U.S. patent application number 12/798696 was filed with the patent office on 2010-09-09 for bio-flexible spinal fixation apparatus with shape memory alloy.
Invention is credited to Kyung-Woo Park.
Application Number | 20100228289 12/798696 |
Document ID | / |
Family ID | 36075050 |
Filed Date | 2010-09-09 |
United States Patent
Application |
20100228289 |
Kind Code |
A1 |
Park; Kyung-Woo |
September 9, 2010 |
Bio-flexible spinal fixation apparatus with shape memory alloy
Abstract
A spinal fixation apparatus has a segment flexible rod for
connecting pedicle screws and a transverse link for spacing out the
rods, which are made from a shape memory alloy, thereby easily and
simply connecting the rods and the pedicle screws. The rods can be
easily and simply fit to the misaligned pedicle screw, even if
there is a failure of alignment of the pedicle screws in surgery.
The transverse link can be easily set up on a pair of the
longitudinal rods, even if the longitudinal rods are declined or
are not in parallel.
Inventors: |
Park; Kyung-Woo; (Seoul,
KR) |
Correspondence
Address: |
COLLARD & ROE, P.C.
1077 NORTHERN BOULEVARD
ROSLYN
NY
11576
US
|
Family ID: |
36075050 |
Appl. No.: |
12/798696 |
Filed: |
April 9, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11044268 |
Jan 28, 2005 |
7727259 |
|
|
12798696 |
|
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|
Current U.S.
Class: |
606/250 |
Current CPC
Class: |
A61B 17/7008 20130101;
A61B 17/7004 20130101; A61B 2017/00867 20130101; A61B 17/7005
20130101; A61B 17/7011 20130101; A61B 2017/0645 20130101; A61B
17/7032 20130101; A61B 17/7028 20130101; A61B 17/7007 20130101;
A61B 17/7026 20130101; A61B 17/7052 20130101 |
Class at
Publication: |
606/250 |
International
Class: |
A61B 17/70 20060101
A61B017/70 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 22, 2004 |
KR |
1020040076105 |
Sep 22, 2004 |
KR |
1020040076106 |
Nov 26, 2004 |
KR |
1020040097833 |
Nov 26, 2004 |
KR |
1020040097834 |
Dec 15, 2004 |
KR |
PCT/KR2004/003301 |
Claims
1. A spinal fixation apparatus comprising: first and second pedicle
screw arrays perpendicularly arranged, substantially being in
parallel to each other, wherein each of the first and second
pedicle screw arrays includes: a plurality of pedicle screws joined
to vertebras of human spine, each pedicle screw includes: 1) a head
having a plurality of reception means; and 2) a male thread formed
on a leg part to be implanted into the vertebras; and first and
second rod arrays respectively connected the first and second
pedicle screw arrays, wherein each of the first and second rod
arrays includes a plurality of segment rods and wherein an end of
each the segment rod is safely secured to one of the plurality of
reception means, wherein the segment rods are a shape memory
alloy.
2. The spinal fixation apparatus in according with claim 1, further
comprising at least one transverse link connecting the segment
rods.
3. The spinal fixation apparatus in according with claim 1, wherein
the segment rod has an elastic section to provide flexibility.
4. The spinal fixation apparatus in according with claim 2, wherein
the segment rods are in a martensite phase at a temperature of
approximately +10.degree. C. and below and are in an austenite
phase at a temperature of approximately +35.degree. C. and over.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 11/044,268 filed on Jan. 28, 2005, which is a continuation
under 35 U.S.C. .sctn.120 of International Application No.
PCT/KR2004/003301 filed on Dec. 15, 2004 which claims priority
under 35 U.S.C. .sctn.119 from Korean Application No.
10-2004-0076105 filed on Sep. 22, 2004; Korean Application No.
10-2004-0076106 filed on Sep. 22, 2004; Korean Application No.
10-2004-0097833 filed on Nov. 26, 2004 and Korean Application No.
10-2004-0097834 filed on Nov. 26, 2004.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a spinal fixation apparatus
which can correct and immobilize injured or deformed human spine;
and, more particularly, to a spine fixation apparatus for easily
carrying out an operation on the spine, by using segment flexible
rods and a transverse link which are made from a shape memory
alloy, so that the rod and the transverse link can elongate in
different shapes with flexibility.
[0004] 2. Description of the Related Art
[0005] Typically, the vertebra typically consists of 24 bones
(except for sacral vertebra). They are connected to each other
through joint segments and there are discs between the joint
segments. By this structure, the vertebra has man's posture kept
and a shock absorbed. Also, the vertebra is essential to exercises
and protects all internal organs from an external shock. However,
the vertebra of the spine can be injured or wrenched by external
environments, abnormal postures for a long time and anaplastia and
so on, which may induce a serious back pain by pressing the nerve
system passing through the spine.
[0006] Patients, who have been injured in a part of his spine,
cannot take their activities in daily life, because the injured
part of the spine is compressed by adjacent other parts of the
spine. This spinal disorder requires a surgical intervention to
treat the pain which is induced in nerve root by the compression
and unstableness of intervertebral joints.
[0007] As shown in FIG. 1, a conventional spinal fixation apparatus
includes a plurality of pedicle screws 200 which are respectively
inserted through the pedicle into injured or deformed vertebra,
wherein each of the pedicle screws 200 has a head 201 formed at a
top portion thereof, wherein the head 201 has a U-shaped rod
passage 201a and a female thread 201b is formed on an inner surface
thereof, and wherein a thread 202 is formed below the head 201 in
order that the pedicle screws 200 can be implanted into the
vertebra; a pair of longitudinal rods 250 which are located in both
laterals of the spine and coupled to the pedicle screws 200 for
preventing a movement of the vertebra; a number of set screws 300,
each of which has a male thread and a wrench hole 300a on an upper
surface thereof, being inserted into the rod passage 201a of the
head 201 of the pedicle screw 200 for preventing a movement of the
rod; and a transverse link 400 for holding the longitudinal rods
250.
[0008] In the conventional spinal fixation apparatus, the rods and
the pedicle screws will be described in short, referring to the
accompanying drawing.
[0009] As shown in FIG. 2, the thread 202 of the pedicle screws 200
is implanted into the vertebral body 500. The rod 250 is then put
into the rod passage 201a. In this situation, the set screw 300 is
joined to the female thread 201b of the rod passage 201a.
[0010] Also, the set screw 300 is joined to the rod passage 201a,
by inserting it into a groove 300a and turning it with a wrench on
the top thereof. As a result, the bottom side of the set screw 300
compresses the top of the rod 250 within the rod passage 201a of
the pedicle screws 200.
[0011] According to this assembly, the rod 250 is definitely
tightened up on the pedicle screw 200 to correct the diseased or
injured vertebral body 500. The both ends of the transverse link
400 are coupled to the pair of the rods 250 so that the transverse
link 400 is laid across the rods 250 which is connected to the
pedicle screws 200. When a patient gets to do a wrenched action
toward his left or right sides, the transverse link 400 prevents a
rotation and migration of the rod 250.
[0012] In the conventional spinal fixation apparatus, the rod 250
functions as a basic element to correct the vertebra. Therefore,
the material of the rods or the properties of the rod, such as
elasticity, has a large effect on human body, after it is
inseparably fused together with the vertebra. The rod 250 itself is
not elastic because it is made from a titan alloy for medicine. It
is very difficult to keep the line of his lumber normal since the
vertebra segment is fused together with the rod to correct the
vertebra bodies.
[0013] Also, after the vertebra is integrally fused together with
the rod, the weight is concentrated upon the upper segment or the
lower segment so that it will cause another vertebra stegnotic or
instability of a lumbar vertebra within a few years after the
vertebra fusion.
[0014] In particular, it has some problems in that the rod can be
broken and buried in the vertebra, when a shock is inflicted upon
the lumbar vertebra.
[0015] The rod is made to have a normal spinal curvature shape
without being related to a specific spinal shape of individual.
That causes the difficulty of standardizing each single products
and making various shapes, thereby increasing the cost of products.
Also, the rod structure induces a series of bottlenecks in
connecting the pedicle screw to the rod because the rod has a
straight shape. That is, the individual spinal shape is different
from each other. Therefore, if the pedicle screws are not fixed
uniformly between the segments, it was very difficult to install
the straight rod on the pedicle screws. This is caused by the
physical properties of the rod. In this case, an operator has to
adjust a distance and direction of the pedicle screw based on the
location of the rod, by making the pedicle screw slanted. Also, the
operator has to adjust an angle of the pedicle screw's head, using
the polyaxial type screw, which can freely rotate a head around the
screw in a range of predetermined angle and set the rod up thereon.
The operating work using the conventional vertebra fixation
apparatus needs accuracy, because he must correctly grasp the
location to install the pedicle screw and then have to make a hole
in vertebra with a burden on the surgeon. Also, it takes a lot of
times to make the rod based on a curved shape of patient's vertebra
and to set the location of pedicle screw.
[0016] To solve the problems of the conventional vertebra fixation
apparatus, the various types of the rods has been provided with
elasticity,
[0017] An example of an elastic rod for connecting the pedicle
screws is illustrated in Korean utility model No. 0,338,006. This
rod comprises a rod body 601 and an elastic connection portion 603
formed in the middle of the rod body 601. As shown in FIG. 3, the
elastic rod is in various types, such as a semicircular ring, a
coil spring, a bar type smaller then the diameter of the rod body,
and the like.
[0018] These types provide the elastic connection portion for the
rod in order that the rod body can be bent. This structure is
capable of giving fluidity to the rod in a predetermined range
between the pedicle segments. However, the rod structure results in
a lose of the basic function of the spine correction since the
elastic connection portion causes large movement. That is, the rod
has to support and connect the spinal segments. In the
above-mentioned structure, the pieces of the rod body are
detachable so that they are freely movable in a given elastic
range. Therefore, the secure connection between the spinal segments
is not achieved.
[0019] Also, when the pedicle screws are out of the straight line,
the rod structure has a problem in that it is difficult to connect
the rod to the pedicle screw.
[0020] FIG. 4 shows a perspective view of the conventional
transverse link 400 for preventing the pedicle from a minute
movement.
[0021] The transverse link 400 comprises a fixed type housing 410
and a movable type housing 420 which are respectively hooked on
both ends of the rod 250; a space bar 430 supported on the rod 250;
and a set screw 440 connected with the fixed type housing 410 and
the movable type housing 420 so that the space bar 430 is fixed to
the rod 250.
[0022] The fixed type housing 410 and the movable type housing 420
respectively include half circle hooks 410a and 420a for connection
on the rod 250; support holes 410b and 420b inserted into the both
ends of the rod 250; screw holes 410c and 420c into which set
screws 440 are inserted.
[0023] The hook 410a of the fixed type housing 410 is hooked on the
rod 250 and then one end of the space bar 430 is inserted into the
support hole 410b. The hook 420a of the movable type housing 420 is
hooked on the rod 250 and then another end of the space bar 430 is
inserted into the support hole 420b. The set screws 440 are joined
to the screw holes 410c and 420c respectively, for securely
tightening the rod 250 under the space bar 430.
[0024] In the structure of the transverse link 400, the inner
diameter of the hook 410a is almost equal to that of the rod 250.
Therefore, if one of the rods 250 is tilted or they are not in
parallel, the transverse link 400 cannot comply with such a
declination or unbalance of the rods 250. In case of the
declination or unbalance of the rods 250, the support holes 410a
and 420a of the fixed type housing 410 and movable type housing 420
are also unbalanced and thus the space bar 430 cannot be inserted
into the support holes 410b and 420b. If strength is put on the
space bar 430 for fixation on the support holes 410b and 420b, the
position of the movable type housing 420 may be wrenched and
distorted so that the rod 250 may be separated from the hook 420a
of the movable type housing 420. In this case, even if the set
screw 440 is joined to the screw hole 430, it is impossible to
securely support the space bar 430 upon the rod 250. This problem
in the transverse link 400 requires to take a long time for an
operation on the surgery. In case where it is difficult to assemble
the transverse link 400, it may be omitted; however, this will
cause a defect of the surgery.
SUMMARY OF THE INVENTION
[0025] To solve the problems, a primary object of the present
invention is to provide a spinal fixation apparatus which can
easily and simply achieve a connection between a pedicle screw and
a rod, even if it is slightly out of alignment of the pedicle
screws during surgery, by deforming the shape and length of each of
the rods and the transverse link which are made from a shape memory
alloy of which the shape is changed at a specific temperature.
[0026] Another object of the present invention is to provide a
spinal fixation apparatus which has a strength enough to correct
the spine during the restoration from an elastic force so that the
spinal fixation apparatus gives flexible behavior to corrected
vertebral segments.
[0027] Further, another object of the present invention is to
provide a staple type rod which is made from a shape memory alloy.
The staple type rod of the present invention can easily and simply
perform an operation of the vertebra correction and reduce the
number of parts, being implanted directly into selected vertebra
without a pedicle screw.
[0028] In accordance with one aspect of the present invention,
there are provided a spinal fixation apparatus comprising: a
plurality of pedicle screws, each of which has a head formed at a
top portion thereof and a thread formed below the head to be
implanted into a pedicle of a vertebra, wherein the head has a
reception cavity and at least one rod groove on a bottom surface of
the reception cavity; a pair of rods connected to the pedicle
screws for preventing a movement of the vertebra, wherein the rods
has an elasticity section therein and are mounted on the rod groove
in the reception cavity; at least one transverse link which has an
elasticity section in a straight member and hooks extended from
both ends of the straight member for rigidly holding the pair of
rods; and a plurality of set screws, each of which is rigidly
inserted into the reception cavity of the head, preventing a
movement of the rod, wherein the rods and the transverse link are
made from a shape memory alloy which can be deformed at a
predetermined temperature.
[0029] In accordance with another aspect of the present invention,
there are provided a spinal fixation apparatus comprising: a
plurality of pedicle screws, each of which has a head formed at a
top portion thereof and a thread formed below the head to be
implanted into a pedicle of a vertebra, wherein the head has a
first rod groove formed in a bottom surface of the head; a
plurality of head caps for covering the head of the pedicle screw,
wherein the head cap has a second rod groove formed on an inner
surface thereof; a pair of rods surrounded by the first rod groove
of the head and the second rod groove of the head cap, preventing a
movement of the vertebra, wherein the rods has an elasticity
section therein; at least one transverse link which has an
elasticity section in a straight member and hooks extended from
both ends of the straight member for rigidly holding the pair of
rods; and a plurality of fixing means, each of which tightens the
head cap to the head of the pedicle screw, being inserted into the
reception cavity of the head of the pedicle screws for preventing a
movement of the rod, wherein the rods and the transverse link are
made from a shape memory alloy which can be deformed at a
predetermined temperature
[0030] In accordance with further another aspect of the present
invention, there are provided a spinal fixation apparatus
comprising: a plurality of pedicle screws, each of which has a head
formed at a top portion thereof and a thread formed below the head
to be implanted into a pedicle of a vertebra, wherein the head has
a reception cavity and two parallel rod grooves in a bottom surface
of the reception cavity; a pair of rods connected to the pedicle
screws for preventing a movement of the vertebra, wherein the rod
is made of shape memory alloy which can be transformed in
designated temperature and wherein the rods includes: 1) a straight
bar placed in line with a center of the heads; 2) an elastic
section formed in the straight bar; and 3) support bars having
bending portions extended from both ends of the straight bar and
bent along an outer surface of the head and line portions extended
from both ends of the bending portions and put in the rod grooves,
and a plurality of set members, each of which is inserted into the
reception cavity of the head of the pedicle screws for preventing a
movement of the rods.
[0031] In accordance with still another aspect of the present
invention, there are provided a spinal fixation apparatus
comprising: a plurality of pedicle screws, each of which has a head
formed at a top portion thereof, and a thread formed below the head
to be implanted into a pedicle of a vertebra, wherein the head has
at least one circular groove on an outer surface thereof; and a
pair of rods connected to the pedicle screws for preventing a
movement of the vertebra, wherein each of the rods has a straight
bar placed in line with a center line of the heads, an elastic
section formed in the straight bar, support rings wound on the
circular grooves of the heads, wherein the rods are made from a
shape memory alloy which can be deformed at a predetermined
temperature.
[0032] In accordance with still another aspect of the present
invention, there are provided a spinal fixation apparatus
comprising: a plurality of pedicle screws, each of which has a head
formed at a top portion thereof, and a thread formed below the head
to be implanted into a pedicle of a vertebra, wherein the head has
a horizontal opening passing through a head body and a
perpendicular thread hole to receive a fixing means; a pair of rods
connected to the pedicle screws for preventing a movement of the
vertebra, wherein the rods has a straight bar, and hooks extended
from both ends of the straight bar and bent to be inserted into the
horizontal opening, wherein the rods are made from a shape memory
alloy which can be deformed at a predetermined temperature; and a
plurality of fixing means for preventing a movement of the rod
through the perpendicular thread hole of the head.
[0033] In accordance with still another aspect of the present
invention, there are provided a spinal fixation apparatus
comprising: a plurality of pedicle screws, each of which has a head
formed at a top portion thereof and a thread formed below the head
to be implanted into a pedicle of a vertebra, wherein the head has
a reception cavity and two parallel rod grooves in a bottom surface
of the reception cavity; a pair of rods connected to the pedicle
screws for preventing a movement of the vertebra, wherein each of
the rods has a "U" shape and wherein the rods are made from a shape
memory alloy which can be deformed at a predetermined temperature;
and a plurality of set members, each of which is inserted into the
reception cavity of the head of the pedicle screws for preventing a
movement of the rod.
[0034] In accordance with still another aspect of the present
invention, there are provided a spinal fixation apparatus
comprising: at least one pedicle screw which has a head at a top
portion thereof and a thread formed below the head to be implanted
into a pedicle of a vertebra, wherein the head has a reception
cavity and two parallel sockets formed in a bottom of the reception
cavity; a pair of staple rods connected to the pedicle screws for
preventing a movement of the vertebra, wherein one side of each of
the rods is directly implanted into a pedicle of the vertebra and
the other side is inserted into one of the sockets; and at least
one set member which is inserted into the reception cavity of the
head of the pedicle screws for preventing a movement of the
rod.
[0035] In accordance with still another aspect of the present
invention, there are provided a spinal fixation apparatus
comprising: at least one staple rods each of which has a bridge
member for providing a space between a selected vertebra and an
adjacent vertebra, an elastic section formed in the bridge member
and a spike member to be implanted into the pedicle of a vertebra,
wherein the spike member is downwardly extended from both ends of
the bridge member, wherein the rod is made of shape memory alloy
which can be deformed at a predetermined temperature.
[0036] In accordance with still another aspect of the present
invention, there are provided a spinal fixation apparatus
comprising: a plurality of pedicle screws having a head part; and a
pair of rods for connecting the pedicle screws, wherein the rods
are in a first structure at a first temperature range and are in a
second structure at a second temperature range, wherein the second
structure is a memorized shape of a shape memory alloy, and wherein
the rods provide a handling margin in the first structure so that
the rods of the memorized shape are more tight than those of the
first structure, wherein the head part has a fixating means for
securely fixing the rod and end parts of the rod are joined to the
fixating means.
[0037] In accordance with still another aspect of the present
invention, a spinal fixation apparatus comprising: first and second
pedicle screw arrays perpendicularly arranged, substantially being
in parallel to each other, wherein each of the first and second
pedicle screw arrays includes: a) a plurality of pedicle screws
joined to vertebras of human spine, each pedicle screw includes: 1)
a head having a plurality of reception means; and 2) a male thread
formed on a leg part to be implanted into the vertebras; and b)
first and second rod arrays respectively connected the first and
second pedicle screw arrays, wherein each of the first and second
rod arrays includes a plurality of segment rods and wherein an end
of each the segment rod is safely secured to one of the plurality
of reception means, wherein the segment rods are a shape memory
alloy.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] Other objects and benefits of the present invention will
become apparent upon consideration of the following written
description taken in conjunction with the following figures:
[0039] FIG. 1 is a perspective view illustrating a conventional
spine fixation apparatus;
[0040] FIG. 2 is a perspective view illustrating a conventional
spine fixation apparatus applied to the lumbar spine;
[0041] FIG. 3 is a plan view illustrating various forms of
conventional rods;
[0042] FIG. 4 is a perspective view illustrating a conventional
transverse link applied to the rods;
[0043] FIG. 5 is a perspective view illustrating a spine fixation
apparatus according to a first embodiment of the present
invention;
[0044] FIG. 6 is a perspective view illustrating an assembly of the
spine fixation apparatus shown in FIG. 5;
[0045] FIG. 7 is a cross-section view taken along A-A line shown in
FIG. 6;
[0046] FIG. 8 is a plan view illustrating another form of the rod
in the first embodiment of the present invention;
[0047] FIG. 9 is a sectional view illustrating a pedicle screw in
the first embodiment of the present invention;
[0048] FIG. 10 is a plan view illustrating a serial connection of
the rods and the pedicle screws shown in FIG. 9;
[0049] FIG. 11 is a perspective view illustrating a transverse link
applied to the rods according to a first embodiment of the present
invention;
[0050] FIG. 12 is a front view illustrating a connection between
the transverse link and rods;
[0051] FIG. 13a is a perspective view illustrating another form of
the rod;
[0052] FIG. 13b is a plan view illustrating another form of the
rod;
[0053] FIG. 14 is a perspective view illustrating a connection
between the transverse links to a head of the pedicle screw;
[0054] FIG. 15 is a front view illustrating a spine fixation
apparatus according to a second embodiment of the present
invention;
[0055] FIG. 16 is a perspective view illustrating a spine fixation
apparatus according to a third embodiment of the present
invention;
[0056] FIG. 17 is a plan view illustrating a serial connection the
rods to a head of a pedicle screw shown in FIG. 16;
[0057] FIG. 18 is a perspective view illustrating a spine fixation
apparatus according to a fourth embodiment of the present
invention;
[0058] FIG. 19 is a perspective view illustrating a serial
connection the rods to a head of a pedicle screw shown in FIG.
18;
[0059] FIG. 20 is a plan view illustrating an assembly of spine
fixation apparatus shown in FIG. 18;
[0060] FIG. 21 is a perspective view illustrating a spine fixation
apparatus according to a fifth embodiment of the present
invention;
[0061] FIGS. 22a and 22b are perspective views illustrating a spine
fixation apparatus according to a sixth embodiment of the present
invention;
[0062] FIG. 23 is a perspective view illustrating a spine fixation
apparatus according to a seventh embodiment of the present
invention;
[0063] FIG. 24 is a perspective view illustrating a staple rod in
the seventh embodiment of the present invention;
[0064] FIG. 25 is plan view illustrating a pedicle screw in the
seventh embodiment of the present invention;
[0065] FIG. 26 is a perspective view illustrating a serial
connection of the stapling rods to a head of the pedicle screw
shown in FIG. 23;
[0066] FIG. 27 is a perspective view illustrating a spine fixation
apparatus according to an eight embodiment of the present
invention;
[0067] FIG. 28 is a perspective view illustrating another form of
the staple rod.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0068] Hereinafter, the present invention will be described in
detail referring to the accompanying drawings. A spinal fixation
apparatus according to the present invention can easily correct
injured spines by using rods and transverse links which are made
from a shape memory alloy. In particular, the rods and transverse
links are made out of Nitinol alloy (Ni--Ti alloy) which has a
superelastic characteristic.
[0069] A first embodiment will be described in detail referring to
FIGS. 5 to 14.
[0070] According to the first embodiment of present invention, the
spinal fixation apparatus includes a plurality of pedicle screws 1
implanted into the patient's vertebra; a pair of rods 2 located in
both laterals of the spine and connected to the pedicle screws for
preventing a movement of the vertebra; and a number of transverse
links 3 for providing space between the rods.
[0071] Referring now to FIGS. 5 to 7, the pedicle screw 1 comprises
a head 11 formed at a top portion thereof and a thread 13 formed
below the head to be implanted into the vertebra. The head 1 has a
reception cavity 11a to receive the rod 2 and at least one rod
groove 12 at the bottom of the reception cavity 11a. A diameter of
the rod groove 12 corresponds to that of the rod 2.
[0072] The rod 2 has a rod body 15 which is bent and then has a
hook shape at both ends thereof and the rod 2 has an elasticity
section 16 formed in the middle of the rod body 15 to generate an
elastic force corresponding to a shock which is inflicted on the
patient's vertebra.
[0073] The elasticity section 16 is made of a coil spring. The coil
spring is equal to the rod body 15 in their diameters. Another form
of the elasticity section 16 is shown in a wave shape as shown in
FIG. 8. The diameter of the rod is approximately in a range of 2 to
7 mm and it can be adjusted on a basis of unit diameter of 0.5
mm.
[0074] The elasticity section 16 serves as a buffer between spinal
segments when the pedicle screw 1 is fused together with the spine.
That is, when patients bends or wrenches his waist or an shock is
inflicted on his waist, the elasticity section 16 can alleviate
stimuli which are caused by patients' activities or the external
shock.
[0075] A set screw 17 is inserted into the reception cavity 11a of
the head 11 of the pedicle screws 1 for preventing a movement of
the rod 2. The set screw 17 has an outer thread 17a for securely
tightening the rod 2 and a recess 17b having a hexagonal
cross-section view on the upper portion thereof so that the set
screw 17 is inserted into the reception cavity 11a of the head 11.
The length of the set screw 17 should be short enough not to
protrude from the upper surface of the reception cavity 11a of the
head 11.
[0076] The reception cavity 11a of the head 11 also has an inner
thread 11b to be joined to the outer thread 17a of the set screw
17.
[0077] The head 11 of the pedicle screw 1 has a rod fixing recess
14 for tightening an end of the rod 2. The rod 2 is inserted into
the reception cavity 11a and is put into the rod groove 12 as the
end of the rod is tightly inserted into the rod fixing recess
14.
[0078] The rod fixing recess 14 and the rod 2 have the same
diameter or the diameter of the rod fixing recess 14 is slightly
larger than that of the rod 2.
[0079] A head cap 18 can be adopted on the upper portion of the
head 11 to eliminate the change from a misaligned fixation of the
set screw 17. Since the head cap 18 provides an additional support
to improve the rod holding power, this can be used as an additional
rod such as a fastening element. The head cap 18 is additionally
set as needed, not essential.
[0080] The head 11 of the pedicle screw 1 is able to have two rod
grooves 12 and 12' and two rod fixing recess 14, 14', as shown in
FIG. 9. According to this structure, it is able to serially set the
rods 2 without using an additional connector by inserting the rods
2 and 2' into the rod grooves 12 and 12' alternately, as shown in
FIG. 10.
[0081] The first embodiment of the present invention is restricted
within the above structure. For example, the rod can be formed in a
straight bar shape or a right angle bar shape which is
perpendicular to both ends of the rod body. In such a modified rod,
the structure of the pedicle screw 1 is formed with a single rod
groove without the rod fixing recess 14. Besides, it may be
employed in different structures of the pedicle screw corresponding
to the modified rod. Furthermore, the modified rod 2 is securely
fixed by the set screw 17 within the reception cavity 11a of the
head 11.
[0082] A transverse link 3 will be described in detail referring to
FIGS. 11 and 12.
[0083] The transverse link 3 includes one straight member 31 and
two hooks 32 which are respectively extended and bent from both
ends of the straight member 31. The transverse link 3 is formed in
a rectangular plate. The length of the transverse link 3 is
approximately in a range of 20 to 80 mm and it can be adjusted on a
basis of unit length of 2 mm. As shown in FIG. 12, the transverse
link 3 keeps a space between the rods 2 and 2' by grasping the rods
2 and 2' through the hooks 32. Here, the transverse link 3 of a
plate shape has strength to maintain the space between the rods 2
and 2' even if an external force is applied to the rods 2 and 2'
and the rods 2 and 2' are then wrenched.
[0084] FIG. 13a and FIG. 13b are views illustrating transverse
links which are different from that of FIG. 11. That is, an
elasticity section 33 is formed in the middle of a straight member
31. The elasticity section 33 has a coil spring as shown in FIG.
13a or a wave shape as shown in FIG. 13b. The elasticity section 33
of the transverse link 3 absorbs a load which is applied to the rod
2.
[0085] FIG. 14 illustrates an S-shaped transverse link 3 which is
different from that of FIG. 11.
[0086] The S-shaped transverse link 3 includes one bending member
36 and two hooks 32 which are horizontally extended and bent from
both ends of the bending member 36 for holding the head 11 of the
pedicle screw 1. A slit 25 is provided on the circumference of the
head 11 of the pedicle screw 1 in order to insert the hooks 32 of
the S-shaped transverse link 3 into the head 11.
[0087] The above-mentioned rods 2 and 2' and transverse links 3 in
the first embodiment of present invention are made from a shape
memory alloy causing deformation at a specific temperature.
[0088] The rods 2 and 2' and the transverse links 3 have a
temperature characteristic that they are in a martensite phase at a
temperature of +10.degree. C. and below and in an austenite phase
at a temperature of more than +35.degree. C. to return back to a
memorized original shape. In particular, the deformed shape is kept
unchanged up to +26.degree. C. and the memorized shape is gradually
restored by a heat treatment up to +35.degree. C.
[0089] The rods 2 and 2' and the transverse link 3 are obtained by
performing a heat treatment at a temperature of 650.degree. C. to
750.degree. C. for one hour or so, after forming the hooks and
elastic section at both ends and the middle section of the shape
memory material, respectively. Thus, the rods 2 and 2' and the
transverse link 3 have a deforming characteristic at a specific
temperature.
[0090] Hereinafter, the installation procedures of according to the
first embodiment of the present invention will be described in
detail.
[0091] The pedicle screws 1 are implanted into a selected pedicle
of the vertebras in a predetermined angle and depth. At this time,
that is not considered configuration of screws that are not well
aligned in general. It lengthens the elastic section 16 of the rod
2 by deforming the rod 2 at a temperature of +10.degree. C. and
below so that the rod 2 is easily set into the reception cavity 11a
of the head 11 of the pedicle screw 1, before the rod 2 is inserted
into the reception cavity 11a of head 11 for coupling the rod 2 to
the plurality of the screws 1. Then, the end of the rod 2 of the
hook shape is inserted into the rod fixing recess 14, while a
deformed straight member (the rod body 15) of the rod 2 is inserted
to the rod groove 12 which is formed in the bottom of the reception
cavity 11a of head 11. The outer thread 17a of the set screw 17 is
downwardly joined to the reception cavity 11a of the head 11 so
that the set screw 17 is tightly fixed to the inner thread 11b of
the reception cavity 11a using a wrench tool. The rod 2 is pressed
by the set screw 17 and the rod 2 is securely and rigidly fixed to
the pedicle screw 1.
[0092] After the installation of the rods 2, a heat treatment is
applied to the rod 2 at a temperature of more than +35.degree. C.
using a surgical heating source. And thus, the lengthened elastic
section 16 of the rod 2 is shrunk and returns back to the memorized
original shape in the transforming austenite phase. At this time,
the end of the hook-shaped rod is rigidly fix to the rod fixing
recess 14 of the head 11 while the rode 2 is returning back to the
memorized original shape. Thus, both ends of the rod 2 are fixed to
the rod fixing recess 14 of the head 11 without any separation.
[0093] According to the above mentioned description, although the
pedicle screws are not well aligned with others, the rode can be
easily and simply connected to the pedicle screw 1 because the rod
2 can be freely bent toward the pedicle screw 1. In additional, the
rod 2 provides a movement of between the spinal segments through
the superelastic action of the elastic section 16 when the patients
bend or wrench his back, after the spine fusion.
[0094] In the installing procedures of the rods 2, when the rods 2
and 2' are respectively coupled to the rod grooves 12, the pedicle
screw 1 having the two rod grooves 12 and 12 are used. That is, the
rods 2 and 2' are respectively and alternately set to the rod
grooves 12 and 12' positioned in the reception cavity 11a, as shown
in FIG. 10. Therefore, in case that the pedicle screw 1 having two
rod grooves 12 and 12' are used, it is not necessary to take an
additional connector for a serial connection.
[0095] Next, an installation procedure of the transverse link 3
will be described in detail.
[0096] After coupling the rods 2 and 2' to the pedicle screws 1,
the transverse link 3 is hung on a pair of the rods 2 to provide a
space between the two rods 2. The installing work of the transverse
link 3 is taken in the same manner as it done in the
above-mentioned rod installation procedure. That is, it lengthens a
body 31 or widens a space of the hooks 32 thereof, by deforming the
transverse link 3 at a temperature of +10.degree. C. and below. The
deformed hook 32 of the transverse link 3 is inserted into the
outer surface of the rod 2. In case of the S-shaped transverse
link, it is inserted into a slit 25 of the head 11. After the
installation of the transverse link 3, it returns back to the
memorized original shape, being transformed to the austenite phase
through the heat treatment at a temperature of more than
+35.degree. C. so that the transverse link 3 is rigidly fixed on
the rod and, in case of the S-shaped transverse link 3, it is fixed
on the slit 25 of the pedicle screw 1.
[0097] Thus, in case of the above-mentioned structure of the
transverse link 3, it easily holds the rod 2 even if a space
between the rods 2 and 2' is not in parallel.
[0098] A second embodiment of the present invention will be
described in detail referring to FIG. 15 and the same reference
numerals denote the same elements as illustrated in the first
embodiment of the present invention.
[0099] In the second embodiment, the head 11 of the pedicle screw 1
is formed with a pair of first rod grooves 21 and 21' to locate the
rod 2 on an upper portion thereof. Also, a pair of rod inserting
recesses 22 and 22' are respectively formed below the rod grooves
21 and 21' and the rod inserting recesses 22 and 22' are positioned
in the same axis of the rod grooves 21 and 21', respectively. A
female thread 23 is formed on an inner surface of the head 11 at a
predetermined depth.
[0100] A head cap 20 is provided on the upper portion of the head
11 and the head cap 20 has a pair of second rod grooves 24 and 24'
corresponding the first rod grooves 21 and 21'. A fixing screw 25
is joined to the female thread 23 passing through the head cap 20
so that the head 11 is strongly fixed to the head cap 20.
[0101] A diameter of the first rod grooves 21 and 21' and the
second rod grooves 24 and 24' is correspondent to that of the rods
2 and 2'. And the rod inserting grooves 22, 22' have the same or
slightly large diameter than that of the rod 2.
[0102] If only one of the first rod grooves 21 and 21' is provided,
two female threads may be positioned at both sides of the first rod
groove. If two rod grooves are provided, one female thread may be
positioned in the middle of the first rod grooves 21 and 21'. In
this drawing, the pair of the first rod grooves 21 and 21' are
shown. These two grooves are required to serially and alternately
set the two rods 2 and 2' on the first rod grooves 21 and 21'.
[0103] A third to eight embodiments of the present invention will
be described in detail referring to FIGS. 16 to 28.
[0104] A rod, a staple rod and a middle connection rod in the these
embodiments are made from a shape memory alloy which is in a
martensite phase at a temperature of +10.degree. C. and below and
in an austenite phase at a temperature of more than +35.degree. C.
to return back to the memorized original shape. The shape memory
alloy of these embodiments undergoes a preliminary deformation at a
temperature of +10.degree. C. and below. A deformed shape is kept
unchanged up to temperature +26.degree. C. A shape restoration is
occurs under the heating up to +35.degree. C.
[0105] A third embodiment of the present invention will be
described in detail referring to FIGS. 16 and 17.
[0106] A plurality of pedicle screws 40 according to this
embodiment comprises; a head formed at a top portion thereof,
wherein the head has a reception cavity 41a and two parallel rod
grooves 42 and 42' in bottom surface of the reception cavity 41a;
and a thread 43 formed below the head to be implanted into a
pedicle of the vertebra.
[0107] Two parallel rod grooves 42 and 42' in the reception cavity
41a contributes to a connection of the rods 50 and the pedicle
screws 40 without an additional connector. Here, the rod grooves
42, 42' have a diameter equivalent to the rod 50.
[0108] A set screw 44 is inserted into the reception cavity 41a of
the head 41 of the pedicle screws 40 for preventing a movement of
the rod 50. In order to securely tighten the rod 50, the set screw
44 has an outer thread 44a and a recess 44b which has a hexagonal
cross-section view in the reception cavity 41a of the head 41. The
length of the set screw 44 should be short enough not to protrude
from the upper surface of the reception cavity 41a of the head 41.
The reception cavity 41a of the head 41 has an inner thread 41b to
be joined to the outer thread 44a of the set screw 44.
[0109] A head cap 45 can be adopted on the upper portion of the
head 41 to eliminate the change from a misaligned fixation of the
set screw 44. The head cap 45 serves as an additional supporter to
improve the rod holding power using an additional rod-fastening
element.
[0110] A pair of rods 50 according to this embodiment comprises; a
straight bar 51 placed at the center line of the heads; an elastic
section 52 formed in the middle of the straight bar 51 to generate
an elastic force for absorbing a shock which is inflicted on the
patient's vertebra; and a support bar 53 extended from both ends of
the straight bar 51 to be put in one of the rod grooves 42 and
42'.
[0111] The diameter of the rod is approximately in a range of 2 to
7 mm and it can be adjusted on a basis of unit diameter of 0.5
mm.
[0112] The elasticity section 52 is similar to a coil spring. The
coil spring is equal to the straight bar 51 in their diameters. The
elasticity section 52 can has a wave shape as another form.
[0113] The support bar 53 have a line portion 53a, which can be put
on one of the rod grooves 42a and 42', and a bending portion 53b
which is extend from both ends of the straight bar 51 and curved
along the outer surface of the head 41.
[0114] The straight bar 51 of the rod 50 is positioned on the
central axis of the head 41 by the shape of the support bar 53.
[0115] One of the two support bars 53 is opposite to the other in
the same head 41; however, the two support bars 53 can be in a
reverse phase to each other, even if it is not shown in the
drawings. That is, the rod 50 can be serially and alternately
connected to the pedicle screw 40 with the support bar 53 of which
the bending portions 53b are reversibly positioned and are curved
along the outer surface of the heads 41.
[0116] Referring to FIG. 17, the support bars 53 at both sides of
the rod 50 are respectively put into the rod grooves 42 and 42'.
Also, the set screws 44 are coupled to the inner threaded 41b of
the reception cavity 41a of the head 41, being rigidly fixed to the
rod 50.
[0117] A forth embodiment of the present invention will be
described in detail referring to FIGS. 18 to 20.
[0118] Referring now to FIG. 18, it comprises only a plurality of
pedicle screws 60 and a rod 70.
[0119] The pedicle screws 60 includes a head 61 formed at the top
portion thereof and a thread 62 formed below the head 61. The head
61 has first and second circular grooves 61a and 61a ' formed in an
outer surface thereof.
[0120] The rod 70 includes two straight bars 71 and 71' placed at
the center line of the head 61 of the pedicle screw 60, an elastic
section 72 formed in a type of wave between the two straight bars
71 and 71', and support rings 73 and 73' respectively extended from
both ends of the straight bars 71 and 71' to be inserted into one
of the first and second circular grooves 61a, 61a'.
[0121] The support rings 73 and 73' of the rod 70 are in reverse
phase to each other; however, they may be opposite to each other in
the same head 61, even if it is not shown in the drawings.
[0122] Referring now to FIGS. 19 and 20, the rods 70 are serially
and alternately connected to the plurality of circular grooves 61a
and 61a' of the heads 61 of the pedicle screws 60, using the above
support rings 73 and 73'.
[0123] A fifth embodiment of the present invention will be
described in detail referring to FIG. 21.
[0124] Referring now to FIG. 21, the fifth embodiment comprises a
plurality of pedicle screws 80 have a head 81, which is formed at
the top portion thereof and has a cylindrical type block, and a
thread 82 formed below the head 81. The head 81 has an opening 81a
horizontally passing through the cylindrical type block to receive
both ends of a rod 90 and a thread hole 81b which is upwardly
formed and is perpendicular to the opening 81a. The thread hole 81b
of the head 81 is joined to a bolt 83 in order to tight the rod
90.
[0125] The rod 90 has a straight bar 91 and hooks 92 and 92' which
are roundly extended from both ends of the straight bar 91 to be
inserted to the opening 81a. The straight bar 91 can be provided
with an elastic section in the middle of the rod 90.
[0126] Hereinafter, the installation procedure of the rod 90 will
be described in detail.
[0127] In this embodiment, when the rod 90 is coupled to the
pedicle screw 80, the roundly curved hooks 92 of the rod 90 is
deformed to a straight bar shape at a temperature +10.degree. C.
and below. On the other hand, the straight bar shaped hooks 92 of
the rod 90 is inserted to the opening 81a. Thereafter, a heat
treatment is applied to the rod 90 at a temperature of more than
+35.degree. C. the deformed hooks 92 of the rod 90 are returned
back to the memorized original shape and is rigidly fixed to the
head 81. After the rod 90 is inserted into the pedicle screw 80,
the bolt 83 is joined to the thread hole 81b of the head 81 for
tightening the rod 90 to the pedicle screw 80.
[0128] A sixth embodiment of the present invention will be
described in detail referring to FIG. 22.
[0129] This sixth embodiment makes the connecting work simple, by
simply coupling the rod to the pedicle screw after a plurality of
the pedicle screws are installed in the pedicles of the
vertebras
[0130] Referring now to FIG. 22a, the detailed description of the
pedicle screw will be omitted because the structure of the pedicle
screw 40 is the same as that in the above-mentioned third
embodiment. The same reference numerals denote the same elements as
illustrated in the third embodiment.
[0131] A rod 100 of this sixth embodiment is formed in "U" shape.
The U-shaped rod 100 is put into the rod grooves 42 and 42' of the
head 41, after the pedicle screws 40 is inserted into pedicle of
the vertebras. The connecting work of the rod 100 is achieved by
tightening the set screw 44 to the reception cavity 41a of the head
41 in order to fix the rod 100 to the pedicle screw 40. If the
pedicle screws 40 are not well aligned, the U-shaped rod 100 may be
deformed to comply with the misaligned pedicle screw 40.
Accordingly, the deformed rod 100 is easily positioned in the rod
grooves 42 and 42' of the reception cavity 41a of the head 41. The
deformed rod 100 is returned back to the original shape according
to a memorized shape of the rod 100, thereby correcting a position
of the misaligned pedicle screw 40.
[0132] The U-shaped rods 100 can be replaced with a straight bar
type rods 101 and 101' as shown in FIG. 22b. An elastic section 102
is provided in the middle of the straight rods 101 and 101'. The
straight rods 101 and 101' are respectively and alternately set to
the rod grooves 42 and 42' which are positioned in the reception
cavity 41a. Therefore, in case that the straight rods 101 and 101'
having the elastic section 102 are used, it is not necessary to
have an additional connector for such a serial connection.
[0133] A seventh embodiment of the present invention will be
described in detail referring to FIGS. 23 to 26.
[0134] Referring now to FIGS. 23 to 25, the seventh embodiment
comprises at least one pedicle screw 110, a pair of stapling rods
120, and a middle connecting rod 140.
[0135] Referring now to FIGS. 25, the pedicle screw 110 has a head
111 at the top portion thereof and a thread 113 formed below the
head 111 to be implanted into the pedicle of the vertebra, wherein
the head 111 has a reception cavity 111a and first and second
sockets 112 and 112' formed in the bottom surface of a reception
cavity 111a.
[0136] The rod 120 is formed in a staple structure for preventing a
movement of the vertebra.
[0137] One side of the staple rod 120 is directly implanted into
the pedicle of the vertebra and other side thereof is inserted into
one of the sockets 112 and 112'.
[0138] The middle connecting rod 140 is employed for serially
connecting the staple rod 120 to the pedicle screw 110 by inserting
both ends thereof to the sockets 112 and 112' of the head 111,
respectively.
[0139] Referring to FIG. 24, the staple rod 120 has a first bridge
121 for providing a space between selected vertebra and adjacent
vertebra, an elastic section 126 formed in the middle of the first
bridge 121, a spike 122 downwardly extended from one end of the
first bridge 121 to be implanted directly into the pedicle of the
vertebra, and a first connecting pole 123 downwardly extended from
the other end of the first bridge 121 to be fixed to the pedicle
screws 110. The length of the first connecting pole 123 is shorter
than the depth of the reception cavity 111a of the head ill so that
the first connecting pole 123 is inserted into the socket 112 of
the pedicle screw 110. The spike 122 has a plurality of scarred
regions 125 for preventing the spike 122 from being detached from
the pedicle of the vertebra. The scarred regions 125 may be formed
by an electro discharge machine. The diameter of the staple rod 120
is approximately in a range of 2 to 7 mm and it can be adjusted on
a basis of unit diameter of 0.5 mm.
[0140] Once a spinal fusion has been finished, the staple rod 120
is not separated from the vertebra because the scarred regions 125
are buried in the vertebra.
[0141] According to the embodiment of the present invention, it is
able to make a connection among three adjacent vertebras, using two
staple rods 120 and one pedicle screw 110.
[0142] The middle connecting rod 140 has a second bridge 141 for
providing a space between the pedicle screws 110, an elastic
section 146 formed in the middle of the second bridge 141, and
second connecting poles 142 downwardly extended from both ends of
the second bridge 141, wherein the length of the second connecting
poles 142 is shorter than the depth of the reception cavity 111a of
the head 111. The reason why is that a volume should be prepared
for the insertion of a fixing member such as a set screw.
[0143] The first connecting pole 123 of the staple rod 120 and the
second connecting poles 142 are substantially equal to each other.
In the serial connection, one of the second connecting poles 142
extended at both ends of the middle connecting rod 140 is inserted
into the socket 112 of head 111 of the pedicle screw 110 and the
other is inserted into the socket 112' of head 111' of the adjacent
pedicle screw 110'.
[0144] The elastic sections 126 and 146 can be made up of a coil
spring or a wave shape element. The diameter of each elastic
sections 126 and 146 is substantially the same as that of first and
second bridge 121 and 141.
[0145] In this embodiment, at least one set screw 130 is joined to
the reception cavity 111a of the head 111 of the pedicle screws 110
for preventing a movement of the staple rod 120.
[0146] Likewise, in this embodiment, at least one head cap 131 is
adopted to the upper surface of the head 111. The head cap 131 is
provided to improve holding power of the staple rod 120 without an
additional rod such as a fastening element.
[0147] Hereinafter, an installation procedure of the staple rod 120
among the first to fourth vertebras will described in detail.
[0148] Referring to FIGS. 23 and 26, the first and second pedicle
screws 110 and 110' are implanted into second and third middle
vertebras, respectively. The first connecting pole 123 of the first
staple rod 120 is inserted into one of the sockets 112 and 112' of
the first pedicle screw 110 and another connecting bar (123') of
the second staple rod 120' is inserted into the socket 112'' of the
second pedicle screw 110'.
[0149] The spikes 122 and 122' of the first and second staple rods
120 and 120' are implanted into the first vertebra and forth
vertebra, respectively. The two second connecting poles 142 at both
sides of the middle connecting rod 140 are inserted into the
sockets 112' an 122'' of the first and second pedicle screws 110
and 110, respectively.
[0150] After the installation of the staple rods 120 and 120' and
the middle connecting rod 140, the outer thread 130a of the set
screw 130 is joined to the reception cavity 110a of the head 110
and the set screw 130 is then joined to the inner thread 110b of
the reception cavity 110a by a wrench tool. Accordingly, the staple
rod 120 and the middle connecting rod 140 are simultaneously
pressed by the set screw 130 so that the staple rod 120 and the
middle connecting rod 140 are securely and rigidly fixed in the
pedicle screw 110. Although the pedicle screws 110 and 110' are not
well aligned, the staple rods 120 are easily and simply connected
to the pedicle screw 110. This can be further achieved by the
deformation of the staple rods 120 and the middle connecting rod
140.
[0151] Before the first connecting poles 123 and 123' of the first
and second staple rods 120, 120' are inserted into the sockets 112,
112' of the head 111, the staple rod 120 will be deformed at a
phase transformation point (+10.degree. C. and below) on condition
that one end of the first staple rod 120 is optimally connected to
the socket 112 of the head 111. Further, the spikes 122 and 122' of
the deformed first and second staple rods 120 and 120' are
implanted into bores of the vertebras. Also, the first connecting
poles 123 and 123' of the first and second deformed staple rods 120
and 120' are joined to the sockets 112 and 112' of the head 111.
Finally, the rod connection is completed among the pedicle screws
110 and 110', the staple rods 120 and 120' and the middle
connecting rod 140.
[0152] Next, a heat treatment is applied to the staple rods 120 and
the middle connecting rod 140 at a restoration point (+35.degree.
C. and over), using a surgical tool to have a heating source. The
lengthened elastic sections 126 and 146 are returned back to the
memorized original shape and are transformed to an austenite
phase.
[0153] At this time, the first and second connecting poles 123 and
142, the staple rod 120 and the middle connecting rod 140 is
rigidly fixed to the sockets 112 and 112' of the head 110, during
the restoration to the memorized original shape.
[0154] According to this embodiment, a movement between spinal
segments is given by the superelastic action of the elastic section
126 and 146, which are respectively formed in the staple rod 120
and the middle connecting rod 140, when the patients bend or wrench
his back after the spine fusion.
[0155] According to the above-mentioned structure of the seventh
embodiment, the first and second staple rods 120 and 120' are
formed in the symmetric structure. Thus, it is necessary to have
four pedicle screws even though all of them are needed in the
conventional spinal fixation system; however, it is necessary to
have only two pedicle screws in the present invention. Therefore,
according to this embodiment, the number of the pedicle screw is
reduced. In particular, in case of the correction of two vertebras,
it may be possible to perform the correcting work of the vertebras
by using only one single staple rod 120 without an additional
pedicle screw. In case of correction of three vertebras, it is
necessary to have only one pedicle screw.
[0156] An eighth embodiment of the present invention will be
described in detail referring to FIGS. 27 and 28.
[0157] In this embodiment, the staple rod 150 is directly implanted
into the pedicle of the vertebra without any pedicle screw.
[0158] Referring now to FIGS. 27 and 28, at least one staple rod
150 is located at both laterals of the spine
[0159] The staple rod 150 has a bridge 152 for providing a space
between a selected vertebra and an adjacent vertebra, a spike 153
downwardly extended from both ends of the bridge 152 for
implantation into the pedicle of the vertebra, and an elastic
section 154 formed in the bridge 152.
[0160] The elastic section 154 can be made of a coil spring (see
FIG. 27) or a wave shape element or a S-shaped element (see FIG.
28). Also, The spike 153 has a plurality of scarred regions 155
which prevents the spike 153 from being detached from the pedicle
of the vertebra.
[0161] The scarred regions 125 may be formed by an electro
discharge machine.
[0162] Although the preferred embodiments of the invention have
been disclosed for illustrative purposes, those skilled in the art
will appreciate that various modifications, additions and
substitutions are possible, without departing from the scope and
spirit of the invention as disclosed in the accompanying
claims.
[0163] According to the first to eighth embodiment of the present
invention, the rods and transverse links are made of a shape
memorized Nitinol alloy (Ni--Ti alloy) which has a superelastic
characteristic. Thus, although the pedicle screws are out of
alignment during the surgery, the present invention can easily and
simply make a structural connection between the rods and the
pedicle screws without excessive force on the spine and/or
implants.
[0164] In addition, in the present invention, the rods and
transverse links have an elastic section in an optional range
thereof. The elasticity section of the rod allows a delicate
movement after the spinal segments fusion. Thus, it disperses a
load, which is put on the spinal segments which have been fused,
through the rods and the transverse links having super-elasticity.
As a result, a burden on lumbar vertebra is reduced. Also, in case
of using the spinal fixation apparatus of the present invention, it
has another effect on the decrease of a complication that can be
caused between an upper segment and a lower segment.
* * * * *