U.S. patent application number 16/331793 was filed with the patent office on 2020-01-09 for intervertebral fusion device comprising an intervertebral stabilising screw and a composition for bone remodelling.
The applicant listed for this patent is INSTITUTO BIOMECANICO DE BARCELONA, S.L.. Invention is credited to CHRISTIAN RUDOLF MORGENSTERN DE MULLER, RUDOLF MORGENSTERN LOPEZ.
Application Number | 20200008944 16/331793 |
Document ID | / |
Family ID | 62075815 |
Filed Date | 2020-01-09 |
![](/patent/app/20200008944/US20200008944A1-20200109-D00000.png)
![](/patent/app/20200008944/US20200008944A1-20200109-D00001.png)
![](/patent/app/20200008944/US20200008944A1-20200109-D00002.png)
![](/patent/app/20200008944/US20200008944A1-20200109-D00003.png)
![](/patent/app/20200008944/US20200008944A1-20200109-D00004.png)
![](/patent/app/20200008944/US20200008944A1-20200109-D00005.png)
![](/patent/app/20200008944/US20200008944A1-20200109-D00006.png)
![](/patent/app/20200008944/US20200008944A1-20200109-D00007.png)
![](/patent/app/20200008944/US20200008944A1-20200109-D00008.png)
![](/patent/app/20200008944/US20200008944A1-20200109-D00009.png)
![](/patent/app/20200008944/US20200008944A1-20200109-D00010.png)
View All Diagrams
United States Patent
Application |
20200008944 |
Kind Code |
A1 |
MORGENSTERN LOPEZ; RUDOLF ;
et al. |
January 9, 2020 |
INTERVERTEBRAL FUSION DEVICE COMPRISING AN INTERVERTEBRAL
STABILISING SCREW AND A COMPOSITION FOR BONE REMODELLING
Abstract
The invention relates to an intervertebral fusion device
comprising an intervertebral stabilizing screw and a composition
for bone remodeling. The intervertebral stabilizing screw
comprises: a main body with an axial through-hole and a distal
thread that is secured to the bone, located at a distal end of the
main body; a hollow proximal secondary body that can slide along
the length of the main body; and a travel stop for the proximal
secondary body, located on an outer surface of the main body.
According to the invention, the proximal secondary body also
includes an external thread for securing to the bone, and the main
body comprises at least one fill hole, located between the distal
thread and the travel stop, for connecting an intervertebral space
to the aforementioned axial hole.
Inventors: |
MORGENSTERN LOPEZ; RUDOLF;
(ESPLUGUES DE LLOBREGAT (BARCELONA), ES) ; MORGENSTERN DE
MULLER; CHRISTIAN RUDOLF; (ESPLUGUES DE LLOBREGAT
(BARCELONA), ES) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INSTITUTO BIOMECANICO DE BARCELONA, S.L. |
BARCELONA |
|
ES |
|
|
Family ID: |
62075815 |
Appl. No.: |
16/331793 |
Filed: |
October 24, 2017 |
PCT Filed: |
October 24, 2017 |
PCT NO: |
PCT/ES2017/070712 |
371 Date: |
March 8, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61L 27/14 20130101;
A61L 2430/02 20130101; A61F 2002/3085 20130101; A61F 2/446
20130101; A61B 17/70 20130101; A61F 2002/30235 20130101; A61L
24/0084 20130101; A61F 2002/30322 20130101; A61L 24/0015 20130101;
A61B 17/864 20130101; A61F 2002/30622 20130101; A61B 17/8685
20130101; A61L 2300/412 20130101; A61F 2/28 20130101; A61F
2002/30593 20130101; A61L 27/56 20130101; A61F 2002/2835 20130101;
A61L 27/54 20130101 |
International
Class: |
A61F 2/28 20060101
A61F002/28; A61F 2/44 20060101 A61F002/44; A61L 24/00 20060101
A61L024/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 7, 2016 |
ES |
201631413 |
Claims
1. An intervertebral stabilizing screw comprising a main body with
an axial through hole and a distal thread for securing to the bone,
located at a distal end of the main body, a hollow proximal
secondary body that can slide along the length of the main body and
a travel stop for the proximal secondary body, located on an outer
surface of the main body, wherein the proximal secondary body also
includes an external thread for securing to the bone, and said main
body comprises at least one fill hole, located between the distal
thread and said stop, for connecting an intervertebral space to
said axial hole.
2. The screw, according to claim 1, wherein the external diameter
of the thread of the proximal secondary body is greater than the
diameter of the distal thread.
3. The screw, according to claim 1, wherein said stop consists of a
step which impedes the travel of the proximal secondary body up to
said fill.
4. The screw, according to claim 3, wherein the step is formed by a
variation in the external diameter of the main body.
5. The screw, according to claim 1, wherein said screw comprises at
least two fill holes.
6. The screw, according to claim 1, wherein said fill hole or holes
has or have a radial course.
7. The screw, according to claim 6, wherein said fill hole or holes
has or have a diametric course, with two outlets that connect
opposite points of the wall of the main body.
8. The screw, according to claim 1, wherein both the main body and
the proximal secondary body have at the proximal end thereof
devices for receiving a percutaneous tool.
9. The screw, according to claim 1, further comprising a proximal
cover to close off access to the axial hole once the screw is
installed.
10. The screw, according to claim 1, wherein the main body and the
proximal secondary body are threaded together, in such a way that
said sliding along the length of the main body comprises a relative
rotation therebetween.
11. A composition for bone remodelling comprising: polymerizable
bone cement, a calcium phosphate provider, and an oxygen providing
compound.
12. The composition, according to claim 1 further comprising an
osteogenic factor.
13. The composition, according to claim 11 further comprising a
contrast agent.
14. The composition, according to claim 11, wherein the oxygen
providing compound is selected from the group consisting of
oxygenated water, ozone and an oxygen solution.
15. The composition, according to claim 14, wherein the oxygen
provider is oxygenated water.
16. The composition, according to claim 11, wherein the
polymerizable e bone cement comprises a polymer selected from the
group made up of poly(methyl methacrylate) (PMMA), bisphenol A
glycidyl methacrylate (bis GMA) and poly(lactic co glycolic acid)
(PLGA).
17. The composition, according to claim 16, wherein the
polymerizable e bone cement comprises PMMA.
18. The composition, according to claim 11, wherein the calcium
phosphate provider is hydroxyapatite, brushite or tricalcium
phosphate.
19. The composition, according to claim 18, wherein the calcium
phosphate provider is hydroxyapatite.
20. The composition, according to claim 11, wherein the osteogenic
factor is selected from blood derived growth factors, whole blood
or osteogenic stem cells.
21. The composition, according to claim 20, wherein the osteogenic
factor is a blood derived growth factor.
22. The composition, according to claim 11, wherein the contrast
factor is a non ionic contrast factor.
23. The composition, according claim 11, wherein the polymerizable
bone cement is present in a quantity of between 55% and 80% by
weight of the composition.
24. The composition, according to claim 11, wherein the calcium
phosphate provider is present at between 15% and 30% by weight of
the composition.
25. The composition, according to claim 11, wherein the oxygen
providing compound is present in a quantity equal to or less than
5% by weight.
26. The composition, according to claim 12, wherein the osteogenic
factor is present in a quantity of less than 5% by weight.
27. The composition, according to claim 13, wherein the contrast
agent is present in a quantity of less than 1% by weight.
28. An intervertebral fusion device comprising: at least one
vertebral stabilizing screw according to claim 1 and a composition
for bone remodeling, which comprises: polymerizable bone cement, a
calcium phosphate provider, and an oxygen providing compound.
29. The device, according to claim 28, comprising at least two of
said vertebral stabilizing screws.
Description
[0001] The present invention relates to an intervertebral fusion
device comprising an intervertebral stabilising screw and a
composition for bone remodelling, to said screw and to said
composition.
[0002] The process of bone creation between adjacent vertebrae,
thus connecting said vertebrae together, is known as vertebral
fusion or arthrodesis.
[0003] Intervertebral fusions are performed at present by putting
in place a bone graft either from the patient him or herself
(normally from the vertebra concerned or from the iliac crest) or
from another (external or artificial) source. The graft may be
secured to the affected vertebrae by screws. In addition, a
structure for securing to the affected vertebrae must be put in
place which comprises bars or plates that follow the shape of the
spinal column and are secured to each vertebra by screws
(subsequent instrumentation). Said structure is needed to overcome
the intervertebral instability (spondylolisthesis) usually
associated with these conditions and to protect the graft during
the consolidation (bone creation) phase. This operation normally
requires open surgery. Intervertebral fusion or bone consolidation
continues for months or years, and in some cases does not produce
anything (pseudoarthrosis). 100% effective healing is not
necessarily the norm. The structure for securing to the affected
vertebrae, despite being somewhat conspicuous, is only removed in
cases where said structure causes considerable inconvenience and
only once completely satisfactory bone mineral consolidation that
can be verified by radiological techniques has taken place.
[0004] An object of the present invention is to disclose a device
for immediate intervertebral fusion (vertebral fusion device) which
provides a solution to the problems raised. In particular, the
vertebral fusion device allows fusions to be carried out
immediately using percutaneous techniques and outpatient surgical
centres. The novel fusion device eliminates the need for subsequent
instrumentation to protect the area from movements during the bone
consolidation phase and provides a solution to the problems that
occur when on occasion bone formation fails. Local anaesthesia may
be used. The novel fusion device also eliminates the need for other
metal inserts which project from the spinal column and may be the
source of problems. The novel fusion device also allows some
correction of intervertebral displacements. The novel fusion device
comprises, in combination, a novel intervertebral stabilising screw
and a novel composition for bone remodelling which comprises a bone
cement. Both the screw and the bone remodelling composition are
novel and can usually be developed and manufactured by different
technical teams.
[0005] The present invention is particularly applicable to
spondylolisthesis at any level, whether single or multiple,
although it can also be applied to the treatment of other spinal
pathologies. In a general case, the device according to the present
invention may be installed using percutaneous techniques and even
without the need to dilate soft tissue to facilitate surgical
access.
[0006] To do this, the present invention also discloses a bone
remodelling composition which produces a bed which promotes bone
formation in difficult growth conditions inside the intervertebral
ring (disk) and an insert (formed typically by two screws for each
fused level) which allows said bed to be positioned in the
intervertebral disk space and which cooperates with the bed in
stabilising the intervertebral area during the bone formation
phase. During the bone formation phase, stabilisation and
preservation of the intervertebral space take place in conjunction,
both through the insert or inserts and through the bone cement
contained in the bone remodelling composition.
[0007] The bone remodelling composition according to the present
invention is based on the use of what is known as bone cement.
Different types of bone cements are known, generally biocompatible
polymers which are polymerised during application. Polymerisation
`in situ` allows application in a liquid state and the subsequent,
immediate hardening thereof. Although the word `cement` is used in
the sector, it should be noted that this does not imply connection
of the cement to the bone, but rather the cement simply fills the
existing hollow. In other words, bone cements could also be
referred to generally as `mortar` or `filler` rather than
`cement`.
[0008] Bone cements are used in orthopaedic surgery as an implant
or for remodelling lost bone. Said bone cements are also used to
fill vertebral fractures. When the cement hardens, the continuous
pain associated with the fracture is alleviated.
[0009] Among known cements are poly(methyl methacrylate) (PMMA),
bisphenol A-glycidyl methacrylate (bis-GMA) and
poly(lactic-co-glycolic acid) (PLGA). The use of PMMA is the most
widespread. By suitable selection of initiators and monomers,
commercial versions are marketed with a polymerisation temperature
that is very close to body temperature, which is advisable to
prevent thermal necrosis of the surrounding tissue. Equipment is
also supplied to control the viscosity of the cement during the
initial phases of polymerisation, so as to control the injection
thereof. An example of a commercial polymerisable bone cement that
allows said control is the one marketed under the name
StabiliT.RTM..
[0010] In `Targeted therapy of low back pain associated with de
novo degenerative lumbar scoliosis in the elderly: prospective
observation cohort study` (Eur Spine J (2014) 23 (Suppl
5):5496-5496), Yamada et al. disclosed the percutaneous
transpedicular injection of PMMA. Yamada applies the cement using
an 11 G needle to very painful degenerated disks but where the
integrity of the ring is preserved and N.sub.2 is formed inside
said ring, which is not usually the case. Yamada does not carry out
cleaning of the nucleus and restricts himself to filling existing
hollows. This technique does not involve vertebral fusion with bone
formation, but rather putting cement in place as an insert, which
prevents the vertebrae from coming closer together. As already
mentioned, if connection of the insert in the space occurs, this
may be problematic. In addition, the technique is only applicable
if the intervertebral space has not be damaged or significantly
reduced.
[0011] A problem associated with bone cements, in particular with
PMMA, and therefore with the Yamada technique, is that its Young
modulus is very different to that of human bone, and therefore
stresses are concentrated in the cement. As the nearby bone lacks
stress stimulation, resorption of said bone might occur, which in
turn may cause new fractures in the bone surrounding the bone
cement. Ultimately, the lifespan of the bone cement prosthesis may
be limited.
[0012] The addition of hydroxyapatite to bone cement is known in
order to make the physical properties of the bone cement more like
those of bone. For example, in `PMMA-hydroxyapatite composite
material increases lifetime of augmented bone and facilitates bone
apposition to PMMA: Biomechanical and histological investigation
using a sheep model` (European Cells and Materials Vol. 28 Suppl.
1, 2014 (page 15), Arbmotlagh et al. found that the addition of 30%
hydroxyapatite improved the cycles until the failure of the
surrounding bone compared with the use of PMMA alone. The
histological section at six months found weak areas of bone within
the PMMA matrix when hydroxyapatite was used with PMMA.
[0013] Furthermore, vertebral stabilising screws are also known,
for example that known commercially as Perpos.RTM.. This screw is
intended for installation by passing through the facet of a
vertebra and being inserted in the pedicle of the lower vertebra
(without affecting the vertebral ring). The vertebral stabilising
screw comprises a distal thread intended to be threaded into the
vertebra, in the area of the pedicle. Said screw also comprises an
axial through-hole which is used for guiding the screw. The screw
also comprises a proximal portion which is able to move on the main
body, the function of which is to adjust the operating length of
the screw. The screw comprises a locking mechanism or catch which
secures the proximal portion at the required point of travel along
the length of the main body.
[0014] According to another aspect, the present invention also
discloses an intervertebral stabilising screw which comprises a
main body with an axial through-hole (cannulated screw) and a
distal thread for securing to the bone, located at a distal end of
the main body, a hollow proximal secondary body that can slide
along the length of the main body and a travel stop for the
proximal secondary body, located on an outer surface of the main
body, in which the proximal secondary body also includes an
external thread for securing to the bone, and between the distal
thread and said main body comprises at least one fill hole, located
between the distal thread and said stop, for connecting an
intervertebral space to said axial hole.
[0015] The screw according to the present invention comprises two
threads, each intended to be threaded to contiguous vertebrae. The
area between the distal thread and the limit stop is intended to
remain within the space of the intervertebral ring. The fill hole
allows the intervertebral space (intra-annular space) to be filled
with a bone remodelling composition. The thread of the proximal
secondary body (proximal thread) allows the screw to be secured to
a vertebra that is adjacent to the vertebra that receives the
distal thread.
[0016] According to the present invention, the preferred
installation of the screw may be carried out in a transpedicular
manner. The present invention provides for the insertion of two
screws, one on either side, for each level to be fused. In this
arrangement, the screws, owing to the proximal thread, allow
lordosis and lateral deviations of the spine to be corrected before
the injection of the bone remodelling composition.
[0017] The present invention provides, preferably, for the outer
diameter of the thread of the proximal secondary body (proximal
thread) to have a greater diameter than the diameter of the distal
thread. Thus the distal thread passes more easily through the
proximal thread installation area, without impairing the securing
of the proximal thread to the bone of the vertebra and also moving
the main body of the screw, by pushing said screw to thread the
secondary body into the lower vertebra.
[0018] The limit stop may take different forms and the function
thereof is to prevent the proximal secondary body from blocking the
fill hole or holes during its travel. Preferably, the main body has
a step which performs said function. Said step may be obtained,
preferably, by a variation in the external diameter of the main
body. The proximal body can therefore slide around the area with
the smaller external diameter, but not through the area with the
greater external diameter.
[0019] The course of the fill holes is preferably radial, which
minimises the length thereof. To provide the fill function, the
main body has at least two fill holes. Very preferably, the course
of the fill holes is diametric, with two outlets which connect
opposite points of the wall of the main body. This arrangement
allows the doctor who is carrying out the operation to check that
there is at least one hole in the intervertebral space. To do this,
the doctor must orient the screw so that the diametric direction of
the hole coincides with the emission direction of the X-rays from
the fluoroscope. The hole will therefore be visible using the
fluoroscope.
[0020] The present invention also provides for the screw to also
have a cover to close off access to the axial hole once the bone
cement has been injected.
[0021] To facilitate the placement thereof by percutaneous surgery,
the present invention provides for both the main body and the
proximal body to have a device at the proximal end thereof for
receiving a percutaneous tool, such as a hexagonal or similar
screwdriver.
[0022] In particularly preferred embodiments, the main body and the
proximal secondary body are threaded together. In this way, said
sliding along the length of the main body is associated with a
relative rotation between the main body and the proximal secondary
body. This allows the bodies to be actuated by means of concentric,
percutaneous sleeves, facilitating the forward and backward motion
of both bodies simultaneously in both of the vertebrae in which
said bodies are situated. The thread mechanism between the two
bodies makes possible the additional distraction or contraction of
the intervertebral space as required by the surgeon. This
arrangement also allows the selective injection of the cement from
the most distal point to the most proximal portion by moving the
cement or composition injector forwards or backwards through both
bodies at the same time.
[0023] The bone remodelling composition according to the present
invention comprises polymerisable bone cement, a calcium phosphate
provider and an oxygen-providing compound. Preferably said
composition also comprises an osteogenic factor and/or a contrast
agent.
[0024] The oxygen-providing compound in the composition according
to the present invention has the dual function of increasing the
porosity of the bone cement, creating hollows in the polymeric
matrix of the cement and of providing the oxygen required to
stimulate bone formation. This allows not only the formation of
bone in an area such as the intervertebral area without supplying
blood, but also leaves space for the coherent formation of said
bone. The oxygen-providing compound may preferably be oxygenated
water, ozone or an oxygen solution. More preferably, said
oxygen-providing compound is oxygenated water. Oxygenated water has
the advantage of being liquid, and of breaking down into water and
oxygen under suitable conditions, which allows said oxygenated
water to be mixed with the bone cement and injected during the bone
cement polymerisation process.
[0025] The hollows produced by the release of oxygen help ensure
that the bed formed by the bone cement matrix has mechanical
properties that are very similar to those of bone.
[0026] The polymerisable bone cement may be of any type, but those
that comprise at least one of the following: poly(methyl
methacrylate) (PMMA), bisphenol A-glycidyl methacrylate (bis-GMA)
and poly(lactic-co-glycolic acid) (PLGA) are preferable. More
preferably, the polymerisable bone cement comprises PMMA. PLGA may
also be preferred owing to its biocompatibility.
[0027] The calcium phosphate-providing substance may preferably be
hydroxyapatite, brushite, calcium phosphate or tricalcium
phosphate. Hydroxyapatite is preferable owing to its superior
biocompatibility and because it is the main form in which calcium
phosphate is found in bone. The preferred functions of the calcium
phosphate provider are to promote bone formation and to render the
properties of the bed of bone cement more like those of bone, in
order to minimise the possibility of fracture of the bone
surrounding the vertebral platforms.
[0028] The osteogenic factors promote and establish the bone
creation pathways. Preferably, the osteogenic factor in the
composition according to the present invention comprises at least
one of the following: whole blood, blood-derived growth factors and
osteogenic stem cells. Blood-derived growth factors are preferred
owing to the efficacy and ease of obtaining said blood-derived
growth factors.
[0029] The components of the composition according to the present
invention may be present in any proportion.
[0030] Preferably, the calcium phosphate provider is between 30%
and 15% by weight.
[0031] Preferably, the oxygenated water is present in a quantity
equal to or less than 5% by weight. Also preferably, the osteogenic
factor is present in a quantity of less than 5% by weight. Also
preferably, the contrast is present in a quantity of less than 5%
by weight, more preferably in a quantity of less than 1% by
weight.
[0032] The polymerisable bone cement will preferably be present in
a quantity of between 55% and 80% depending on the rest of the
components present and on the hardness required for the bed that is
to be formed.
[0033] Particularly preferably, the presence of a contrast agent,
preferably a non-ionic contrast agent, allows the placement of the
composition in the disk space to be controlled during an operation
to install the device according to the present invention
percutaneously.
[0034] Thus, the vertebral fusion device comprises the bone
remodelling composition according to the present invention and at
least one screw, preferably at least two screws.
[0035] The device according to the present invention may be
installed using percutaneous techniques, preferably by guiding the
vertebral stabilising screws. Installation comprises, preferably,
the phases of cleaning the disk space, scraping, and the
transpedicular installation of the screws; if necessary, correction
of the relative position of the vertebrae by threading the proximal
thread against the limit stop and injecting the bone remodelling
composition into the intervertebral space through the axial hole
and the fill hole. To facilitate bone formation from the vertebrae,
the vertebral platforms must be scraped with a flexible or bendable
osteotome, before introducing the bone remodelling composition.
[0036] The use of one or two screws for transpedicular access helps
preserve the integrity of the intervertebral disk and, in
particular, the seal of the disk ring during surgical access of the
intradiskal space, thus allowing the bone remodelling composition
to be injected without causing leaks thereof before final
solidification. The preservation of the seal and the immediate
solidification (polymerisation) make it possible to achieve an
immediate fusion which until now was impossible using conventional
intervertebral arthrodesis surgical techniques.
[0037] For a better understanding, the accompanying drawings of two
embodiments of the subject of the present invention are provided by
way of non-limiting example.
[0038] FIG. 1 is a side view of an embodiment of a screw according
to the present invention.
[0039] FIG. 2 is a view in cross section through the lateral
mid-plane of the screw of FIG. 1.
[0040] FIG. 3 is a view in cross section through a mid-plane
perpendicular to the cutting plane of FIG. 2.
[0041] FIG. 4 is a view from a sagittal plane of the vertebral
level that will be fused. The figure shows the lower vertebra and
the disk space, the upper vertebra having been omitted. The
trajectory of introduction of the screw according to the present
invention has also been shown.
[0042] FIG. 5 is a view from an axial plane of the level to be
fused of the previous figure, in which the placement trajectory of
the screw has also been marked.
[0043] FIG. 6 is a view from a coronal plane of the spine shown in
the previous figures, with the placement trajectory of two screws
according to the present invention also marked.
[0044] FIG. 7 shows a first phase of an example of the process of
putting in place the device according to the present invention, in
which the disk content (nucleus) has been omitted.
[0045] FIG. 8 shows diagrammatically a second phase of the device
placement process.
[0046] FIG. 9 shows diagrammatically a third phase of the device
placement process.
[0047] FIG. 10 shows diagrammatically a fourth phase of the device
placement process.
[0048] FIG. 11 shows diagrammatically a fifth phase of the device
placement process.
[0049] FIG. 12 shows diagrammatically a sixth phase of the device
placement process.
[0050] FIG. 13 shows diagrammatically a seventh phase of the device
placement process.
[0051] FIG. 14 shows diagrammatically an eighth phase of the device
placement process.
[0052] FIG. 15 shows from a lateral viewpoint a device according to
the present invention already in place and prepared for the fusion
of a vertebral level.
[0053] FIG. 16 is a perspective view of a second embodiment of a
screw according to the present invention.
[0054] FIG. 17 is an exploded perspective view of the second
embodiment.
[0055] FIG. 18 is a view in cross section through the lateral
mid-plane of the screw of the second embodiment.
[0056] FIG. 19 is a perspective view of three auxiliary tools for
actuating the screw of the second embodiment.
[0057] FIGS. 20 and 21 are diagrammatic views of a first method of
actuating the screw of the second embodiment.
[0058] FIGS. 22 and 23 are diagrammatic views of a second method of
actuating the screw of the second embodiment.
[0059] FIG. 24 shows a third embodiment of a screw according to the
present invention.
[0060] FIGS. 25 to 27 show diagrammatically a process of putting in
place the third embodiment, using two concentric sleeves.
[0061] FIGS. 1 to 3 show an embodiment of a screw according to the
present invention.
[0062] The example of a screw shown in the figures comprises two
parts that can move relative to one another:
[0063] a main body -1- and a proximal secondary body, hereinbelow,
a proximal body -2-. The proximal body -2- slides along the length
of the main body, in an axial direction. The references to distal
and proximal take as their reference the transcutaneous process of
placing a screw in a patient.
[0064] The main body -1- has at its distal end a distal thread -11-
for securing to bone. The rest of the main body is separated into
two areas -12-, -13- separated by a limit stop -123- formed by a
step produced by a sudden change in the external diameter thereof.
A proximal body -2-, which also has a proximal thread -21- for
securing to bone, is able to travel over the outside of the most
proximal area -13-. Since the proximal thread -21 must be secured
to bone in an area through which the distal thread -11- has already
passed, it may be advantageous for the external diameter of the
proximal thread -21- to be greater than that of the distal thread
-11-, in order to improve securing. The limit of travel of the
proximal portion -2- is defined by the interference of the most
distal face -213- thereof with the limit stop -123-.
[0065] Both the main body -1- and the proximal body -2- have at
their proximal ends areas or devices -19-, -29- which allow said
bodies to be suitably operated using percutaneous devices. It will
be appreciated that said areas may be different from those
shown.
[0066] Both the main body -1- and the proximal body -2- are hollow,
and have an axial hole. In the case of the proximal body, this
allows said body to slide along the length of the main body -1-,
but it would also be possible, alternatively, for both bodies to be
threaded together.
[0067] The axial hole of the main body terminates in a distal hole
-14-. This allows the main body to be guided in its travel. In
addition, the example has fill holes arranged diametrically with
opposite outlets -17-, 17'-, -18-, -18'- in the area -12- between
the limit stop -123- and the distal thread -11-. Said holes will
allow the intervertebral space (inside the vertebral disk) to be
filled with a bone remodelling composition through the axial hole
and the fill holes.
[0068] The fill holes preferably have two or more cores and the
arrangement thereof may be symmetrical. The ideal fill hole core
and the composition thereof depend on the anatomy and vertebral
condition of the patient.
[0069] FIGS. 4 to 6 show the preferred placement trajectory of two
screws according to the present invention for fusing a vertebral
level. Two screws are sufficient. The introduction thereof is
transpedicular, passing through the disk space in such a way that
the distal thread will be threaded in the upper vertebra and the
proximal thread in the lower vertebra.
[0070] The preferred access point for percutaneous placement is
situated in the pedicle, in the centre of the upper articular
process and approximately 1 mm below the lower edge of the
transverse process of the vertebra, varying according to the
specific anatomy and other factors.
[0071] The angle of introduction (defined by the value of the
angles -A-, -B-, -C-) also varies depending on the specific anatomy
of the vertebra. An optimal value for an L4-L5 fusion would be
35.+-.5.degree. for each of the three values (-A-, -B-, -C-), more
preferably 35.degree..
[0072] FIGS. 7 to 14 show an example of an installation process of
an embodiment of an intervertebral fusion device according to the
present invention.
[0073] In said figures, elements that are the same or equivalent to
those shown in the previous figures have been identified with
identical numerals and will therefore not be explained in
detail.
[0074] Initially, the guides may be installed following the
direction shown in FIGS. 4 to 6. For reasons of clarity, the guides
have not been shown in any of the figures. For the application
shown, an 11G Jamshidi-type trocar may be used for example for
accessing and penetrating the pedicle and a Kissner needle as a
guide for the placement of the screw. Placement is transcutaneous,
bilateral and pedicular. Using fluoroscopic techniques, its passage
through the disk space and penetration 5-10 mm into the body of the
upper vertebra and through the lower platform of the upper vertebra
can be controlled.
[0075] At any time in the process (not shown in the figures) it may
be useful to check the state of the seal of the ring using
radiological discography, in order to verify that the technique is
viable and/or to adjust the viscosity of the bone cement.
[0076] The process begins with ablation or nucleolisis, for example
by radiofrequency, of the material inside the disk -1000-. This can
be carried out with a Jamshidi-type cannula, as shown in FIG. 7.
This technique appears viable, as it has already been applied to
the ablation of metastatic posterior vertebral body osseous tumours
using a bipolar device for ablation by radiofrequency.
Alternatively, the material may also be removed mechanically. The
cannula -901- may have been inserted by guiding, using sufficiently
known percutaneous techniques. In the figure, a single cannula has
been shown, but two may be inserted, one on either side. This
technique has the advantage of making possible the preservation of
the disk ring.
[0077] Next the waste disk material produced by the nucleolisis is
drawn off. To do this, a cleaning fluid is introduced at one side
and removed at the other side, which draws out the waste material.
To do this, two transpedicular cannulas may be used such as the
cannula -901- shown in FIG. 7, one on either side. In FIGS. 8 and 9
an alternative technique has been shown in which two screws are
introduced, said screws being threaded using the appropriate tool
-900-, until the distal hole -14- of both screws is situated in the
distal space and the cleaning fluid is then circulated through the
two axial holes of both screws.
[0078] Once the disk space has been cleaned, the vertebral
platforms of the adjacent vertebrae -1001-, -1002- are scraped (or
stippled) (see FIG. 10). This can be done in various ways and with
different tools. For example, as an alternative to the tool shown
in FIG. 10, an osteotome may be used, for example the osteotome
marketed under the name DFINE Midline.RTM., or the like, to make
multiple perforations in the platforms. Using this technique, new
bone will grow from the platforms and will remain connected
thereto.
[0079] Once the nucleus of the ring has been cleaned and the
vertebral platforms have been scratched, the screw according to the
present invention can be introduced up to the end of its travel
(see FIGS. 11 to 13).
[0080] Initially, the main body -1- enters until the distal thread
-11- is threaded into the upper vertebra -1001- and the holes -17-,
-18- are in the interior disk space -1000-. The bilateral placement
process, with two screws, allows some correction of any vertebral
deviations.
[0081] Next, the proximal body -2- is threaded inside the pedicle
and the body of the lower vertebra -1002- until reaching the limit
stop. Once the limit stop has been reached, it is possible to
continue threading the proximal thread -21- against the limit stop.
This creates a distraction which produces slight intervertebral
lordosis. This effect is recommended, as most patients who require
fusion have lost lordosis. The use of this over-threading also
allows vertebral distractions to be corrected.
[0082] Once the screws have been put in place, the Kissner-type
guide needle (not shown in the figures) can be removed and the void
created in the disk space can be filled with a bone remodelling
composition.
[0083] To produce the bone regeneration composition according to
the present invention any type of polymerisable bone cement can be
used. Polymerisation allows the cured bone cement to be introduced
in a liquid or semi-liquid state with immediate hardening of the
bone cement inside the intervertebral disk.
[0084] There are different grades of commercial polymers which are
biocompatible and which, owing to the selection of components
and/or additives, have polymerisation temperatures that are close
to body temperature. Said polymers are generally commercialised in
the form of a powder which must be mixed with a liquid
polymerisation activator. Once the activator and powder have been
mixed, with some commercial bone cements, the viscosity can be
modified, for example by heating. An example of such a bone cement
is that named StabiliT.RTM., the main component of which is PMMA.
The hardening time is under 30 minutes, which allows the relative
position of the vertebrae to have consolidated by the end of the
operation, which makes it possible to dispense with splints and
exoskeletons during the bone formation period.
[0085] Control of viscosity may allow a bone-growth-promoting bed
to be produced inside the disk which serves as a support including
in cases where the ring is damaged. In particular, greater
viscosity allows for controlled delivery and solidification before
the composition leaves the disk space.
[0086] The process of producing the composition according to the
present invention comprises the addition of a calcium phosphate
provider, an oxygen provider and, optionally, an osteogenic factor
and a contrast agent, more preferably, a non-ionic contrast
agent.
[0087] For example, to produce a composition according to the
present invention, StabiliT.RTM. bone cement (PMMA) is used, using
a mixture of commercial activator with 5% by weight of oxygenated
water as an activator, which is mixed with a mixture of StabiliT
and hydroxyapatite powders at 20% by weight. It was observed that
polymerisation was not stopped by the presence of oxygenated water.
Once hardened, it was observed that greater porosity of the
hardened bone cement was visible with the naked eye.
[0088] The same test was carried out by also adding blood-derived
bone growth factors and a contrast agent (Lopamir or similar) to
the activator liquid in quantities of less than 5%. Polymerisation
was also successful.
[0089] Before the end of polymerisation the composition is
introduced into the disk void that has been produced (see FIG. 4)
while checking that said composition does not come out of the disk
space limited and contained by the disk ring and waiting for a few
minutes until polymerisation is complete. The composition comes out
through the outlet fill holes -17-, -18-, -17'-, -18'-.
[0090] In addition, a cover -920- should be put in place which
closes off access to the disk space by extraneous items.
[0091] Once hardened, the composition introduced inside the disk
-1000- produces a bed -30- with numerous pores -31- in which bone
will grow from the damaged areas of the platforms of the upper
-1001- and lower -1002- vertebrae. Growth is maximised by the
presence of oxygen and osteogenic growth factors inside the disk
space and enhanced by the availability of calcium phosphate,
preferably hydroxyapatite.
[0092] FIGS. 16 to 23 show a second embodiment of the screw
according to the present invention. Elements that are identical or
similar and/or equivalent to those explained earlier have been
identified with identical numerals and will not be explained in
greater detail.
[0093] In the second embodiment, the proximal ends -19'-, -29'- of
the main body -1- and of the proximal body respectively have been
modified. In particular, the proximal end -19'- of the main body
-1- does not project from/beyond the proximal body -2- and consists
of an indented area. Furthermore, the proximal end -29'- of the
proximal body -2- comprises a hexahedron-shaped outer portion for
receiving an actuation tool and an inner thread -31'- for
receiving, for example, a cover -3- (or other actuation tool).
[0094] The cover -3- has a thread -31- that fits with the inner
thread -31'- of the proximal body and a hexahedral recess -39- for
receiving an actuation tool.
[0095] Compared with the first embodiment shown in FIGS. 1 to 15,
an extra pair of holes -16- has been arranged positioned at 90o
relative to the rest of the fill holes -17-, -18-.
[0096] FIG. 19 shows three auxiliary tools, in particular, an
adaptor head -903- and two actuation tools -901-, -902-, which can
be used alternately. Either of the two actuation tools produces a
relative movement between the main body -1- and the proximal body
-2- of the screw, which also produces a relative rotation between
the main body -11- and the proximal body -2- (using the auxiliary
tool -901-) or not (using the auxiliary tool -902-).
[0097] More specifically, the adaptor head -903- comprises an outer
surface which is adapted to a tool -913- (which has a hexagonal
surface) and a thread -933- that fits with the inner thread -31- of
the proximal end -29'- of the proximal body -2-. The body of the
adaptor head is hollow, and has a through-hole with a section of
internal thread (not visible in FIG. 19).
[0098] Both auxiliary tools -901-, -902- have tool adaptor heads
-911-, -912- and threaded rods -921-, -922-, the thread of which
fits with the thread of the through-hole of the adaptor head -903-.
The distal ends -931-, -932- of both tools vary. In one case
(-901-), the distal end -931- is indented and fits with the
proximal end -19'- of the main body. In the other case (-902-), the
distal end -932- is planar. As a result, both tools actuate the
main body -1- differently.
[0099] FIGS. 20 and 21 show the actuation produced by the first
auxiliary tool -901-. The adaptor head -903- is threaded into the
proximal head -29'- of the proximal body -2- and the threaded rod
of the first auxiliary tool -901- is inserted in the through-hole
of the adaptor head -903- until said rod reaches the internal
threaded section, so that subsequent advances of the auxiliary tool
-901- must be made by rotation. When the distal end -931- of the
first auxiliary tool -901- touches the proximal end -19- of the
main body, the indented elements fit together, which means that the
main body -1- as well as moving relative to the proximal body -2-
(increasing the distance -A-) rotates drawn by the first auxiliary
tool -901-, as can be seen by comparing FIGS. 20 and 21, in which
the angular position of the fill holes -16-, -17-, -18,
changes.
[0100] FIGS. 22 and 23 show the equivalent process with the second
auxiliary tool -902-, the distal end -932- of which is planar and
not hollowed out. In this case, the second auxiliary tool pushes
the main body -9-, but without transmitting any rotation thereto.
Using the first auxiliary tool -901- it is possible to go deeper
into the thread of the main body into the corresponding vertebra,
whereas with the second auxiliary tool -902- the distance between
vertebrae can be increased.
[0101] FIG. 24 shows a third embodiment of a screw according to the
present invention. Elements that are the same or equivalent to
those shown in previous figures will be identified with identical
numerals and will therefore not be described in detail.
[0102] In this embodiment auxiliary fill holes -99- have been
arranged in the thread area -11- of the main body -1-. Said holes
are useful in cases of osteoporosis which require distal cementing
of the vertebral body. Said holes -19- may, of course, be
implemented in other embodiments, for example, in those shown
above.
[0103] Another modification compared with the previous embodiments
is to add various threads -98-, -97- that fit together between the
proximal body -2- and the main body -1-. This causes movement
between both bodies to also be associated with a rotation between
both portions. In addition, the proximal end -29- of the main body
has an internal surface for receiving an actuation tool, for
example a standard tool.
[0104] The use of two concentric external sleeves -1001-, -1002-,
one inside the other (not shown in the figure) is therefore
possible in order to advance both portions of the screw
simultaneously while, nevertheless, being able to screw the main
body -1-, the proximal body -2- independently to the bone, or both
bodies at the same time.
[0105] FIGS. 25 to 27 show diagrammatically a process for the
placement of a screw according to the present invention using two
concentric sleeves -1001-, -1002-. The sleeves have been shown
diagrammatically and without detail. It will be understood that the
distal ends thereof are of a suitable shape to actuate the
different bodies of the screw -1-, -2-.
[0106] With reference to FIG. 25, the screw is put in place with
the aid of the internal sleeve -1001- (or alternatively the screw
is put in place by other means after the internal sleeve -1001- has
been put in place). The internal sleeve has a central through-hole
-1011- in which the bolt that was inserted initially is housed and
is used for testing the screw and internal sleeve -1001-. The
internal sleeve -1001- has a pointed or conical distal end -1021-
to prevent the through-hole of the screw from being blocked by
unwanted particles from the patient's body. The screw may also have
a conical distal point. Next (see FIG. 26), the outer sleeve
-1002-, which has a through-hole -1012- in which the inner sleeve
-1001- is housed, is put in place.
[0107] With the two sleeves in position, the main body of the screw
can be threaded and/or moved forward (by means of the inner sleeve)
or the proximal body (by means of the outer sleeve) or both at the
same time (with both sleeves being actuated simultaneously). This
can be achieved using tools at the proximal end that are known in
the field of non-invasive surgery.
[0108] Once the screw is in place, the inner sleeve -1001- and the
bolt (not shown in FIGS. 25 to 27) are withdrawn, leaving the outer
sleeve -1002- in place, and the through-hole thereof -1012- is used
as a guide for the bone filler or tool for injecting the bone
cement or substance for treating the interdiskal space and/or
vertebra. Next, the outer sleeve is withdrawn.
[0109] The divergent characteristics of the embodiments shown are
applicable to other embodiments shown, either grouped together or
individually.
[0110] The installation process may be different from that shown,
and different percutaneous techniques or even non-percutaneous
techniques may also be used. The order of the operations is also
subject to change.
[0111] Although the invention has been described with respect to
preferred embodiments, said embodiments should not be considered as
limiting the invention, which will be defined by the widest
interpretation of the following claims.
* * * * *