U.S. patent application number 17/351839 was filed with the patent office on 2022-03-10 for modular tulip assembly.
The applicant listed for this patent is Spinal Elements, Inc.. Invention is credited to David Brett Cain, Joshua David Gunn, Geoffrey Toon.
Application Number | 20220071665 17/351839 |
Document ID | / |
Family ID | 61757457 |
Filed Date | 2022-03-10 |
United States Patent
Application |
20220071665 |
Kind Code |
A1 |
Toon; Geoffrey ; et
al. |
March 10, 2022 |
MODULAR TULIP ASSEMBLY
Abstract
A modular tulip assembly has a rod receiving tulip and a saddle.
The saddle is interlockingly held inside a distal portion of the
tulip. The saddle has a locking projection. The tulip has a pair of
grooves or recesses. The locking projection is positioned into the
proximal tulip groove or recess and holds the saddle in a
pre-loaded unlocked state ready to be pushed onto a head of an
implanted bone screw. Upon receiving the head of the bone screw,
the saddle can be moved distally relative to the tulip to a locked
state by moving the locking projection distally into the distal
tulip locking groove or recess.
Inventors: |
Toon; Geoffrey; (Vista,
CA) ; Cain; David Brett; (Marietta, GA) ;
Gunn; Joshua David; (Woodstock, GA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Spinal Elements, Inc. |
Carlsbad |
CA |
US |
|
|
Family ID: |
61757457 |
Appl. No.: |
17/351839 |
Filed: |
June 18, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15609127 |
May 31, 2017 |
11154331 |
|
|
17351839 |
|
|
|
|
15284929 |
Oct 4, 2016 |
10485594 |
|
|
15609127 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 17/7035 20130101;
A61B 17/7076 20130101 |
International
Class: |
A61B 17/70 20060101
A61B017/70 |
Claims
1.-12. (canceled)
13. A method of assembling a tulip comprises the step of: providing
a tulip with a pair of grooves or recesses, the pair of grooves or
recesses being a proximal groove or recess and a distal locking
groove or recess; and positioning a saddle with a concave locking
surface inside the tulip into a proximal groove or recess inside
the tulip in a pre-loaded unlocked state to receive a head of a
bone screw.
14. The method of claim 13 further comprises the step of: pushing
the tulip with the pre-loaded unlocked saddle onto an implanted
bone screw previously threaded into bone.
15. The method of claim 14 further comprises the step of: moving
the saddle to a locked state by moving the locking projection from
the proximal tulip groove or recess distally into the distal tulip
locking groove or recess.
16. The method of claim 15 of moving the saddle to a locked
position further includes engaging internal threads of the saddle
with a threaded end of a tool, rotating the tool to move the saddle
from the pre-loaded unlocked state to the locked state after
attaching the implanted screw.
17. The method of claim 16 further comprises the step of: unlocking
the locked tulip assembly by moving the saddle by moving the saddle
from the locked state to the pre-loaded unlocked state.
18. The method of claim 17 wherein the step of unlocking the tulip
assembly includes engaging threads of the saddle with the threaded
end of the tool and rotationally pulling the saddle proximally
relative to the tulip.
19.-30. (canceled)
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 15/609,127 filed on May 31, 2017, which is a continuation in
part of U.S. application Ser. No. 15/284,929 filed on Oct. 4, 2016,
which are hereby incorporated by reference herein in their
entireties.
TECHNICAL FIELD
[0002] The present invention relates to an improved modular head
tulip assembly.
BACKGROUND OF THE INVENTION
[0003] Bone anchor screws come in a variety of shapes and sizes.
One of the more common styles has a polyaxial head that allows for
the screw to enter the bone structure at an ideal or preferred
inclination. To achieve this polyaxial inclination, the head has a
shape configured to allow a complimentary implant device being held
by the screw to rotate about its lower external surface. This lower
surface can be one of a number of shapes like conical or spherical
or hemispherical. This ability is often used in rod receiving
implant devices having a modular head assembly.
[0004] The modular head pedicle screw assembly generally includes a
tulip. A tulip is a body structure having two opposing sides spaced
by a slotted opening to receive a spinal rod. The tulip often
employs internal threads to receive a rod locking set screw to
anchor or fix the rod in the tulip. The lower portion of the tulip
has an opening to receive the pedicle screw in a base seat. Often,
the tulip can have a saddle that also supports the rod along an
underside of the rod. The saddle having an upper recessed curvature
into which the rod sits and a lower cup like opening to receive the
top of the pedicle screw head. When the saddle and rod and set
screw are tightened, the screw angle is fixed against the tulip
seat.
[0005] Often, it is preferred that the pedicle screw is first
placed securely in the bone structure leaving the head protruding
above the bone surface. In this surgical procedure the tulip
assembly must be adapted to fit down onto the projecting screw
head. To accomplish this, the surgeon must push the tulip onto and
over the screw head without a clear path of vision. Accordingly,
the placement must be accomplished without any way of knowing if
the tulip or other device is properly secured. Thereafter, the
device is tightened to complete the assembly and the only way to
insure the assembly is secure requires an upward pulling of the
tightened assembly. This is not a good test because the assembly
may be loosened or the screw to bone interface weakened.
[0006] It is, therefore, an objective of the present invention to
provide a way for a surgeon to place a tulip assembly onto a
pedicle screw already threaded into bone in such a way the surgeon
can make a proper and secure connection easily.
[0007] It is a further objective that the device has properly
fitted the tulip assembly onto the pedicle screw head by the very
nature of the design. It is another objective that the device
provides a self-locking feature that when tightened by assembly,
the surgeon can lock the assembly engagement insuring he has made a
proper assembly. These and other objectives are achieved by the
invention as described hereinafter.
SUMMARY OF THE INVENTION
[0008] A modular tulip assembly has a rod receiving tulip and a
saddle. The saddle is interlockingly held inside a distal portion
of the tulip. The saddle has a locking projection. The tulip has a
pair of grooves or recesses, a first proximal groove or recess and
a second or distal locking groove or recess. The locking projection
is positioned into the tulip proximal groove or recess and holds
the saddle in a pre-loaded unlocked state ready to be pushed onto a
head of an implanted bone screw. Upon receiving the head of the
bone screw, the saddle can be moved distally relative to the tulip
to a locked state by moving the locking projection distally into
the distal locking groove or recess to where the proximal end of
the saddle is past abutting the locking projection.
[0009] The tulip has a pair of opposing internally threaded walls
defining a slotted opening for receiving a rod, an open bore with
an open distal end for passing the polyaxial head of the bone
screw, and the tulip grooves or recesses are axially spaced below
the internal threads of the opposing walls and above the open
distal end.
[0010] The saddle has an axis defined by a center opening. The
saddle has a proximal end with a concavity for holding a rod and a
distal portion with a plurality of arcuate fingers spaced by slots.
The plurality of arcuate fingers are curved to form at least a
hemispherical shaped concavity for receiving and holding the head
of the bone screw. The fingers extend to a distal end. The saddle
has the locking projection positioned between the proximal end and
above the arcuate fingers. The saddle is sized to pass through the
open distal end of the tulip and move axially inside the tulip
below the internal threads. The tulip has an enlarged internal
chamber to accommodate the arcuate fingers and sized to allow the
fingers to flex outwardly over and past a maximum diameter of the
screw head on attachment.
[0011] In one embodiment, the saddle center opening at the proximal
end has internal threads to engage threads of an end of a tool
configured to axially move the saddle relative to the tulip. The
saddle is pre-positioned in an unlocked bone screw receiving state
when the locking projection is moved onto the proximal tulip groove
or recess and after being attached onto an implanted bone screw
polyaxial hemispherical head, the saddle is configured to be moved
relative to the tulip by rotation of the tool to the locked state
by moving the locking projection distally from the proximal tulip
groove or recess and having the proximal end of the saddle moved
distally past moving the locking projection into the distal tulip
locking groove or recess causing the arcuate fingers at the distal
end to flex and be compressed at the open distal end of the tulip.
The locked saddle can be repositioned to the unlocked state by
attaching the threaded end of the tool to the saddle and rotating
the tool as it abuts a proximal end of the tulip causing the
locking projection to disengage the distal tulip locking groove or
recess and move to the proximal tulip groove or recess allowing the
arcuate fingers to release the screw head and the tulip assembly to
be removed from the bone screw.
[0012] In a preferred embodiment, a modular tulip assembly is
configured to receive and lock onto an implanted bone screw having
a threaded shank and a hemispherical polyaxial head. The tulip
subassembly has a tulip and a saddle. The tulip has a pair of
opposing internally threaded walls defining a slotted opening for
receiving a rod, an open bore with an open distal end for passing
the polyaxial head of the bone screw, and a pair of locking grooves
or recesses being axially spaced below the internal threads of the
opposing wall and above the open distal end. The saddle has an axis
defined by a center opening. The saddle has a proximal end with a
concavity for holding the rod and a distal portion with a plurality
of arcuate fingers spaced by slots. The plurality of fingers are
curved to form at least a hemispherical shaped concavity for
receiving and holding the head of the bone screw. The fingers
extend to a distal end, the saddle has an locking projection
positioned between the proximal end and above the arcuate fingers.
The saddle is sized to pass through the open distal end and move
axially inside the tulip below the internal threads. When assembled
to the tulip, the saddle is pre-positioned in an unlocked bone
screw receiving state when the locking projection is moved onto the
proximal tulip groove or recess. Thereafter, the saddle in the
unlocked state can be attached onto an implanted bone screw
polyaxial hemispherical head. The saddle is configured to be moved
to a second locked state by moving the locking projection distally
off the proximal tulip groove or recess and having the proximal end
of the saddle moved distally into the distal tulip locking groove
or recess causing the arcuate fingers at the distal end of the
tulip to flex and be compressed at the open distal end of the
tulip.
[0013] In this preferred embodiment, the tulip has an enlarged
internal chamber to accommodate the arcuate fingers and sized to
allow the fingers to flex outwardly over and past a maximum
diameter of the screw head on attachment. The saddle center opening
at the proximal end has internal threads to engage threads of an
end of a tool configured to axially move the saddle relative to the
tulip. The modular tulip assembly has the saddle pre-positioned in
an unlocked bone screw receiving state when the locking projection
is moved onto the proximal tulip groove or recess and after being
attached onto an implanted bone screw polyaxial hemispherical head,
the saddle is configured to be moved relative to the tulip by
rotation of the tool to the locked state by moving the locking
projection distally off the proximal tulip groove or recess and
having the proximal end of the saddle moved distally past and into
the distal tulip locking groove or recess causing the arcuate
fingers at the distal end to flex and be compressed at the distal
end of the tulip. The modular tulip assembly allows the locked
saddle to be repositioned to the unlocked state by attaching the
threaded end of the tool to the saddle and rotating the tool as it
abuts a proximal end of the tulip causing the locking projection to
disengage the distal tulip locking groove or recess and move onto
the proximal tulip groove or recess allowing the arcuate fingers to
release the screw head allowing the tulip assembly to be removed
from the bone screw.
[0014] A method of assembling a modular tulip has the step of
providing a tulip with a distal and a proximal groove or recess;
and positioning a saddle with a proximal locking projection inside
the tulip past the distal locking groove or recess and into the
proximal groove or recess inside the tulip in a pre-loaded unlocked
state to receive a head of a bone screw. The method further has the
step of pushing the tulip with the pre-loaded unlocked saddle onto
an implanted bone screw previously threaded into bone and moving
the saddle to a locked state by moving the locking projection
distally off the proximal tulip groove or recess and the proximal
end distally abuts the distal tulip locking groove or recess. The
step of moving the saddle to a locked position further includes
engaging internal threads of the saddle with a threaded end of a
tool, rotating the tool to move the saddle from the pre-loaded
unlocked state to the locked state after attaching the implanted
screw. The method further has the step of unlocking the locked
tulip assembly by moving the saddle from the locked state to the
pre-loaded unlocked state. The step of unlocking is accomplished by
engaging threads of the saddle with the threaded end of the tool
and rotationally pulling the saddle proximally relative to the
tulip.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The invention will be described by way of example and with
reference to the accompanying drawings in which:
[0016] FIG. 1 is a perspective view of the tulip assembly
positioned above an exemplary bone screw.
[0017] FIG. 2 is an explode perspective view of the tulip and
saddle of the present invention above an exemplary bone screw.
[0018] FIG. 3 is a perspective view of the tulip assembly shown
attached to the exemplary bone screw.
[0019] FIG. 4 is a cross-sectional view of the tulip assembly in a
pre-loaded unlocked state with the saddle shown attached onto the
head of an exemplary bone screw.
[0020] FIG. 5 is a cross-sectional view showing the tulip assembly
wherein an internal saddle has been moved to the locked position or
state.
[0021] FIG. 6 is a plan view of a tool end with a threaded end for
attaching to internal threads of the saddle.
[0022] FIG. 7 is a cross-sectional view taken from FIG. 6 showing
the tool end threaded into the saddle with the saddle having been
moved relative to the tulip into the locked state.
[0023] FIG. 8 is a perspective view of the tool end above the tulip
assembly and bone screw illustrating removal of the tool after
locking or alternatively showing how the tool can be used to unlock
the saddle to allow the tulip assembly to be removed from an
implanted bone screw.
[0024] FIG. 9 shows the tulip assembly attached to the tool for
either attachment to the exemplary bone screw or alternatively
after removal from the bone screw.
[0025] FIG. 10 shows in cross-section the tulip assembly and
unlocked saddle attached to the tool for attachment to or
alternatively as occurs on removal from said bone screw.
[0026] FIG. 11 is a cross-sectional view illustrating the tulip
assembly with the saddle in a preloaded unlocked state over an
exemplary bone screw.
[0027] FIG. 12 is a cross-sectional view showing the tulip assembly
wherein the internal saddle has been moved to the locked position
or state and an exemplary fixation rod is being held in the
proximal end of the saddle securely fixed by the exemplary set
screw threadingly engaged in the internal threads of the two
opposing walls of the tulip.
[0028] FIG. 13 is a perspective view of the tulip of the present
invention.
[0029] FIG. 14 is a cross-sectional plan view of the tulip taken
from FIG. 13.
[0030] FIG. 15 is a perspective view of the saddle of the present
invention.
[0031] FIG. 16 is a plan view of the saddle taken from FIG. 15.
[0032] FIG. 17 is a cross-sectional view illustrating an
alternative embodiment of the present invention tulip assembly with
the saddle in a preloaded unlocked state over an exemplary bone
screw.
[0033] FIG. 18 is a cross-sectional view of the alternative
embodiment showing the tulip assembly wherein the internal saddle
has been moved to the locked position or state and an exemplary
fixation rod is being held in the proximal end of the saddle
securely fixed by the exemplary set screw threadingly engaged in
the internal threads of the two opposing walls of the tulip.
[0034] FIG. 19 is a plan view of the alternative tulip of the
present invention.
[0035] FIG. 20 is a cross-sectional plan view of the tulip taken
from FIG. 19.
[0036] FIG. 21 is a perspective view of the alternative embodiment
saddle of the present invention.
[0037] FIG. 22 is a cross-sectional view of the saddle taken from
FIG. 21.
[0038] FIG. 23 is a cross-sectional view of a tool used to unlock a
screw from a tulip.
DETAILED DESCRIPTION OF THE INVENTION
[0039] With reference to FIG. 1, a perspective view of the modular
tulip assembly 10 of the present invention is shown. As shown, the
modular tulip assembly 10 has a rod receiving tulip 20, and
internal of the rod receiving tulip 20 is shown a saddle 40, the
saddle 40 is interlockingly held inside a distal portion of the
tulip 20. Below the tulip assembly 10, is shown an exemplary bone
screw 2. The bone screw 2 has a threaded shank 4 for engaging bone
and a rounded spherical or hemispherical head 6 at the proximal end
of the shank 4. This head 6 is configured to provide polyaxial
movement of the bone screw 2 relative to the tulip assembly 10 on
assembly. This polyaxial movement is maintained as long as the
tulip assembly 10 is not locked into position and fixed.
[0040] The modular tulip assembly 10 is basically a two part device
with the tulip 20 and the preloaded saddle 40 for use with a bone
screw 2. The bone screw 2 can be preloaded into the assembly 10 to
make a three component device or system if desired. An important
feature of the present invention is a binary locking aspect where a
single locking projection 25 in combination with a groove or recess
42 holds the saddle 40 in a preloaded state inside the modular
tulip 20 and when the modular tulip assembly 10 is moved onto the
head 6 of a bone screw 2 the saddle 40 can be moved into a locked
state and, if desired, can be unlocked in a reversible fashion
making the modular tulip assembly 10 most convenient to use. These
features are fully described in detail as follows.
[0041] With reference to FIG. 2, the modular tulip assembly 10 is
shown in an exploded view with the saddle 40 shown below and
between the tulip 20 and the bone screw 2.
[0042] In FIG. 3, the tulip assembly 10 is shown attached to the
exemplary bone screw 2 in a perspective view. The tulip 20 is fully
separately illustrated in FIGS. 13 and 14.
[0043] With reference to FIG. 4, a cross-sectional view of the
tulip assembly 10 is shown wherein the saddle 40 is positioned over
the polyaxial hemispherical head 6 of the exemplary bone screw 2.
As shown in cross-section, the tulip 20 is shown with opposing
walls 22, 23 with internal threads 24 defining a rod receiving slot
or channel 33. Below the internal threads 24 is illustrated the
saddle 40. The saddle has a locking groove or recess 42 affixed to
a locking projection 25 in the tulip 20 of the tulip assembly 10.
As further shown, and with reference to FIGS. 15 and 16, the saddle
40 has a proximal end 44 with a rod receiving concavity 45 that is
aligned with the channel 33 of the tulip 20. At the proximal end 44
of the saddle 40 there is a central opening 41 that is threaded
with threads 43, as illustrated. The locking groove or recess 42 is
shown near the proximal end 44 of the saddle 40. Below the locking
groove or recess 42 is shown a plurality of axially extending
flexible fingers 52 that are spaced apart by slots or slits 54. At
a distal end 51, these arcuate curved flexible fingers 52 are bowed
slightly inwardly. At the proximal end of the slot 54 is an
enlarged circular hole 55 to provide stress relief and also
increase the flexibility of the fingers 52. This is important in
that the fingers 52 must flex or bow outwardly in order to expand
as they slide over the hemispherical head 6 of the exemplary bone
screw 2. As shown in FIG. 4, the plurality of arcuate fingers 52
extend downward past the maximum diameter (d max) of the polyaxial
hemispherical bone screw head 6. The fingers 52 extension creates
at least a hemispherical concavity 53 that extends beyond the
maximum diameter d max and as such, the curvature of the fingers 52
bends outwardly at the proximal end and bows inwardly towards the
distal end 51, however, when attached to the bone screw 2, all of
the fingers 52 are shown deflected outwardly. As shown in FIG. 4
and also in FIG. 14, in cross-section, the tulip 20 has a large
internal chamber 30 above the distal end 31. This chamber 30 is
configured to allow the fingers 52 of the saddle 40 to bow
outwardly on assembly. Once the fingers 52 have bowed or flexed
outwardly to pass the maximum diameter d max of the bone screw head
6, they will conform or flex back inwardly compressing and sliding
against the surface 8 of the hemispherical bone screw head 6.
Preferably, the concavity 53 formed by the plurality of arcuate
fingers 52 is sized to complimentarily fit the head 6 of the bone
screw 2 to which it is to be attached.
[0044] With reference to the proximal end 44 of the saddle 40, as
shown, the proximal end 44 is shown above where the grove or recess
42 is positioned over a projection 25 in the tulip 20. The outer or
exterior surface of the proximal end 44 has a small rounded edge or
chamfer 48 to facilitate sliding over the projection 25. When the
saddle 40 is oriented in this position, it is in a preloaded and
unlocked position wherein the arcuate extended fingers 52 are
allowed to move inwardly and outwardly relative to an axis of the
tulip 20. with reference to FIG. 5, the saddle 40 is shown moved in
a locking position wherein the proximal end 44 of the saddle 40 is
moved past the locking projection 25 of the tulip 20 and the groove
or recess 42 is moved from the locking projection 25 and the
proximal end 44 of the saddle 40 is move past abutting the locking
projection 25. In this state, the saddle 40 is prevented from any
proximal movement relative to the tulip 20 and the arcuate fingers
52 have been pressed into the distal opening 32 of the tulip 20
between the head 6 of the polyaxial screw 2 and the distal end 31
of the tulip 20. This causes the arcuate fingers 52 to be flexed
inwardly, tightly grasping against the polyaxial head 6 of the bone
screw 2. This assembly can be accomplished when the bone screw 2 is
implanted in bone. In such a case, the modular tulip assembly 10
with the saddle 40 in the unlocked position can be positioned over
the head 6 of the bone screw 2, pushed onto the bone screw 2 and
thereafter the saddle 40 moved into the locking position.
[0045] With reference to FIGS. 6-10, the tulip assembly 10 is shown
attached to the bone screw 2 with the assistance of a tool 100. The
tip 102 of the tool 100, illustrated in FIG. 6, has a threaded end
103, also illustrated in FIG. 7 in a cross-sectional view, that is
engaged with the internal threads 43 of the saddle 40. The end 102
of this tool 100 is configured to threadingly engage the saddle 40
and in so doing enables the tool 100 to push against the saddle 40,
the outer shoulder 106 of the tool 100 is adapted and precisely
dimensioned to abut a proximal end 27 of the tulip 20 along the
opposing walls 22, 23. When this occurs and the internal shaft 101
of the tool 100 is rotated, it will push the saddle 40 directly
axially distally moving the saddle 40 from the preloaded unlocked
position to the locked position as illustrated in FIG. 7. FIG. 8
shows the tool 100 separated from the tulip assembly 10 as the tool
100 is being removed after the assembly is accomplished or FIG. 8
can be viewed alternatively as a removal tool 100 assisted
illustration wherein the tulip assembly 10 when attached and locked
onto an implanted bone screw 2 can be physically removed by
threading the end 103 of the tool 100 into the internal threads 43
of the saddle 40 and rotating in such a fashion that is pulls the
saddle 40 in the proximal direction relative to the tulip 20. When
this occurs, the saddle 40 will move from the locked position as
the fingers 52 will be released from the distal end 51 and moved
upward into the chamber 30 within the tulip 20 as the groove or
recess 42 is positioned onto the locking projection 25, when this
occurs, the tool 100 can be used to pull the tulip 20 with unlocked
saddle 40 away from the implanted bone screw 2, as illustrated in
FIG. 9. It is understood while the bone screw is shown not embedded
in bone just for simplification, it is to be appreciated that this
procedure can be accomplished while the bone screw 2 is implanted
in a vertebral body. The cross-sectional view of FIG. 10
illustrates how the fingers 52 are allowed to flex when the bone
screw 2 has been removed and a saddle 40 is prepositioned in the
unlocked state.
[0046] FIG. 11 shows the tool 100 being removed from the tulip
assembly 10.
[0047] With reference to FIG. 12, once the assembly is made, it is
possible to place a spinal fixation rod 60 into the concavity at
the proximal end 44 of the saddle 40. Once the rod 60 is in
position, a threaded set screw 80 can be driven down into the
internal threads 24 of the opposing walls 22, 23 of the tulip 20.
The set screw 80 will then lock the rod 60 into position. When this
occurs, the entire assembly is locked into a locked position.
[0048] While the embodiment shown shows a single projection 25 is
used for the locked position, and a movement of the saddle 40 from
an unlocked initial state with the groove or recess 42 on the
projection 25 to a locked position when in use, it is understood
that a resistance or force required to move the saddle 40 into the
preloaded unlocked position for assembly can be adjusted depending
on the amount of interference that is provided between the
projection 25 and the groove or recess 42 and the exterior surface
of the proximal end 44 of the saddle 40. It is believed to have
sufficient locking strength, it is preferable that the exemplary
tool 100 be used so that the forces required to overcome the
initial unlocked state where the recess 42 is positioned over the
projection 25 are such that a tool 100 is preferred. The tool 100
designed provides a force between the tulip 20 and the saddle 40,
but provides no lifting or pulling forces against the bone screw 2
which can be embedded in bone. This is important in that one does
not want to loosen a bone screw 2 that has been attached into a
vertebral body, but rather would like the forces for locking the
saddle 40 in positon relative to the tulip 20 be absorbed between
the tool 100, the tulip 20 and the saddle 40 without any particular
axially loads pulling or loosening the bone screw 2.
[0049] With reference to FIG. 17, a cross-sectional view of the
modular tulip assembly 10A of the present invention is shown. As
shown, the modular tulip assembly 10A has a rod receiving tulip
20A, and internal of the rod receiving tulip 20A is shown a saddle
40A, the saddle 40A is interlockingly held inside a distal portion
of the tulip 20A. Below the tulip assembly 10A, is shown an
exemplary bone screw 2. The bone screw 2 has a threaded shank 4 for
engaging bone and a rounded spherical or hemispherical head 6 at
the proximal end of the shank 4. This head 6 is configured to
provide polyaxial movement of the bone screw 2 relative to the
tulip assembly 10A on assembly. This polyaxial movement is
maintained as long as the tulip assembly 10A is not locked into
position and fixed.
[0050] The modular tulip assembly 10A is basically a two part
device with the tulip 20A and the preloaded saddle 40A for use with
a bone screw 2. The bone screw 2 can be preloaded into the assembly
10A to make a three component device or system if desired. An
important feature of the present invention is a binary locking
aspect where a single locking projection 49 in combination with a
proximal tulip groove or recess 21 holds the saddle 40A in a
preloaded state inside the modular tulip 20A and when the modular
tulip assembly 10A is moved onto the head 6 of a bone screw 2 the
saddle 40A can be moved into a locked state and, if desired, can be
unlocked in a reversible fashion making the modular tulip assembly
10A most convenient to use. These features are fully described in
detail as follows.
[0051] With reference to FIG. 17, a cross-sectional view of the
tulip assembly 10A is shown wherein the saddle 40A is positioned
over the polyaxial hemispherical head 6 of the exemplary bone screw
2 in an unlocked position. As shown in cross-section, the tulip 20A
is shown with opposing walls 22, 23 with internal threads 24
defining a rod receiving slot or channel 33. Below the internal
threads 24 is illustrated the saddle 40A. The saddle 40A has a
locking projection 49 affixed to a tulip proximal groove or recess
21 in the tulip 20A of the tulip assembly 10A. The locking
projection 49 is shown near the proximal end 44 of the saddle 40A.
Below the locking projection 49 is shown a plurality of axially
extending flexible fingers 52 that are spaced apart by slots or
slits 54. At a distal end 51, these arcuate curved flexible fingers
52 are bowed slightly inwardly. At the proximal end of the slot 54
is an enlarged circular hole 55 to provide stress relief and also
increase the flexibility of the fingers 52. This is important in
that the fingers 52 must flex or bow outwardly in order to expand
as they slide over the hemispherical head 6 of the exemplary bone
screw 2. As shown in FIG. 17, the plurality of arcuate fingers 52
extend downward past the maximum diameter (d max) of the polyaxial
hemispherical bone screw head 6. The fingers 52 extension creates
at least a hemispherical concavity 53 that extends beyond the
maximum diameter d max and as such, the curvature of the fingers 52
bends outwardly at the proximal end and bows inwardly towards the
distal end 51, however, when attached to the bone screw 2, all of
the fingers 52 are shown deflected outwardly. The tulip 20A has a
large internal chamber 30 above the distal end 31. This chamber 30
is configured to allow the fingers 52 of the saddle 40A to bow
outwardly on assembly. Once the fingers 52 have bowed or flexed
outwardly to pass the maximum diameter d max of the bone screw head
6, they will conform or flex back inwardly compressing and sliding
against the surface 8 of the hemispherical bone screw head 6 when
in the locked position illustrated in FIG. 18. Preferably, the
concavity 53 formed by the plurality of arcuate fingers 52 is sized
to complimentarily fit the head 6 of the bone screw 2 to which it
is to be attached.
[0052] With reference to the proximal end 44 of the saddle 40A, as
shown, the proximal end 44 is shown above where the projection 49
is positioned in a groove or recess 21, 21L in the tulip 20A. The
outer or exterior surface of the proximal end 44 has a small
rounded edge or chamfer 48 to facilitate sliding past the tulip
grooves or recesses 21, 21L. When the saddle 40A is oriented in a
preloaded and unlocked position, as shown in FIG. 17, the arcuate
extended fingers 52 are allowed to move inwardly and outwardly
relative to an axis of the tulip 20. With reference to FIG. 18, the
saddle 40A is shown moved in a locking position wherein the locking
projection 49 of the saddle 40A is moved past the proximal groove
or recess 21 of the tulip 20A and into the distal tulip locking
groove or recess 21L. In this state, the saddle 40A is prevented
from any proximal movement relative to the tulip 20A and the
arcuate fingers 52 have been pressed into the distal opening 32 of
the tulip 20A between the head 6 of the polyaxial screw 2 and the
distal end 31 of the tulip 20A. This causes the arcuate fingers 52
to be flexed inwardly, tightly grasping against the polyaxial head
6 of the bone screw 2. This assembly can be accomplished when the
bone screw 2 is implanted in bone. In such a case, the modular
tulip assembly 10A with the saddle 40A in the unlocked position can
be positioned over the head 6 of the bone screw 2, pushed onto the
bone screw 2 and thereafter the saddle 40A moved into the locking
position.
[0053] With reference to FIGS. 17-23, the alternative embodiment
tulip assembly 10A is shown attached to the bone screw 2 with the
assistance of a tool 100. The tip 102 of the tool 100, illustrated
in FIG. 23, has a threaded end 103 that is engaged with the
internal threads 43 of the saddle 40A. The end 102 of this tool 100
is configured to threadingly engage the saddle 40A and in so doing
enables the tool 100 to push against the saddle 40A, the outer
shoulder 106 of the tool 100 is adapted and precisely dimensioned
to abut a proximal end 27 of the tulip 20A along the opposing walls
22, 23. When this occurs and the internal shaft 101 of the tool 100
is rotated, it will push the saddle 40A directly axially distally
moving the saddle 40A from the preloaded unlocked position of FIG.
17 to the locked position as illustrated in FIG. 18. FIG. 23 shows
the tool 100 inserted in the tulip assembly 10A as the tool 100 is
being removed after the assembly is accomplished or FIG. 23 can be
viewed alternatively as a removal tool 100 assisted illustration
wherein the tulip assembly 10A when attached and locked onto an
implanted bone screw 2 can be physically removed by threading the
end 103 of the tool 100 into the internal threads 43 of the saddle
40A and rotating in such a fashion that is pulls the saddle 40A in
the proximal direction relative to the tulip 20A. When this occurs,
the saddle 40A will move from the locked position as the fingers 52
will be released from the distal end 51 and moved upward into the
chamber 30 within the tulip 20A as the locking projection 49 is
positioned into the proximal tulip locking groove or recess 21,
when this occurs, the tool 100 can be used to pull the tulip 20A
with unlocked saddle 40A away from the implanted bone screw 2. It
is understood while the bone screw is shown not embedded in bone
just for simplification, it is to be appreciated that this
procedure can be accomplished while the bone screw 2 is implanted
in a vertebral body. The cross-sectional view of FIG. 17
illustrates how the fingers 52 are allowed to flex when the bone
screw 2 is not locked and saddle 40A is prepositioned in the
unlocked state.
[0054] These and other objectives are achieved by the application
of the present invention as described above.
[0055] Variations in the present invention are possible in light of
the description of it provided herein. While certain representative
embodiments and details have been shown for the purpose of
illustrating the subject invention, it will be apparent to those
skilled in this art that various changes and modifications can be
made therein without departing from the scope of the subject
invention. It is, therefore, to be understood that changes can be
made in the particular embodiments described, which will be within
the full intended scope of the invention as defined by the
following appended claims.
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