Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~i 94/17736 PCT/CA94/00068
APP TUS FOR TREATING SPINAL DISORDER
TECHNICAL FIEhD
The present invention relates to an appara-
tus for use in the treatment of scoliosis.
BACKGROUND ART
Prior to 1962, scoliosis was treated with
various external casts and/or bone grafts. Successive
body casts of ever increasing height would be utilized
to try to correct the spine from a disorder such as a
lateral curve in the spinal column. External braces
would still be employed in the treatment of minor
scoliosis . However in. the event of severe deformity of
the spine, major surgery involving bone grafts and the
fusion of several vertebrae would be the only solution.
The bone grafts and vertebrae fusion would sometimes
cause serious complications throughout the patient's
adult life.
In 1962, Paul Harrington proposed the use of
implantable stainless steel rods which were placed ad-
jacent the vertebral bodies and hooks on the rods were
inserted under the laminae of selected vertebra. An
excellent summary of the prior art devices based on the
Harrington procedures can be found in U.K. patent ap-
plication G.B. 2 096 465 A published October 20, 1982
in the name of Kevin A. Bobechko. However it has since
been found that it is still necessary to supplement the
stainless steel rod with bone grafts as described in
the Bobechko patent application.
Canadian Patent 1,262,322 issued Octo-
ber 17, 1989 to Yves Cotrel also described a rod and
hook system. Cotrel mounts the hooks with hook brackets
to the vertebrae and then the hook brackets can be con-
nected to a pair of rods as shown in Fig. 12. The
assembly is rigid in that the hook brackets are locked
to the rods against rotational or longitudinal move-
WO 94/17736 PCT/CA94/00068
-2-
ment. That section of the spine is thus kept rigid.
However given the lack of flexibility, and the fact
that the loads are completely transferred to the rod
assembly, the assembly is not considered sufficiently
strong and thus bone graft and fusion of the vertebrae
must also be resorted to.
DISCLOSURE OF THE INVENTION
It is an aim of the present invention to
provide an internal brace system to correct the spine
disorder in the treatment of scoliosis.
It is a further aim of the present invention
to provide an internal system which will eliminate the
need in most cases of resorting to bone graft to sup-
plement the support offered by the system.
It is still a further aim of the present in-
vention to provide an internal brace system which will
rely on normal loads being transmitted through the
spine including the portion of the spine being sub-
jected to treatment.
It is a further aim of the present invention
to provide an internal brace system which would avoid
the introduction of extraneous elements within the spi-
nal canal such as hooks or wires.
It is a further aim of the present invention
to provide an internal brace system made of material
which is sufficiently strong to resist normal forces
and loads which will be subjected to the spinal column
and internal brace system.
A construction in accordance with the pre
sent invention comprises an internal brace system
including at least a pair of implantable rods for
mounting on either side of the spinal column coexten
sive with a portion of the spinal column to be treated,
means for rigidly connecting the rods together in
spaced apart parallel arrangement to provide a unitary
internal brace stabilizing structure, pairs of anchor
2~.~~~8~
94/17736 PCT/CA94/00068
- 3 -
means provided one of each pair on respective trans-
verse processes of each selected vertebra in the por-
tion of the spinal column to be treated, first tie
means extending from each anchor means to connection
means on a respective rod on either side of the spinal
column for retaining individual vertebra in a predeter-
mined location relative to the internal brace system
and against torsional forces applied through the spinal
column.
In a more specific embodiment of the present
invention, a further anchor means is provided on the
spinous process of the selected vertebra, the anchors
on the transverse processes are in the form of cuffs
mounted on each transverse process and second tie means
extend from the respective cuffs on the transverse
processes to the anchor on the spinous process in order
to prevent the cuffs from slipping off the transverse
processes.
In a still more specific embodiment of the
present invention, the means for connecting the f irst~
tie means to the respective rods includes a plurality
of separate sleeves on the rods adapted to slide
thereon and each first tie means is connected to a re-
spective sleeve.
Thus, an internal brace system is provided
to retain individual vertebra in a position approximat-
ing a correct position in a normal spine. The provision
of at least a pair of rods in a unitary structure with
tie means from each rod to a corresponding transverse
process of a vertebra, retains the vertebra against the
torsional forces inherent in the disorder which would
cause the vertebra to rotate in the horizontal plane of
' the vertebra. The fact that the tie means are flexible
permits loads to be transmitted through the portion of
the spine coextensive with the internal brace system.
WO 94/17736 ~. . PCT/CA94/00068 ~
21 ~ ~ 6 '~ ~.
- 4 -
The portion of the spinal column also has a limited
flexibility since bone grafts are not used.
BRIEF DESCRIPTION OF THB DRAWINGS
Having thus generally described the nature '
of the invention, reference will now be made to the ac-
companying drawings, showing by way of illustration, a
preferred embodiment thereof, and in which:
Fig. 1 is a rear elevation view of an em
bodiment of the internal brace system in accordance
with the present invention as it would appear on a por
tion of a spinal column;
Fig. 2 is a side elevation of the embodiment
shown in Fig. 1;
Fig. 3 is a fragmentary perspective view
showing a single vertebra and details of the internal
brace system in relation to the vertebra;
Fig. 4 is a top plan view of the embodiment
shown in Fig. 3;
Fig. 5 is a plan view partly in cross-
section of a detail shown in Fig. 3;
Fig. 6 is an end elevation of the detail
shown in Fig. 5; and
Fig. 7 is a fragmentary perspective view
showing a modified version of the detail shown in
Figs. 5 and 6.
MODES FOR CARRYING OUT THE INVENTION
An internal brace system 10 is shown in
Figs. 1 and 2 in its assembled condition. The internal
brace system 10 would be sold as a kit for implanting
within the human body in a surgical procedure for the
purpose of correcting a spinal column disorder involv-
r
ing a lateral curve with some torsion or rotation. It
has been found that in patients suffering from scolio
sis, that the vertebrae in the curved portion may be
rotated horizontally due to torsional forces acting
94/17736 PCT/CA94/00068
- 5 -
thereon. The internal brace system 10 would, as will be
seen, retain the individual vertebra in a reoriented
position approximating their position in a normal spi-
nal column.
The kit making up the internal brace system
would include a pair of rods 12 and 14. Each of the
rods 12 and 14 may be curved to approximate a desirable
longitudinal curve of the portion of the spinal column
in which the correcting system is to be implanted. The
10 rods 12 and 14 would, when assembled, include bars 16
and 18 which lock the rods 12 and 14 in a unitary
structure. The rods 12 and 14 are preferably made of
titanium.
The spinal column S to which the internal
brace system is to be applied includes a number of ver-
tebrae Va.._.Vn, each including, for the purposes of
this description transverse processes PL and PR and a
spinous process T. The vertebrae Va..._Vn would, in a
patient suffering from scoliosis be curved laterally
out of a longitudinal plane of the spine S and it would
be necessary to rotate and realign each vertebra in
longitudinal alignment and to be harnessed to the
internal brace system 10.
In the present embodiment, the internal
brace system 10 includes, a plurality of cuffs 20 which
can be mounted to individual transverse processes P and
tie means in the form of U-shape tie members 22 con
necting the cuffs 20 in an articulated manner to indi
vidual sleeves 24 slidably mounted on the rods 12
and 14.
Referring now to Figs. 3 and 4, the vertebra
harness will be described in more detail. As shown in
'' Figs. 3 and 4, there is a cuff 20a which is clasped to
the transverse process PL and an identical cuff 20b
clasps to the transverse process PR. The U-shaped
tie 22a connects the cuff 20a to the sleeve 24a on
WO 94/17736 _ ~ ~ PCT/CA94/00068 '
- 6 -
rod 12. Likewise the U-shape tie member 22b connects
the cuff 20b to the sleeve 24b on rod 14.
The cuff 20 is shown, in Figs. 5 and 6, in
detail and includes a base member 26 and a pair of
arms 28 and 30 with hinges 32 and 34 therebetween. A
locking pin 36 is hinged to the arm 30 by means of
hinge 38. The pin 36 is threaded and adapted to receive
a nut 40. The nut 40 locks the pin to the base 26 as
shown in Figs. 5 and 6. Accordingly the cuff 20 will be
able to fit any irregularity or size of transverse
process because of the particular adjustable structure
shown. The base 26 also has a jaw 42 to receive the
bight portion 68 of the U-shaped tie 22. A locking
bolt 44 will close the jaw 42 once the bight 68 has
been mounted in the jaw 42.
The tie member 22 is best shown in Figs. 3
and 4 and includes a bight 68 with a pair of parallel
arms 70 and 72. These arms 70 and 72 include slots 71
and 73 which engage the cap pins 74 on sleeve 24. The
slots 71 and 73 are provided with enlarged openings at
the ends thereof in order for the arms 70 and 72 to be
engaged on the cap pins 74. Accordingly the construc-
tion of the tie member 22 allows articulation and a
degree of lateral movement to the vertebra V. However,
since both transverse processes PL and PR are likewise
anchored to the respective rods 12 and 14 the amount of
horizontal rotation of the vertebra V will be very
limited.
It is also believed that the structure will
retain the vertebra in its assumed position approximat-
ing a normal position of the vertebra in a correct spi- '
nal column.
In order to prevent the cuffs 20a and 20b
from slipping off the ends of the transverse proc
esses PL and PR an anchor tube 78 will be provided on
the spinous process T. In one embodiment a bore is
~O 94/17736 ~ PCT/CA94/00068
7 _
<.
drilled through the spinous process T and the anchor
tube 78 is fitted therein. Locking nuts 80 and 82 are
provided at each end of the tube 78 and a flexible cord
of synthetic material such as nylon is attached to each
cuff 20a and 20b as shown in Figs. 3, 5, and 6. Thus
the cord 84 will prevent the cuffs 20a and 20b from
slipping off the ends of the transverse processes.
The internal brace system 10 is selected to
be long enough to be coextensive with the portion of
the spinal column S which is to be corrected. The ends
of the rods 12 and 14 are provided with heads 67 of
square cross-section as shown, for instance, in Fig. 7.
The square heads 67 of the rods 12 and 14 will accommo-
date a modified version of the cuffs as shown in
Fig. 7. The cuff 46 in Fig. 7 includes the articu-
lated arms 50 and 52 as well as a locking pin 58 and
nut 60. However, the base 48 will also include a
tube 64 (rigid tie means) having a bore or opening 66
which has a square cross-section similar to the square
cross-section of the head 67 of the rod 12.
The base 48 will have a length which is se-
lected depending on the distance of the internal brace
system 10 from a correct vertebra as shown in Fig. 2.
Likewise, at the other end of the rod 12, a similar
cuff 46a will be locked to a transverse process PL of
a
correct vertebra. Thus, the internal brace assembly
system 10 will be locked at each end to a correct ver-
tebra, in this case the vertebra Vb and Vn while the
vertebrae to be realigned are harnessed by means of the
cuffs 20a and 20b and tie members 22 connected on the
sliding sleeve 24a and 24b.
The provision of the sliding sleeves 24 and
flexible ties 22 will allow limited movement of each
vertebra and will allow the loads to be carried by the
realigned spinal column S so as to simulate a more nor-
WO 94/17736 PCT/CA94/00068 '~
2~~~~~~ -
mal spinal column. The sleeve may have a polyethylene
liner 76 to reduce friction.
The bars 16 and 18 are provided with bores
of square cross-section at each end thereof. These
bores are dimensioned to the square heads 67 of the
rods 12 and 14, and with suitable set screws 13 the
bars 16 and 18 can be locked to the ends of rods 12
and 14.
When the internal brace system 10 is
implanted, it is necessary to sever certain ligaments
particularly between the spinous processes. It has been
contemplated to attach biodegradable polymer ligaments
between the spinous processes and probably between
respective transverse processes. The polymer material,
in one example, could include from 0~ to 30~ hydroxy
valerate and from 100 to 70$ poly-hydroxybutyrate.
Ligaments of this material would slowly degrade while
natural ligaments are regenerated. The material and its
uses are described in G.B. Patent 1034 123 in the name
of W. R. Grace & Co.
