U.S. patent application number 13/966748 was filed with the patent office on 2014-01-16 for polyaxial bone anchor with pop-on shank, friction fit retainer, winged insert and low profile edge lock.
The applicant listed for this patent is Roger P Jackson, James L. Surber. Invention is credited to Roger P Jackson, James L. Surber.
Application Number | 20140018863 13/966748 |
Document ID | / |
Family ID | 64100519 |
Filed Date | 2014-01-16 |
United States Patent
Application |
20140018863 |
Kind Code |
A1 |
Jackson; Roger P ; et
al. |
January 16, 2014 |
POLYAXIAL BONE ANCHOR WITH POP-ON SHANK, FRICTION FIT RETAINER,
WINGED INSERT AND LOW PROFILE EDGE LOCK
Abstract
A polyaxial bone screw assembly includes a threaded shank body
having an integral upper portion receivable in an integral
receiver, the receiver having an upper channel for receiving a
longitudinal connecting member and a lower cavity cooperating with
a lower opening. A down-loadable compression insert, a
down-loadable friction fit split retaining ring having inner and
outer tangs and an up-loadable shank upper portion cooperate 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.
The shank and receiver once assembled cannot be disassembled.
Inventors: |
Jackson; Roger P; (Prairie
Village, KS) ; Surber; James L.; (Kansas City,
KS) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Jackson; Roger P
Surber; James L. |
Prairie Village
Kansas City |
KS
KS |
US
US |
|
|
Family ID: |
64100519 |
Appl. No.: |
13/966748 |
Filed: |
August 14, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13573874 |
Oct 10, 2012 |
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13966748 |
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13573516 |
Sep 19, 2012 |
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13573874 |
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13573303 |
Sep 7, 2012 |
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13573874 |
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13506365 |
Apr 13, 2012 |
8444681 |
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13573874 |
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13385212 |
Feb 8, 2012 |
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13573874 |
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13374439 |
Dec 29, 2011 |
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13573874 |
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13373289 |
Nov 9, 2011 |
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13374439 |
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13136331 |
Jul 28, 2011 |
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13573874 |
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12924802 |
Oct 5, 2010 |
8556938 |
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13573874 |
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12802849 |
Jun 15, 2010 |
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13573874 |
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61627374 |
Oct 11, 2011 |
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61626250 |
Sep 23, 2011 |
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61573508 |
Sep 7, 2011 |
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61517088 |
Apr 13, 2011 |
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61463037 |
Feb 11, 2011 |
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61456649 |
Nov 10, 2010 |
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61460234 |
Dec 29, 2010 |
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61400504 |
Jul 29, 2010 |
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61403915 |
Sep 23, 2010 |
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61278240 |
Oct 5, 2009 |
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61336911 |
Jan 28, 2010 |
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61343737 |
May 3, 2010 |
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61395564 |
May 14, 2010 |
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61395752 |
May 17, 2010 |
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61396390 |
May 26, 2010 |
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61398807 |
Jul 1, 2010 |
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61400504 |
Jul 29, 2010 |
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61402959 |
Sep 8, 2010 |
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61403696 |
Sep 20, 2010 |
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61403915 |
Sep 23, 2010 |
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61268708 |
Jun 15, 2009 |
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61270754 |
Jul 13, 2009 |
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61336911 |
Jan 28, 2010 |
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61395564 |
May 14, 2010 |
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61395752 |
May 17, 2010 |
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61396390 |
May 26, 2010 |
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Current U.S.
Class: |
606/305 |
Current CPC
Class: |
A61B 2090/0808 20160201;
A61B 17/864 20130101; A61B 17/7091 20130101; A61B 17/7005 20130101;
A61B 17/702 20130101; A61B 17/7038 20130101; A61B 2017/681
20130101; A61B 17/7037 20130101; A61B 17/7008 20130101; A61B
17/7082 20130101; Y10T 29/49826 20150115; A61B 2017/567
20130101 |
Class at
Publication: |
606/305 |
International
Class: |
A61B 17/86 20060101
A61B017/86; A61B 17/70 20060101 A61B017/70 |
Claims
1. A bone anchor comprising: a) a shank having a body for fixation
to a bone and an integral upper head; b) a receiver having a top
portion and a base and an outer surface, the receiver top portion
having an open channel with a first width, the base having a
chamber and a lower opening, the chamber communicating with both
the channel and the lower opening; the interior of the receiver
including a surface with a pair of opposed wing receiving
apertures; c) an insert disposed within the receiver, the insert
having a surface sized and shaped for frictional mating cooperation
with the shank head, the insert further having a pair of outwardly
extending arms having a second width greater than the channel first
width and each arm having a distal wing; the insert being received
in the receiver in a first orientation wherein the insert is
positioned such that the wings extend outward to either side of the
channel; the insert is rotated ninety degrees to a second
orientation such that the wings are each located in a respective
wing receiving aperture so as to secure the insert in the receiver;
the insert further including a pair of radially inward directed
tool receiving apertures sized and shaped to be adapted to receive
opposite sides of a rotation tool for effecting rotation of the
insert in the receiver; and d) a retainer operably capturing the
shank within the chamber.
2. The anchor of claim 1 wherein a pair of shallow grooves and a
pair of respective through apertures are formed in the outer
surface of the receiver, each groove communicating with a
respective aperture, each groove extending from the respective
aperture to a top surface of the top portion of the receiver, each
groove having a width for receiving a manipulation tool.
3. The anchor of claim 1 wherein the insert has an outer surface
releasably frictionally lockable against the receiver chamber.
4. The anchor of claim 1 wherein the receiver channel is a first
channel and the insert has a second channel, the insert being top
loaded into the receiver and then rotated into a position above the
retainer with the second channel aligned with the first channel.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/573,874, filed Oct. 10, 2012 which claims
the benefit of U.S. Provisional Patent Application Ser. No.
61/627,374 filed Oct. 11, 2011 all of which are is incorporated by
reference herein.
[0002] U.S. patent application Ser. No. 13/573,874 application is
also a continuation-in-part of U.S. patent application Ser. No.
13/573,516 filed Sep. 19, 2012 that claims the benefit of U.S.
Provisional Patent Application Ser. No. 61/626,250 filed Sep. 23,
2011, both of which are incorporated by reference herein. U.S.
patent application Ser. No. 13/573,874 application is also a
continuation-in-part of U.S. patent application Ser. No. 13/573,303
filed Sep. 7, 2012 that claims the benefit of U.S. Provisional
Patent Application Ser. No. 61/573,508 filed Sep. 7, 2011, both of
which are incorporated by reference herein. U.S. patent application
Ser. No. 13/573,874 application is also a continuation-in-part of
U.S. patent application Ser. No. 13/506,365 filed Apr. 13, 2012
that claims the benefit of U.S. Provisional Patent Application Ser.
No. 61/517,088 filed Apr. 13, 2011, both of which are incorporated
by reference herein. U.S. patent application Ser. No. 13/573,874
application is also a continuation-in-part of U.S. patent
application Ser. No. 13/385,212 filed Feb. 8, 2012 that claims the
benefit of U.S. Provisional Patent Application Ser. No. 61/463,037
filed Feb. 11, 2011, both of which are incorporated by reference
herein. U.S. patent application Ser. No. 13/573,874 application is
also a continuation-in-part of U.S. patent application Ser. No.
13/374,439 filed Dec. 29, 2011 is incorporated by reference herein.
U.S. patent application Ser. No. 13/573,874 application is also an
continuation-in-part of U.S. patent application Ser. No.
13/373,289, filed Nov. 9, 2011 that claims the benefit of U.S.
Provisional Patent Application Ser. No. 61/456,649 filed Nov. 10,
2010 and Provisional Patent Application Ser. No. 61/460,234 filed
Dec. 29, 2010, all of which are incorporated by reference herein.
U.S. patent application Ser. No. 13/573,874 application is also a
continuation-in-part of U.S. patent application Ser. No. 13/136,331
filed Jul. 28, 2011 that claims the benefit of U.S. Provisional
Patent Application Ser. Nos. 61/400,504 filed Jul. 29, 2010, and
61/403,915 filed Sep. 23, 2010, all of which are incorporated by
reference herein. U.S. patent application Ser. No. 13/573,874
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. Provisional Patent Application 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. U.S. patent application Ser. No. 13/573,874
application is also a continuation-in-part of U.S. patent
application Ser. No. 12/802,849 filed Jun. 15, 2010 that claims the
benefit of the following U.S. Provisional Patent Application Ser.
Nos. 61/268,708 filed Jun. 15, 2009; 61/270,754, filed Jul. 13,
2009; 61/336,911 filed Jan. 28, 2010; 61/395,564 filed May 14,
2010; 61/395,752 filed May 17, 2010; and 61/396,390 filed May 26,
2010, all of which are incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0003] 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 lock 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.
[0004] 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.
[0005] 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.
[0006] 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. Open-ended polyaxial
bone screws typically allow for a loose or floppy rotation of the
head or receiver about the shank until a desired rotational
position of the receiver is achieved by fixing such position
relative to the shank during a final stage of a medical procedure
when a rod or other longitudinal connecting member is inserted into
the receiver, followed by a locking screw or other closure. This
floppy feature can be, in some cases, undesirable and make the
procedure more difficult. 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.
[0007] 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.
[0008] 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.
[0009] 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 or constrained from being able to be pushed or manipulated
back up into the receiver bore or cavity, or unless the screw
assemblies are otherwise uniquely configured to prevent this from
happening.
SUMMARY OF THE INVENTION
[0010] 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.
[0011] Embodiments of the present invention also differentiate from
the prior art by providing a split retainer ring with inner
friction fit surfaces that may be partially radiused that do not
participate in the final locking engagement for the shank head with
respect to the receiver. In addition, the retainer ring itself is
uniquely characterized by a base portion providing expansion to
receive and capture the shank head and then having expansion (not
contraction) locking engagement between the shank head and the
retainer ring base and between the retainer ring base and
horizontal and vertical loading surfaces near a bottom opening of
the receiver.
[0012] The expansion-only retainer ring base portion is positioned
entirely 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. The retainer ring base can also be better
supported on a generally horizontal loading surface near the lower
opening in the bottom of the receiver. This design 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.
[0013] Thus, an embodiment of a polyaxial bone screw assembly
according to the invention includes a shank having an integral
upper portion or integral radiused or 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 top
drop and turn in place lower compression insert; and a friction fit
resilient expansion locking split retainer for capturing the shank
head in the receiver lower cavity, the shank head being
frictionally engaged with, but still movable in a non-floppy manner
with respect to the friction fit retainer and the receiver prior to
locking of the shank into a desired configuration. The shank is
finally locked into a fixed position relative to the receiver by
frictional engagement between the insert and a lower split
ring-like portion of the retainer, as described previously, due to
a downward force placed on the compression insert 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 compression inserts are downloaded into
the receiver, but uploaded 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.
In some embodiments, the compression insert 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. Also, in
some embodiments, the shank (as well as other components of the
assembly, including the closure top) can be cannulated for
minimally invasive surgery applications. The retainer includes
upwardly extending tangs that are deployed in the receiver cavity
so that the retainer and captured shank head are stabilized and
retained in the region of the receiver locking chamber once, but
are free to rotate within the cavity. In this way, the shank head
and retainer are partially constrained and cannot go back up into
the receiver cavity, but can be manipulated there-within.
[0014] Again, a pre-assembled receiver, compression insert and
friction fit 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 portion of the split
retainer ring and expanding the resilient lower open retainer
portion out into an expansion portion or chamber of the receiver
cavity followed by an elastic return of the retainer back to a
nominal or near nominal shape thereof after the hemisphere of the
shank head or upper portion passes through the lower ring-like
portion of the retainer. The shank head enters into friction fit
engagement with portions of the retainer, defined at least in part,
by inner tangs of the retainer. The retainer snapping onto the
shank head as the retainer returns to a neutral or close to neutral
orientation, providing a non-floppy connection between the retainer
and the shank head. In the illustrated embodiments, when the shank
is ultimately locked between the compression insert and the lower
portion of the retainer, at least one lower, inner retainer edge
surface locks against the shank head. The final fixation occurs as
a result of a locking expansion-type of contact between the shank
head and the lower edge portion of the split retainer and an
expansion-type of non-tapered locking engagement between the lower
portion of the retainer ring and the locking chamber in the lower
portion of the receiver cavity. The retainer can expand more in the
upper portion or expansion chamber of the receiver cavity to allow
the shank head to pass through, but has restricted expansion to
retain the shank head when the retainer lower ring portion is
against the locking chamber surfaces in the lower portion of the
receiver cavity and the shank head is forced down against the
retainer ring during final locking. In some embodiments, when the
polyaxial mechanism is locked, the pressure or compression insert
is forced or wedged against a surface of the receiver resulting in
an interference 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 independent locking feature allows the polyaxial screw to
function like a fixed monoaxial screw.
[0015] The lower pressure insert may also be configured to be
independently locked 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 receiver from the sides and
then engages outwardly extending winged arms of the insert to force
or wedge the insert down into a locked position 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.
[0016] 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.
[0017] 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
[0018] FIG. 1 is an exploded perspective view of a polyaxial bone
screw assembly of an embodiment according to the present invention
including a shank, a receiver, an open friction fit retainer and a
top drop and turn in place lower compression insert, further shown
with a portion of a longitudinal connecting member in the form of a
rod and a closure top.
[0019] FIG. 2 is an enlarged top plan view of the shank of FIG.
1.
[0020] FIG. 3 is a reduced cross-sectional view taken along the
line 3-3 of FIG. 2.
[0021] FIG. 4 is an enlarged side elevational view of the receiver
of FIG. 1.
[0022] FIG. 5 is a perspective view of the receiver of FIG. 4.
[0023] FIG. 6 is a front elevational view of the receiver of FIG.
4.
[0024] FIG. 7 is a bottom plan view of the receiver of FIG. 4.
[0025] FIG. 8 is a top plan view of the receiver of FIG. 4.
[0026] FIG. 9 is a cross-sectional view taken along the line 9-9 of
FIG. 8.
[0027] FIG. 10 is a cross-sectional view taken along the line 10-10
of FIG. 8.
[0028] FIG. 11 is an enlarged perspective view of the retainer of
FIG. 1.
[0029] FIG. 12 is a reduced front elevational view of the retainer
of FIG. 11.
[0030] FIG. 13 is a reduced bottom plan view of the retainer of
FIG. 11.
[0031] FIG. 14 is a top view of the retainer of FIG. 11.
[0032] FIG. 15 is a reduced bottom perspective view of the retainer
of FIG. 11.
[0033] FIG. 16 is an enlarged cross-sectional view taken along the
line 16-16 of FIG. 14.
[0034] FIG. 17 is an enlarged perspective view of the insert of
FIG. 1.
[0035] FIG. 18 is a side elevational view of the insert of FIG.
17.
[0036] FIG. 19 is another perspective view of the insert of FIG.
17.
[0037] FIG. 20 is a top plan view of the insert of FIG. 17.
[0038] FIG. 21 is a bottom plan view of the insert of FIG. 17.
[0039] FIG. 22 is an enlarged cross-sectional view taken along the
line 22-22 of FIG. 20.
[0040] FIG. 23 is an enlarged cross-sectional view taken along the
line 23-23 of FIG. 20.
[0041] FIG. 24 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, the retainer being shown
downloaded into the receiver (in phantom) to a tipped, partially
inserted stage of assembly.
[0042] FIG. 25 is a front elevational view of the retainer and
receiver with portions broken away, similar to what is shown in
FIG. 24, showing the retainer in a subsequent stage of assembly and
in a maximum state of compression.
[0043] FIG. 26 is an enlarged and partial bottom perspective view
of the receiver and retainer of FIG. 25.
[0044] FIG. 27 is an enlarged front elevational view of the
retainer and receiver with portions broken away, similar to what is
shown in FIG. 25, showing the retainer positioned lower in the
receiver cavity and further shows the inert in position for
assembly with the receiver.
[0045] FIG. 28 is an enlarged front elevational view of the
retainer, receiver and insert with portions broken away, similar to
what is shown in FIG. 27, further showing the insert being
downloaded into the receiver to a location suitable for rotation
within the receiver.
[0046] FIG. 29 is a reduced front elevational view of the retainer,
receiver and insert, similar to what is shown in FIG. 28, further
showing the insert being partially rotated within the receiver.
[0047] FIG. 30 is an enlarged perspective view of the retainer,
receiver and insert of FIG. 29, showing the insert rotated into a
desired position for assembly with the shank of FIG. 1 and showing
the receiver crimped against the insert.
[0048] FIG. 31 is a reduced front elevational view of the assembly
of FIG. 30, the figure further showing the shank of FIG. 1 in a
partial front elevational view and implanted into a portion of a
vertebra, a hemisphere of the shank head and the vertebra portion
are both shown in phantom.
[0049] FIG. 32 is an enlarged and partial front elevational view
with portions broken away, similar to FIG. 31, and further showing
the shank in a first stage of assembly with the receiver and
retainer.
[0050] FIG. 33 is an enlarged and partial front elevational view
with portions broken away, similar to FIG. 32, showing the retainer
lower portion in an expanded state about a mid-portion of the shank
head.
[0051] FIG. 34 is a reduced and partial front elevational view with
portions broken away, similar to FIG. 33, the spherical shank upper
portion or head shown fully captured by the retainer.
[0052] FIG. 35 is an enlarged and partial front elevational view
with portions broken away, similar to FIG. 34, the shank upper
portion with attached retainer being shown pulled down into a
seated position within the lower receiver cavity, the retainer
spring tabs in a substantially neutral state, extending outwardly
and captured beneath a surface of the receiver, further shown is
the rod and closure top of FIG. 1, also shown in an enlarged and
partial front elevational view with portions broken away to show
the detail thereof.
[0053] FIG. 36 is a reduced and partial front elevational view with
portions broken away, similar to FIG. 35, the shank being shown in
a maximum possible push upped position prior to locking with the
rod and closure top.
[0054] FIG. 37 is a reduced and partial front elevational view with
portions broken away, similar to FIG. 35, the insert being shown
pushed down into a fully seated position within the lower receiver
cavity by pressure being placed thereon from above by the rod and
closure top, the insert being placed in locking interference fit
with the receiver.
[0055] FIG. 38 is a reduced and partial front elevational view with
portions broken away, similar to FIG. 37, but with the rod and
closure top removed, the locking insert keeping the shank locked in
place, the figure further showing an alternative locking insert, a
deformable rod and cooperating closure top being installed in the
receiver.
[0056] FIG. 39 is an enlarged and partial front elevational view
with portions broken away, similar to FIG. 38, showing the
alternative rod and closure top fixed to the receiver.
[0057] FIG. 40 is a reduced side elevational view of the assembly
of FIG. 1, shown fully assembled with the shank disposed at an
eighteen degree (cephalad) angle with respect to the receiver.
[0058] FIG. 41 is an enlarged perspective view of the assembly of
FIG. 40.
[0059] FIG. 42 is an enlarged and partial side elevational view of
the assembly of FIG. 40 with portions broken away to show the
detail thereof.
[0060] FIG. 43 is a reduced side elevational view of the assembly
of FIG. 1, shown fully assembled with the shank disposed at a
thirty degree (caudad) angle with respect to the receiver.
[0061] FIG. 44 is an enlarged perspective view of the assembly of
FIG. 43.
[0062] FIG. 45 is an enlarged and partial side elevational view of
the assembly of FIG. 43 with portions broken away to show the
detail thereof.
[0063] FIG. 46 is an enlarged perspective view of an alternative
retainer for use in lieu of the retainer in the assembly of FIG.
1.
[0064] FIG. 47 is another perspective view of the retainer of FIG.
46.
[0065] FIG. 48 is en enlarged bottom plan view of the retainer of
FIG. 46.
[0066] FIG. 49 is a cross-sectional view taken along the line 49-49
of FIG. 48.
[0067] FIG. 50 is an enlarged and partial side elevational view of
the assembly of FIG. 1 modified to include the retainer of FIG. 46
in lieu of the retainer shown in FIG. 1, and shown with portions
broken away to show the detail thereof.
[0068] FIG. 51 is an enlarged perspective view of an alternative
extended or favored angle receiver of an embodiment according to
the invention having opposed lower concave surfaces for cooperating
with the retainer of FIG. 1 to allow for up to a forty degree angle
of the shank of FIG. 1 with respect to the alternative
receiver.
[0069] FIG. 52 is an enlarged bottom plan view of the alternative
receiver of FIG. 51.
[0070] FIG. 53 is an enlarged perspective view of the assembly of
FIG. 1 modified to include the alternative receiver of FIG. 51 in
lieu of the receiver shown in FIG. 1.
[0071] FIG. 54 is an enlarged and partial front elevational view of
the assembly of FIG. 53 with portions broken away to show the
detail thereof.
[0072] FIG. 55 is a perspective view of another alternative
extended or favored angle embodiment of a receiver according to the
invention, similar to the receiver of FIG. 51, but having lower
concave stepped surfaces.
[0073] FIG. 56 is an enlarged and partial front elevational view of
the assembly of FIG. 1 modified to include the alternative receiver
of FIG. 55 in lieu of the receiver shown in FIG. 1.
[0074] FIG. 57 is an enlarged perspective view of an alternative
non-locking embodiment of an insert according to the invention for
use in lieu of the locking insert shown in FIG. 1.
[0075] FIG. 58 is an enlarged front elevational view of the
receiver and retainer of FIG. 1 shown in a stage of assembly with
the alternative insert of FIG. 57, also in front elevation, with
portions broken away to show the detail thereof.
[0076] FIG. 59 is an enlarged and partial front elevational view of
the receiver, retainer, rod and closure top of FIG. 1 shown fully
assembled with the alternative insert of FIG. 57, also in front
elevation, with portions broken away to show the detail
thereof.
DETAILED DESCRIPTION OF THE INVENTION
[0077] 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.
[0078] With reference to FIGS. 1-45, the reference number 1
generally represents an embodiment of 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 8; a
receiver 10; a friction fit retainer 12, and a crown-like
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 35-37 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 head 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. In some embodiments, the
rod 21 may be elastic, deformable and/or of different materials and
cross-sectional geometries (see, e.g., FIGS. 38 and 39). As shown
in FIG. 39, in some embodiments of the invention, the closure top
presses directly on the insert 14, for example, when the rod is
deformable.
[0079] 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 and different thread
types) 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
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 shown in FIG.
31, for example, and more fully described in the paragraphs below.
The shank 4 has an elongate axis of rotation generally identified
by the reference letter A.
[0080] 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.
[0081] 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 that terminates at a substantially
annular, planar rim surface 38 that is perpendicular to the shank
central axis A. In some embodiments, a frusto-conical surface
extends from the spherical surface 34 inwardly to the top surface
38, providing additional clearance during pivoting of the shank
with respect to the receiver 10 and the insert 14. The spherical
surface 34 has an outer radius configured for temporary frictional,
non-floppy, sliding cooperation with one or more edges and/or
surfaces of the retainer 12, as well as ultimate frictional
engagement with the retainer 12 at, at least one lower inner edge
thereof and ultimate frictional engagement with the insert 14 at an
inner partially spherical surface thereof and/or stepped or ridged
surfaces thereof, as will be discussed more fully in the paragraphs
below. In FIG. 1 and some of the other figures, a dotted line 40
designates a hemisphere of the spherical surface 34. 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 a lower ring-like edge of the
retainer 12. The shank spherical surface 34 is locked into place
exclusively by the insert 14 and the retainer 12 lower edged
portion and not by inner surfaces defining the receiver cavity.
[0082] A counter sunk and stepped or graduated annular seating
surface or base 45 partially defines a portion of an internal drive
feature or imprint 46. In some embodiments of the invention, the
surface 45 is substantially planar. The illustrated internal drive
feature 46 is an aperture formed in the top 38 and has a hex shape
designed to receive a tool (not shown) of an Allen wrench type,
into the aperture for rotating and driving the bone screw shank 4
into the vertebra 17. 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 pair
of spaced apart apertures or a multi-lobular or star-shaped
aperture. The graduated seat or base surfaces 45 of the drive
feature 46 are disposed substantially perpendicular to the axis A
with the drive feature 46 otherwise being coaxial with the axis A.
As illustrated in FIGS. 2 and 3, the drive seat 45 having beveled
or stepped surfaces advantageously further enhances gripping with
the driving tool. In operation, the driving tool (not shown) is
received in the internal drive feature 46, being seated at the base
45 and engaging the faces of the drive feature 46 for both driving
and rotating the shank body 6 into the vertebra 17, either before
or after the shank 4 is connected to the receiver 10 via the
retainer 12, the driving tool extending into the receiver 10 when
the shank 4, retainer 12 and receiver 10 combination is driven into
the vertebra 17.
[0083] 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 circular 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 or head 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. It is foreseen that the shank could be
solid and made of different materials, including metal and
non-metals.
[0084] 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.
[0085] With particular reference to FIGS. 1 and 4-10, the receiver
10 has a generally U-shaped appearance with partially discontinuous
cylindrical inner and outer profiles as well as planar and other
curved surfaces. 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.
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. 40-45.
[0086] The receiver 10 includes a base 60 with various curved
surfaces 58, opposed outer planar surfaces 59, and opposed outer
planar surfaces 59', the base 60 defining a bore or inner cavity,
generally 61, the base 60 being integral with a pair of opposed
upstanding arms 62. At the base 60, the planar surfaces 59 are
located between the arms 62 and an inset surface portion 63 is
located above and adjacent to each planar surface 59, each inset
surface portion 63 spanning between the pair of arms 62. The arms
62 form a cradle and define a U-shaped 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 (or sleeve of a tensioned cord connecting
member) between the arms 62, the channel 64 communicating with the
base cavity 61. Inner opposed substantially planar arm surfaces 69
partially define the channel 64 above the curved seat 68 and
partially define outer sides of each arm 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 62 could have break-off extensions.
[0087] An opposed pair of vertically extending outer grooves,
generally 74, running substantially parallel to the receiver axis B
are centrally formed in outer curved convex surfaces 76 of the arms
62. Each groove 74 runs centrally from the respective arm top
surface 73 and terminates at a a lower through aperture 77. Each
aperture 77 extends through the respective arm surface 77 to the
respective inner arm surface 70 and is located spaced from the
receiver base 60. Each groove 74 has an upper opening partially
defined by a pair of opposed surfaces 79 and 80 and a substantially
planar outer wall surface 81 extending between the surfaces 79 and
80. The planar wall surface terminates at the top arm surface 73
and at a lower surface 82 partially defining the aperture 77. The
opposed surfaces 79 and 80 are disposed at a slight angle with
respect to each other, forming the groove 74 as a dovetail-like
space for easily receiving an elongate tool (not shown) that enters
into the groove 74 at the arm top surface 73 and is kept in close
sliding contact with the surface 81 by the orientation of the
surfaces 79 and 80 angling toward one another with the tool sliding
along the surface 81 and ultimately into contact with winged
portions of the insert 14 that extend through the aperture 77 as
will be described in greater detail below. At the through aperture
77, the dovetail surfaces 79 and 80 terminate near facing generally
c-shaped ears 83 that do not extend completely through the
respective arm 62, but rather include a thin wall that provides a
crimping portion or wall 84. The crimping portions or walls 84 are
sized and shaped for pressing or crimping some or all of the wall
material into grooves or arms surfaces adjacent to the wings of the
insert 14 to prohibit rotation and misalignment of the insert 14
with respect to the receiver 10 as will be described in greater
detail below. In other embodiments of the invention, other surfaces
at or near the grooves 74 may be inwardly crimped. The illustrated
through aperture 77 located below each grooves 74 is substantially
the same width as the groove 74 there-above, each aperture 77 being
partially defined by a pair of opposed side walls 86 and a bottom
surface 87, resulting in the aperture 77 having a substantially
rectangular profile. Each surface 87 slants outwardly and
downwardly from the inner arm surface 70 toward the receiver base
60 outer planar surface 59'. The through apertures 77 are sized and
shaped for receiving tooling and also the outer tangs of the
retainer 12 during assembly as shown, for example, in FIG. 24.
[0088] The receiver 10 is a one-piece or integral structure and is
devoid of any spring tabs or collet-like structures. Preferably the
insert and/or receiver are configured with structure for blocking
rotation of the insert with respect to the receiver, such as the
crimp walls 84, but allowing some up and down movement of the
insert with respect to the receiver during the assembly and implant
procedure. Also formed in each outer arm surface 76 near the top
surface 73 is an undercut tool receiving and engaging groove 89.
Some or all of the apertures and grooves described herein,
including, but not limited to grooves 74, apertures 77, and grooves
89 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 insert embodiments according to 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 or apertures may be configured in a variety of
shapes and sizes and be disposed at other locations on the receiver
arm 62 outer surfaces 76 and/or inner surfaces 70 as well as the
base 60 outer or inner surfaces.
[0089] Returning to the interior surface 70 of the receiver arms
62, located below the guide and advancement structure 72 is a
discontinuous cylindrical surface 90 partially defining a run-out
feature for the guide and advancement structure 72. Adjacent the
surface 90 is a ledge or upper annular surface 91 that in turn is
adjacent to another cylindrical surface 92 having a larger diameter
than the cylindrical surface 90. As best shown in FIG. 9, the upper
annular surface 91 includes the upper surface 82 that partially
defines the aperture 77. The cylindrical surface 92 is sized and
shaped to receive an upper winged portion of the insert 14 as will
be described in greater detail below. Therefore, the surface 92 has
a diameter greater than a greater diameter of the guide and
advancement structure 72. The receiver 10 may further includes
sloped, stepped or chamfered surfaces above and below the surface
92. The surface 92 is divided not only by the U-shaped channel 64,
but also by each of the through apertures 77, resulting in the
surface 92 being in four sections. At each aperture 77, the surface
92 includes a surface portion 92' that is located at the inside of
ears 83 of the crimping wall portions 84, the surface portions 92'
eventually in contact with the insert 14 as will be described
below. A lower, substantially annular ledge 93 faces each upper
ledge or annular surface 91 and is adjacent the cylindrical surface
92. An inwardly and downwardly sloping surface or chamfer 93' is
adjacent to each surface 93 and also adjacent to another
discontinuous cylindrical arm surface 94. Each cylindrical surface
94 has a diameter smaller than the surface 92 and extends all the
way down to the U-shaped channel seat 68. A portion of each
aperture 77 extends through each surface 94. A lower partially
sloping or stepped ledge 94' at the base of the cylindrical surface
92 slopes downwardly toward the receiver base 60 and extends
inwardly toward the axis B, the surface 94 terminating at a
cylindrical surface 95 that extends completely around the receiver
base 60 and thus runs beneath each arm 62 and is adjacent to the
lower seat 68. The inner surface 95 thus defines an upper and inner
portion of the receiver base 60. The cylindrical surface has a
diameter slightly smaller than the diameter of the surface 94. The
surface 95 terminates at a ledge surface or chamber ceiling 96 that
extends outwardly away from the axis B, the surface 96 being
substantially perpendicular to the axis B, but could be oblique.
The surface 96 is annular and defines an upper ceiling or stop of a
retainer ring expansion portion or chamber of the inner cavity 61
that is further defined by an adjacent outwardly sloping surface 97
and a cylindrical surface 98 that is adjacent the surface 97. The
surface 97 also acts as a stop for and slidingly cooperates with
outwardly and upwardly projecting retainer tangs or panels as will
be described in greater detail below. The cylindrical surface 98
has a diameter greater than the diameter of the cylindrical surface
95. The cylindrical surfaces 92, 95 and 98 are all centrally
aligned with and run parallel to the receiver axis B. The surface
98 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. It is foreseen that the recess could be tapered or
conical in configuration.
[0090] A pair of cylindrical surfaces 100 and 101 with an annular
step surface 102 therebetween as well as a lower annular step 103
located below and adjacent to the surface 101 provide a lower seat
for the retainer 12 as will be described in greater detail below.
The surfaces 102 and 103 are substantially perpendicular to the
surfaces 100 and 101 and the receiver axis B. The surfaces 100,
101, 102 and 103 are located below the cylindrical surface 98 in
the lower part of the base 60 and are sized and shaped to closely
receive and surround a lower base portion and lower skirt or
sub-structure of the retainer 12 when the retainer is in a nominal
or reduced deployment position as shown in FIGS. 35-37, for
example. Thus, the cylindrical surface 101 has a diameter smaller
than the diameter of the cylindrical surface 98 that defines the
expansion area or expansion chamber for the retainer 12. The
surface 101 is joined or connected to the surface 98 by one or more
beveled, curved or conical transition step surfaces 104. The
surfaces 104 allow for sliding and nominal or deployment
positioning of the retainer 12 into the space defined by the
surfaces 100 and 101 and ultimate seating of the retainer 12 on the
lower substantially horizontal annular surfaces 102 and 103.
[0091] Located below and adjacent to the annular seating surface
103 is a lower edge or rim surface 106 that communicates with a
beveled or flared bottom opening surface 107, the surface 107
communicating with an exterior base or bottom surface 108 of the
base 60, defining a lower opening, generally 110, into the base
cavity 61 of the receiver 10. In some embodiments of the invention,
it is foreseen that one or more curvate cut-out or cupped surfaces
may be formed in a portion of the base surface 108, as well as in
portions of the surfaces 107, 106 and 100-104, typically located
substantially centrally and directly below an arm 62. Such a cupped
surface may be sized and shaped for providing clearance for an
increased angle of articulation between the shank 4 and the
receiver 10 (see, e.g., FIG. 55).
[0092] With particular reference to FIGS. 1 and 11-16, the lower
open or split friction fit retainer 12, that operates to capture
the shank upper portion 8 within the receiver 10 is shown. In
certain stages of assembly and operation, the retainer 12 is
partially constrained within the receiver, being captured within
the receiver cavity 61 at a location below the surface 96, the
retainer 12 being rotatable with respect to the receiver, but not
pivotable thereto and not readily removable out of the receiver
once deployed downward into the receiver cavity 61. The retainer 12
has a central axis that is operationally the same as the axis B
associated with the receiver 10 when the shank upper portion 8 and
the retainer 12 are installed within the receiver 10. The retainer
12 includes a substantially annular, cylindrical discontinuous body
115. Extending upwardly and outwardly from the body 115, and
integral thereto, is a super-structure in the form of two sets of
flexible panels or tangs, in particular, inner panels or tangs 117
and outer panels or tangs 118, the panels 117 and 118 extending
upwardly in aligned pairs, allowing for lateral spaces between the
pairs panels or tangs to provide clearance during assembly of the
retainer 12 with the receiver 10 inner surfaces (see, e.g., FIGS.
24 and 25). The illustrated embodiment includes six pairs of inner
and outer panels or tangs 117, 118, but it is foreseen that more or
fewer panels or tangs may be used. The pairs of panels or tangs are
generally equally spaced about the body 115. Also integral to the
body 115 are six outer discontinuous cylindrical support surfaces
120, each surface 120 located beneath one of the outer panels 118
and extending radially outwardly from the body 115. Below the
surfaces 120, the cylindrical body 115 forms a lower outer
cylindrical skirt 121 broken only by a gap that will be described
in greater detail below. The outer surface 121 is adjacent a bottom
surface 122. The body 115 also includes outer surface portions 123
that are located between each outer panels 118 and support surfaces
120. The surface portions 123 are illustrated as substantially
planar, but may be cylindrical. At each of the panels 118, a lower
ledge surface 124 is adjacent to one of the outer support surfaces
120. Each lower ledge 124 spans between one of the surfaces 120 and
the cylindrical skirt surface 121. The lower skirt 121 and the
ledge surfaces 124, as well as the surfaces 120 are receiver
seating surfaces as will be described in greater detail below. In
the illustrated embodiment, transition areas where the body 115
meets the panels 117 and 118 or the retainer bottom 122 are curved
or chamfered. Each body portion 123 is adjacent to a substantially
planar body top surface 126 that is substantially located between
pairs of panels 117 and 118 forming a planar surface with a
trapezoidal profile and also includes a narrow strip that runs
between the inner panels 117 and the outer panels 118.
[0093] The inner panels or tangs 117 each include a substantially
planar outer surface 128 and a concave inner surface 129, the
surfaces 129 each being partially radiused and partially
cylindrical, making up a discontinuous curved surface sized and
shaped for friction fit engagement with the shank head 8 as best
shown in FIG. 35 and as will be described in greater detail below.
However, it is foreseen that the panel inner surfaces 129 may also
be planar or include edges or other surfaces features for gripping,
but not locking the retainer 12 to the shank head 8 during assembly
and manipulation, but prior to locking of the polyaxial mechanism
of the bone screw assembly 1. The panels 117 generally slant or
curve inwardly towards the central axis of the retainer 12 and thus
ultimately inwardly toward the shank head 8. Each panel 117
includes a top surface 130 that is substantially planar and runs
substantially parallel to the bottom surface 122 when the retainer
is in a neutral position such as that shown in FIG. 16.
[0094] The outer panels or tangs 118 each have a planar outer
surface 132, a planar inner surface 133 and a planar top surface
134 that slopes at an oblique angle with respect to the retainer
bottom surface 122. The surfaces 134 are perpendicular to adjacent
surfaces 132. The panels 118 generally extend outwardly away from
the panels 117 as well as outwardly and upwardly from the central
axis of the retainer body 115. Each surface 133 faces an outer
surface 128 of one of the panels 117. The body top surface 126 is
reduced to a narrow strip between each pair of panels 117 and 118.
The panels or tangs 117 and 118 are resilient, the panels being
expandable about the shank head 8 and the panels 118 being
compressible inwardly and resiliently holding against the receiver
inner surfaces during shipping and certain assembly steps. The
panels 118 then return to an original or near original shape within
the receiver cavity 61, capturing the retainer 12 within the
receiver 10, but still allowing for rotation of the retainer 12
with respect to the receiver 10 about the receiver central axis
B.
[0095] The retainer ring 12 is made from a resilient material, such
as a stainless steel or titanium alloy, so that the retainer 12
body 115 may be expanded and the tabs or panels 117 and 118 of the
retainer may be manipulated 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 141, that passes
entirely through the retainer 12 from the inner panel top surfaces
130 to the bottom surface 122 of the retainer body 115. Surfaces
that define the channel or bore 141 at the body 115 include a
discontinuous inner lower frusto-conical surface 143 adjacent to
the retainer body bottom surface 122, a discontinuous,
substantially cylindrical surface 145 adjacent the frusto-conical
surface 143 and a discontinuous annular step 146 located adjacent
the cylindrical surface 145, the surface 146 being substantially
parallel to the bottom surface 122 and extending between the
surface 145 and a lower cylindrical portion 129' of the inner
surface 129 that partially forms the inner panels 117. The surfaces
145 and 146 terminate and join together at an edge 147 that is
positioned and configured to engage the shank surface 34 as will be
described in greater detail below. The inner cylindrical surface
129' adjacent the step 146 forms a continuous inner cylindrical
wall except at a slit, generally 148 that runs through the body
115. The slit 148 creates a split or open ring retainer 12, the
slit cutting entirely through the retainer body 115. In some
embodiments, such a slit may run at an angle obtuse to the bottom
surface 122. In the illustrated embodiment, the slit 148 runs
substantially perpendicular to the surfaces 122. The slit 148 is
primarily for expansion of the retainer 12 during pop-on or snap-on
assembly with the shank head 8. However, the slit 148 also
compresses during assembly with the receiver 10 as will be
described in greater detail below. The slit 148 extends between the
body top surface 126 and the bottom surface 122 and is located
substantially centrally between two pairs of panels 117 and 118.
Furthermore, at the location of the slit 148, a curved concave,
cut-out surface 149 is formed in the bottom surface 122 and the
frusto-conical surface 143. The cut-out surface 149 also extends
into the cylindrical surface 145 and removes a portion of the step
146 at either side of the slit 148. The surface 149 is radiused or
otherwise curved for engagement with the shank head 8 at the
surface 34 as will be described in greater detail below. In the
illustrated embodiment, the cut-out surface 149 is located
substantially equally on either side of the slit 148 to provide for
a desirable increased angle of orientation between the shank 8 and
the retainer 12 and thus a desirable increased or extended angle of
articulation between the shank 8 and the receiver 10. The
rotatability of the semi-constrained retainer 12 with respect to
the receiver 10 allows for manipulation and placement of such an
increased angle of articulation to a location desired by a surgeon.
The through slit 148 of the resilient retainer 12 is defined by
first and second end surfaces, 152 and 153 disposed in
substantially parallel spaced relation to one another when the
retainer is in a neutral or nominal state. Both end surfaces 152
and 153 are disposed perpendicular to the bottom surface 122, but
in some embodiments may be disposed at an obtuse angle thereto. A
width between the surfaces 152 and 153 is narrow to provide
stability to the retainer 12 during operation, but wide enough to
allow for some compression of the retainer during assembly as will
be described in greater detail below. Because the retainer 12 is
top loadable in a substantially neutral state and ultimately
expands during locking of the polyaxial mechanism, the width of the
slit 148 may be much smaller than might be required for a bottom
loaded compressible retainer ring.
[0096] With particular reference to FIGS. 1 and 17-23, the locking
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 as well as engaging the receiver 10 in
an interference fit engagement, locking the shank 4 in a desired
angular position with respect to the receiver 10 that remains in
such locked position even if, for example, a rod and closure top
are later removed and the rod is replaced with another rod or other
longitudinal connecting member or member component, such as a
sleeve of a tensioned cord connecting member. Such locked position
may also be released by the surgeon if desired with insert engaging
tools (not shown). As will be described in greater detail below
with respect to the alternative insert 14'' shown in FIGS. 57-59,
in some embodiments of the invention, the insert does not have the
receiver interference fit feature. The locking insert 14, the
non-locking insert 14'' and an alternative locking insert 14' for
use with a deformable rod (shown in FIGS. 38 and 39) are preferably
made from a solid resilient material, such as a stainless steel or
titanium alloy, so that portions of the insert may be grasped,
pinched or pressed, if necessary, and un-wedged from the receiver
10 with a release tool (not shown).
[0097] The locking compression insert 14 includes a body 156 with
cylindrical surfaces of a variety of diameters, the body 156 being
integral with a pair of upstanding arms 157. Located between the
arms 157, the body 156 has an outer partial cylindrical surface
158. Located beneath each upstanding arm 157 is a discontinuous,
cylindrical, interference fit surface or band 159 that extends
outwardly from an arm and body outer substantially cylindrical
surface 160, a diameter of the surface 159 being larger than a
diameter of the surface 160. Beneath each surface 159 is a
discontinuous cylindrical surface 161 having a diameter the same or
similar to the surface 160. A lower ledge surface 162 spans between
each surface 159 and the corresponding lower cylindrical surface
161. The lower surface 161 is adjacent to a chamfered surface 163
that is in turn adjacent a substantially planar and annular bottom
surface 164.
[0098] The insert 14 further includes substantially planar arm top
surfaces 165 located opposite the bottom surface 164. Adjacent the
top surfaces 165 of the arms 157 are opposed inwardly facing
cut-outs or grooved surfaces 167. The arms 157 are sized and
configured for ultimate placement at or beneath the cylindrical
run-out surface 90 located below the receiver guide and advancement
structure 72. The grooves or apertures 167 provide holding surfaces
for tools and also provide some clearance between the closure top
18 and the insert 14 when both are within the cylindrical run-out
surface 90 of the receiver so that the closure top 18 frictionally
engages the rod 21 only, pressing the rod 21 downwardly against the
insert 14 that in turn presses against the shank 4 upper portion 8
that presses against the retainer 12 to lock the polyaxial
mechanism of the bone screw assembly 1 at a desired angle.
Additionally, the grooves 167 may be sized and shaped to cooperate
with protrusions or extensions on sleeves that cooperate with a
tensioned cord of a longitudinal connecting member assembly to
center such a sleeve within the bone screw assembly 1.
[0099] An alternative locking insert 14' shown in FIGS. 38 and 39
includes all the features of the insert 14 with the exception of
the grooves 167. Top surfaces 165' of the insert 14' that have more
surface area than the surfaces 165 of the insert 14 directly engage
the alternative closure top 18' for better locking of the polyaxial
mechanism when an alternative deformable rod 21' is being captured
between the insert 14' and the closure top 18'.
[0100] Returning to the insert 14 shown in FIGS. 17-23, located on
the arms 157 and extending outwardly from each surface 160 at a
location spaced from the top surfaces 165 are a pair of opposed
extensions or wings 168. The wings 168 are partially defined by
upper surfaces 169, by outer partially cylindrical surfaces 170 and
by lower surfaces 171, the upper surfaces 169 and the lower
surfaces 171 being substantially parallel to on another. Opposed
side surfaces 172 span between top and bottom surfaces 169 and 171
respectively, of each wing 168, the side surfaces 172 being
substantially perpendicular to adjacent top and bottom surfaces 169
and 171. The cylindrical surfaces 170 are sized and shaped for
sliding rotation within the receiver arm cylindrical surfaces 92
during assembly of the insert 14 with the receiver 10 as will be
described in greater detail below.
[0101] Returning to the inner surfaces of the insert 14, a through
bore, generally 173, is disposed primarily within and through the
body 156 and communicates with a generally U-shaped through channel
formed by a saddle surface 174 that is substantially defined by the
upstanding arms 157. Near the top surfaces 165, the saddle surface
174 is substantially planar, with the apertures 167 extending
thereinto. The saddle 174 has a lower seat 175 sized and shaped to
closely, snugly engage the rod 21 or other longitudinal connecting
member. 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 tensioned cord longitudinal connecting member. A
second set of opposed, inwardly facing apertures 176 are located in
the saddle 174 near the lower seat 175 and substantially directly
below, but spaced from, the upper grooves or apertures 167. The
grooves 176 are sized and shaped to receive tooling for rotation
and other manipulation of the insert 14.
[0102] The bore, generally 173, is substantially defined at the
body 156 by an inner cylindrical surface 177 that communicates with
the seat 175 and also communicates with a lower concave, radiused
or otherwise curved portion 178 having shank gripping surfaces or
ridges 180, the portion 178 generally having a radius for closely
mating with the surface 34 of the shank upper portion 8. The
portion 178 terminates at the base surface 164. In some embodiments
of the invention, the gripping surfaces or ridges 180 are located
near the cylindrical surface 177 and a lower part of the portion
178 is a smooth, radiused or spherical surface. In the illustrated
embodiment, the gripping ridges or steps 180 are sized and shaped
to grip and penetrate into the shank head 8 when the insert 14 is
locked against the head surface 34. It is foreseen that there may
be more or fewer steps or ridges 180. It is foreseen that the
gripping ridges 180 as well as a remainder of the lower shank
engaging portion 178 may additionally or alternatively include a
roughened or textured surface or surface finish, or may be scored,
knurled, or the like, for enhancing frictional engagement with the
shank upper portion 8.
[0103] The compression insert 14 through bore 173 is sized and
shaped to receive a 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 some locking
embodiments of the invention, the bore receives a manipulation tool
(not shown) used for releasing the insert from a locked position
with the receiver, the tool pressing down on the shank and also
gripping the insert at the apertures 176 and/or 167, or with other
tool engaging features. Each of the arms 157 and the insert body
156 may include more surface features, such as cut-outs notches,
bevels, etc. to provide adequate clearance for inserting the insert
14 into the receiver and cooperating with the retainer 12 during
the different assembly steps as will be described in greater detail
below.
[0104] The insert body 156 cylindrical surface 158 has a 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 157 of the insert 14 being located between the
receiver arms 62 during insertion of the insert 14 into the
receiver 10. Once the arms 157 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 with the wings
168 entering the receiver groove formed by the cylindrical surface
92, the adjacent upper annular surface 91 and the adjacent lower
annular surface 93 until the wings are located in the apertures 77
as will be described in greater detail below.
[0105] With reference to FIGS. 1 and 35-37, 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, metal alloys, non-metals and
deformable and less compressible plastics, including, but not
limited to rods made of elastomeric, polyetheretherketone (PEEK)
and other types of materials, such as polycarbonate urethanes (PCU)
and polyethelenes.
[0106] 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 the particular longitudinal connecting member used in
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 deformable plastics to
hard metals, depending upon the desired application. Thus, bars and
rods 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.
[0107] With reference to FIGS. 1 and 35-37, 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 embodiments according to
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 any reduced
profile of the receiver 10 that may more advantageously engage
longitudinal connecting member components. 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-shaped 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 186 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 for
engagement and penetration into the surface 22 of the rod 21 in
certain embodiments of the invention. It is noted that in some
embodiments, the closure top bottom surface 188 may further include
a central point for penetration into the rod. It is also noted that
other embodiments may or may not include the point and/or the rim.
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.
[0108] An alternative closure top, such as the top 18' shown in
FIGS. 38 and 39 for use with a deformable rod, such as a PEEK rod
21', for example, includes a bottom surface 188' that has domed
portion 190' with a central nub 189' in lieu of the point and rim
surface of the closure top 18. Otherwise, the closure top 18'
includes a guide and advancement structure 182', a top surface 184'
and an internal drive feature 186' the same or substantially
similar to the respective guide and advancement structure 182, top
surface 184 and internal drive feature 186 of the closure top
18.
[0109] The assembly 1 receiver 10, retainer 12 and compression
insert 14 are typically assembled at a factory setting that
includes tooling for holding and alignment of the component pieces
and manipulating the retainer 12 and the insert 14 with respect to
the receiver 10. 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 and improving
logistics and distribution.
[0110] Pre-assembly of the receiver 10, retainer 12 and compression
insert 14 is shown in FIGS. 24-30. With particular reference to
FIG. 24, first the retainer 12 is inserted into the upper receiver
opening 66, leading with the outer panels 118 with the panel 118
top surfaces 134 facing one arm 62 and the retainer bottom surface
122 facing the opposing arm 62 (shown in phantom). The retainer 12
is then lowered in such sideways manner into the channel 64 and
partially into the receiver cavity 61, followed by tilting the
retainer 12 such that at least one outer panel 118 is received into
one of the apertures 77 and the opposed panel 118 is located
beneath the guide and advancement structure 72. Then, with
reference to FIG. 25, the retainer 12 is tilted into a position
wherein the central axis of the retainer 12 is generally aligned
with the receiver central axis B. As shown in FIG. 25, the retainer
outer surfaces 120 engage the receiver inner cylindrical surface 95
and the retainer slit 148 is reduced such that the surfaces 152 and
153 that define the slit 148 are touching or almost touching as
shown in FIG. 26 while the surfaces 120 are slid past the receiver
surface 95. With reference to FIG. 27, the retainer 12 is pressed
downwardly into the receiver to a location wherein the outer tangs
118 resiliently press against the receiver surface 95, holding the
retainer within the receiver cavity 61 at a desired temporary
position, but not allowing the retainer 12 to drop downwardly onto
the receiver seating transition surfaces 104. At this time, the
retainer 12 is not yet fully captured within the receiver base
cavity 61, but cannot be readily removed unless the panels 118 are
squeezed toward one another using a tool or tools.
[0111] With further reference to FIG. 27 and with reference to
FIGS. 28 and 29, the compression insert 14 is then downloaded into
the receiver 10 through the upper opening 66 with the bottom
surface 164 facing the receiver arm top surfaces 73 and the insert
arm outer surfaces 160 located between the opposed receiver arms
62. The insert 14 is then lowered toward the receiver base 60 until
the insert 14 arm upper surfaces 165 are adjacent the run-out area
below the guide and advancement structure 72 defined in part by the
cylindrical surface 92 and the wings 168 are generally aligned with
the receiver groove defined in part by the cylindrical surface 92.
Thereafter, the insert 14 is rotated about the receiver axis B
until the upper arm surfaces 165 are directly below the guide and
advancement structure 72 with the U-shaped channel 173 of the
insert 14 aligned with the U-shaped channel 64 of the receiver 10
and the insert wings 168 located at the apertures 77. In some
embodiments, the insert arms may need to be compressed slightly
during rotation to clear some of the inner surfaces 70 of the
receiver arms 62. With particular reference to FIG. 30, at this
time, the four crimping wall portions 84 are pressed inwardly
towards the insert 14 at either side 172 of each wing 168, the
crimping wall material pressing against the insert 14 near the wing
sides 172 and thereby prohibiting the insert 14 from rotating with
respect to the receiver axis B. At this time, there can be some
upward and downward movement of the insert 14, but such movement is
limited as the upper wall 82 defining the receiver aperture 77
stops further upward movement of the insert wings 168 and the
retainer outer tang top surfaces 134 stop downward movement of the
now trapped insert 14. Thus, the frictional engagement between the
tangs or panels 118 and the receiver inner surfaces 95 prohibit the
retainer 12 and also the insert 14 from dropping further down into
the receiver 10 cavity 61. The retainer 12 and the insert 14 are
now in a desired position for shipping as an assembly along with
the separate shank 4.
[0112] Typically, the receiver and retainer combination are shipped
or otherwise provided to the end user with the spring-like tangs
118 wedged against the receiver as shown in FIG. 32. The receiver
10, retainer 12 and insert 14 combination is now pre-assembled and
ready for assembly with the shank 4 either at the factory, by
surgery staff prior to implantation, or directly upon an implanted
shank 4 as will be described herein.
[0113] As illustrated in FIG. 31, 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 (shown in phantom), 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 and
attachable tower tools mating with the receiver. 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.
[0114] With reference to FIG. 32, 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.
With particular reference to FIGS. 32-37, as the shank upper
portion 8 is moved into the interior 61 of the receiver base, the
shank upper portion 8 presses upwardly against the retainer 12 in
the receiver recess partially defined by the cylindrical surface
98, specifically the surface portions 120 press against the surface
98 as the retainer 12 expands about the shank 8. As the shank head
8 continues to move upwardly toward the channel 64, the shank head
surface 34 also forces the retainer 12 against the insert 14.
However, the insert 14 is prohibited from moving upward by the wing
upper surfaces 169 abutting against the surfaces 82 (that is also
the ceiling annular surface 91 adjacent the groove 92) defining the
apertures 77. Therefore, the upwardly moving shank head 8 forces a
widening of the retainer slit 148 and corresponding outward
movement of the body 115 of the retainer 12 towards the receiver
cylindrical surfaces 98 and stepped or curved surface 104 defining
the receiver expansion recess or chamber as best shown in FIG. 33,
while the retainer tangs 118 near the top surfaces 134 thereof are
generally maintained in a location below the insert 14 bottom
surface 164, with the tangs 118 being pressed inwardly toward the
axis B at the termination of the receiver wall surface 95. At this
time, the spherical surface 34 of the head 8 comes into contact
with the retainer inner cylindrical body 145 and the edge 147. With
reference to FIG. 34, the retainer 12 begins to return towards a
neutral or nominal state as the center of the sphere of the shank
head 8 passes beyond the retainer inner edge 147. By the time the
hemisphere of the spherical surface 34 extends into a desired
captured location within the retainer central bore 141, the shank
surface 34 is in contact with the edge 147 as well as with the
inner panels 117 at surfaces 129. The combination of the rim or
edge 147 surface contact and the panel 117 surfaces 129 contact
resiliently pressing against the radiused surface 34, provides a
fairly tight friction fit between the head 8 and the retainer 12,
the surface 34 being pivotable with respect to the retainer 12 with
some force. Thus, a tight, non-floppy ball and socket joint is now
created between the retainer 12 and the shank upper portion 8.
[0115] With reference to FIG. 35, the receiver is then pulled
upwardly or the shank 4 and attached retainer 12 are then moved
manually downwardly into a position wherein the retainer tangs 118
are disengaged from the receiver surfaces 95, allowing the tangs
118 to resiliently release and extend outwardly into a neutral or
near-neutral position at a location below the receiver annular
surface 96 that defines the ceiling of the receiver inner chamber
61. The tangs 118 are now captured within the receiver. Any upward
movement of the retainer 12 results in the tang top surfaces 134
abutting against the receiver surfaces 96 and/or 97. However,
although fully capture, the retainer 12/shank 4 combination is
advantageously only partially restrained with respect to the
receiver 10, as a user is able to rotate the retainer 12 about the
receiver axis B prior to final locking of the shank head 8 with
respect to the receiver 10. At this time also, the retainer surface
121 and bottom surface 122 that forms a lower skirt beneath the
retainer body surfaces 120 and 124 are all seated within the
stepped surfaces of the receiver. Specifically, the retainer lower
surfaces 124 are seated on the receiver annular surface 102 and the
bottom surface 122 is seated on the annular surface 103. Downward
pressure of the shank head 8 on the retainer edge 147 further
expands the retainer body 115 outwardly, with the outer surfaces
120 pressing against the receiver inner cylindrical surface 100 and
the lower skirt surface 121 pressing against the receiver inner
cylindrical surface 101. The retainer body formed in part by the
lower skirt surface 121 advantageously allows for the head 8 to
seat lower within the receiver than in other known polyaxial bone
anchors. As will be described in greater detail below, the skirt
feature that allows for a more stable lower seating surface in
combination with the retainer cupped surface 149 that allows for a
favored increased or extended angular orientation of the shank with
respect to the retainer, and thus with respect to the entire bone
screw assembly, allows for such an angular increase without the
need to provide a cut-out or cupped surface at and near the
receiver bottom 108. Also advantageous is the fact that the
partially constrained retainer 12 may be rotated with respect to
the receiver 10 about the axis B, allowing for the user to choose
the location of the increased angle of orientation between the
receiver 10 and the shank 4.
[0116] With further reference to FIG. 35, after the retainer 12 is
moved downwardly into the receiver 10 and seated on the surfaces
102 and 103, the insert 14 remains located spaced above the shank
head 8 as the outer surfaces 159 rest upon the receiver cylindrical
surfaces 95, prohibiting downward movement of the insert 14 unless
a downward force is applied on the insert either by a tool or the
rod 21 and closure top 18, also shown in FIG. 35, for example. It
is noted that FIG. 36 simply illustrates the extent of movement of
the shank 4 if the shank would be pressed upwardly into the
receiver during this stage of assembly. In such case, the retainer
12 would remain in a relatively fixed position due to the outer
tangs 118 being blocked from upward movement by the receiver
ceiling surface 96. The shank head 8 would abut against the insert
14 at the surface 178 and gripping ridges 180, but the inner tangs
117 would continue to grip the shank spherical surface 34, so a
friction fit would still be possible, even if the shank gets moved
upwardly. With reference to FIG. 37, downward movement of the
closure top 18 presses the rod 21 downwardly that in turn pressed
the insert 14 (and possibly the shank 4) downwardly into locking
engagement with the retainer 12.
[0117] In some embodiments, when the receiver 10 is pre-assembled
with the shank 4, the entire assembly 1 may be implanted by
inserting the driving tool (not shown) into the receiver and the
shank drive 46 and rotating and driving the shank 4 into a desired
location of the vertebra 17. At such time, prior to locking with a
closure top, the receiver 10 may be articulated to a desired
angular position with respect to the shank 4(such as the angular
orientations shown in FIGS. 40-45, for example), that will be held,
but not locked, by the frictional engagement between the retainer
12 inner tangs 117 and the shank upper portion 8. In some cases it
may be desirable to lock the insert 14 into the receiver 10 at this
time, the insert 14 being pressed downwardly into locking
engagement with the shank head 8 by a tool pressing downwardly on
the insert, for example, with a tool (not shown) entering through
the receiver outer grooves 74 and pressing downwardly on the insert
wings 168. Such a tool may also include (or alternatively be) a
structure for gripping the receiver, for example, a pronged tool or
tool portion with some of the tool extending into the receiver
channel 64. Or, as explained above, the insert 14 may remain spaced
above the shank head 8 until locked into place by the rod 21 and
the closure top 18 pressing down upon the insert 14.
[0118] As explained above and as best shown in FIGS. 35 and 37, the
diameter of the insert outer surface or band 159 is sized large
enough to require that the surface 159 must be forced into the
cylindrical surface 95 of the receiver by a tool or tools or by the
closure top 18 forcing the rod 21 downwardly against the insert 14
with sufficient force to interferingly frictionally lock or wedge
the insert 14 into the receiver 10 at the surface 159. This
independent lock-and-release feature gives the surgeon flexibility
to loosen the closure top and even remove the closure top and rod
without affecting the locking of the polyaxial mechanism of the
assembly 1, the anchor assembly functioning like a fixed monoaxial
screw with the shank 4 in fixed relation with the receiver 10, but
with the shank remaining in a desired angle with respect to the
receiver. Thus, once a locking insert is in an interference fit
locking engagement with the receiver as shown in FIG. 37, if a rod
and closure top have been assembled with the receiver 10, the
closure top 18 may be loosened or removed and/or the rod 21 may be
adjusted and/or removed and the frictional engagement between the
insert 14 and the receiver 10 at the receiver surface 95 will
remain locked in place, advantageously maintaining a locked angular
position of the shank 4 with respect to the receiver 10. At such
time, another rod, such as a deformable rod 21' and cooperating
alternative closure top 18' may be loaded onto the already
locked-up assembly to result in an alternative assembly.
[0119] With reference to FIGS. 38 and 39, there is illustrated an
alternative insert 14' that is identical to the insert 14 with the
exception that an upper surface 165' is sized and shaped for direct
engagement with the alternative closure top 18'. The illustrated
rod 21' has the same or similar dimensions as the rod 21, with a
cylindrical surface 22', but is made from a material, such as PEEK,
that deforms in response to pressure from the closure top, thus
making the closure top 18' having the domed surface 190' and
central nub 189' a more desirable locking mechanism for keeping the
deformable rod 18' in place within the receiver 10. Because the
locking of the polyaxial mechanism of the assembly is not dependent
on the force of the rod 21' and closure top 18' on the insert 14,
any further deformation or eventual loosening of the rod with
respect to the closure top 18' or the insert 14 does not affect the
secure locking between the insert 14 and the receiver 10 and thus
the shank 4 stays frictionally locked against both the insert 14
and the retainer 12, locking the shank 4 in a desired angular
position with respect to the receiver 10.
[0120] If unlocking of the insert 14 or 14' with respect to the
receiver 10 is desired, a tool (not shown) may be inserted into the
through apertures 77 below the insert wings 168 and the insert 14
or 14' may be pulled away from the receiver 10. Such a tool may
include a piston-like portion for pushing directly on the shank
while the insert 14 is pulled away from the receiver. At such time,
the shank 4 may be articulated with respect to the receiver 10, and
the desired friction fit returns between the retainer 12 and the
shank surface 34, so that an adjustable, but non-floppy
relationship still exists between the shank 4 and the receiver 10.
If further disassembly if the assembly is desired, such is
accomplished in reverse order to the procedure described previously
herein for the assembly 1.
[0121] Returning to FIGS. 35 and 36, the rod 21 is positioned in an
open or percutaneous manner in cooperation with the at least two
bone screw assemblies 1. The closure structure 18 is then 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 saddle 173 of the compression insert 14,
further pressing the insert spherical surface 178 and stepped shank
gripping surfaces 180 against the shank spherical surface 34, the
edges 180 penetrating into the spherical surface 34, pressing the
shank upper portion 8 into locked frictional engagement with the
retainer 12. Specifically, as the closure structure 18 rotates and
moves downwardly into the respective receiver 10, the rim 190
engage and penetrate 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 at the
retainer edge surface 147, the retainer 12 frictionally abutting
the receiver surfaces 102 and 103 and pressing outwardly against
the receiver cylindrical surfaces 100 and 101. For example, about
80 to about 120 inch pounds of torque on the closure top may be
applied for fixing the bone screw shank 6 with respect to the
receiver 10. At this time, the retainer inner edge 147 engages and
digs into the shank head 8. At this time, the inner tangs 117 may
be slightly spaced from the shank head 8 or may be still touching
the shank spherical surface 34, but are no longer in tight or close
frictional engagement with the surface 34 and thus are not
participating in the final locking engagement between the shank 4
and the retainer 12. As best shown in FIG. 37, due to the position
and geometry of the lower skirt surfaces 121 and 122 with respect
to the receiver 10 and also due to the location of the inner edge
147, the shank head 8 sits low in the receiver cavity 61, allowing
for desirable increased articulation of the shank 4 with respect to
the retainer 12 and thus with respect to the receiver 10 as
compared to a retainer that does not include such a lower skirt,
for example. If disassembly if the assembly 1 is desired, such is
accomplished in reverse order to the procedure described previously
herein for assembly.
[0122] With reference to FIGS. 40-45, different angular or
articulated positions of the shank 4 with respect to the receiver
10 are shown, some making full use of the slit 148 and adjacent
cut-out or cupped surfaces 149 of the retainer 12. For example,
compare FIGS. 43-45 wherein the shank 8 is pivoted toward and into
engagement with the cupped surfaces 149 as compared to the
arrangement shown in FIGS. 40-42, wherein the shank 4 is pivoted in
a direction opposite to the retainer slit 148. In FIGS. 40-42
wherein the shank is pivoted in a direction away from the slit 148
and cupped surfaces 149, a resulting shank to receiver articulation
is about eighteen degrees (cephalad, for example), which is a
desirable degree of articulation in some instances. FIGS. 43-45
show a thirty degree (caudad) or slightly further articulation,
possible when the shank head 8 abuts against both surfaces 149 as
well as moving slightly into the gap formed by the slit 148.
[0123] FIGS. 46-50 illustrate an alternative retainer 12' that
includes cupped or cut-out surfaces 149' that are graduated or
stepped as compared to the smooth surfaces 149 of the retainer 12.
Otherwise, the retainer 12' is identical or substantially similar
in form and function to the retainer 12 previously discussed
herein. Thus, the retainer 12' fully cooperates with the receiver
10, insert 14, shank 4, rod 21 and closure top 18 in a manner
substantially identical to what has been described above with
respect to the assembly 1, with the exception that the stepped
surfaces 149' grip or dig into the shank 4 at the neck 26 when the
shank is pivoted to an about thirty degree articulation with
respect to the receiver as shown in FIG. 50. It is foreseen that
greater or fewer stepped surfaces may be included along the cupped
surface portion 149'.
[0124] FIGS. 51-54 illustrate an alternative receiver 10' that
includes a bottom surface 108' further defined by a pair of
opposed, concave curved bottom surfaces 109'. Otherwise, the
receiver 10' is identical to the receiver 10 described above and
thus fully cooperates with the retainer 12, insert 14, shank 4, rod
21 and closure top 18 in a manner substantially identical to what
has been described above with respect to the assembly 1. FIGS.
55-56 illustrate another alternative receiver 10'' that is
substantially similar to the receiver 10', also having opposed,
concave curved bottom surfaces 109''. The receiver 10'' differs
from the receiver 10' only in that the surfaces 109'' are graduated
or stepped. Just like the receiver 10, when the retainer 12 is
fully assembled with the receiver 10' or the receiver 10'', the
retainer 12 is captured within the receiver inner cavity, but is
only partially constrained therein, the retainer being rotatable
about the central axis of the receiver 10' or 10''. Thus, the
retainer 12 slit 148 and surfaces 149 can be aligned with either of
the receiver concave surfaces 109' or 109''. When the retainer
surfaces 149 are aligned with one of the surfaces 109' or 109'', at
least a forty degree angle of articulation between the shank 4 and
the receiver 10' or 10'' is possible.
[0125] With reference to FIGS. 57-59, an alternative non locking
compression insert 14' is illustrated for use with the shank 4,
receiver 10, retainer 12, closure top 18 and rod 21 previously
described herein. The insert 214 is substantially similar to the
insert 14 previously described herein, having all the features of
the insert 14 with the exception of the through apertures 167 and
the enlarged interference fit surface 159. Instead, the insert
includes an other lower surface or band 159'' having a diameter
sized to easily slidingly fit within the receiver surface 95 rather
than interferingly fit with such surface. The insert 14'' is
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 insert
14'' need not be forced downwardly into a locking interference fit
with the receiver 10 when the shank 4 is locked in place. If the
closure top 18 is loosened or if the closure top 18 and the rod 21
are removed from the assembly 1, the insert 14'' will also shift
upwardly in the receiver 10 and the shank 4 will not remain locked
with respect to the retainer 12 and the receiver 10. Tooling (not
shown) cooperating with the receiver grooves 74 to press downwardly
on wings 168'' of the insert 14'' advantageously provides for a
temporary locking of the polyaxial mechanism during surgery, if
desired by the surgeon.
[0126] 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.
* * * * *