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Claims  |
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We claim:
1. A hand-held apparatus for accurately and reproducibly inserting a
catheter through an orifice in a human cranium and guiding said catheter
into a ventricle of a human brain, said apparatus comprising:
open tubular means;
support means for said open tubular means, said support means being adapted
to rest unsecured on said human cranium in surrounding spaced relation to
an orifice therein, and
a rigid catheter guide member inserted within said open tubular means and
having a diameter larger than that of said catheter and smaller than that
of said open tubular means, said catheter guide member adapted and
configured for positioning and aligning said open tubular means and said
support means directly over said cranium orifice; said support means, said
open tubular means and said catheter guide member being related to each
other and to said cranium so as to guide said catheter through said
orifice and in a direction perpendicular to an imaginary plane defined by
a tangent to the cranium at said orifice,
said catheter guide member adapted to be in guiding engagement with said
catheter and adapted to contact and extend at least partially into said
cranium orifice.
2. The apparatus of claim 1 wherein said support means comprises a
plurality of legs.
3. A hand-held apparatus for accurately and reproducibly inserting a
catheter through an orifice in a human cranium and guiding said catheter
into a ventricle of a human brain, said apparatus comprising:
(a) guide means comprising
(i) open tubular means;
(ii) support means for said open tubular means, said support means being
adapted to rest unsecured on said human cranium in surrounding spaced
relation to an orifice therein; and
(iii) a rigid catheter guide member inserted within said open tubular means
and having a diameter larger than that of said catheter and smaller than
that of said open tubular means, said catheter guide member adapted and
configured for positioning and aligning said open tubular means and said
support means directly over said cranium orifice; said support means, said
open tubular means and said catheter guide member being related to each
other and to said cranium so as to guide said catheter through said
orifice and in a direction perpendicular to an imaginary plane defined by
a tangent to the cranium at said orifice, and
(b) catheter means insertable through said catheter guide member and said
orifice and thereafter into a ventricle of said brain,
said catheter guide member adapted to be in guiding engagement with said
catheter and adapted to contact and extend at least partially into said
cranium orifice.
4. A hand-held apparatus for accurately and reproducibly inserting a
catheter through an orifice in a human cranium and guiding said catheter
into a ventricle of a human brain, said apparatus comprising:
(a) open tubular means;
(b) support means for said open tubular means, said support means being
adapted to rest unsecured on said human cranium in surrounding spaced
relation to an orifice therein; and
(c) a rigid catheter guide member inserted within said open tubular means,
said catheter guide member comprising an elongated tubular portion having
a first end and a second end, said tubular portion having a relatively
larger diameter than said catheter and a relatively smaller diameter than
said open tubular means, said catheter guide member further comprising, at
said first end, a top portion formed integrally therewith which is wider
than said second end and is configured and adapted to position said guide
member within said open tubular means, said catheter guide member adapted
and configured for positioning and aligning said open tubular means and
said support means directly over said cranium orifice; said support means,
said open tubular means and said catheter guide member being related to
each other and to said cranium so as to guide said catheter through said
orifice and in a direction perpendicular to an imaginary plane defined by
a tangent to the cranium at said orifice,
said catheter guide member adapted to be in guiding engagement with said
catheter and adapted to contact and extend at least partially into said
cranium orifice.
5. A hand-held apparatus for accurately and reproducibly inserting a
catheter through an orifice in a human cranium and guiding said catheter
into a ventricle of a human brain, said apparatus comprising:
(a) guide means comprising
(i) open tubular means adapted to receive and guide catheter means
therethrough, and
(ii) a plurality of leg members configured and adapted to support said
tubular means, said legs being adapted to rest unsecured on said human
cranium in surrounding spaced relation to said orifice,
(b) a catheter guide member adapted for insertion through said open tubular
means and adapted to extend at least partially into said cranium orifice,
said catheter guide member comprising an elongated tubular portion having
a first end and a second end, said tubular portion having a relatively
larger diameter than that of said catheter and a relatively smaller
diameter than that of said open tubular means, said guide member further
comprising, at said first end, a relatively wider top portion formed
integrally therewith and configured and adapted to position said guide
member within said open tubular means, said guide member in addition
adapted and configured for positioning and aligning said open tubular
means and said leg members directly over said orifice; said legs, said
open tubular means and said catheter guide member being related to each
other and to said cranium so as to guide said catheter through said
orifice and in a direction perpendicular to an imaginary plane defined by
a tangent to the cranium at said orifice, and
(c) catheter means insertable through said catheter guide member and said
orifice and thereafter into a ventricle of said brain,
said catheter guide member adapted to be in guiding engagement with said
catheter means while the free end of said catheter is inserted into said
human brain.
6. The apparatus of claim 5 wherein said open tubular means ranges between
about 2-10 cm in length.
7. The apparatus of claim 6 wherein each of said plurality of legs
terminates in a free end, said free ends forming a polygon defining a
plane.
8. The apparatus of claim 7 wherein the distance between the free ends of
each pair of said plurality of legs ranges between about 1-6 cm.
9. The apparatus of claim 8 wherein said plurality of legs comprises three
support legs of equal length wherein an equilateral triangle is formed by
said free ends of said legs.
10. The apparatus of claim 5 wherein said legs are connected to said open
tubular means through a connecting platform.
11. The apparatus of claim 5 wherein said guide means is made of a rigid,
non-deformable material.
12. The apparatus of claim 11 wherein said rigid, non-deformable material
is a rigid engineering plastic or stainless steel.
13. The apparatus of claim 5 wherein said catheter guide member is made of
a rigid, non-deformable material.
14. The apparatus of claim 13 wherein said rigid, non-deformable material
is a rigid engineering plastic or stainless steel.
15. A hand-held apparatus for accurately and reproducibly inserting a
catheter through an orifice in a human cranium and guiding said catheter
into a ventricle of a human brain, said apparatus comprising:
(a) guide means constructed of a rigid, non-deformable material, said guide
means comprising
(i) an open tubular member having a first end and a second end, said member
ranging between about 2-10 cm in length and adapted to receive and guide a
catheter therethrough,
(ii) three leg members of equal length, each said leg member terminating in
a free end, each pair of said free ends spaced apart an equal distance,
said distance ranging between about 1-6 cm, and forming an equilateral
triangle on said cranium, and
(iii) a platform for connecting said leg members to said open tubular
member,
(b) a catheter guide member adapted for insertion through said open tubular
member and adapted to extend at least partially into said cranium orifice,
said guide member comprising an elongated tubular portion having a first
end and a second end, said tubular portion having a relatively larger
diameter than that of said catheter and a relatively smaller diameter than
that of said open tubular member, said guide member further comprising, at
said first end, a relatively wider top portion formed integrally therewith
a configured and adapted to position said guide member within said open
tubular member and said leg members directly over said orifice; said legs,
said open tubular member and said catheter guide member being related to
each other and to said cranium so as to guide said catheter through said
orifice and in a direction perpendicular to an equilateral triangle
defined by a tangent to the cranium at said orifice, said catheter guide
member further adapted to be in guiding engagement with said catheter
means while the free end of said catheter is inserted into said human
brain, and
(c) catheter means insertable through said catheter guide member and said
orifice and into a ventricle of said brain.
16. A hand-held apparatus for accurately and reproducibly inserting a
catheter through an orifice in a human cranium and guiding said catheter
into a ventricle of a human brain, said apparatus comprising:
open tubular means;
support means for said open tubular means, said support means being adapted
to rest unsecured on said human cranium in surrounding spaced relation to
an orifice therein; and
a catheter guide member inserted within said open tubular means and having
a diameter larger than that of said catheter and smaller than that of said
open tubular means, said catheter guide member including means for
positioning and aligning said open tubular means and said support means
directly over said cranium orifice; said positioning and aligning means
including a forward end thereof adapted to extend partially into said
cranium orifice but not into said ventricle, said support means, said open
tubular member and said catheter guide member being related to each other
and to said cranium so as to guide said catheter through said orifice in a
direction perpendicular to an imaginary plane defined by a tangent to the
cranium at said orifice.
17. The apparatus of claim 16 wherein said support means comprises a
plurality of legs and said catheter guide member is made of a rigid
material.
18. A hand-held apparatus for accurately and reproducibly inserting a
catheter through an orifice in a human cranium and guiding said catheter
into a ventricle of a human brain, said apparatus comprising:
(a) open tubular means;
(b) support means for said open tubular means, said support means being
adapted to rest unsecured on said human cranium in surrounding spaced
relation to an orifice therein; and
(c) a catheter guide member inserted within said open tubular means and
having a diameter larger than that of said catheter and smaller than that
of said open tubular means, said catheter guide member including means for
positioning and aligning said open tubular means and said support means
directly over said cranium orifice; said positioning and aligning means
including a forward end thereof adapted to extend partially into said
cranium orifice but not into said ventricle, said catheter guide member
further including a rearward end which is of larger diameter than said
forward end so that said rearward end rests upon said open tubular means,
said support means, said open tubular member and said catheter guide
member being related to each other and to said cranium so as to guide said
catheter through said orifice in a direction perpendicular to an imaginary
plane defined by a tangent to the cranium at said orifice.
19. A hand-held apparatus for accurately and reproducibly inserting a
catheter through an orifice in a human cranium and guiding said catheter
into a ventricle of a human brain, said apparatus comprising:
(a) guide means comprising
(i) open tubular means;
(ii) support means for said open tubular means, said support means being
adapted to rest unsecured on said human cranium in surrounding spaced
relation to an orifice therein; and
(iii) a catheter guide member inserted within said open tubular means and
having a diameter larger than that of said catheter and smaller than that
of said open tubular means, said catheter guide member including means for
positioning and aligning said open tubular means and said support means
directly over said cranium orifice; said positioning and aligning means
including a forward end thereof adapted to extend partially into said
cranium orifice but not into said ventricle, said support means, said open
tubular member and said catheter guide member being related to each other
and to said cranium so as to guide said catheter through said orifice in a
direction perpendicular to an imaginary plane defined by a tangent to the
cranium at said orifice, and
(b) catheter means insertable through said catheter guide member and said
orifice and thereafter into a ventricle of said brain. |
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Claims |
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Description |
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TECHNICAL FIELD
The invention relates to a method and apparatus for penetrating a human
cranium at an angle of 90.degree. to the surface. More particularly, the
invention relates to a drilling device and a guide therefore to ensure
that the perforation is oriented at the correct angle. An additional
member may subsequently be inserted into the drill guide to facilitate the
correct positioning of a catheter device within a ventricular portion of
the patient's brain.
BACKGROUND OF THE INVENTION
The four ventricles of the human brain are interconnected cavities that
produce and circulate cerebral-spinal fluid (CSF). Procedures involving
ventriculostomy, i.e., placement of a catheter into the ventricular system
of the brain, form a major part of a neurosurgeon's clinical practice.
General areas of application of ventricular catheter placement include
intracranial pressure monitoring (ICP), draining or shunting of CSF and
the instillation of pharmacological therapeutic agents.
Intracranial pressure monitoring, i.e., a monitoring of ventricular
pressure, is critical to the management of patients after severe head
trauma, fulminant meningitis, Reyes' syndrome, encephalitis, stroke,
cerebral hemorrhage, or subarachnoid hemorrhage producing stupor or coma.
However, the ventricles are usually compressed after head trauma and thus
technically difficult to cannulate for ICP monitoring. Accordingly,
subarachnoid pressure monitoring, which is not as true a measure of
cerebral pressure as intraventricular pressure monitoring, is generally
used.
CSF drainage is essential for patients with congenital or acquired
hydrocephalus. This procedure, which can only be performed with an
intraventricular catheter, is a life-preserving step, because it can
immediately reduce intracranial pressure. The ventricular catheter used to
drain cerebral-spinal fluid is connected to a peripheral subcutaneous
drainage system, i.e., to the peritoneal cavity or systemic circulation
via the heart. In hydrocephalus, the ventricles are enlarged and are an
easier target for cannulation. However, recent reports in neurosurgical
literature indicate that suboptimal placement in dilated ventricles can
subsequently produce catheter obstruction when the ventricles are
decompressed and become smaller, thus emphasizing the need for accurate
placement.
Catheter placement in cerebral ventricles is widely performed on patients
with carcinomatous and fungal meningitis for the administration of
well-known antineoplastic and antifungal chemotherapetuic agents,
respectively. Invariably, the ventricles in these patients are small or
normal sized and difficult to cannulate.
Standard procedures for ventricular catherization are disclosed in the
textbook literature. See, for example, Neurosurgery, edited by Robert H.
Wilkins and Setti S. Rengachary, Section A, Chapter 13, Techniques of
Ventricular Puncture (McGraw Hill 1984).
The most frequently chosen site for ventricular catheterization is the
coronal region. In most cases, a catheter is inserted in the anterior horn
of the lateral ventricle through an orifice or burr hole drilled just
anterior to the coronal suture in the midpupillary line of the cranium,
i.e., in the frontal bone over the ventricle. This is known in the field
as Kocher's point. The burr hole, only slightly larger than the diameter
of the selected catheter to insure a snug fit and provide a seal against
CSF leakage, is placed approximately 1 cm. anterior to the coronal suture,
approximately 10 to 12 cm. above the nasion, and approximately 2 to 3 cm.
from the midline over the nondominant hemisphere. After the burr hole is
made, the dura and underlying pia-arachnoid are opened and coagulated, for
example, with a fine-tipped blade, after cauterizing the dural surface.
The lateral ventricles of the human brain form an arc parallel to the arc
of the cranium, i.e., the contour of the lateral ventricles parallels the
arc of the surface of the skull. Thus, a catheter guided perpendicular to
the cranial surface at the point of entry into the cranium will enter the
ventricular system. Specifically, any line penetrating a burr hole in the
surface of the skull at a 90.degree. angle also bisects the lateral
ventricle.
Various methods have been utilized in the prior art in an attempt to ensure
the correct placement of a catheter device in the patient's cerebral
ventrical. One such method involves the use of a pre-measured catheter
having a stylet which may be introduced and directed freehand through the
burr hole, approximately in the coronal plane, and angled towards the
medial canthus of the ipsilateral eye, using external landmarks such as
the inner canthus of the eye in the frontal plane and a point just in
front of the external auditory meastus in the lateral plane as guided to
placement. CSF should flow freely from the catheter tip at a depth of
approximately 4 to 5 cm. from the interior cranial surface.
A distinctive "give", or release of opposition, can often be felt when the
ventricle is penetrated. Pressure should be measured at this point,
however, since an artificially low value will be obtained even if small
amounts of fluid are lost. Then, after removal of the stylet from the
catheter, advancement another 1 cm. or so should insure placement in the
frontal horn at a depth of about 5 to 6 cm. from the external table of the
skull, care being taken that CSF continues to flow.
Intraoperative fluoroscopy and air ventriculography, well known techniques
in the art, have been used to confirm freehand catheter placement. While
these procedures can be helpful in placing the catheter if the ventricles
are small, they also add to the complexity of the overall procedure.
Aside from the cost and time constraints of such radiographic confirmation
of catheter placement, many published reports of postoperative studies
have revealed misplacement of catheter tips in cerebral matter or
subarachnoid space. This misplacement results in increased neurological
morbidity and the need for additional operation time. Moreover, multiple
passes of the catheter into cerebral matter are quite common before the
ventricles are properly penetrated. Finally, the anxiety a neurosurgeon
experiences when trying to place a catheter by freehand into the
ventricular system makes first pass success that much more difficult and
further increases the risks involved in the procedure.
A more recently developed procedure to ensure correct catheter placement
was disclosed and claimed by one of the present applicants in U.S. Pat.
No. 4,613,324, issued Sept. 23, 1986. The disclosure of that patent is
therefore specifically incorporated herein by reference. The apparatus
comprises a guide assembly which, when positioned over an orifice drilled
in the cranium above the anterior horn of the lateral ventricle, guides a
catheter and obdurator through the orifice and into the lateral ventricle
at an angle normal to an imaginary plane formed by a tangent to the
cranium at the orifice.
The method of utilizing the claimed device comprises providing an orifice
in the cranium just anterior to the coronal suture in a midpupillary line
of the cranium and inserting a ventricular catheter containing an
obdurator through the orifice towards a lateral ventricle, wherein the
catheter containing the obdurator is guided through the orifice, by means
of a novel guide assembly, at an angle normal to an imaginary plane formed
by a tangent to the cranium at the orifice.
Although the procedures described above may be effective in positioning a
catheter in a patient's lateral ventricle once a correctly aligned burr
hole has been prepared for its passage, there is no art which the
applicants are aware of which ensures that the initial perforation in the
patient's cranium can be prepared and aligned so as to extend through the
skull at an angle of substantially 90.degree. to the surface thereof.
This orientation is required for proper placement of the catheter within
the ventricular portion of the patient's brain since, if the burr hole
deviates by more than about 7 degrees from the perpendicular to a plane
tangent to the point on the cranium where the catheter is inserted, the
catheter will be directed away from the ventricular region and into other
areas of the organ not conducive to the intended purposes of the apparatus
disclosed. Thus, aligning the burr hole in such a precise manner greatly
simplifies the subsequent task of correctly aligning the catheter within
the ventricular cavity.
The difficulty in obtaining such a precisely aligned burr hole has thus led
to the search for a rapid, simple, inexpensive and accurate method and
apparatus for perforating the patient's cranium at an angle of
substantially 90.degree. to the surface prior to the insertion of a
catheter into the patient's cerebral ventricle.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method and apparatus for
perforating a human cranium at an angle of substantially 90.degree. to the
surface thereof. This procedure facilitates the insertion of a catheter
through the surface of the cranial bone and into the anterior horn of a
lateral ventricle of the patient's brain, thus eliminating the problems,
inaccuracies and risks associated with prior art methods.
Another object of the invention is to provide a method and apparatus for
drilling through the cranial surface and inserting a catheter into the
anterior horn of the lateral ventricle of the human brain which optimizes
accurate and reproducible placement of the catheter.
Another object of the present invention is to provide a method and
apparatus for accurately and reproducibly perforating the patient's skull
and inserting a catheter through the cranial surface into the anterior
horn of a lateral ventricle of the patient's brain in a manner which
prevents insertion of the catheter into the cerebral matter or
subarachnoid space.
A first embodiment of the present invention comprises an apparatus for
drilling a hole in a human cranium at an angle of substantially 90.degree.
to a surface portion thereof. The apparatus comprises a guide member to
direct and align a drill for cutting through the substrate at a proper
angle, i.e., substantially 90.degree. to a plane defined by a tangent to
the substrate during the perforation thereof. The apparatus further
comprises a drill which is insertable within an open bore portion of the
drill guide member, which is operable to perforate the substrate. A
catheter guide member, having an open bore portion with a diameter reduced
in relation to the bore of the drill guide member, is insertable within
the open bore portion of the drill guide member upon removal of the drill
therefrom so as to effectively reduce the diameter of the drill guide
member. Subsequently, fluid transport means, such as a catheter, may be
inserted through the catheter guide member and thereafter into a
ventricular portion of the patient's brain, in order to, for example,
drain or shunt CSF therefrom or for the instillation of pharmacological
therapeutic agents.
The apparatus may also include means for preventing penetration of said
drilling means beyond a predetermined distance into said cranium.
A further object of the present invention is the correct placement of fluid
transport means within this ventricular portion. Further, the fluid
transport means described above may be a catheter which is adapted for the
passage of fluid therethrough.
The drill guide member of the embodiment comprises a tube adapted to
receive and guide the catheter therethrough and a support for the tube.
This support is adapted to rest unsecured on the patient's cranium in
surrounded spaced relation to the orifice. The support and the tube are
related to each other and to the cranium so as to guide the catheter
through the orifice and in a direction perpendicular to a plane defined by
a tangent to the cranium at the orifice, independent of the orientation of
the orifice. An insert within the tube, forming a catheter guide member,
is adapted to be in guiding engagement with the catheter while the free
end of the catheter is inserted into the ventricle of the brain.
Advantageously, this catheter guide at least partially extends into the
orifice which has been formed in the cranium.
The support may comprise a plurality of legs, each leg terminating in a
free end. The free ends of these legs form a polygon defining a plane and
the tube portion guides the catheter through the orifice in a direction
perpendicular to this plane defined by the polygon and through the
geometric center thereof. In a preferred embodiment, the legs are three in
number and of equal length. Therefore, a polygon, i.e, a triangle formed
by the free ends of these legs is an equilateral triangle. Further, the
support may be connected to the tube through a connecting platform.
Preferably, the guide as described above should be constructed of a rigid,
non-deformable material such as as thermoplastic or stainless steel.
Another embodiment of the invention comprises a method for drilling an
orifice in a human cranium at an angle at substantially 90.degree. to a
plane defined by a tangent to the cranium at the orifice and subsequently
inserting a catheter into a ventricular portion of the brain within the
cranium. The method initially comprises positioning a drill guide upon a
portion of an outer surface of the patient's cranium such that an open
tubular portion of the drill guide is oriented at an angle of
substantially 90.degree. to a plane defined by a tangent to the cranium at
the orifice. The drill guide, as described above, comprises a tube and a
support therefore.
The method further comprises drilling an orifice in the cranium by drilling
means proximally anterior to a coronal suture in a midpupillary line of
the cranium. The orifice extends through the cranium at an angle of
substantially 90.degree. to a plane defined by a tangent to the cranium at
the orifice. A catheter guide is thereafter inserted into the open tubular
portion of the drill guide so as to render the diameter of the drill guide
more consistent with that of a standard catheter. A catheter is
subsequently guided through the the open portion of the catheter guide and
thereafter through the orifice in a direction perpendicular to a plane
defined by a tangent to the cranium at the orifice. Through the use of the
present invention, therefore, the catheter accurately penetrates the
ventricular portion of the brain upon the first insertion.
In a further embodiment of the invention, the method additionally comprises
supporting the drill guide by a support comprising a plurality of legs.
The legs are preferably three in number, each terminating in a free end.
The free ends thus form a triangle defining a plane. An alternate
embodiment of the invention comprises guiding the catheter through a
catheter guide inserted within the drill guide and into the orifice and
into the ventricular portion of the patient's brain in a direction
perpendicular to the plane defined by the triangle formed by the legs of
the support and through the geometric center thereof.
The drilling of the cranium can be performed manually, pneumatically,
electrically or hydraulically by use of suitable drilling means. Also, the
method includes the step of limiting the depth of penetration of the
drilling means to a predetermined distance within the cranium by providing
stop means on the drilling means for contacting the drilling guide means.
BRIEF DESCRIPTION OF THE DRAWINGS
The method and apparatus of the present invention will now be described
with reference to the accompanying drawing figures, in which:
FIG. 1 is a side elevational view of applicants' drill guide;
FIG. 2 is a lower plan view of a base portion of applicants' drill guide;
FIG. 3 is a side elevational view of applicants' twist drill and handle
assembly;
FIG. 4 is a top plan view of applicants' twist drill handle;
FIG. 5 is a side elevational view of applicants' catheter guide, configured
for insertion into the drill guide of the invention;
FIG. 6 is a sectional view illustrating the insertion of applicants' twist
drill within the drill guide;
FIG. 7 is a sectional view illustrating the placement of applicants'
catheter guide within the drill guide of the invention; and
FIG. 8 is a view, partially in section, illustrating the usefulness of
applicants' device for the insertion of a catheter into the lateral
ventricle of a human brain.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Turning initially to FIG. 1 there is illustrated member 10 for controlling
and directing a twist drill device (see FIGS. 3 and 4) during the
formation of a burr hole through the cranium of a patient. The initial
function of member 10 is to control the drill during the perforation of
the cranium, thus preventing the bit from skipping on the bone or the
scalp, especially at the start of the drilling procedure.
Member 10 may be seated, for example, directly upon the scalp of the
patient, above an incision therein measuring on the order of from about
1-2 millimeters. Since, however, the skin of the scalp is loose and prone
to movement relative to the cranial bone, the placement of member 10 in
one position throughout the operative procesure serves to provide a means
for readily locating the burr hole located beneath the incision. Since the
diameter of the catheter placed within the burr hole ranges between only
about 2-3 millimeters, the hole in the cranium need not be much greater in
size, if at all, and it may therefore be difficult to relocate without the
assistance of guide member 10.
Alternately, in the event a larger incision is made and member 10 is seated
directly upon the surface of the skull, its legs spread apart the
surrounding scalp tissue and prevent such tissue from being gathered or
drawn to the drill bit during the operation, thus protecting the scalp
from injury. Member 10 is thus preferably constructed of a rigid,
non-deformable material such as a rigid engineering plastic or a metal
such as stainless steel in order to fulfill these functions. The entire
apparatus may be manufactured inexpensively from a plastic material, as a
disposable assembly, thus reducing the cost of the assembly and assuring a
sharp, sterilized drilling device for each operation. The availability of
such a pre-sharpened, sterilized drilling device also serves to reduce the
time required to complete each operation.
As shown in FIGS. 1 and 2, member 10 further comprises platform 12.
Extending from platform 12 in a diverging manner are three legs 14, which
terminate in free ends 16. Free ends 16 of legs 14 define a triangle lying
within a defined plane.
Member 10 further includes guide means for guiding the drill in a direction
perpendicular to the plane defined by the triangle formed by legs 14 and
through the geometric center thereof. The guide means comprises a tubular
member 18 extending through platform 12 in a direction perpendicular to
the triangular plane described above.
Tubular member 18 is hollow, defining a central lumen to permit the passage
therethrough of a drilling device (described below). The diameter of this
lumen is not critical but it must, at a minimum, be sufficient to permit
the passage of the drill. When member 10 is placed on the patient's
cranium with the free ends 16 of legs 14 resting thereupon, the plane of
the triangle defined by free ends 16 coincides with a plane tangent to the
cranial surface directly below tubular member 18.
Accordingly, member 10 directs the drilling device perpendicular to this
tangential plane, ensuring the production of a burr hole through the
cranial bone at an angle of 90 degrees to the surface of a plane tangent
to the cranium. This alignment assures that a ventricular catheter,
inserted into the brain in a direction perpendicular to the curvature of
the cranium, will not deviate from a preferred course due to a misaligned
skull hole. As noted above, if the orientation of the bore hole deviates
by more than about 7 degrees from the perpendicular to a plane tangent to
the cranium at the point of insertion of the catheter, the catheter is
much more likely to be misaligned and to miss the ventricular portions of
the brain entirely.
Preferably, legs 14 of member 10 are of equal length, equidistantly spaced
and symmetrically disposed relative to each other, whereby the free ends
16 define an equilateral triangle. Guide means 18 directs the drill
perpendicular to the plane defined by this equilateral triangle at the
geometric center thereof and hence, perpendicular to the tangent plane
upon the surface of the patient's cranium.
It is, however, nevertheless possible to practice the invention with a
member 10 having an asymmetric arrangement of legs 14, as long as the
guide means, i.e., tubular member 18, of member 10 extends perpendicularly
to the plane defined by the free ends 16 of legs 14 and the member 10 is
placed on the cranial surface such that this plane coincides with a plane
tangent to the cranium at the orifice.
Similarly, the invention may be practiced with a guide member 10 having
more than three legs, as long as the above-described directional criteria
are maintained. Additionally, while tubular member 18 is illustrated as
being cylindrical in shape, any shape which allows an unencumbered passage
of the drill therethrough may be employed.
FIG. 2 is a bottom plan view of member 10, further illustrating the
perpendicular intersection of guide means 18 with the plane of the
triangle defined by free ends 16 of legs 14.
While the preferred embodiment of member 10, as described above, includes
platform 12 for connecting legs 14 to tubular member 18, platform 12 is
not an essential element of member 10. Thus, legs 14 may be connected
directly to tubular member 18 as long as tubular member 18 guides the
drill in a direction perpendicular to the plane of the triangle formed by
the free ends 16 of legs 14 and through the geometric center of this
triangle.
The height of member 10 and the distance between free ends 16 of legs 14
may be varied, as long as the following principles are observed. First,
the base portion of member 10 must preferably form an equilateral triangle
defined by free ends 16 of legs 14. Secondly, a line passing through the
central lumen of tubular member 18 must be normal to the plane of the
triangle thus defined and must pass through the geometric center thereof.
Furthermore, the internal diameter of the central lumen may be varied, as
long as the lumen is constructed of a sufficient width to accept
applicants' twist drill.
Preferably, the distance between free ends 16 of legs 14 ranges from about
1 cm to about 6 cm. The lower limit is established based on the smallest
burr hole or orifice necessary for passing a catheter therethrough. These
catheters may range from about 2-3 millimeters in diameter. The upper
limit is established based on the change in skull curvature which occurs
when the midline of the skull is crossed.
Specifically, since the orifice or burr hole is drilled generally from
about 2 cm to about 3 cm from the midline, an upper limit of about 6 cm is
preferred so that one or more legs do not rest on the skull at a point
beyond the midline where the skull curvature has changed. This would place
member 10 at such an angle that tubular member 18 would not be directed
normal to the imaginary plane defined by a tangent to the orifice at the
point of entry.
The specific height of member 10 is also not a critical parameter. A
preferred height range is about 2 cm to about 10 cm. The lower limit is
established on the basis of the usual length of a catheter (15 cm) minus
the standard intracranial distance to the ventricle (5 cm).
Although the member 10 of the present invention has been illustrated with
three legs 14, this is not a critical limitation. For example, member 10
of the present invention may be constructed with four legs. In such an
embodiment, the free ends of each of the four legs define the corners of a
polygon such as a square or rectangle and the axis of tubular member 18
passes through the geometric center of the square or rectangle, wherein
the axis is normal to the plane thereof.
Turning now to FIG. 3 there is illustrated applicants' twist drill device
20 comprising handle 22, shaft 24 and drill bit 26. Drill 20 must be
constructed of a material such as steel having a high degree of structural
strength, so as to facilitate the penetration of the patient's cranium
thereby. However, handle 22 may be formed of a different material, such as
a rigid plastic, since it serves as a grip for drill 20 and does not
penetrate the bony surface of the skull. Although applicants' device is
depicted as a hand-operated twist device, various other drills, such as
pneumatic drilling devices may be utililized and the invention should thus
not be limited to the embodiment illustrated herein.
Drill 20 is further provided with a number, i.e., preferably three, of
spacer rings 21 which are preferably "C"-shaped, but which may be circular
or of some other alternate shape and whose open portion engages shaft 24.
The purpose of spacer rings 21 is to prevent the penetration of drill 20
past a predetermined distance into the patient's cranium. As drill 20
penetrates the cranium at a certain depth, a lower surface of lower ring
21 contacts the upper portion of tubular member 18 and thus prevents
further passage of drill 20 therethrough until at least one ring member 21
is removed. Rings 21 may preferably be fabricated of plastic and each is
approximately 1 cm in thickness. They may either be constructed as
separate units, or alternately, they may be produced as a single unit
having a perforated portion 23 at various positions along the width, e.g.,
preferably 1 cm apart. This permits 1 cm thicknesses of ring 21 to be
snapped off and removed from drill shaft 24, thus permitting shaft 24 of
drill 20 to travel deeper into member 10 in the event that the patient's
cranium is thicker than originally anticipated.
In the event, therefore, that a patient is to undergo a ventriculostomy
procedure, guide 10 is seated upon the patient's scalp over a small
incision made therein or, alternately, directly over the skull itself.
Shaft 24 of drill 20 is then inserted into tubular member 18 of | | |
