 6 into a vertebra when the shank is pre-assembled with the
receiver 10; during assembly of the bone anchor assembly 1 with the
rod 21 and the closure structure 18; and during lock and release
adjustment of the some inserts of the invention with respect to the
receiver 10, either into or out of frictional engagement with the
inner surfaces of the receiver 10 as will be described in greater
detail below. It is foreseen that tool receiving grooves,
depressions or apertures may be configured in a variety of shapes
and sizes and be disposed at other locations on the receiver arms
62.
[0068] Returning to the interior surface 70 of the receiver arms
62, located below the guide and advancement structure 72 is a
discontinuous cylindrical surface 88 partially defining a run-out
feature for the guide and advancement structure 72. The cylindrical
surface 88 has a diameter equal to or slightly greater than a
greater diameter of the guide and advancement structure 72. Moving
downwardly in a direction toward the base 60, adjacent the
cylindrical surface 88 of each, arm is a run-out seat or surface 89
that extends inwardly toward the axis B and slopes toward the axis
B. Adjacent to and located below the surface 84 is another
cylindrical surface 90 having a diameter smaller than the diameter
of the surface 82. The through bore surfaces 75 and 75' extend
through the arms primarily at the surfaces 90, with an upper
portion of each arch 75 extending through one of the surfaces 88.
Located near each aperture surface 75 is an inner surface portion
92 of the crimp areas or portions 79, the surface portions 92
engaging the insert 14 when the thin wall at the surface portion 79
is crimped toward the insert 14 during assembly of such insert in
the receiver 10 as will be described in greater detail below. The
inner discontinuous surface 90 found on the receiver arms 62 also
extends downwardly into the receiver cavity 61 and thus defines an
upper expansion area for the retainer 12. The surface 90 is
disposed parallel to the receiver axis B and is sized to receive
portions of the insert 14, and in some embodiments may be sized to
provide a locking interference fit with a cylindrical portion of a
locking insert.
[0069] Further, with respect to the base 60 and more specifically,
the base cavity 61, a lower portion of the surface 90 that extends
into the base and partially defines the base cavity 61 terminates
at a stepped or sloping surface or surfaces 95 inwardly directed
toward the axis B and sized and shaped to receive the retainer 12.
The surface 90 defines a circumferential recess that is sized and
shaped to receive the retainer 12 as it expands around the shank
upper portion 8 as the shank 8 moves upwardly toward the channel 64
during assembly. The insert 14 provides an upper stop or
restriction to prevent the expanded retainer 12 from moving
upwardly with the shank portion 8, the insert 14 preventing the
retainer 12 from passing upwardly out of the cavity 61 whether the
retainer 12 is in a partially or fully expanded position or state.
Adjacent and below the stepped or sloping surfaces 95 is an inner
spherical surface 100 sized and shaped for sliding relation and
ultimate frictional contact with an outer surface of the retainer
12 as will be described in greater detail below. The stepped
surfaces 95 allow for sliding gradual movement of the retainer 12
into the space defined by the surface 100 and ultimate seating of
the retainer 12 against the surface 100 and above and along a
terminal edge 102 of the surface 100. Located below and adjacent to
the edge 102 is a beveled or flared bottom opening surface 107, the
surface 107 communicating with an exterior base surface 108 of the
base 60, defining a lower opening, generally 110, into the base
cavity 61 of the receiver 10.
[0070] With particular reference to FIGS. 1 and 11-15, the lower
open or split retainer 12, that operates to capture the shank upper
portion 8 within the receiver 10, has a central axis C that may be
operationally the same or different than the axis B associated with
the receiver 10 or the axis A associated with the shank 4 when the
shank upper portion 8 and the retainer 12 are installed within the
receiver 10. The retainer ring is thus articulatable and slidable
with respect to both the shank 4 and the receiver 10 until locked
into place. The retainer ring 12 is made from a resilient material,
such as a stainless steel or titanium alloy, so that the retainer
12 may be expanded during various steps of assembly as will be
described in greater detail below. The retainer 12 has a central
channel or hollow through bore, generally 121, that passes entirely
through the ring 12 from a top surface 122 to a bottom surface 124
thereof. The bore 121 is defined by an inner discontinuous
spherical surface 125 that runs from adjacent the top surface 122
to adjacent the bottom surface 124. The retainer 12 further
includes an outer spherical surface 130 that runs from adjacent the
top surface 122 to adjacent the bottom surface 124. The inner
spherical surface 125 is sized and shaped for closely slidingly
receiving the shank head 8 at the surface 34 and ultimate
frictional locking there-against and the outer spherical surface
130 is sized and shaped for close sliding engagement with the inner
spherical surface 100 of the receiver 10 and ultimate frictional
locking there-against. In some embodiments of the invention, spaced
notches (not shown) may be formed in the spherical surface 130 to
receive a holding and manipulation tool (not shown). In some
embodiments further notches on inner or outer surfaces of the
retainer may be made to evenly distribute stress across the entire
retainer 12 during expansion thereof.
[0071] The resilient retainer 12 further includes first and second
end surfaces, 134 and 135 disposed in spaced relation to one
another when the retainer is in a neutral non-compressed state. The
surface 134 and 135 may also be touching when the retainer is in a
neutral state. Both end surfaces 134 and 135 run from the top
surface 122 to the bottom surface 124 and are illustrated as
running at an oblique angle to such top and bottom surfaces. In
other embodiments of the invention, the surfaces 134 and 135 may be
disposed substantially perpendicular to the top surface 122 and the
bottom surface 124. A width X between the surfaces 134 and 135 is
very narrow (slit may be made by EDM process) to provide stability
to the retainer 12 during operation. Because the retainer 12 is top
loadable in a neutral state and the retainer 12 does not need to be
compressed to fit within the receiver cavity 61, the width X may be
much smaller than might be required for a bottom loaded
compressible retainer ring. The gap X functions only in expansion
to allow the retainer 12 to expand about the shank upper portion 8.
This results in a stronger retainer that provides more surface
contact with the shank upper portion 8 upon locking, resulting in a
sturdier connection with less likelihood of failure than a retainer
ring having a greater gap. Furthermore, because the retainer 12 is
only expanded and never compressed inwardly, the retainer 12 does
not undergo the mechanical stress that typically is placed on
spring ring type retainers known in the prior art that are both
compressed inwardly and expanded outwardly during assembly. It is
foreseen that in some embodiments of the invention, the retainer 12
inner surfaces may include a roughening or additional material to
increase the friction fit against the shank upper portion 8 prior
to lock down by the rod 21 or other longitudinal connecting
member.
[0072] With particular reference to FIGS. 1 and 16-22, the crown
compression insert 14 is illustrated that is sized and shaped to be
received by and down-loaded into the receiver 10 at the upper
opening 66. The compression insert 14 has an operational central
axis that is the same as the central axis B of the receiver 10. In
operation, the insert advantageously frictionally engages the bone
screw shank upper portion 8, allowing for un-locked but non-floppy
placement of the angle of the shank 4 with respect to the receiver
10 during surgery prior to locking of the shank with respect to the
receiver near the end of the procedure. In some embodiments of the
invention, the insert that has locked the shank 4 in a desired
angular position with respect to the receiver 10, by, for example,
compression from the rod 21 and closure top 18, may also be forced
into an interference fit engagement with the receiver 10 at the
inner cylindrical surface 90, for example, and thus be capable of
retaining the shank 6 in a locked position even if the rod 21 and
closure top 18 are removed. Such locked position may also be
released by the surgeon if desired by features included in the
insert 14, such as ridges, grooves and/or apertures, bores or
holes. The non-locking insert 14 (as well as an alternative locking
insert) is preferably made from a solid resilient material, such as
a stainless steel or titanium alloy, so that portions of the insert
may be snapped or popped onto the shank upper portion 8 as well as
pinched or pressed against and un-wedged (in certain embodiments)
from the receiver 10 with a release tool.
[0073] The non-locking crown collet compression insert 14 includes
a substantially cylindrical body 136 integral with a pair of
upstanding arms 137. A bore, generally 140, is disposed primarily
within and through the body 136 and communicates with a generally
U-shaped through channel formed by a saddle 141 that is partially
defined by the upstanding arms 137 and partially by the body 136.
The saddle 141 is sized and shaped to closely, snugly engage the
cylindrical rod 21 and includes a curved lower seat 142. It is
foreseen that an alternative embodiment may be configured to
include planar holding surfaces that closely hold a square or
rectangular bar as well as hold a cylindrical rod-shaped, cord, or
sleeved cord longitudinal connecting member. The arms 137 disposed
on either side of the saddle 141 extend upwardly from the body 136.
The arms 137 are sized and configured for ultimate placement at or
near the cylindrical run-out surface 88 and inner surface 90
located below the receiver guide and advancement structure 72. It
is foreseen that in some embodiments of the invention, the insert
arms 137 may be extended and the closure top configured such the
arms ultimately directly engage the closure top 18 for locking of
the polyaxial mechanism, for example, when the rod 21 is made from
a deformable material. In such embodiments, the insert 14 would
include a rotation blocking structure or feature on an outer
surface thereof that abuts against cooperating structure located on
an inner wall of the receiver 10, preventing rotation of the insert
with respect to the receiver when the closure top is rotated into
engagement with the insert, especially when there is no rod in
place. In the present embodiment, each of the arms 137 includes an
outer surface 143 that is illustrated as partially cylindrical and
runs from the substantially planar top surfaces 144 to an inwardly
sloping lower surface 150 of the insert 14, the surface 150
extending about the body 136 and the arms 137 and terminating at an
annular rim or edge 151. The surface 150 is advantageously sloped
or angled to provide clearance between the insert 14 and the
retainer 12 when the retainer and shank 4 are articulated or
pivoted with respect to one another and with respect to the
receiver 10. Also, the sloping surface 150 that runs from the lower
edge or rim 151 outwardly and upwardly away from the axis B and
toward the upper surfaces 144 provides a sliding outwardly and
upwardly directed surface for guiding the top surface 122 of the
retainer 12 during expansion of the retainer inner spherical
surface 125 about the shank head 8 spherical surface 34 as will be
discussed in greater detail below.
[0074] The surfaces 143 are sized and shaped to generally fit
within the receiver arms 62. The arm outer surfaces 143 further
include notches or grooves formed thereon for receiving
manipulation, unlocking and locking tools. Although not shown, each
surface 143 may include one or more through bores or other
apertures for receiving tooling, particularly useful for
alternative locking embodiments (not shown). Centrally located (in
some embodiments below a through bore) and formed in each surface
143 is a delta or triangular notch or recess, generally 156, for
receiving tooling defined in part by an upper sloping surface 157
and intersecting a lower planar surface 158 disposed substantially
perpendicular to a central axis of the insert 14 (and the axis B of
the receiver when the insert is disposed within the receiver). Each
of the surfaces 167 and surface 168 cooperate and align with the
respective receiver aperture through bore surfaces 77 and 75' when
the insert 14 is captured and operationally positioned within the
receiver 10 as will be described in greater detail below. In the
illustrated embodiments, also formed in each surface 143 are a pair
of spaced v- or squared-off notches or grooves 160 and 161 that run
from the respective top surface 144 to near the sloping surface 157
of the central delta cut or notch 156. The grooves 160 and 161
cooperate with the receiver crimp wall 79 inner surfaces 92 to aid
in alignment of the insert channel saddle 141 with the receiver
channel 64 as shown, for example in FIGS. 25-27. The illustrated
pair of grooves 160 and 161 are disposed substantially parallel to
the central axis of the insert 14, running from one of the top
surfaces 144 to respective lower or bottom surfaces 162 and
163.
[0075] The u-shaped channel formed by the saddle 141 is also
partially defined by opposed inner planar surfaces 165 located near
the arm top surfaces 144. The saddle 141 also communicates with the
bore 140 at an inner cylindrical surface 166, the surface 166
located centrally within the insert body 136 and further
communicating with a lower concave surface portion 168 having a
generally spherical profile with a radius the same or substantially
similar to a radius of the surface 34 of the shank upper portion or
head 8. The surface 168 terminates at the edge or rim 151. It is
foreseen that in some embodiments of the invention a portion or all
of the surface 168 may include ridges, stepped surfaces or a
surface roughening or texture, such as scoring or knurling, or the
like, for enhancing frictional engagement with the shank upper
portion 8.
[0076] The insert bore 140 is sized and shaped to receive the
driving tool (not shown) therethrough that engages the shank drive
feature 46 when the shank body 6 is driven into bone with the
receiver 10 attached. Also, in alternative locking embodiments, the
bore 140 may receive a manipulation tool used for releasing the
such insert from a locked position with the receiver, the tool
pressing down on the shank and also gripping the insert at the
opposed through bores or with other tool engaging features. A
manipulation tool for un-wedging a locking insert from the receiver
10 may also access the such tooling bores from the receiver through
bores 74. The illustrated insert 14 may further include other
features, including grooves and recesses for manipulating and
holding the insert 14 within the receiver 10 and providing adequate
clearance between the retainer 12 and the insert 14.
[0077] The insert body 136 located between the arms 137 has an
outer diameter slightly smaller than a diameter between crests of
the guide and advancement structure 72 of the receiver 10, allowing
for top loading of the compression insert 14 into the receiver
opening 66, with the arms 137 of the insert 14 being located
between the receiver arms 62 during insertion of the insert 14 into
the receiver 10. Once the arms 137 of the insert 14 are generally
located beneath the guide and advancement structure 72, the insert
14 is rotated into place about the receiver axis B until the top
surfaces 144 are located directly below the guide and advancement
structure 72 as will be described in greater detail below.
[0078] With reference to FIGS. 1 and 38, the illustrated elongate
rod or longitudinal connecting member 21 (of which only a portion
has been shown) can be any of a variety of implants utilized in
reconstructive spinal surgery, but is typically a cylindrical,
elongate structure having the outer substantially smooth,
cylindrical surface 22 of uniform diameter. The rod 21 may be made
from a variety of metals, including hard and soft metal alloys and
hard and soft or deformable and less compressible plastics,
including, but not limited to rods made of elastomeric,
polyetheretherketone (PEEK) and other types of materials.
[0079] Longitudinal connecting members for use with the assembly 1
may take a variety of shapes, including but not limited to rods or
bars of oval, rectangular or other curved or polygonal
cross-section. The shape of the insert 14 may be modified so as to
closely hold, and if desired, fix or slidingly capture the
longitudinal connecting member to the assembly 1. Some embodiments
of the assembly 1 may also be used with a tensioned cord. Such a
cord may be made from a variety of materials, including polyester
or other plastic fibers, strands or threads, such as
polyethylene-terephthalate. Furthermore, the longitudinal connector
may be a component of a longer overall dynamic stabilization
connecting member, with cylindrical or bar-shaped portions sized
and shaped for being received by the compression insert 14 of the
receiver having a U-shaped, rectangular- or other-shaped channel,
for closely receiving the longitudinal connecting member. The
longitudinal connecting member may be integral or otherwise fixed
to a bendable or damping component that is sized and shaped to be
located between adjacent pairs of bone screw assemblies 1, for
example. A damping component or bumper may be attached to the
longitudinal connecting member at one or both sides of the bone
screw assembly 1. A rod or bar (or rod or bar component) of a
longitudinal connecting member may be made of a variety of
materials ranging from soft deformable plastics to hard metals,
depending upon the desired application. Thus, bars and rods of the
invention may be made of materials including, but not limited to
metal and metal alloys including but not limited to stainless
steel, titanium, titanium alloys and cobalt chrome; or other
suitable materials, including plastic polymers such as
polyetheretherketone (PEEK), ultra-high-molecular
weight-polyethylene (UHMWP), polyurethanes and composites,
including composites containing carbon fiber, natural or synthetic
elastomers such as polyisoprene (natural rubber), and synthetic
polymers, copolymers, and thermoplastic elastomers, for example,
polyurethane elastomers such as polycarbonate-urethane
elastomers.
[0080] With reference to FIGS. 1 and 38, the closure structure or
closure top 18 shown with the assembly 1 is rotatably received
between the spaced arms 62 of the receiver 10. It is noted that the
closure 18 top could be a twist-in or slide-in closure structure.
The illustrated closure structure 18 is substantially cylindrical
and includes a an outer helically wound guide and advancement
structure 182 in the form of a flange that operably joins with the
guide and advancement structure 72 disposed on the arms 62 of the
receiver 10. The flange form utilized in accordance with the
present invention may take a variety of forms, including those
described in Applicant's U.S. Pat. No. 6,726,689, which is
incorporated herein by reference. Although it is foreseen that the
closure structure guide and advancement structure could
alternatively be a buttress thread, a square thread, a reverse
angle thread or other thread like or non-thread like helically
wound advancement structure, for operably guiding under rotation
and advancing the closure structure 18 downward between the arms 62
and having such a nature as to resist splaying of the arms 62 when
the closure structure 18 is advanced into the channel 64, the
flange form illustrated herein as described more fully in
Applicant's U.S. Pat. No. 6,726,689 is preferred as the added
strength provided by such flange form beneficially cooperates with
and counters any reduction in strength caused by the inset surfaces
69 resulting in a reduced profile of the illustrated receiver 10 at
the U-shape channel, such surfaces advantageously engaging
longitudinal connecting member components as will be further
described below. The illustrated closure structure 18 also includes
a top surface 184 with an internal drive 186 in the form of an
aperture that is illustrated as a star-shaped internal drive such
as that sold under the trademark TORX, or may be, for example, a
hex drive, or other internal drives such as slotted, tri-wing,
spanner, two or more apertures of various shapes, and the like. A
driving tool (not shown) sized and shaped for engagement with the
internal drive 166 is used for both rotatable engagement and, if
needed, disengagement of the closure 18 from the receiver arms 62.
It is also foreseen that the closure structure 18 may alternatively
include a break-off head designed to allow such a head to break
from a base of the closure at a preselected torque, for example, 70
to 140 inch pounds. Such a closure structure would also include a
base having an internal drive to be used for closure removal. A
base or bottom surface 188 of the closure is planar and further
includes a rim 190 and may or may not include a further include a
central point (not shown), the rim 190 and or the point (not shown)
for engagement and penetration into the surface 22 of the rod 21 in
certain embodiments of the invention. The closure top 18 may
further include a cannulation through bore (not shown) extending
along a central axis thereof and through the top and bottom
surfaces thereof. Such a through bore provides a passage through
the closure 18 interior for a length of wire (not shown) inserted
therein to provide a guide for insertion of the closure top into
the receiver arms 62.
[0081] Preferably the receiver 10, the retainer 12 and the
compression insert 14 are assembled at a factory setting that
includes tooling for holding, pressing and alignment of the
component pieces as well as compressing or expanding the insert 14
arms, if needed, as well as crimping a portion of the receiver 10
toward the insert 14. In some circumstances, the shank 4 is also
assembled with the receiver 10, the retainer 12 and the compression
insert 14 at the factory. In other instances, it is desirable to
first implant the shank 4, followed by addition of the
pre-assembled receiver, retainer and compression insert at the
insertion point. In this way, the surgeon may advantageously and
more easily implant and manipulate the shanks 4, distract or
compress the vertebrae with the shanks and work around the shank
upper portions or heads without the cooperating receivers being in
the way. In other instances, it is desirable for the surgical staff
to pre-assemble a shank of a desired size and/or variety (e.g.,
surface treatment of roughening the upper portion 8 and/or
hydroxyapatite on the shank 6), with the receiver, retainer and
compression insert. Allowing the surgeon to choose the
appropriately sized or treated shank 4 advantageously reduces
inventory requirements, thus reducing overall cost.
[0082] Pre-assembly of the receiver 10, retainer 12 and compression
insert 14 is shown in FIGS. 23-28. First, the retainer 12 is
downloaded in a sideways manner into the receiver 10 through the
upper opening 66 with the outer surface 130 facing the receiver
channel seat 68. The retainer 12 is then lowered between the arms
62 and toward the receiver base 60 as shown in phantom in FIG. 23,
the retainer being turned or tilted to a position within the
receiver base 60 inner cavity 61 wherein the retainer bottom
surface 124 is manipulated to a position facing the spherical
surface 100 and then the surface 130 is seated upon the inner
spherical surface 100 as shown in solid lines in FIG. 23. With
reference to FIG. 24, the compression insert 14 is then downloaded
into the receiver 10 through the upper opening 66 with the bottom
rim 151 facing the receiver arm top surfaces 73 and the insert arms
137 located between the opposed receiver arms 62. The insert 14 is
then lowered toward the channel seat 68 until the insert 14 arm
upper surfaces 144 are adjacent the run-out area defined by the
surfaces 88 of the receiver 10 located below the guide and
advancement structure 72. Thereafter, the insert 14 is rotated in a
clockwise or counter-clockwise manner about the receiver axis B
until the upper arm surfaces 144 are directly below the guide and
advancement structure 72 as illustrated in FIG. 25 with the
U-shaped channel 141 of the insert 14 aligned with the U-shaped
channel 64 of the receiver 10. In some embodiments, the insert arms
137 may need to be compressed slightly during rotation to clear
inner surfaces of the receiver arms 62. As shown in FIGS. 25-27,
the outer cylindrical surfaces 143 of the insert 14 are received
within the cylindrical surfaces 88 and 90 of the receiver. With
particular reference to FIGS. 26 and 27, the receiver thin walls of
the crimping area 79 are then pressed inwardly toward the axis B by
inserting a tool (not shown) into the receiver apertures 74, the
tool pressing the sloped surface walls 77 until the receiver inner
wall surfaces 92 engage the insert 14 at each of the grooves 160
and 161 formed into the outer cylindrical surface 143 of each of
the insert arms 137. The crimping of the opposed wall surfaces 87
into the groves 160 and 161 keeps the insert 14 U-shaped channel
141 substantially aligned with the receiver U-shaped channel 64,
but allows for upward and downward movement of the insert 14 along
the receiver axis B during bottom loading of the shank 4 as shown
in FIG. 29, for example. However, such upward and downward movement
requires some force, as the four-point frictional engagement
between the insert and the receiver advantageously keeps the insert
at a desired axial location and is not a floppy or loose sliding
engagement. Thus, the crimping of the receiver walls 77 prohibits
rotation of the insert 14 about the receiver axis B but allows for
limited axial movement of the insert 14 with respect to the
receiver 10 along the axis B when some force is exerted to slide
the crimped surfaces 87 up or down along the grooves 160 and 161.
As illustrated in FIG. 28, the insert 14 arms 137 are fully
captured within the receiver 10 by the guide and advancement
structure 72 prohibiting movement of the insert 14 up and out
through the receiver opening 66 as well as by the retainer 12 and
the receiver annular surface 104 located in the receiver 10 base 60
below the insert 14. Also as illustrated in FIG. 28, the insert 14
may be desirably moved upwardly in the receiver 10 until an insert
top surface 144 abuts against the guide and advancement structure
72. FIG. 28 illustrates a preferred arrangement for shipping of the
receiver, retainer and insert combination as well as a preferred
upward and out-of-the-way position for the insert 14 during
assembly with the shank 4. In some embodiments of the invention,
top or side surfaces of the insert 14 may include a resilient
projection or projections for temporarily frictionally engaging
with an inner surface of the receiver 10 to hold the insert 14 in
an upper portion of the receiver 10 during some of the assembly
steps, also providing a frictional but slidable fit between the
insert 14 and the receiver 10.
[0083] At this time, the receiver, insert and retainer combination
are ready for shipping to an end user, with both the compression
insert 14 and the retainer 12 captured within the receiver 10 in a
manner that substantially prevents movement or loss of such parts
out of the receiver 10. The receiver 10, compression insert 14 and
the retainer 12 combination may now be assembled with the shank 4
either at the factory, by surgery staff prior to implantation, or
directly upon an implanted shank 4 as shown, for example, in FIG.
29, with the shank axis A and the receiver axis B either being
aligned during assembly as shown in FIG. 30 and most of the
drawings figures illustrating the assembly process, or the axes
being at an angle with respect to one another as shown in FIG.
29.
[0084] As illustrated in FIG. 29, the bone screw shank 4 or an
entire assembly 1 made up of the assembled shank 4, receiver 10,
retainer 12 and compression insert 14, is screwed into a bone, such
as the vertebra 17, by rotation of the shank 4 using a suitable
driving tool (not shown) that operably drives and rotates the shank
body 6 by engagement thereof at the internal drive 46.
Specifically, the vertebra 17 may be pre-drilled to minimize
stressing the bone and have a guide wire (not shown) inserted
therein to provide a guide for the placement and angle of the shank
4 with respect to the vertebra. A further tap hole may be made
using a tap with the guide wire as a guide. Then, the bone screw
shank 4 or the entire assembly 1 is threaded onto the guide wire
utilizing the cannulation bore 50 by first threading the wire into
the opening at the bottom 28 and then out of the top opening at the
drive feature 46. The shank 4 is then driven into the vertebra
using the wire as a placement guide. It is foreseen that the shank
and other bone screw assembly parts, the rod 21 (also having a
central lumen in some embodiments) and the closure top 18 (also
with a central bore) can be inserted in a percutaneous or minimally
invasive surgical manner, utilizing guide wires. When the shank 4
is driven into the vertebra 17 without the remainder of the
assembly 1, the shank 4 may either be driven to a desired final
location or may be driven to a location slightly above or proud to
provide for ease in assembly with the pre-assembled receiver,
compression insert and retainer.
[0085] With reference to FIGS. 29, 30 and 31, the pre-assembled
receiver, insert and retainer are placed above the shank upper
portion 8 until the shank upper portion is received within the
opening 110. As the shank upper portion 8 is moved into the
interior 61 of the receiver base defined by the spherical surface
100, the shank upper portion 8 presses the retainer 12 upwardly
into the portion of the receiver cavity 61 defined by the
cylindrical surface 90. With particular reference to FIGS. 30 and
31, as the portion 8 continues to move upwardly toward the channel
64, the top surface 122 of the retainer 12 abuts against the lower
or bottom frusto-conical or otherwise outwardly sloping surface 150
of the insert 14, limiting and directing upward movement of the
retainer 12 and forcing outward movement of the retainer 12 towards
the cylindrical surface 90 that defines an expansion area or
chamber for the retainer 12 as the shank 4 continues to move
upwardly with respect to the retainer 12. As is shown in FIGS.
30-32, the insert 14 is prohibited from moving upwardly in the
receiver by contact between the insert arm top surface 144 with the
receiver guide and advancement structure 72. With further reference
to FIG. 31 and also with reference to FIGS. 32 and 33, the retainer
12 begins to contract about the spherical surface 34 as the center
of the sphere of the head 8 passes beyond the center of the
retainer expansion recess defined by the surface 125. At this time
also, the spherical surface 34 moves into engagement with the
insert 14 spherical surface 168.
[0086] With reference to FIG. 33, the shank 4 and retainer 12 may
then be manipulated further downwardly into a desired seated
position on the receiver inner spherical surface 100 by either an
upward pull on the receiver 10 or, in some cases, by driving the
shank 4 further into the vertebra 17. Then, with reference to FIG.
34, the insert 14 may be pressed downwardly with a tool (not shown)
onto the shank head 8 spherical surface 34. At this time, the
insert 14 surface 168 and the surface 34 are in a fairly tight
friction fit, the surface 34 being pivotable with respect to the
insert 14 with some force. Thus, a tight, non-floppy ball and
socket joint is now created between the insert 14 and the shank
upper portion 8 as well as between the retainer inner and outer
surfaces and adjacent surfaces of the shank head 8 and the receiver
seating surface 100. At this time, the receiver 10 and may be
articulated to a desired angular position with respect to the shank
4, such as that shown in FIGS. 36 and 37, but prior to insertion of
the rod or closure top, that will be held, but not locked, by the
frictional engagement between the retainer 12, the shank upper
portion 8 and the receiver 10. With reference to FIG. 36, angular
pivoting or articulation of the shank 4 with respect to the
retainer 12 is shown. With reference to FIG. 37, angular pivoting
or articulation of the retainer 12 with respect to the receiver 10
is shown as well as articulation of the shank 4 with respect to the
retainer 12.
[0087] With reference to FIG. 38, the rod 21 is eventually
positioned in an open or percutaneous manner in cooperation with
the at least two bone screw assemblies 1. The closure structure 18
is then inserted into and advanced between the arms 62 of each of
the receivers 10. The closure structure 18 is rotated, using a tool
engaged with the inner drive 186 until a selected pressure is
reached at which point the rod 21 engages the U-shaped seating
surface 142 of the compression insert 14, pressing the insert
surface 168 into locked frictional engagement with the shank
spherical surface 34. Specifically, as the closure structure 18
rotates and moves downwardly into the respective receiver 10, the
rim 190 engages and penetrates the rod surface 22, the closure
structure 18 pressing downwardly against and biasing the rod 21
into compressive engagement with the insert 14 that urges the shank
upper portion 8 toward the retainer 12 and into locking engagement
therewith, the retainer 12 frictionally abutting and expanding
outwardly against the spherical surface 100. For example, about 80
to about 120 inch pounds of torque on the closure top may be
applied for fixing the bone screw shank 4 with respect to the
receiver 10.
[0088] An alternative lock-and-release compression insert (not
shown) may be identical or substantially similar to the insert 14
previously described herein, with the exception that the locking
insert is sized for a frictional interference fit with the receiver
10; specifically, a locking interference between the cylindrical
inner surface 90 of the receiver 10 and a part or portion of the
outer body surface 143 that is sized and shaped to have a greater
diameter than the diameter of the illustrated surface 143. Such a
locking insert would preferably further include a pair of opposed
through bores extending through the insert arm surfaces or some
other feature for receiving tooling for unlocking of such insert
from the receiver. Such an insert may be assembled with the
receiver 10, retainer 12, shank 4, rod 21 and closure top 18, in a
manner the same as previously described above with respect to the
assembly 1, with the exception that the alternative insert would be
forced downwardly into a locking interference fit with the receiver
10 when the shank 4 is locked in place, as compared to the easily
sliding relationship between the insert 14 and the receiver 10. One
way in which to force the alternative insert into locking
interference is by assembly with the rod and closure top. After
being fully locked down, the closure top may be loosened or removed
and/or the rod may be adjusted and/or removed and the frictional
engagement between the alternative insert and the receiver 10 at
the interferingly fixed surfaces would remain in place,
advantageously maintaining a locked angular position of the shank 4
with respect to the receiver 10. At this time, another rod, such as
a deformable rod and cooperating alternative closure top may be
loaded onto the already locked-up assembly to result in an
alternative assembly. The drive of such a closure top may
advantageously be made smaller than the drive of the closure 18,
such that the deformable rod is not unduly pressed or deformed
during assembly since the polyaxial mechanism is already
locked.
[0089] With reference to FIG. 35, a temporary locking and
manipulation tool, generally 700, is illustrated in phantom for
independently, temporarily locking the insert 14 against the shank
head 8 and thus temporarily locking the angle of the shank 4 with
respect to the receiver 10. The tool 700 includes a pair of opposed
arms 712, each having an engagement extension 716 positioned at an
angle with respect to the respective arm 712 such that when the
tool is moved downwardly toward the receiver, one or more inner
surfaces 718 of the engagement extension 716 slide along the
surfaces 77 of the receiver and along the surfaces 157 of the
insert 14 to engage the insert 14, with a surface 720 pressing
downwardly on the insert surfaces 158, pushing the insert
downwardly and pressing the spherical surface 168 into locking
frictional fit with the spherical surface 34 of the shank 4. It is
foreseen that the tool 700 may include a variety of holding and
pushing/pulling mechanisms, such as a pistol grip tool, that may
include a ratchet feature, a hinged tool, or, a rotatably threaded
device, for example for temporarily holding or fixing the polyaxial
mechanism of the assembly 1 in a desired position or
orientation.
[0090] It is to be understood that while certain forms of the
present invention have been illustrated and described herein, it is
not to be limited to the specific forms or arrangement of parts
described and shown.
* * * * *