U.S. patent application number 09/790611 was filed with the patent office on 2001-06-28 for transconnector for coupling spinal rods.
This patent application is currently assigned to Synthes (U.S.A.). Invention is credited to Troxell, Thomas N..
Application Number | 20010005468 09/790611 |
Document ID | / |
Family ID | 23099641 |
Filed Date | 2001-06-28 |
United States Patent
Application |
20010005468 |
Kind Code |
A1 |
Troxell, Thomas N. |
June 28, 2001 |
Transconnector for coupling spinal rods
Abstract
The present invention is directed to a transconnector for
coupling first and second spinal fixation rods or other elongate
fixation elements. The transconnector includes a male member, a
female member, and a locking member. The male member has a body
with a linking element (such as a hook) associated with the lateral
end for receiving one of the fixation elements, and a projection
extending from the medial end. The female member has a body with a
linking element associated with the lateral end for receiving the
other fixation element, and a cavity with an opening on the medial
end for receiving a portion of the male member projection. The
locking member adjustably and rotatably secures the male member
projection portion in the cavity in order to accommodate different
orientations and separation distances between the first and second
fixation elements. The male member may be made as a two component
assembly in which the two components can rotate relative to one
another for accommodating rod convergence or divergence.
Inventors: |
Troxell, Thomas N.;
(Pottstown, PA) |
Correspondence
Address: |
PENNIE & EDMONDS LLP
1667 K STREET NW
SUITE 1000
WASHINGTON
DC
20006
|
Assignee: |
Synthes (U.S.A.)
|
Family ID: |
23099641 |
Appl. No.: |
09/790611 |
Filed: |
February 23, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09790611 |
Feb 23, 2001 |
|
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09286669 |
Apr 6, 1999 |
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Current U.S.
Class: |
403/92 |
Current CPC
Class: |
Y10T 403/32327 20150115;
Y10T 403/32591 20150115; Y10S 606/907 20130101; F16B 7/0433
20130101; Y10T 403/32549 20150115; Y10T 403/46 20150115; Y10T
403/32557 20150115; Y10T 403/1616 20150115; Y10T 403/32581
20150115; Y10T 403/32057 20150115; F16B 7/22 20130101; F16B 2200/40
20180801; Y10T 403/32073 20150115; A61B 17/7052 20130101 |
Class at
Publication: |
403/92 |
International
Class: |
F16D 001/12; F16D
003/00; F16C 011/00 |
Claims
What is claimed is:
1. A transconnector for coupling first and second elongate spinal
fixation elements that have different orientations, the
transconnector comprising: a male member comprising a body with
lateral and medial ends, a linking element associated with a
lateral end and being configured and dimensioned to receive one of
the fixation elements, and a projection extending from the medial
end; a female member comprising a body with lateral and medial
ends, a linking element associated with the lateral end and being
configured and dimensioned to receive one of the fixation elements,
and a cavity with an opening on the medial end which is configured
and dimensioned to receive a portion of the projection; a locking
member for adjustably and rotatably securing the projection portion
in the cavity in order to accommodate different orientations and
separation distances between the first and second fixation
elements; a pin having a diameter and extending perpendicularly
from a longitudinal axis of the projection; and a slot located on a
wall of the female member cavity, wherein side edges of the slot
are configured and dimensioned to angle outwardly and the pin is
slideable in the slot for adjusting the portion of the projection
received in the cavity and the slot has a width which is wider than
the diameter of the pin to allow rotational movement of the pin in
the slot and rotation of the projection in the cavity.
2. The transconnector of claim 1 wherein the projection is
substantially cylindrical.
3. The transconnector of claim 1 wherein the locking member
comprises: a threaded hole in the body of the female member; and a
set screw threadably received in the threaded hole and having a
first end for receiving a tool to turn the set screw and a second
end contactable with the projection for pressing the projection
against the cavity.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a device for spinal
fixation, and in particular to a transconnector for coupling spinal
rods, plates, or other elongate members.
BACKGROUND OF THE INVENTION
[0002] It is often necessary to surgically treat spinal disorders
such as scoliosis. Numerous systems for use in spinal correction
and fixation have been disclosed. These systems usually include a
pair of elongate members, typically either rods or plates, placed
on opposite sides of the vertebral colunm. Each rod is attached to
the spine with various attachment devices. These attachment devices
include pedicle screws, plates, spinous process hooks, sublaminar
hooks, and pedicle hooks.
[0003] It is also well known that the strength and stability of the
dual rod assembly can be increased by coupling the two rods with a
cross-brace or transconnector which extends substantially
horizontal to the longitudinal axes of the rods across the spine.
The simplest situation in which a transconnector could be used
occurs when the two rods are geometrically aligned. Specifically,
the two rods are parallel to each other, i.e. there is no rod
convergence or divergence in the medial-lateral direction; the two
rods have the same orientation with respect to the coronal plane in
the anterior-posterior direction, i.e. the rods are coplanar from a
lateral view; and the two rods are located a fixed, predetermined
distance from each other.
[0004] Due to a wide variety of factors, the two rods are rarely
geometrically aligned in clinical situations. There are several
ways to address the variations from geometrical alignment. First,
one or both of the rods can be bent to accommodate the
transconnector. However, any bending in either of the rods can
adversely affect the fixation to the spine and comprise clinical
outcome. Furthermore, the bending can also adversely affect the
mechanical properties of the rods. The transconnector can also be
bent so that the disturbance to the rod positioning is minimized.
As was the case with bending of the rods, the mechanical properties
of the transconnector could be compromised.
[0005] Transconnectors with some adjustability have been designed
to adapt for variations from geometrical alignment. However, most
are multi-piece systems that can be difficult to assemble and use
in the surgical environment. Even those that are one-piece designs
do not allow for adjustments to compensate for all three modes in
which there may be variation from geometrical alignment:
convergence or divergence, non-coplanar rods, and variability in
rod separation distances.
[0006] Thus, there exists a need for an improved transconnector for
coupling spinal rods.
SUMMARY OF THE INVENTION
[0007] The present invention relates to a transconnector for
coupling first and second elongate spinal fixation elements that
have different orientations with respect to a plane. The
transconnector includes a male member, a female member and a
locking member and can be made of any suitable material such as
titanium, a titanium alloy, or stainless steel. The male member
comprises a body with lateral and medial ends, a linking element
associated with the lateral end and being configured and
dimensioned to receive one of the fixation elements, and a
projection extending from the medial end. The female member
comprises a body with lateral and medial ends, a linking element
associated with the lateral end and being configured and
dimensioned to receive one of the fixation elements, and a cavity
with an opening on the medial end which is configured and
dimensioned to receive a portion of the male member projection. The
locking member adjustably and rotatably secures the male member
projection portion in the cavity in order to accommodate different
orientations and separation distances between the first and second
fixation elements.
[0008] In a preferred embodiment, the male member projection is
substantially cylindrical and has a pin extending perpendicularly
from its longitudinal axis. The pin is slidable in a slot located
in a wall of the female member cavity for adjusting the portion of
the projection received in the cavity. The slot has a width which
is wider than the diameter of the pin so that the projection can
rotate in the cavity. In order to further increase the degree of
rotation, the side edges of the slot may angle outwardly.
[0009] Preferably, the locking member comprises a threaded hole in
the body of the female member and a set screw threadably received
in the threaded hole. The set screw has a first end for receiving a
tool to turn the set screw and a second end contactable with the
projection for pressing the projection against the cavity.
[0010] The male member body may comprise a link terminal having a
lateral end with the male member linking element, an intermediate
link having a medial end with the projection of the male member and
a lateral end engaging the medial end of the link terminal, and a
locking element for securing the link terminal to the intermediate
link. Preferably, the medial end of the link terminal includes a
first textured surface and the lateral end of the intermediate link
includes a second textured surface mating with the first textured
surface. The first textured surface is rotatable with respect to
the second textured surface for accommodating convergence or
divergence between the first and second rods. An example of
suitable first and second textured surfaces includes a star-grind
pattern.
[0011] The locking element preferably comprises a first hole
through the medial end of the link terminal, a second hole through
the lateral end of the intermediate link aligned with the first
hole, and a cap screw insertable in the first and second holes. The
cap screw may have a second end with a retaining ring for
preventing removal of the cap screw from the first and second
holes. The retaining ring may include a resilient member which
flexes inward upon insertion of the cap screw through the first and
second holes and flexes outward once the resilient member is past a
collar in the second hole. Preferably, the resilient member
includes an end of the cap screw with a lip and a plurality of
slits.
[0012] If rods are used for the elongate fixation elements, then
the male member linking element preferably comprises a hook and the
female member linking element preferably comprises a hook. The
lateral ends of the male and female members each may include a
threaded hole and a clamping screw threadably received in the
respective threaded hole for securing the fixation elements to the
respective hook. The fixation elements are preferably clamped
between a conical second body portion of the respective clamping
screw and a region near the tip portion of the respective hook when
the fixation elements are secured to the transconnector.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Preferred features of the present invention are disclosed in
the accompanying drawings, wherein similar reference characters
denote similar elements throughout the several views, and
wherein:
[0014] FIG. 1 shows a top perspective view of a transconnector
according to the present invention with an elongate fixation
element attached at each end;
[0015] FIG. 2 shows a bottom perspective view of the transconnector
without the fixation elements;
[0016] FIG. 3 shows a cross-sectional view of the transconnector
with one fixation element attached;
[0017] FIG. 4 shows a perspective view of the female member of the
transconnector;
[0018] FIG. 5 shows a side view of the female member;
[0019] FIG. 6 shows a cross-sectional view of the female member
taken along line A-A of FIG. 5;
[0020] FIG. 7 shows a side view of a link terminal of the male
member with portions cut out;
[0021] FIG. 8 shows a cross-sectional view of an intermediate link
of the male member; and
[0022] FIG. 9 shows a perspective view of a cap screw used to join
the link terminal and intermediate link.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] FIG. 1 shows a transconnector 10 according to the present
invention for coupling a first elongate spinal fixation element 12
to a second elongate spinal fixation element 14. Transconnector 10
can be made of any suitable material typically used in orthopaedic
applications such as titanium, titanium alloy, or stainless steel.
If transconnector 10 is made of a metallic material, preferably it
is the same metallic material used for fixation elements 12, 14 to
avoid galvanic (mixed-metal) corrosion. First and second fixation
elements 12, 14 can be cylindrical rods, rectangular bars, plates,
or any other device suitable for spinal fusion. In use, first
fixation element 12 extends along one side of the vertebral column
and second fixation element 14 extends along the other side of the
vertebral column. A wide variety of attachment devices such as
hooks, screws, and clamps, can be used to attach first and second
fixation elements 12, 14 to the spine.
[0024] Transconnector 10 includes a male member 16, a female member
18, and a locking member 20. Male member 16 has a body with a
linking element 22 on a lateral end for receiving first fixation
element 12 and a projection 24 extending from a medial end of the
body. Female member 18 has a body with a linking element 26 on a
lateral end for receiving second fixation element 14 and a cavity
28 with an opening 30 (FIG. 5) on a medial end of the body for
receiving a portion of projection 24. Locking member 20 secures the
portion of projection 24 in cavity 28. The portion of projection 24
received in cavity 28 is adjustable for accommodating different
separation distances d between first and second fixation elements
12, 14. This feature allows transconnector 10 to be readily
adjusted for different patient anatomies and used in different
regions of the spine. For example, the lumbar vertebrae are
typically larger than the thoracic vertebrae. As a result, the
distance between fixation elements in the lumbar region would be
greater than fixation elements in the thoracic region. Because the
length of projection that slides into cavity 28 can be changed,
transconnector can be adjusted for use in different spinal regions
without the need to bend either fixation rods or transconnector 10.
In order to further increase the adjustability of transconnector
10, female member 18, cavity 28, and projection 24 can be
manufactured in different sizes.
[0025] Projection 24 is rotatable in cavity 28 for accommodating
differences between the angular orientation of first fixation
element 12 with respect to the coronal plane and the angular
orientation of second fixation element 14 with respect to the
coronal plane. Specifically, first fixation element 12 has a
longitudinal axis L.sub.1 which runs at an angle .alpha..sub.1 with
respect to coronal plane C and second fixation element 14 has a
longitudinal axis L.sub.2 which runs at an angle .alpha..sub.2 with
respect to coronal plane C, the plane which divides the body in
half from front to back. Because projection 24 can rotate in cavity
28, transconnector can be used in situations in which .alpha..sub.1
differs from .alpha..sub.2 without the need to bend either fixation
element or transconnector 10.
[0026] As seen best in FIGS. 2 and 3, projection 24 is
substantially cylindrical and cavity 28 has a corresponding shape
to facilitate rotation of projection 24 in cavity 28. Projection 24
has a pin 32 extending perpendicularly therefrom which travels
within a slot 34 located on a wall 36 of cavity 28. The engagement
of pin 32 with front and back edges 38 limits the length of
projection 24 that can slide in cavity 28 and prevents projection
24 from coming completely out of cavity 28. Because the diameter of
pin 32 is smaller than the width of slot 34, projection 24 can
rotate in cavity 28. The engagement of pin 32 with side edges 40
limits the amount of rotation of projection 24 in cavity 28. Side
edges 40 can angle outward to increase the angle of rotation
.beta.. A .beta. of 45.degree.should be sufficient to accommodate
even the most extreme differences between .alpha..sub.1 and
.alpha..sub.2.
[0027] As previously noted, locking member 20 secures the portion
of projection 24 in cavity 28. FIGS. 1, 3, and 5 show that locking
member 20 includes a threaded hole 42 in female member 18 and a set
screw 44. Set screw 44 threads into threaded hole and a second end
46 presses projection 24 to clamp it against the walls of cavity
28. A first end 48 of set screw 44 has an appropriately shaped and
sized hole 50 (or a slot) for receiving a surgical instrument like
a screwdriver to turn set screw 44.
[0028] FIGS. 1, 7, and 8 show the body of male member 16 as a two
piece assembly which includes a link terminal 52, an intermediate
link 54, and a locking element 56 to secure the two together. A
lateral end of link terminal 52 has male member linking element 22
and intermediate link 54 has a medial end with projection 24 and a
lateral end 58 which engages a medial end 60 of link terminal 52.
Medial end 60 of link terminal 52 includes a first textured surface
62 which mates with a second textured surface 64 of lateral end 58
of intermediate link 54 in such a fashion that first textured
surface 62 is rotatable with respect to second textured surface 64
to accommodate for any convergence or divergence between first and
second fixation elements 12, 14. First and second textured surfaces
62, 64 are provided with a plurality of teeth, such as a star-grind
pattern, in order to help maintain link terminal 52 at the desired
angular orientation. Locking element 56 includes a first hole 66
through medial end 60 of link terminal 52 and a second hole 68
through lateral end 58. First and second holes 66, 68 align so that
a cap screw 70 can be inserted therethrough.
[0029] Referring to FIG. 9, cap screw 70 has a first end 72 with a
slot 74 for receiving a tool to turn cap screw 70 and a second end
76 with a retaining ring 78 for preventing removal of cap screw 70
from first and second holes 66, 68. Retaining ring 78 has slits 80
which allow retaining ring to flex inward to be inserted through a
collar 82 in second hole 68. Once retaining ring 78 is inserted
past collar 82, retaining ring 78 flexes back outward so that cap
screw 70 can not be completely screwed out of first and second
holes 66, 68. A body 84 of cap screw 70 is provided with threads 86
which engage threads 88 on the walls of second hole 68.
[0030] The structure of linking elements 22, 26 will depend on the
structure of fixation elements 12, 14. For example, if fixation
rods 12, 14 are elongate plates, then linking elements 22, 26 are
configured and dimensioned to receive elongate plates. Such
configurations and configurations for other types of fixation
elements are well known in the art. If fixation elements 12, 14 are
cylindrical rods as shown in the drawings, then linking elements
22, 26 each comprises a hook 90. The lateral ends of male and
female members 16, 18 each includes a threaded hole 92 and a
clamping screw 94 threadably received in threaded hole 92 for
securing first and second fixation elements 12, 14 to hook 90.
[0031] As seen best in FIGS. 2 and 3, each clamping screw 94 has a
first end 96 with a slot 98 for receiving a tool to turn clamping
screw 94, a threaded cylindrical first body portion 100, and a
conical second body portion 102. Each hook 90 comprises a tip
portion 104 and a curved portion 106. Curved portion 106 has a
radius of curvature larger than the radius r of fixation elements
12, 14. As a result, the only contact between hooks 90 and fixation
elements 12, 14 is at a region near tip portion 104. Furthermore,
the only contact between clamping screws 94 and fixation elements
12, 14 is on conical second body portion 102. Thus, fixation
elements 12, 14 is clamped between conical second body portion 102
and the region near tip portion 104.
[0032] While various descriptions of the present invention are
described above, it should be understood that the various features
can be used singly or in any combination thereof. Therefore, this
invention is not to be limited to only the specifically preferred
embodiments depicted herein.
[0033] Further, it should be understood that variations and
modifications within the spirit and scope of the invention may
occur to those skilled in the art to which the invention pertains.
Accordingly, all expedient modifications readily attainable by one
versed in the art from the disclosure set forth herein that are
within the scope and spirit of the present invention are to be
included as further embodiments of the present invention. The scope
of the present invention is accordingly defined as set forth in the
appended claims.
* * * * *