U.S. patent application number 12/310207 was filed with the patent office on 2010-08-26 for neurological apparatus.
This patent application is currently assigned to RENISHAW PLC. Invention is credited to Hugo George Derrick, Stephen Streatfield Gill, Mathew David Frederick Stratton.
Application Number | 20100217236 12/310207 |
Document ID | / |
Family ID | 37081179 |
Filed Date | 2010-08-26 |
United States Patent
Application |
20100217236 |
Kind Code |
A1 |
Gill; Stephen Streatfield ;
et al. |
August 26, 2010 |
NEUROLOGICAL APPARATUS
Abstract
A guide element for insertion into the brain to guide
implantable instruments, wherein the guide element comprises an
elongate part, the elongate `part having a composition of at least
80% tungsten carbide. The guide element may have a coating, such as
a biocompatible plastics material which is more resilient than the
elongate part.
Inventors: |
Gill; Stephen Streatfield;
(Bristol, GB) ; Stratton; Mathew David Frederick;
(Stroud, GB) ; Derrick; Hugo George; (Bristol,
GB) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 320850
ALEXANDRIA
VA
22320-4850
US
|
Assignee: |
RENISHAW PLC
WOTTON-UNDER-EDGE
GB
|
Family ID: |
37081179 |
Appl. No.: |
12/310207 |
Filed: |
August 20, 2007 |
PCT Filed: |
August 20, 2007 |
PCT NO: |
PCT/GB2007/003169 |
371 Date: |
February 17, 2009 |
Current U.S.
Class: |
604/528 |
Current CPC
Class: |
A61L 31/06 20130101;
A61M 25/0045 20130101; A61M 25/0097 20130101; A61M 25/09 20130101;
A61M 2025/0048 20130101; A61M 25/02 20130101; A61M 2210/0687
20130101; A61L 31/10 20130101; A61M 25/0053 20130101; A61M
2025/0042 20130101; A61M 5/142 20130101; A61M 2025/09091 20130101;
A61M 25/00 20130101; A61B 90/11 20160201; A61L 31/028 20130101;
A61M 2025/0681 20130101; A61M 2025/0046 20130101; A61M 25/0662
20130101; A61M 25/005 20130101; A61M 2210/0693 20130101; A61M
2025/0004 20130101; A61M 2025/0047 20130101 |
Class at
Publication: |
604/528 |
International
Class: |
A61M 25/09 20060101
A61M025/09 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 18, 2006 |
GB |
0616411.5 |
Claims
1. A guide element for insertion into the brain to guide
implantable instruments, wherein the guide element comprises an
elongate part, the elongate part having a composition of at least
80% tungsten carbide.
2. A guide element according to claim 1, wherein the elongate part
has a diameter of less than 1 mm.
3. A guide element according to claim 2 wherein the elongate part
has a diameter of less than 0.6 mm.
4. A guide element according to claim 3 where the elongate part has
a diameter of less than or equal to 0.4 mm.
5. A guide element according to claim 1 wherein the elongate part
includes between 5-20% cobalt or nickel.
6. A guide element according to claim 1 wherein the elongate part
includes about 5% cobalt or nickel.
7. A guide element according to claim 1 wherein the guide element
further comprises a coating surrounding the elongate part.
8. A guide element according to claim 7 wherein the coating
comprises a different material than the elongate part.
9. A guide element according to claim 7 wherein the material of the
coating is more resilient than the material of the elongate
part.
10. A guide element according to claim 7 wherein the coating
comprises a bio compatible material.
11. A guide element according to claim 7 wherein the coating
comprises a plastics material.
12. A guide element according to claim 7 wherein the coating
comprises a material from one of polyimide, peek optima or
technical polyurethane.
13. A guide element according to claim 7 wherein the guide element
is a guide wire or guide rod.
14. A guide element for insertion into the brain to guide
implantable instruments, wherein the guide element comprises an
elongate part, the elongate part comprising a material which fails
rather than bends under force.
15. A guide element according to claim 14 wherein the guide element
further comprises a coating surrounding the elongate part.
16. A guide element according to claim 15 wherein the coating is
more resilient than the material of the elongate part.
17. A guide element according to claim 14 wherein the coating
comprises a bio compatible material.
18. A guide element for insertion into the brain to guide
implantable instruments, wherein the guide element comprises an
elongate part, the elongate part comprising a non ductile
material.
19. A guide element according to claim 18 wherein the guide element
further comprises a coating surrounding the elongate part.
20. A guide element according to claim 19 wherein the coating is
more resilient than the material of the elongate part.
21. A guide element according to claim 19 wherein the coating
comprises a bio compatible material.
Description
[0001] The present invention relates to apparatus for use in
neurosurgery, for positioning neurosurgical apparatus. In
particular, it relates to a guide element for insertion into the
brain for guiding tubular instruments such as catheters and guide
tubes.
[0002] The blood-brain barrier represents a considerable hurdle to
the delivery of therapeutic agents to the nervous system. The term
therapeutic agents includes substances which have a therapeutic
effect, such as pharmaceutic compounds, genetic materials,
biologics (i.e. preparations synthesised from living organisms such
as stem cells). The development of techniques to bypass this
barrier could revolutionise the management of Parkinson's,
Huntingdon's and Alzheimer's disease as well as Glioblastoma
Multiforme. Novel agents that could potentially suppress or even
reverse the underlying pathological processes of these conditions
have been developed. However, the limitations of these therapeutic
agents lie in their inability to cross the blood-brain barrier and
consequently their failure to reach the necessary structures within
the brain when delivered by conventional methods (e.g. oral or
intravenously).
[0003] Convection-enhanced delivery (CED) allows the delivery of a
therapeutic agent directly to the central nervous system, without
the requirement of the therapeutic agent crossing the blood brain
barrier. CED utilises fine intracranial catheters and low infusion
rates to impart drugs directly into the brain extracellular space.
In contrast to direct intraparenchymal injection, encapsulated
cells and biodegradable polymers, CED does not depend on diffusion.
The use of a carefully designed cannula with a precisely controlled
infusion rate leads to the development of a pressure gradient,
along which a therapeutic agent passes directly into the
extracellular space. Consequently, it is possible to achieve
controlled, homogeneous distribution even for relatively large
molecules, over large volumes of the brain and spinal cord.
[0004] International patent application WO 03/077764 discloses the
implantation of a catheter in a human or non-human brain for
intraparenchymal drug delivery. A drug may thus be pumped
intermittently or continuously through the catheter to the desired
brain target.
[0005] WO 03/077764 further discloses a stereoguide used for the
longitudinal guidance of instruments towards a target with the
brain which defines an axis along which the instruments are
inserted. The stereoguide is carried by a stereotactic frame which
is securely attached to the skull of the patient. The stereoguide
can be adjusted on the stereotactic frame in order to be positioned
very accurately to direct a surgical instrument to the desired
position. A guide wire may be used to rigidify tubular instruments
inserted into the brain or guide tubular instruments, such as
catheters for delivery of therapeutic agents or guide tubes which
are inserted into the brain and through which other instruments may
be passed.
[0006] A first aspect of the present invention provides a guide
element for insertion into the brain to guide implantable
instruments, wherein the guide element comprises an elongate part,
the elongate part having a composition of at least 80% tungsten
carbide.
[0007] Preferably the elongate part has a diameter of less than 1
mm.
[0008] More preferably the elongate part has a diameter of less
than 0.6 mm. Even more preferably, the elongate part has a diameter
of less than or equal to 0.4 mm.
[0009] The elongate part may include between 5-20% cobalt or
nickel. More preferably, the elongate part includes about 5% cobalt
or nickel.
[0010] The guide element may further comprise a coating surrounding
the elongate part. The coating may comprise a different material
than the elongate part. The coating may comprise a bio compatible
material. The coating may comprise a plastics material. The coating
may be one of polyimide, peek optima or technical polyurethane.
Preferably the material of the coating is more resilient than the
material of the guide element core.
[0011] Preferably the guide element is a guide wire or guide
rod.
[0012] A second aspect of the present invention provides a guide
element for insertion into the brain to guide implantable
instruments, wherein the guide element comprises an elongate part,
the elongate part comprising a material which fails rather than
bends under force.
[0013] A third aspect of the present invention provides a guide
element for insertion into the brain to guide implantable
instruments, wherein the guide element comprises an elongate part,
the elongate part comprising a non ductile material.
[0014] Embodiments of the invention will now be described by way of
example with reference to the following drawings:
[0015] FIG. 1 illustrates a side view of a guide tube;
[0016] FIG. 2 illustrates a side view of an inner tube;
[0017] FIG. 3 illustrates a side view of a catheter;
[0018] FIG. 4A is a side view of the assembled guide tube, inner
tube and catheter;
[0019] FIG. 4B illustrates the assembled guide tube, inner tube and
catheter inserted into the brain; and
[0020] FIG. 5 shows a guidewire inserted into the brain using a
stereoguide.
[0021] FIGS. 1-3 illustrate a guide tube, inner tube and catheter
respectively according to the present invention.
[0022] The guide tube 10 is shown in FIG. 1 and comprises a length
of tube 12 with a hub 14 at one end. In this example it is made
from a polyurethane plastic such as carbothane 55DB20. However, it
may be made from any material which is biocompatible and
sufficiently rigid at room temperature to maintain its central
aperture. In this example, the tube 12 has an outer diameter of 0.6
mm and an inner diameter of 0.5 mm.
[0023] The guide tube is inserted into the brain through an
aperture (e.g. burr hole) in the skull created by the surgeon. Once
the length of tubing is inserted into the brain, the hub can be
attached to the patient's skull, for example by bonding into a burr
hole in the skull using an acrylic cement. A wire may be used to
guide the guide tube into place, as disclosed in WO03/07784.
Before, insertion, the guide tube is cut to a length short of the
target. The distal end of the guide tube will typically fall
several millimetres short of the target.
[0024] The hub of the guide tube is preferably domed and has a cut
out slit 16 which links the central aperture of the tube to a side
of the hub.
[0025] The inner tube 18 is illustrated in FIG. 2 and comprises two
connected lengths of tubing, the distil tubing 20, which in this
example has an outer diameter of 0.42 mm and an inner diameter of
0.2 mm and proximal tubing 22 which has a larger diameter. A stop
element 24 links the proximal and distil tubing. The distal and
proximal lengths of tubing are typically made of a polyurethane
plastic, such as carbothane 85AB20, although other material could
also be used. The stop element 24 is in this case also constructed
using polyurethane plastic, such as carbothane 72DB20. Again other
suitable materials may be used.
[0026] The stop element 24 has a central body 26 which is generally
cylindrical and a pair of diametrically opposed wings 28,30 each
containing a countersunk hole 32,34 whereby the stop element may be
screwed to the outer surface of the skull of the patient. The inner
tube with distal and proximal lengths of tubing and stop element is
described in more detail in WO03/077785.
[0027] The stop element has two roles. Firstly, when the inner tube
is inserted into the guide tube, the stop element abuts against the
hub of the guide tube, thereby forming a stop and defining the
length of the distil tubing which extends from the tubing of the
guide tube. Secondly, the wings of the stop element are used to fix
the inner tube to the skull of the patient.
[0028] The role of fixing the inner tube to the skull of the
patient may be accomplished by alternative means. For example, a
pair of wings may be provided on the proximal tubing, for example
by overmoulding onto the tubing. These wings may be provided with
apertures to receive screws which when screwed into the skull fix
the wings and proximal tubing in place. This arrangement allows one
wing to be folded onto the other, so that a single screw is
inserted through both apertures of the wings. This arrangement has
the advantage that it causes some clamping of the catheter within
the proximal tubing.
[0029] The catheter 36 is illustrated in FIG. 3 and comprises a
fine length of tubing 38 and is typically made from fused silica.
Alternative materials may be used which are inert and have low
viral binding properties. The fused silica typically has an outer
diameter of 0.2 mm and an inner diameter of 0.1 mm. The catheter is
provided at one end with a barb 40 which acts as a stop. This may
be directly moulded onto the catheter and may be made from a
polyurethane plastic such as carbothane.
[0030] The barb 40 has a stepped cylindrical profile with a central
aperture. A region of greatest diameter 41 has straight sides which
form a stop against which the end of the proximal tubing abuts when
the catheter is inserted into the inner tubing. On either side of
the region of greatest diameter is a cylindrical portion 43 with a
waisted 45 portion of decreased diameter. In use, tubing is pushed
over the cylindrical portion until it abuts the region of greatest
diameter 41. As the tubing passes over the waisted portion 45 it
deforms to form a seal. As the catheter 36 is inserted into the
inner tubing 18, the end of the proximal tubing 22 is pushed over
one of the cylindrical portions 43. Connector tubing (not shown)
which connects the catheter to a pump may be attached to the other
cylindrical portion of the barb in the same manner.
[0031] In order to perform neurosurgery, the surgeon needs, in the
first instance, to understand the patient's neuroanatomy and hence
identify the position of the desired target. This is normally
achieved by fixing a stereotactic reference frame to the patient's
head, elements of which can be seen on diagnostic images, and from
which measurements can be made. The stereotactic frame then acts as
a platform from which an instrument is guided to a desired target
using a stereoguide that is set to the measured co-ordinates. Once
an instrument is guided to the desired target treatment can begin.
This is described in more detail in WO03/077784.
[0032] The stereoguide is used to first insert a guide element into
the brain towards the target. The guide tube is inserted into the
brain by threading it over the guide element using the secured
stereoguide and fixed in place as described above. The guide
element is then removed, leaving the guide tube in place. FIGS. 4A
and 4B illustrate the assembled guide tube 10, inner tubing 18 and
catheter 36. FIG. 4A is the assembly outside the skull and FIG. 4B
is the assembly with the catheter inserted into the brain 42. FIG.
4B illustrates the hub 14 of the guide tube 10 fixed in place in a
hole in the skull 44 by bone cement 46. The inner tube is inserted
into the guide tube by inserting the distil tubing 20 into the
guide tube 10 until the stop element 24 abuts the hub 14 of the
guide tube. The stop element 24 thus acts as a stop to control the
amount the length of the inner tubing which is inserted into the
brain. The catheter 36 is inserted into the inner tube and is
pushed through until its barb abuts the end of the proximal tubing
22 of the inner tubing.
[0033] Once the guide tube, inner tube and catheter are all
inserted, the proximal tubing containing the catheter extending out
of the skull from the hub of the guide tube are bent through 90
degrees so that the stop element lies flat against the skull, as
illustrated in FIG. 4B. This is then fixed in position using screws
48 passing through the countersunk holes. The cut out slit 16 in
the hub 14 of the guide tube allows this 90 degree bend. Further
clamping may be provided by additional fixing means on the inner
tube (such as wings over moulded on the inner tube) through which
screws may be attached to the skull.
[0034] The length of guide tube, inner tube and catheter are
arranged so that the inner tube extends into the brain further than
the guide tube (e.g. 10 mm) and the catheter extends into the brain
further than the inner tube (e.g. 10 mm)
[0035] With the guide tube, inner tube and catheter all in place,
the catheter can be connected to a pump (not shown) via connector
tubing which connects to the barb of the catheter.
[0036] WO03/077784 discloses a method of inserting fine instruments
such as catheters and electrodes into the brain. A small diameter
tungsten guidewire of 0.6 mm diameter is inserted into a fine tube
and fixed within it, with the wire projecting from its end. The
fine tube and wire are lowered together to the target in the brain
using a stereoguide. The fine tube is then removed and the guide
tube is threaded onto the wire and inserted into the brain. Once
the guide tube is installed the guide wire is removed.
[0037] In practice, the guidewire may be inserted without the use
of the fine tube.
[0038] FIG. 5 illustrates a guide wire 52 inserted into the brain
using a stereoguide 50. The stereoguide is carried by a
stereotactic frame (not shown) which is securely attached to the
skull 54 of the patient. FIG. 5 shows a guide wire 52 inserted
though guide elements 54,56 and clamps 58 of the stereoguide,
through an aperture 60 in the skull 54 and into the brain. A guide
tube 10 is shown threaded onto the guide wire, ready to be inserted
into the brain. A stereoguide suitable for insertion of the guide
wire into the brain is disclosed in WO03/077784.
[0039] For insertion of very fine catheters, a guide wire of very
small diameter is required, for example 0.2 mm.
[0040] When the guide wire is inserted into the brain, it must
penetrate the pia mater which is the delicate innermost layer of
the meninges, the membranes surrounding the brain and spinal cord.
The thin, mesh-like pia mater closely envelops the entire surface
of the brain, running down into the fissures of the cortex. It
joins with the ependyma which lines the ventricles to form choroid
plexuses that produce cerebrospinal fluid.
[0041] Tungsten wire has the disadvantage that at these small
diameters it can bend. This bending can cause the tip of the guide
element to reach the wrong target in the brain, resulting in the
subsequent guide tube and catheter being installed incorrectly.
[0042] In the present invention a guide element (e.g. a guide wire
or guide rod) is made from a material, such as tungsten carbide,
which is a stiff and brittle material.
[0043] Tungsten carbide has a different failure mode to tungsten.
As tungsten is a non ductile material, it will fail rather than
bend under force. This is unlike tungsten which will yield and
deform under force. Thus a guide element (e.g. guide wire or guide
element) made from a material which fails rather than bends under
force and/or comprises a non ductile material, such as tungsten
carbide, will not bend and the tip is inserted at the correct
position.
[0044] The guide element comprises an elongate part, for example
made of tungsten carbide. The tungsten carbide may include a
percentage of other elements, for example cobalt. The addition of
cobalt has the function of improving binding properties and is
typically added in a range of 5-20% by weight. A suitable
composition of the tungsten carbide guidewire is 95% WC and 5% Co,
although other compositions may be used. An alternative additive is
nickel, which also improves binding properties. Nickel also has the
effect of increasing corrosion resistance and increasing
biocompatibility. As before, nickel may be added in the range of
5-20% by weight.
[0045] An example of the dimensions of the tungsten carbide
elongate part of the guide element is a diameter of 0.36 mm. The
elongate part of the tungsten carbide guide element preferably has
a diameter of less than 1 mm, although preferably a diameter of
less than 0.6 mm and even more preferably a diameter of less than
or equal to 0.4 mm.
[0046] When the guide element is inserted into the brain, it passes
through the relatively tough pia mater (for approximately 5 mm) and
then a much softer region of brain. Any breakage of the tungsten
carbide will thus occur in the first 5 mm, during which the broken
guide element can easily be removed.
[0047] The elongate part of the guide element may be coated with a
material which will hold it together if it breaks. The coating
comprises a biocompatible material which is more resilient than the
tungsten carbide core.
[0048] It may comprise a biocompatible plastics material, for
example polyimide, peek optima or technical polyurethane. A
suitable coating could be applied by over moulding. The thickness
of the coating is chosen to effectively hold broken pieces of the
guide element together whilst limiting the increase in diameter of
the guide element. The coating thickness will typically be in the
range of 0.1 to 0.25 mm
[0049] The guide element may comprise, for example a guide wire or
guide rod.
[0050] The guide element may be made from materials other than
tungsten carbide which fail rather than bend under force and/or
which are non ductile.
* * * * *