Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1 BACKGROUND OF THE ~NVENTION
This invention rel~tes to a valve in a surgically
implanta~le shunt system for venting cerebrospinal fluid (CSF)
from a cerebroventricular catheter to a drainage catheter and
more particularly to such a valve for presenting a precisely
controllable back pressure to the cerebral ventricles in case of
hydrocephaly and similar conditions of irnpaired circulation and
absorption of cerebrospinal fluid.
Mechanical devices for controlling the drainage of
cerbrospinal fluid into the bloodstream are in use, an example
of which is the shunt device of U.S. Patent 3,288,142. These
devices include valves such that the flow is unidirectional from
the ventricles to drainage into the circulatory system. ~ile
quite successful, such valves are relatively expensive and dif-
ficult to fabricate. These prior valves are also somewhat heavy
and bulky, their metal parts interfering, for example, with x-
ray scanning procedures. Previously known devices also sometimes
become clogged with brain debris or with CSF protein when ele-
vated to abnormally high levelsO This is particularly true of
~ so-called slit valves which have been used for this purpose,
e.g., valves which are merely a thin slit in a silastic tube.
Such debris can prevent the valve from sealing properly, thereby
` degrading its ability to regulate closely the back pressure pre-
sented to the cerebral ventricles. Wide hysteresis between
` opening and closing pressures has been another shortcoming of
known shunt valves for use in treating hydrocephaly, i.e., there
has not been a well defined "popping" pressure at which pressure
the valve opens.
Testing of known valves has been accomplished pre-
viously by subjecting the valves to a vacuum or a gas pressure,
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1 or even exposure to a liquid environment. These methods arecumbersome, time consuming and often foul the valve in the test-
ing process.
An object of this invention, therefore is to develop
a simple, highly reliable cerebroventricular shunt valve which
is compact, light in weight, minimally opaque to ~-rays, and
inexpensive to manufacture.
Another object is to produce a shunt valve having low
hysteresis and low susceptibility to clogging with debris,
0 enabling it to present a precisely controllable back pressure to
the cerebral ventricles.
A still further ob~ect is to develop a method of
testing the sealing effectiveness of such a valve during manu-
facture ~y simple optical means.
Other objects, features and advantages of the present
invention will become apparent in what follows.
SUM~RY OF THE INVENTION
Accordlng to the present invention, a valve for preci
~ sely controlling the back pressure presented to the cerebral
ventricles in a hydrocephalus shunt device has an elongate,
hollow valve body internally partitioned so as to form an inlet
~` chamber and an outlet chamber. The inlet chamber is coupled to
a ventricular catheter; the outlet chamber is coupled to a drain-
age catheter. The valve is designed for use in a hydrocephalus
` treatment sys-tem, for e~ample, as shown in Fig. 1 of applicant's
`" U.S. Patent 3,527,226. The internal partitioning is accomplished
~` by means of a thin, flat plate tightly fitting within the tubular
valve body. This plate is provided with a circular aperture
`- connecting the inlet and outlet chambers. A spherical ball ofdiameter larger than that of the aperture in the thin plate ser~
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1 ves to restrict the Elow through the aperture in a controlled
manner. A spring, including a cantilevered flat portion over-
lying the ~all and touching it at a single point biases it
against the circular periphery of the 1at plate aperture, effect-
ing when the valve is closed, a circular seal between the ball
and aperture. This arrangement provides a precisely defined
~ack pressure with low hyster~sisand low suscepti~ility to
clogging by de~ris.
The effectiveness of the valve seal is tested during
manufacture by optical means. Light energy at a wavelength for
which the ~all is opaque is directed upon the aperture with ball
in place. Absence of light leakage indicates a properly sealing
valve.
RRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be better understood h~
reference to the following drawing in which:
Fig. l is a longitudinal sectional view of the valve
device;
Fig. 2 is a sectional view of the valve device along
section lines 2~2 of Fig. l;
Fig. 3 is an edge view of the flat plate portion of
the valve device;
Fig. 4 is a pian view of the flat plate portion of the
` valve device; and
Fig. 5 is a schematic representation of the optical
method for testing the sealing effectiveness of the valve device.
Corresponding reference characters indicate correspond-
ing parts throughout the several views of the drawings.
DESCRIPTION OF THE PREFERRED EMBODIMF.NT
Referring to Figs. l and 2, the valve device 10 compri-
r3~
1 ses a hollow valve ~ody 11, prefera~ly made of injection molded
polyethersulfone plastic. Valve body 11 couples at its inlet
end to cerebroventricular catheter 12, and its outlet end with
drainage catheter 13 or with a pumping system, inc]uding a second
valve, i.e., in the manner shown in U.S. Patent No. 3,527,226.
Tightly fitting within valve body 11 is a thin, flat plate 14,
preferably made of stainless steel, which partitions valve body
11 into an inlet chamber 15 and an outlet chamber 16. In this
embodiment, thin plate 14 is 0.38 inch long, 0.14 inch wide and
Q.01 inch thick. A highly polished circular aperture 17 of
diameter 0.057 inch is cut through flat plate 14 thereby con-
necting inlet chamber 15 and outlet chamber 16 providing a flow
path for cere~rospinal fluid from the cerebral venticles to
drainage into the circulatory system. As can be seen more
clearly in Fig. 3, circular aperture 17 in flat plate 14 has a
coined rim 18, the radius of curvature of which matches the
radius of spherical ball 19, thereby providing a seat for ball
19. In this embodiment, the radius of curvature of rim 18 is
approximately o.O31 inch. The combination of valve body 11 and
thin plate 14 allows this shunt valve to be light in weight,
compact and inexpensive to manufacture.
Spherical ball 19 for controllably restricting flow
~: through the valve is a highly polished hard material, preferably
~` synthetic sapphire, having a diameter of o.062 inch which is
larger than the diameter of aperture 17 ~o that it rests against
coined rim 18 of aperture 17 without passing through, thereby
forming a seal. The highly polished surfaces of ball 19 and
aperture 17 ensure an effective seal when ball 19 is seated, and
furthermore, lessen any tendency for the ball to become stuck
in the seated position, so enabling a precisely defined and
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1 repeatable opening pressure.
Referring now to Fig. 1 and Fig. 4, flat spring 20,
having a semicircular bend, is attached to flat plate 14 at 21
hy spot welding or other suitable means. The constant of the
spring 20 may be varied ~y altering its width or thickness,
thereby allowing for valves with different op~rating pressures.
Spring 20, parallel to the plane of aperture 17, overlies ~all
19, touching it at essentially a single point and biasing it
against rim 18 of aperture 17. This arrangement achieves a
narrow hysteresis between ope~ing and closing pressures. When
the valve is open, ball 19 is able to spin freely because of the
point contact with spring 20, discouraging the accumulation of
debris and permitting close regulation of the back pressure
presented to the laterial ventricles.
;~ Valve 10 is assembled by insertiny the flat plate-ball-
.
` spring assembly into valve body 11 from the right side of Fig. 1.
The contour of chamber 16 is such that ball 19 will remain with-
` in aperture 17 after assembly. That is, shoulder 28 limits the
extension of spring 20, thereby assuring that ball 19 cannot
become dislodged from aperture 17.
~`~` In Fig. 5, the method of testing the sealing charac-
teristics of the shunt valve disclosed herein is illustrated.
` Light source 25 illuminates one side of flat plate 14 with the
ball 19 seated. The wavelength of the light from source 25 is
selected so that ball 18 is opaque. With a sapphire ball, for
` example, green light is appropriate. A light detector 26 is
` arranged on the opposite side of flat plate 14 to detect: any light
-
which passes through aperture 17 of flat plate 14. Absence of
light reaching the detector indicates a properl~ sealing valve.
Although in this em~odiment injection molded polyether-
3~
1 sulfone plastic has been used for valve body 11 and stainless
steel for flat plate 14 and spring 19, it ls obvious that other
stable, essentially inert and non-toxic materlals could be uti-
lized. Similarly, although synthetlc sapphire is the pre~erred
material for ball 19, other hard, non-toxic and inert materials
could be substituted.
The disclosed valve is, therefore, compact, light in
weight, inexpensive to manufacture and simple to assemble. More
importantly, the valve achieves a tight regulation of the
cerebrospinal fluid pressure within the cerebral venticles.
While the above describes and illustrates a preferred
~ embodiment of the invention, it is to be understood that the
; invention is not so limited/ but covers all modifications which
should be apparent to one skilled in the art and falling within
the scope of the invention.
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SUPPLEMENTARY DISCLOSURE
In addition to the subject matter described in the
principal disclosure, this invention includes valves according
to further embodiments of the invention.
These further embodiments relate to the difficulty
of establishing the desired pressure at which the valve opens.
Accordingly, another object of the invention is to
provide a shunt valve which allows its operating pressure to
be set very accurately.
Still anothex object is a shunt valve whose operating
pressure may be continuously adjusted.
Yet another object of this invention is a shunt valve
whose operating pressure is readily adjustable at the time of
implantation and which is consistent and repeatable.
A still further obJect of this invention is a shunt
valve whose operating pressure is substantially insensiti~e
to changes in viscosity of the cerebro-spinal fluid.
In one embodiment of the invention, the flat plate has
a struck up rear portion which presses against the spring for
adjusting the back pressure of the valve. In another embodiment,
a screw threadably supported by the valve body, presses against
the cantilevered portion of the spring permitting the back
pressure of the valve to be accurately adjusted.
In yet another embodiment of the invention disclosed
herein~ the spring includes a central portion extending from a
rear end of the spring and adapted for overlying the ball, and a ;~
pair of arms flanking the central portion and extending from the
rear end of the spring. The ends of these arms are attached to
the flat plate. A screw supported by the flat plate is posi-
- 30 tioned for engaging the rear end of the spring so that the
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1 openiny pressure of the valve can be accurately ad~usted. In
this embodiment the flanking arms may be splayed apart and also
extend beyond the central portion of the spring. In still
another embodiment, the spring comprises a first spring portion
overlying the ball and a second portion haviny a first and a
second end. The second end is attached to the flat plate and the
first spring portion is attached to the second spring portion
near its second end. A screw supported in the $1at plate is
adapted to engage the first end of the second spring portion so
that the opening pressure of the valve can be adjusted.
Alt~rnatively, the valve includes a spring having a first portion
overlying the ball and a second portion which includes a semicir-
cular bend. The lower portion of the second portion is affixed
to the flat plate and the first portion of the spring attached
to the upper surface of the second portion. In addition, a screw
is provided to engage the second portion for adjusting the
; opening pressure of the valve.
Fig. 6 is a perspective view of another embodiment of
this invention;
Fig. 7 is a perspective yiew of yet another embodiment;
Fig. B is a sectional view along section lines 8-8 of
Fig. 7;
Fig. 9 is a perspective view of yet another embodiment
of the invention disclosed herein;
Fig. 10 is a side view of the embodiment of Fig. 9;
` Fig. 11 is a plan view of the spring assembly of
Figs. 9 and 10;
Fig. 12 is a plan view of another embodiment of the
spring assembly adapted for use with the embodiments of
Figs. 9 and 10;
Fig. 13 is a plan view of yet another embodiemnt of the
spring assembly disclosed herein;
FigO 14 is a side view of yet anothPr embodiment of the
spring assembly of this invention;
Fig. 15 is a side view OL another embodimen~ of the
spring assembly disclosed herein.
Reference is made to Fig. 6 which shows an embodiment
of the invention which provides for adjusting back pressure
other than by selecting the width or thickness of the bolt-
biasing spring. In Fig. 6, a flat plate 60 has a struck uprear portion 61 which presses against the semicircular bend in
a spring 62. To establish a desired value of back pressure,
the spring 62 is first attached to flat plate 60 at 63 by spot
welding or other suitable means. The struck up portion 61 is
then forced ~by means of a conventional tool not shown3 beyond
` its elastic limit so as to take a set against the spring 62.
The spring constant of the spring 62 is thereby altered
depending on the degree to which the struck up portion 61 is
deformed to press against the semicircular ~end in the spring 62.
Thus, by adjusting the level oE force with which the struck up
portion 61 engages the spring 62, the operating back pressure
of a valve incorporating the elements depicted in Fig. 6 may be
very precisely set. An alternative way of accurately establishing
a desired back pressure will now be described, still with
reference to Fig. 6. Instead of first attaching the spring 62
to the flat plate 60, the struck up portion 61 is put into place,
for example, oriented perpendicularly to the flat plate 60. The
semicircular bend of spring 62 is then forced against the
struck up portion 61 while the spring's operating pressure is
continuously measured by conventional means. When the desired
` operating back pressure is attained, the spring 62 is then
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1 secured to the flat plate 60, as by spot welding at 63. The
use of a struck up portion of the flat plate to adjust operating
pressure is superior to attempting to alter operating pressure
by deforming the spriny 62 itself. This is the case because
` the thin spring material, having a large elastic limit, is
difficult to deform with precision so as to achieve a desired
operating pressure.
Yet another embodiment of the inv~ntion allowing for
accurate setting of the operating back pressure is shown in
Figs. 7 and 8. A base portion 70 of a spring 71 is attached, as
by spot welding, to a flat plate 72. The base portion 70 has
a hole 73 through which passes a screw 74O The screw 74 rests
against an enlarged section 75 of the spring 71. The spring 71
also includes a wider, relatively stiff part 76 and a narrower
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section 77 which overlies a ball 80. As can be-seen in Fig. 8,
the screw 74 is threadably supported in a valve body 87 so that
by inserting a tool (not shown) into a slot 78, the screw 74 may
be rotated to adjust the degree to which it presses on the
enlarged section 75 of the spring 71. In this way, the
"popping" pressure of the ball 80 in an aperture 81 may be
very accurately adjusted. In thls embodiment, the operating
pressure can be varied as desired during the operating lifetime
of the valve.
Still another embodiment of the invention is illustrated
in Figs. 9,,lQ and 11. A spring assembly 90 includes a central
portion 92 which overlies a ball 94 shown in phantom. Flanking
` either side of the central portion 92 are arms 96 and 98
which are attached to a flat plate 100 by spot welding or other
suitable means at locations 102 and 104. It is preferred that
the spring assembly 90 be made from a single piece of material
-- 10 --
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588
such as stainless steel. It is also preferred that the central
portion and the flanking arms be created by photo-etching rather
than some other process such as stamping. By means of a photo-
etching process no strains are introduced into the spring
material in the process o~ creating the central portion and
flanking arms. In this-way the repeatability of the opening
pressure of the shunt valve is assured. As can be seen clearly
in Fig. 10 a screw 106 is provided in flat plate 100 to engage
the rear portion of the spring assembly 90. As the screw 106
is rotated, the rear portion of the spring assembly 90 moves up
or down. In this way the opening pressure of the valve can be
adjusted very accurately because changes in the elevation of the
rear portion of the spring assembly 90 effect very small changes
; in the opening pressure. By this arrangement, relativel~ large
motions of the screw 106 cause small variations in opening
- pressure so that its value can be set as desired.
`; Fig. 12 illustrates another embodiment of a spring
assembly adapted for use with a shunt valve as disclosed herein.
In this embodiment a spring assembly 110 includes flanking arms
112 and 114 which are splayed apart from a centr~l member 116.
By this arrangement a stiffer spring assembly is created.
Fig. 13 shows another important embodiment of the invention herein.
In this embodiment flanking arms 120 and 122 extend beyond the
central portion 124. It is preferred that the length Lo of the
central portion 124 be approximately two-thirds the length L of
the flanking arms 1~0 and 122. With such a geometrical relation-
ship, as a screw such as 106 in Fig. 10 is moved up and down,
the portion o~ the central member 124 which overlies the ball
will simply rotate, there being no tendancy for this portion to
translate across the top of the ball 94~ In this way the opening
-- 11 --
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1 pressure of the valve is highly repeatable since khere will be
substantially no forces other than those pushiny the ball down-
ward towards its seat.
For the embodiments of Eigs. g-13, an approximate
relationship has been derived relating the forces on the ball to
the force produced by the screw acting on the rear of the spring
assembly. For a homogeneous spring this relationship is
W:L LoWL2
, Z = -- - - O
3EI 2EI
In this equation, Z is the force biasing the ball into i~s seat,
W is the upward force on the rear of the spring assembly due to
the adjustable screw, L and Lo are as described with referenca
to Fig. 13, E is Young's modulus of the spring, and I is the
cross-sectional moment of inertia of the spring.
Other embodiments of the invention disclosed herein are
found in Figs~ 14 and 15. In Fig. 14 a spring assembl~ 130
includes a first portion 132 which is affixed as by spot welding
to a flat plate 134 at the location 136. Attached to the portion
132 is a spring portion 138 which overlies a ball 140. A screw
142 is adapted for passing through the flat plate 134 and
engaging the spri~g member 132 at its front end. As is apparent,
as the screw 142 moves up and down, the ~orce which the portion
138 applies to the ball 140 is varied. Similarly, in Fig. 15
a first spring portion 150 is semicircular in shape and attached
to a flat plate 152 at the location designated 154. A second
spring portion l56 is attached to the upper portion of the member
150. A screw 158 is adapted for engaging the front portion of
the spring portion 150 so as to adjust the force that the spring
portion 156 applies to a ball 160. In both of the embodiments
illustrated in Fig. 14 and Fig. 15 the sensitivity of opening
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1 pressure to screw position is reduced b~ the geometrical arrange-
ments so that opening pressures can be set very precisely.
The embodiments illustrated in Figs. 9~15 thus enable
the opening pressure of the shunt valve to be adjusted very
;accurately. Bécause in these embodiments sensitivity of opening
pressure to screw location is reduced by the spring arrangements,
accurate settings can be made just before the shunt valve is
installed by the surgeon. This arrangement may also allow
changes in opening pressure to be effected after the shunt valve
has been installed.
As mentioned in the principal disclosure, the ball 19
may be made out of hard, non-toxic and inert materials other
than synthetic sapphire, and one such material which is preferred
is ruby.
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