Advanced compression locking variable length cross-link device

A variable length cross-link device for use with orthopaedic dual rod apparatuses includes a pair of elongate elements, each having a first end which mates with a rod or pedicle screw. The first element has a second end which is narrow and extending. The second element has a second end which is wide and extending, and includes a through hole. The invention further includes a post having an upper threaded portion mounted through the hole in the second element, and a passageway in the lower portion for receiving the second end of the first element. A nut is provided onto the post. Prior to tightening of the nut, the first element is slidable relative to the post and the second element, and the post element has rotational freedom within the through hole such that the first and second elements may be angulated relative to one another. Once the nut is tightened, the first and second elements are compressibly engaged, thereby crush locking the elements together. In a first embodiment, the first ends of the elongate elements are curvate and have set screw hole to hook and lock onto the rods. In a second embodiment the first ends have eyeloops for coupling to the heads of pedicle screws. In a third embodiment, which is compatible with either of the first end configurations, the narrow and extending end of the first element is cylindrical so that the first and second ends may axially rotate relative to one another.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to a mechanical cross-link device for use 
with dual rod orthopaedic implant apparatus. More particularly, this 
invention relates to a novel device which may be fixed to each rod of a 
dual rod implant apparatus, or to the pedicle screws thereof, for 
maintaining and enhancing the rigidity of the apparatus. 
2. Discussion of the Prior Art 
The bones and connective tissue of an adult human spinal column consist of 
an upper portion (the cervical, thoracic, and lumbar regions) having more 
than 20 discrete bones, and a lower portion which consists of the sacral 
bone and the coccygeal bodies. The bones of the upper portion are 
generally similar in shape, as will be more fully described hereinbelow 
with respect to FIGS. 1, 2 and 3. For the purpose of describing this 
invention, the sacral bone shall be distinguished from the spinal column; 
the spinal column, therefore, comprising for the purposes of this 
description, only the cervical, thoracic, and lumbar vertebrae. 
The vertebrae vary in size, but are each similarly coupled to adjacent 
bones by a tri-joint complex. The tri-joint complex consists of an 
anterior disc and the two posterior facet joints, the anterior discs of 
adjacent bones being cushioned by cartilage spacers referred to as 
intervertebral discs. Referring now to FIGS. 1, 2 and 3, top, lateral, and 
posterior views of a typical vertebral bones of the spinal column are 
shown. The spinal cord is housed in the central canal 10, protected from 
the posterior side by a shell of bone called the lamina 12. The lamina 12 
has three large protrusions, two of these extend laterally from the side 
ends thereof and are referred to as the transverse processes 14. The third 
extends back and down from the center of the lamina and is called the 
spinous process 16. The lamina 12 defines an arched shape about the 
posterior of the spinal cord, the arched shape having lateral portions 
13a,13b which are generally straight, and which meet beneath the spinous 
process at a curved surface 15. 
The anterior portion of the spine comprises a set of generally 
cylindrically shaped bones which are stacked one on top of the other. 
These portions of the vertebrae are referred to as the vertebral bodies 
20, and are each separated from the other by the intervertebral discs 22. 
Pedicles 24 are bone bridges which couple the anterior vertebral body 20 
to the corresponding lamina 12 and posterior elements 14,16. 
Referring specifically to FIG. 3, the stacking of vertebrae is shown from 
the posterior. From the posterior, each vertebra is coupled to the one 
above and below via facet joints 19 on either side of an opening into the 
spinal canal 10. 
In its entirety, the spinal column is highly complex in that it houses and 
protects critical elements of the nervous system which have innumerable 
peripheral nerves and arterial and venous bodies in close proximity. In 
spite of these complexities, the spine is a highly flexible structure, 
capable of a high degree of curvature and twist through a wide range of 
motion. Genetic or developmental irregularities, trauma, chronic stress, 
tumors, and disease, however, can result in spinal pathologies which 
either limit this range of motion, or which threaten the critical elements 
of the nervous system housed within the spinal column. A variety of 
systems have been disclosed in the art which achieve this immobilization 
by implanting artificial assemblies in or on the spinal column. 
A variety of systems have been disclosed in the art which achieve this 
immobilization by implanting artificial assemblies in, or on, the spinal 
column. These assemblies may be classified by their position relative to 
the spine, as anterior, posterior, or lateral implants. Anterior and 
lateral assemblies generally comprise short structures which support only 
a few adjacent vertebral bodies. Conversely, posterior implants often 
comprise pairs of elongate vertically aligned rods for stabilizing both 
short and long segments of the spine. Such posterior rods are coupled to 
the back of the spinal column via hooks which slip under the lamina, means 
for attaching to the transverse process, and/or by screws which are 
inserted through the pedicle bone. In order to provide enhanced torsional 
rigidity, these apparatuses generally include cross-linking devices which 
couple the rods together transverse to the axis (vertical axis) of the 
apparatuses. These cross-linking devices may couple directly to the rods 
themselves, or may be attached to the pedicle screws. 
Referring now to FIG. 4, U.S. Pat. No. 5,005,562 to Cotrel teaches such a 
dual rod apparatus which includes a pair of rods 30a,30b, which are each 
coupled to the spine via hooks 32a,34a and 32b,34b, respectively, as well 
as pedicle screws 36a,36d and 36b,36c, respectively. The rods 30a,30b are 
further stabilized by cross-link devices 38a,38b. These cross-link devices 
38a,38b each include a pair of U-shaped gripping element 35a,35b which may 
receive the rod 30a,30b respectively. Each of the gripping elements 
includes a first threaded hole which extends from the outer lateral 
surface into the inner surface of the U-shaped rod receiving region. The 
gripping elements 35a,35b are fixed to the rods 30a,30b by set screws 
37a,37b which are positioned in the first holes such that tightening of 
the set screws locks the rod 30a,30b in the gripping element. The gripping 
elements 35a,35b are coupled together by a threaded rod 33 which permits 
the gripping elements to be selectively spread or brought closer together, 
in accordance with the relative position of the rods 30a,30b. The threaded 
rod 33 extends through a second set of threaded holes in the gripping 
elements 35a,35b. 
The bulkiness of each of the gripping elements 35a,35b, required so that it 
may receive the threaded rod 33, is difficult for the surgeon to use 
easily under operative conditions. The size of the gripping elements, and 
the relative position of the set screws often cause substantial difficulty 
with respect to the tightening of same because of their positions relative 
to the operative access. This bulkiness also reduces available bone graft 
surface area, which is critical for a successful fusion and long term 
immobilization. In addition, in order for a surgeon to selectively vary 
the spread of the gripping elements 35a,35b, one of the gripping elements 
must be rotated relative to the other, thus requiring the cross-link to be 
removed (loosening the set screws and withdrawing the device entirely from 
the operative site). This is particularly burdensome with respect to 
providing the surgeon with the ability to apply an inward force to the 
rods 30a,30b as the spread may not be varied in situ. 
It is therefore, a principal object of the present invention to provide a 
new and novel cross-link device which provides a less bulky profile, 
therein providing increased area for bone grafting. 
It is also an object of the present invention to provide a cross-link 
device which provides the surgeon with the ability to lock the device to 
the rods or to the pedicle screws more easily than prior cross-link 
devices. 
It is also, therefore, an object of the present invention to provide a 
cross-link device which provides the surgeon with the ability to vary the 
spread of the rod or pedicle gripping portions easily. 
Other objects of the present invention not explicitly stated will be set 
forth, and will be more clearly understood, in conjunction with the 
descriptions of the preferred embodiments disclosed hereafter. 
SUMMARY OF THE INVENTION 
In its various embodiments, the preceding objects of the invention are 
achieved by the present invention which is a compression locking variable 
length cross-link device which may be affixed to the rods, or pedicle 
screws, of a dual rod implant apparatus. The present invention may be 
practiced in a variety of different embodiments; the several enclosed 
herein being representative of preferred ones of the invention. 
The invention includes a pair of elements formed of a substantially rigid 
material, for example medical grade steel or titanium. In a first category 
of this invention, the elements each have first ends which are curvate so 
as to securely seat against and hook to the lateral outside surface of a 
rod of a dual rod apparatus. These curvate ends further include a through 
hole for receiving a set screw. The set screw positioned therein is 
designed to be threadably tightened downward onto the rod against which 
the first end is seated, therein locking the rod and element together. 
In a second category of embodiments, the first ends have eyeloops enabling 
them to be mounted about respective pedicle screws, and secured in place 
by the downward pressure supplied by top locking nuts mounted thereon. 
With respect to both of these categories, however, the second ends of the 
two elements are designed to be coupled together by a threaded post, which 
shall be described more fully hereinafter. One of the elements of the 
pair, referred to hereinafter as the first element comprises a flat second 
end which is narrowed to a width which is substantially less than the 
width of the flat material of which the rod securing end is formed (the 
thickness and corresponding structural strength of the flat end is 
desirably the same as that of the rod securing end). In addition, it is 
desirable for the top surface of this flat second end to have a grooved or 
roughened conformation, for example a diamond knurling. 
With respect to the other of the elements (hereinafter referred to as the 
second element), the second end is also flat, but is wider. This widened 
portion includes a through hole having a diameter sufficient to receive 
the above-introduced threaded post. In addition, the undersurface of the 
flat second end of the second rod securing element is correspondingly 
roughened, for example, with a diamond knurl. 
The coupling of these two elements is achieved by the incorporation of a 
threaded post. This threaded post is generally cylindrical and comprises a 
widened base, an intermediate portion having a passageway defined 
therethrough which is transverse to the axis of the post, and a threaded 
upper portion. The flat second end of the first element is inserted 
through the passageway, such that the knurled upper surface of the flat 
end is oriented upward. The threaded upper portion of the post is 
positioned through the hole in the flat portion of the second element such 
that the knurled lower and upper surfaces of the flat ends of the first 
and second elements contact on another. A top locking nut is then threaded 
onto the upper portion of the post. 
Prior to the tightening of the nut, the flat end of the first element may 
slide relative to the flat portion of the second, so that the rod securing 
portions may be spread or drawn together in accordance with the 
positioning of the rods. Tightening of the nut down onto the top surface 
of the second flat portion causes the post to be drawn upwards until the 
roughened surfaces of the first and second flat portions seat and lock to 
one another under the compressive force. 
It shall be understood, from the nature of the coupling of the two elements 
via the post member, that the two elements need not be co-linear to be 
secured. Rather, it is a feature of this invention, in the variations of 
the first and second category, for the element to be selectably variable 
in coupling angle in a given plane such that the device may form a 
non-linear cross-linking structure between two rods. 
In a third category of embodiments of the present invention, the capacity 
to selectively vary the coupling angle is enhanced inasmuch as one of the 
pair of elements (the first) may be rotated about its elongate axis so 
that it may accomodate rods which are not co-planar. This variability is 
achieved by having the second end of the first element be cylindrical, and 
for the passageway formed in the post, in which the second end is to be 
inserted, to be correspondingly round so that the cylindrical end may 
rotate therein. The cylindrical end and the interior of the passageway may 
each include a diamond knurling so that they may mutually lock under the 
compressive forces applied by the second element via the upward drawing of 
the post element. 
It shall be understood that this third category of devices may be affixed 
to the rods as are the embodiments of the first category, or may be 
coupled via the pedicle screws as are the embodiments of the second 
category.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
While the present invention will be described more fully hereinafter with 
reference to the accompanying drawings, in which particular embodiments 
and methods of implantation are shown, it is to be understood at the 
outset that persons skilled in the art may modify the invention herein 
described while achieving the functions and results of this invention. 
Accordingly, the descriptions which follow are to be understood as 
illustrative and exemplary of specific structures, aspects and features 
within the broad scope of the present invention and not as limiting of 
such broad scope. 
Referring now to FIG. 5a, a first rod coupling element 100a of the first 
embodiment of the present invention is provided in a side perspective 
view. As with all elements of this invention, the material of which this 
rod hooking element may comprise a high strength material, for example 
medical grade steel or titanium compounds, which has been found ideally 
suited for implantation into the human body. The rod coupling element 100a 
shown in FIG. 5a is specifically formed of a thin and flat sheet of metal, 
the first end 102a of which has been curved to the shape of a hook. The 
hook has a semi-circular curvature defined by an inner surface 104 and an 
outer surface 106. The lower portion 108 of the semi-circular hook extends 
tangentially for a small distance, parallel to the remainder of the 
element. The curve is semi-circular so that it can cup and hook to the 
lateral outside surface of a first rod of a dual rod apparatus. 
The top portion 111 of the first end 102a comprises a through hole 112 
which is threaded and extends from a point on the top surface of the first 
end 102a which is to adjacent to the initial curvature of the hook to the 
underside of the same. Inasmuch as a set screw (set forth with respect to 
FIG. 6) is to be directed therethrough to lock the element 100a, and more 
specifically the first end 102a thereof, to a rod of the implant assembly, 
the through hole 112 may be angled such that the insertion and subsequent 
tightening of the set screw drives same toward the inner surface 104 of 
the hook. Such a preset angle of the through hole orientation enhances the 
locking strength of the set screw by increasing the cupping surface 
against which the rod is crushed. 
The other end 114a of the rod coupling element comprises a narrowed and 
flat portion which has a width which is substantially reduced as compared 
with that of the first rod securing end 102a. The thickness and 
corresponding structural strength of this second end 114a is, however, 
desirably the same as that of the rod securing end. The top surface 116a 
of this second narrowed end 114a includes a roughening, for example a 
diamond knurling, which provides a greater coefficient of static friction 
to it; this enhanced friction coefficient being desirable for the purposes 
of compression locking this top surface against another surface. 
Referring now to FIG. 6, a side view of the set screw 120 which is used to 
lock the rod to the first end 102a of the rod coupling element 100a (and 
for applying a compression pressure as described in regards to the second 
embodiment set forth herein) is provided. The set screw 120 comprises a 
surface threading 122 which is ideally suited to the threading of the 
through hole 112. The screw 120 further includes a recess 124 in the top 
126 thereof, the recess having an internal conformation which may be 
engaged by a suitable tool for applying a torsional force thereto, for 
example a slot for a screwdriver or a hexagonally angled interior wall for 
an allen wrench. 
Referring now to FIGS. 7 and 8, side view of the post 130a and the top 
locking nut 150, which together provides the compression coupling of the 
elements of this embodiment is provided. Specifically referring to FIG. 7, 
the post 130a has a generally cylindrical shape. The base 132a of the post 
is wider than the upper portions, forming an annular flange 134a. This 
annular flange 134a may include a surface roughening so that it may have 
an enhanced gripping strength against any surface against which it might 
be compressed. 
The upper portion of the base 132a, and the lower portion of the 
intermediate section of the post 130a includes a passageway 136 which 
extends transverse to the axis of the post, and which has a substantially 
rectangular cross-section. This passageway 136 is ideally suited for 
slidably receiving therethrough the flat extending end 114a of the first 
rod coupling element 100a (see FIG. 5a). The height of the passageway 136 
is desirably slightly larger than the thickness of the flat extending end 
114a, but the width of the passageway 136 is desirably the same. These 
dimensions eliminate any rotation or angulation of the first rod hooking 
element 100a relative to the post 130a. 
The upper portion 138a of the post 130a extends upward from the passageway 
136 and the intermediate portion, and comprise a threading 140a which is 
ideally suited for receiving thereon a top locking nut. With reference to 
FIG. 8, the top locking nut 150 comprises a top surface 152 and a bottom 
surface 154, and an interior threading 156. 
Referring now to FIG. 9a, a first embodiment of the second rod coupling 
element 160a is provided in a side perspective view. The second element 
160a includes a rod securing end 162a which is substantially similar to 
the equivalent feature 102a of the first element 100a. More specifically, 
the rod securing end 162a thereof has a curvate shape and an interior 
surface 164 for seating against lateral outside surface the second rod of 
the dual rod apparatus. This curvate end 162a includes a through hole 166 
for receiving a set screw 120 for locking the rod to the curvate shaped 
end. 
The other end 170a of this second rod hooking element 160a is substantially 
wider than the flat end 114a of the first element 100a. The undersurface 
of this end 170a (not shown) may comprise a surface roughening similar to, 
or at least ideally suited for engaging, the roughened top surface 116a of 
the first element. This end 170a comprises a through hole 172a which has a 
width equal to or greater than the width of the upper threaded portion 
1389, and the intermediate portions of the post 1309. 
With additional reference now to FIG. 10a, in which a fully assembled first 
embodiment of the present invention is provided in a side perspective 
view, the method of assembly and the locking of the elements is described. 
First the proper site on the rods for the fixation of the cross-link 
device is identified by the surgeon. The site should provide enough space 
along the rods for engagement of rod securing ends 102a and 162a. Once 
this site is found, and the space separating the rods is cleared of all 
obstacles (for example, the spinous process) the narrow and flat extending 
portion 114a of the first element 100a is inserted into the passageway 136 
of the post 130a, such that the roughened top surface 116a of the 
extending portion 114a is oriented in the direction of the upper section 
138a of the post 130a. 
Once the flat extending portion 114a has been inserted, the upper section 
138a of the post 130a is inserted through the hole 172a in the rod 
coupling flat extending portion 170a of the second element 160a. The post 
130a is inserted upwardly so that the top locking nut 150, and more 
specifically the threads 156 thereof, may engage the threads 140a of the 
upper portion 138a. Initial tightening of the nut 150 downward on the post 
130a causes the bottom surface 154 of the nut to seat against the top 
surface of the flat extending portion 170a. At this point the flat 
extending portion 114a of the first element 100a remains slidable relative 
to both the post 130a and the second element 160a. The rod securing 
portions 102a and 162a may be selectively spread or drawn together by an 
amount determined solely by the length of the flat extending portion 114a 
of the first element 100a. 
In addition, it may be understood that inasmuch as the post 130a is not 
secured to the through hole 172a, the post may be rotated, thus angulating 
the first and second elements 100a and 160a relative to one another from 
their co-linear orientation, within a plane defined thereby. While minimal 
rotation is desired, so as to maximize the contact surfaces of the 
extending portions 114a and 170a, slight angulations may be useful in 
cases wherein the rods are not locally parallel, but comprise a small 
convergence or divergence. 
Continued tightening of the nut 150, however, causes the post 130a to be 
drawn upwards through the hole 172a, thereby causing the intermediate 
section, and the passageway 136 thereof to be similarly drawn upwards. In 
doing so, the roughened top surface 116a of the narrowed flat extending 
portion 114a is compressed against the roughened lower surface of the 
second flat extending portion 170a, locking the two together and locking 
the length of the cross-link. 
Once the length of the cross-link is been set, the set screws 120 may be 
tightened down, thereby locking the element 100a and 160a to the rods 
themselves. 
Referring now to FIGS. 5b, 7, 8, and 9b, the second alternative embodiment 
of this invention is now described. This embodiment is designed for 
coupling the rod apparatuses of the dual rod implant construct together by 
joining to the pedicle screws themselves. More specifically, with respect 
to the first element 100b shown in FIG. 5b, the element comprises a first 
end 102b which is flat and includes a through hole 103. This through hole 
103 is provided such that the top of a pedicle screw may be inserted 
therein, and such that the top locking nut of the pedicle screw may be 
threaded down onto the head of the pedicle screw, thereby securing the 
element 100b to the rod assembly. 
The other end 114b of this first element 100b is identical in every respect 
to the second end 114a of the first element 100a as shown in FIG. 5a. 
Similarly, the post 130a and nut 150 elements utilized in conjunction with 
this second embodiment are identical to the ones used in conjunction with 
the first embodiment. 
Referring now to FIG. 9b, the second element 160b of this second embodiment 
is provided. It comprises a first rod assembly securing end 162b, which 
includes a through hole 163 which is similar in form and function to the 
through hole 103 of the first element 100b of this second embodiment. More 
specifically, this hole 163 is provided to receive the head of a pedicle 
screw, and to provide secure coupling thereto upon the subsequent 
engagement of a top locking nut onto the head of the pedicle screw. The 
second end 170b of this second element 160b comprises the same structure 
and features as the second end of the second element 160a as shown and 
described with respect to FIG. 9a. 
Referring now also to FIG. 10b, in which the fully assembled cross-link 
device, the elements of which are set forth in FIGS. 5b, 7, 8, and 9b, is 
shown in a side perspective view, the implantation of this second 
embodiment is described. As above, the narrow and flat extending portion 
114b of the first element 100b is inserted into the passageway 136 of the 
post 130a, such that the roughened top surface 116b of the extending 
portion 114b is oriented in the direction of the upper section 138a of the 
post 130a. Then the upper section 138a of the post 130a is inserted 
through the hole 172b in the rod coupling flat extending portion 170b of 
the second element 160b. The post 130a is inserted upwardly so that the 
top locking nut 150, and more specifically the threads 156 thereof, may 
engage the threads 140a of the upper portion 138a. Initial tightening of 
the nut 150 downward on the post 130a causes the bottom surface 154 of the 
nut to seat against the top surface of the flat extending portion 170b. At 
this point the flat extending portion 114b of the first element 100b 
remains slidable relative to both the post 130a and the second element 
160b. In this way, the rod securing portions 102b and 162b may be 
selectively spread or drawn together and angulated within the plane 
defined by the two elements. 
In this untightened configuration, the rod coupling ends 102b and 162b of 
the device are positioned over the heads of the pedicle screws such that 
the heads of the screws extend upwardly through the holes 103 and 163, 
respectively. By tightening the locking nuts of the pedicle screws down, 
the elements 100b and 160b are locked in position. 
Continued tightening of the nut 150 causes the post 130a to be drawn 
upwards through the hole 172b, thereby causing the intermediate section, 
and the passageway 136 thereof to be similarly drawn upwards. In doing so, 
the roughened top surface 116b of the narrowed flat extending portion 114b 
is compressed against the roughened lower surface of the second flat 
extending portion 170b, locking the two together and locking the length of 
the cross-link. 
Referring now to FIG. 11, an alternate first element 200 which corresponds 
to a third embodiment of the present invention is shown. This embodiment 
further provides the cross-link with the ability to accommodate pairs of 
rods which are locally not co-planar (they are contoured such that the rod 
and/or coupling sites would not securely receive parallel coupling hooks 
or eyeloops). This embodiment is described with respect to a variation 
which is similar to the first embodiment inasmuch as it couples to the 
rods, not to the pedicle screws, and is locked to the rods with set screws 
in a similar manner. 
More specifically with respect to the first element 200 shown in FIG. 11, 
the first (rod coupling) end 202 of which has been curved to the shape of 
a hook. As with the first element 100a of the first embodiment, the hook 
has a semi-circular curvature defined by an inner surface 204. The lower 
portion 208 of the semi-circular hook extends tangentially for a small 
distance, parallel to the remainder of the element. The curve is 
semi-circular so that it can cup and hook to the lateral outside surface 
of a first rod of a dual rod apparatus. The top portion 211 of the first 
end 202 comprises a through hole 212 which is threaded to receive a set 
screw 120 to lock the element 200 to the rod of the implant assembly. 
The other end 214 of the rod coupling element comprises the distinctive 
feature of this embodiment, as compared with the first elements 100a,100b 
of the first and second embodiments. It comprises a cylindrical shaft. 
This shaft may include a surface roughening, for example a diamond 
knurling, for locking within the post element 130b. 
Referring now to FIG. 12, a side view of the post 130b which corresponds to 
this third embodiment is provided. As previously described, the post 130b 
has a generally cylindrical shape. The base 132b of the post is wider than 
the upper portions, forming an annular flange 134b. The upper portion of 
the base 132b, and the lower portion of the intermediate section of the 
post 130b includes a cylindrical passageway 135 which extends transverse 
to the axis of the post. This passageway 135 is ideally suited for 
slidably receiving therethrough the shaft 214 of the first rod coupling 
element 200. The diameter of the passageway 135 is desirably slightly 
larger than the thickness of the shaft 214, such that the shaft 214 may 
slide and rotate therein (such that the length of the device, and the 
relative angulation of the rod coupling ends may be easily selected). 
As set forth above with respect to the first two embodments, the upper 
portion 138b of the post 130b extends upward from the passageway 136 and 
the intermediate portion, and comprise a threading 140b which is ideally 
suited for receiving thereon a top locking nut 150 (as shown in FIG. 8). 
Referring now to FIG. 13, in which an assembled device corresponding to 
this third embodiment is shown in a side prespective view. The second 
element of this device is identical to the second element 160a of the 
first embodiment (it being understood that if this third embodiment is to 
be coupled to the pedicle screws, then the second element would be 
identical to the second element 160b of the second embodiment). First the 
proper site on the rods for the fixation of the cross-link device is 
identified by the surgeon. The site should provide enough space along the 
rods for engagement of rod securing ends 202 and 162a. Once this site is 
found, and the space separating the rods is cleared of all obstacles (for 
example, the spinous process) the shaft 214 of the first element 200 is 
inserted into the cylindrical passageway 135 of the post 130b, such that 
the shaft is axially rotatable and translatable within the passageway 135. 
Once the shaft 214 has been inserted, the upper section 138b of the post 
130b is inserted through the hole 172a in the rod coupling flat extending 
portion 170a of the second element 160a. The post 130b is inserted 
upwardly so that the top locking nut 150, and more specifically the 
threads 156 thereof, may engage the threads 140b of the upper portion 
138b. Initial tightening of the nut 150 downward on the post 130b causes 
the bottom surface 154 of the nut to seat against the top surface of the 
flat extending portion 170a. At this point the shaft 214 of the first 
element 200 remains slidable and rotatable relative to both the post 130b 
and the second element 160a. The rod securing portions 202 and 162a may be 
selectively spread or drawn together by an amount determined solely by the 
length of the shaft 214. In addition, the elements 200,160a may be rotated 
within the plane defined thereby. Further, the elements 200,160a, and the 
rod securing ends 202,162a thereof, may be axially rotatable relative to 
one another via rotation of the shaft 214 within the passage 135. 
Continued tightening of the nut 150, however, causes the post 130b to be 
drawn upwards through the hole 172a, thereby causing the intermediate 
section, and the passageway 135 thereof to be similarly drawn upwards. In 
doing so, the roughened surface of the narrowed shaft 214 is compressed 
against the roughened lower surface of the second flat extending portion 
170a, locking the two together and locking the length of the cross-link. 
In addition, the compressive force applied to the shaft 214 by the lower 
surface of the second end 170a of the second element 160a causes the 
roughened surface of the shaft 214 to bind to the inner surface of the 
passageway 135, thereby further crush locking the device into a rigid 
configuration. 
Once the length of the cross-link is been set, the set screws 120 may be 
tightened down, thereby locking the element 200 and 160a to the rods 
themselves. 
While there have been described and illustrated cross-link devices for 
coupling dual rods of orthopaedic apparatus together and providing 
enhanced stability thereto, it will be apparent to those skilled in the 
art that variations and modifications are possible without deviating from 
the broad spirit and principle of the present invention which shall be 
limited solely by the scope of the claims appended hereto.