Implantable adjustable fluid flow control valve

A subcutaneously implantable and percutaneously adjustable fluid flow control device includes a magnetically adjustable valve for controlling fluid flow from an inlet to an outlet. The valve includes a housing having a fluid passageway therethrough, a valve element designed to bear upon a valve seat to close the passageway to fluid flow, and a spring which biases the valve element against the valve seat so as to keep the passageway closed until a fluid pressure differential between the inlet and the outlet exceeds a selected valve opening pressure. A fixed dual concentric stair-step array and an overlying rotor assembly permit the amount of bias applied to the valve element by the spring to be adjusted. The rotor assembly is adapted to rotate in response to an external or percutaneously-applied magnetic field. In one embodiment, the rotor assembly may be locked into one of several possible rotational positions relative to the stair-step array to prevent rotation thereof.

BACKGROUND OF THE INVENTION 
This invention relates generally to surgically implanted physiological 
shunt systems and related flow control devices. More particularly, the 
present invention relates to shunt systems including one-way flow control 
valves for controlling the flow of cerebrospinal fluid out of a brain 
ventricle and preventing backflow of fluid into the brain ventricle. 
In the medical arts, to relieve undesirable accumulation of fluids it is 
frequently necessary to provide a means for draining a fluid from one part 
of the human body to another in a controlled manner. This is required, for 
example, in the treatment of hydrocephalus, an ailment usually afflicting 
infants or children in which fluids accumulate within the skull and exert 
extreme pressure and skull deforming forces. 
In treating hydrocephalus, cerebrospinal fluid accumulated in the brain 
ventricles is typically drained away utilizing a drainage or shunt system 
including a catheter inserted into the ventricle through the skull, which 
is connected to a tube that conducts the fluid away from the brain to be 
reintroduced into the peritoneal cavity or into the vascular system, as by 
extending a distal catheter through the patient's jugular vein to the 
atrium portion of the heart. To control the flow of cerebrospinal fluid 
and maintain the proper pressure in the brain ventricle, a pump or valve 
is placed in the conduit between the brain and the peritoneal cavity or 
the heart. An exemplary flow control device is found in U.S. Pat. No. 
4,560,375. 
Although such drainage systems have provided successful results, a problem 
of overdrainage of the cerebrospinal fluid from the brain ventricles 
sometimes exists. Overdrainage of cerebrospinal fluid may result in 
excessive reduction of the cerebrospinal fluid pressure within the brain 
ventricles and predispose the development of a subdural hematoma or 
hydroma, and excessive reduction of ventricular size leading to shunt 
obstruction because of impingement of the ventricular walls on the inlet 
holes of the ventricular catheter. This overdrainage can be caused by the 
siphoning effect of hydrostatic pressure in the distal shunt catheter. The 
siphoning effect of hydrostatic pressure may be created by the elevation 
of the ventricular catheter inlet with respect to the distal catheter 
outlet (i.e., when the patient sits, stands or is held erect). In order to 
prevent such overdrainage caused by the siphoning effect of hydrostatic 
pressure in the distal shunt catheter, siphon control devices have been 
placed in the conduit, typically between the flow control device and the 
peritoneal cavity or the heart. An exemplary siphon control device is 
found in U.S. Pat. No. 4,795,437. 
It is desirable in some instances to permit the physician to be able to 
alter the flow characteristics through the drainage system after it has 
been subcutaneously implanted. To this end, on-off devices have been 
provided for implantation as a portion of the fluid conduit as an 
additional element of the shunt. An exemplary on-off device is shown in 
U.S. Pat. No. 3,827,439. Moreover, flow control devices have been provided 
which utilize a plurality of flow control valves having different flow 
control characteristics, which provide,alternative fluid pathways 
therethrough such that selection of a desired fluid pathway can be made by 
the selective percutaneous manipulation of the device when subcutaneously 
implanted. Such flow control devices having selectable alternative fluid 
pathways are shown in U.S. Pat. Nos. 5,154,693 and 5,167,615, the contents 
of which are incorporated herein. 
These prior fluid shunt devices have all shared one important limitation: 
they only permit fluid flow therethrough upon achieving at most two fluid 
pressure differentials at the inlet and outlet of the device. In treating 
hydrocephalus, however, it is often desirable to vary the device "opening" 
pressure differential in accordance with ventricle size and treatment 
objective. For example, initial treatment may require a lower than normal 
pressure differential to initiate shrinkage of the ventricles, but as the 
ventricles decrease in size, the pressure differential should be increased 
gradually so that when the ventricle is returned to normal size the 
intraventricular pressure is at its normal value and the intracranial 
force systems are in balance (i.e., the opening differential pressure is 
set at a level that will stabilize the ventricles at a desired size). 
Generally speaking, the opening differential pressure should be varied 
inversely with the ventricle size. It is desirable to leave a lower 
pressure valve in a patient after the ventricles are again normal size, 
because the ventricles can further collapse, leading to a condition known 
as "slit" ventricles. 
A further reason for providing adjustability in the opening pressure 
differential is to correct for variations in nominal opening pressure 
differentials typical in manufactured valves. With an adjustable valve, 
the opening pressure differential can be more accurately set at the 
factory and can be checked and corrected if necessary in the operating 
room prior to implantation. 
Accordingly, there has been a continuing need in the medical arts for 
convenient and effective physiological drainage systems for controlling 
the flow of fluid from one part of the body to another, which are 
relatively inexpensive to manufacture, permit fluid flow therethrough only 
when upstream fluid pressure exceeds downstream fluid pressure by a 
selected pressure differential, and also provide means for altering the 
selected pressure differential by percutaneous manipulation of the device 
when it is subcutaneously implanted. Moreover, such a flow control device 
is needed which incorporates an integral siphon control device that opens 
only in response to positive upstream fluid pressure, and recloses or 
remains closed in the absence of such positive upstream fluid pressure or 
in response to negative downstream hydrostatic pressure on the device. As 
will become apparent from the following description, the present invention 
satisfies these needs and provides other related advantages. 
SUMMARY OF THE INVENTION 
The present invention resides in an improved subcutaneously implantable and 
percutaneously adjustable fluid flow control device useful in a 
physiological shunt system for controlling the flow of fluid from one part 
of the body to another. The fluid flow control device of the present 
invention includes components responsive to an external or 
percutaneously-applied magnetic field, to provide the device a variety of 
pressure/flow characteristics. In accordance with the present invention, 
the fluid flow control device comprises an inlet, an outlet and valve 
means for controlling the fluid flow from the inlet to the outlet. The 
valve means comprises a valve housing including a fluid passageway 
therethrough which has a peripheral surface that forms a valve seat, and a 
valve element having a diameter larger than the valve seat. Means are 
provided for biasing the valve element against the valve seat so as to 
keep the fluid passageway closed until a fluid pressure differential 
between the inlet and the outlet exceeds a selected valve opening 
pressure. Further, a pump is situated between the inlet and the valve 
means. The pump provides means for flushing fluid through the device by 
the application of percutaneous pressure to the pump. 
In one preferred form of the invention, the valve housing includes a 
threaded aperture and a flow regulator insert which is threaded into the 
aperture to define the fluid passageway. Means are provided for adjusting 
the amount of bias applied to the valve element by the biasing means. In 
particular, the adjusting means includes a fixed dual concentric 
stair-step array and an overlying rotor assembly having a first surface 
which supports an end of a valve element-biasing spring, and a second 
surface which is supported by the stair-step array. The rotor assembly is 
adapted to rotate in response to an external or percutaneously-applied 
magnetic field and such rotation of the rotor assembly permits selected 
seating of the second surface on the stair-step array to raise or lower 
the rotor assembly with respect to the stair-step array. 
The dual concentric stair-step array includes a central rotor pivot, a 
plurality of inner steps surrounding the rotor pivot, and a plurality of 
outer steps extending peripherally about the inner steps. The rotor 
assembly includes a magnet embedded within a base having an inner leg 
adapted to bear against a selected one of the plurality of inner steps, 
and outer leg disposed diametrically opposite the inner leg and adapted to 
bear against a selected one of the plurality of outer steps, a central 
aperture through which the rotor pivot extends, and a rotor cap fixed to 
the base on a side thereof opposite the inner and outer legs. The rotor 
cap provides the first surface of the rotor assembly and includes a 
central aperture aligned with the central aperture of the base, through 
which the rotor pivot extends. 
A compression spring is provided between a portion of the valve housing 
surrounding the fluid passageway and the first surface of the rotor 
assembly. The compression spring biases the rotor assembly into contract 
with the dual concentric stair-step array. 
Means are also provided for occluding a portion of the fluid flow control 
device adjacent to the inlet by application of manual percutaneous 
pressure to the device. Similarly, means are provided for occluding a 
portion of the fluid flow control device adjacent to the outlet also by 
application of manual percutaneous pressure to the device. Moreover, a 
siphon control device is situated between the valve and the outlet. 
In another preferred form of the invention, means are provided for locking 
the rotor assembly into one of several possible rotational positions 
relative to the stair-step array to prevent rotation thereof. Further, 
means are provided for disengaging the locking means to permit rotation of 
the rotor assembly in response to the external magnetic field. More 
particularly, the locking means comprises a pin having a first end that 
engages one of a plurality of detents in an outer peripheral surface of 
the rotor assembly to prevent rotation thereof. The disengaging means 
comprises pin actuating means for moving the pin between a first extended 
position, wherein the end of the pin engages one of the plurality of 
detents, and a second retracted position. The pin actuating means 
comprises a pivotable lever including a pin engaging shaft that engages a 
second end of the pin, and a manually actuated lever disposed within the 
pump and biased so as to urge the pin into its first position. 
Other features and advantages of the present invention will become apparent 
from the following more detailed description, taken in conjunction with 
the accompanying drawings, which illustrate, by way of example, the 
principles of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As shown in the drawings for purposes of illustration, the present 
invention is concerned with a subcutaneously implantable and 
percutaneously adjustable fluid flow control device, generally designated 
in the accompanying drawings by the reference numbers 20 (FIGS. 1-14) and 
20' (FIGS. 15-18). The improved fluid flow control devices 20 and 20' are 
intended for use in a surgically implanted physiological shunt system for 
draining fluid from one portion of the body to another. In order to 
connect, for example, the devices 20 or 20' in such a system, the devices 
include an inlet connector 22 and an outlet connector 24 which each 
receive one end of a piece of surgical tubing (not shown). The ends of the 
surgical tubing are placed over the connectors 22 and 24 and secured 
thereon by a single ligature just inside of an annular ridge 26 formed 
near the end of each connector. 
When the flow control devices 20 and 20' are used in a drainage system 
intended for the treatment of hydrocephalus, the inlet connector 22 is 
fluidly connected with a proximal catheter which is inserted through the 
skull into a brain ventricle containing cerebrospinal fluid under 
pressure. The outlet connector 24 is fluidly connected to a distal 
catheter which serves to discharge cerebrospinal fluid to, for example, 
the atrium portion of a patient's heart. Ordinarily the flow control 
devices 20 and 20' will be surgically implanted on the patient's skull 
with a flap of skin overlying the device. To facilitate holding the device 
in its desired position after implantation, a generally flexible mounting 
plate 28 can be provided with one or more suture holes. 
As will become apparent from the following description, the present 
invention provides a highly reliable fluid flow control device which has a 
single flow path therethrough and a valve mechanism which can be 
percutaneously adjusted when the device is subcutaneously implanted. The 
present invention is designed to facilitate implantation by eliminating 
components to be connected or adjusted other than the surgical tubing to 
the device itself. 
In accordance with the present invention, the flow control devices 20 and 
20' include a relatively rigid, molded plastic base invested within an 
elastomeric casing 30 which, together, define a fluid flow path through 
the fluid flow control devices from the inlet connector 22 to the outlet 
connector 24. The base comprises an inlet section 32 integrally formed 
with the inlet connector 22, an outlet section 34 integrally formed with 
the outlet connector 24, and an intermediate valve housing 36 disposed 
within the elastomeric casing 30 between the inlet and outlet sections 32 
and 34. The valve housing 36 includes a percutaneously adjustable valve 
mechanism which restricts the flow of fluid through the device 20 or 20'. 
The casing 30 and the outlet segment 34 of the base cooperate to provide a 
siphon control device 38 situated between the valve housing 36 and the 
outlet connector 24, which prevents fluid flow through the devices 20 and 
20' in the absence of positive upstream fluid pressure or in response to 
negative downstream hydrostatic pressure on the device. Further, the 
casing 30 and the inlet segment 32 of the base cooperate to define a pump 
or flushing reservoir 40 between the inlet connector 22 and the valve 
housing 36. 
More specifically, and as shown best in FIGS. 1-3, 15 and 16, the inlet 
segment 32 of the base abuts against a proximal side of the valve housing 
36 which, in turn, itself interfits with the outlet segment 34 of the 
base. The inlet segment 32 defines an inlet flow channel 42 extending 
through the inlet connector 22 to an upwardly facing inlet occluder port 
44. The inlet segment 32 of the base forms a bottom plate 46 for the 
flushing reservoir 40 and an abutment support for a portion of the valve 
housing 36. 
The valve housing 36 includes a snap-fit interlocking barbed connector 48. 
The barbed connector 48 extends from the valve housing 36 toward the 
outlet segment 34 of the base, and forms a valve outlet fluid passageway 
50 for directing fluids into the siphon control device 38. A pair of 
splines (not shown) extend from the valve housing 36 adjacent to the 
connector 48 and, together with the connector 48, interact with 
corresponding portions of the outlet segment 34 of the base to prevent 
tensile and torsional movement of the valve housing 36 and the outlet 
segment 34 of the base with respect to one another. 
The outlet segment 34 of the base is integrally formed with the outlet 
connector 24 which defines an outlet flow channel 52 therethrough. The 
outlet segment 34 defines a portion of the siphon control device 38. A 
connector receptacle 54 is provided in the proximal end of the outlet 
segment 34 for receiving the barbed connector 48 therein. Spline receiving 
slots (not shown) are provided in the proximal end of the outlet segment 
34 to slidably receive and substantially envelope the splines as the 
connector 48 is inserted into the receptacle 54. A similar base connection 
arrangement is illustrated in detail in U.S. Pat. No. 5,176,627, the 
contents of which are incorporated herein. 
The elastomeric casing 30 is provided in two parts: a first or inlet casing 
body 38a into which the inlet segment 32 of the base and the valve housing 
36 are invested, and an outlet or second casing 30b which is sealed by a 
suitable adhesive 56 to the inlet casing 30a in order to provide a 
continuous elastomeric exterior to the devices 20 and 20', with the 
exception of the inlet and outlet connectors 22 and 24 which extend 
therefrom. The inlet casing body 30a is integrally formed with the 
mounting pad 28 and includes an inlet aperture through which the inlet 
connector 22 extends, an inlet occluder wing 58 which generally overlies 
the inlet occluder port 44, and a resiliently flexible dome 60 for the 
flushing reservoir 40. 
In order to provide a fluid-tight seal between the inlet connector 22 and 
the inlet casing body 30a, a tube 62 is placed over a portion of the inlet 
connector and secured in place by means of a Mersilene over-suture 64. A 
silicone adhesive 66 is then injected into any remaining gap between the 
casing 30 and the inlet connector 22, and is also disposed peripherally 
about the inlet connector 22 and adjacent the proximal end of the 
elastomeric casing 30. This same sealing arrangement is utilized between 
the outlet casing body 30b and the outlet connector 24. 
The inlet occluder wing 58 is positioned over the inlet occluder port 44 to 
facilitate occluding a portion of the fluid flow path through the devices 
20 and 20' by pressing the wing 58 downwardly. Depressing the wing 58 and 
occluding the port 44 prevents proximal fluid flow from the flushing 
reservoir 40, defined by the dome 60 and the bottom plate 46, when the 
dome is pressed downwardly by manual percutaneous pressure. The dome 60 is 
preferably molded of a silicone elastomer material and is designed to 
permit injection into the fluid flow control devices 20 and 20' by a 
hypodermic needle through the dome. The inlet segment 32 of the base, as 
well as the outlet segment 34 and the valve housing 36, is preferably 
molded of a polypropylene material which provides sufficient rigidity to 
prevent a needle from inadvertently passing through the devices 20 and 20' 
if an injection is made into the flushing reservoir 40. The construction 
of the base segments 32, 34 and 36, and the elastomeric casing 30, helps 
to guide a physician in manually percutaneously manipulating the devices 
20 and 20' when subcutaneously implanted, for purposes of flushing the 
shunt system and adjusting the valve mechanism, when needed. 
A distal occluder wing 68 is positioned over the valve housing 36 to 
facilitate occluding a valve inlet fluid passageway 70. This is 
accomplished by pressing the wing 68 downwardly, which effectively 
prevents distal fluid flow from the flushing reservoir 40 when the dome is 
pressed downwardly by manual percutaneous pressure. 
The outlet casing body 30b surrounds a portion of the outlet segment 34 of 
the base to define the siphon control device 38 which is similar to that 
shown and described in U.S. Pat. No. 4,795,437, the contents of which are 
incorporated herein. The siphon control device 38 includes an outer wall 
72 and an inner wall 74 which is situated within and encircled about by 
the outer wall. The valve outlet fluid passageway 50 through the barbed 
connector 48 directs fluid from the valve housing 36 to a central SCD 
reservoir 76 defined as the area between the inner wall 74 and the outer 
wall 72. The outlet flow channel 52 extends through the inner wall 74 to 
the distal end of the outlet connector 24. 
The outer wall 72 is generally circular in shape, and is spaced from and 
encircles the inner wall 74. The inner wall 74 is also generally circular 
in shape, and defines an SCD outlet chamber 78 which is adjacent to and in 
fluid communication with the outlet flow channel 52. The inner wall 74 is 
constructed to have substantially parallel upper and lower seating 
surfaces 80, and it effectively forms a barrier separating the SCD 
reservoir 76 from the SCD outlet chamber 78. 
The outlet casing body 30b is provided with a pair of spaced, substantially 
parallel, flexible elastomeric diaphragms 82 which are fixed about their 
peripheries adjacent to the outer wall 72. Each diaphragm 82 has an inner 
surface which defines the upper and lower limits of the SCD reservoir 76 
and the SCD outlet chamber 78, and an outer surface which forms an 
exterior surface of the siphon control device 38. The diaphragms 82 are 
situated on opposite sides of the inner wall 74 to position a portion of 
each inner surface thereof in contact with an adjacent one of the seating 
surfaces 80 to form a seal therebetween which prevents fluid flow between 
the valve outlet fluid passageway 50 and the outlet flow channel 52. 
The second casing body 30b further includes integral offset rings 84 which 
surround each diaphragm 82 to inhibit overlying tissue from occluding the 
siphon control device 38 when implanted into a patient. An aperture is 
provided through the casing body 30b though which the outlet connector 24 
extends. A fluid tight seal is effected between the casing outlet aperture 
and the outlet connector 24 utilizing a tube 62, an over-suture 64 and an 
adhesive 66 as described above in connection with the inlet casing body 
30a and the inlet connector 22. 
In use, the diaphragms 82 normally lie against and interact with the 
seating surfaces 80 of the inner wall 74 to close the devices 20 and 20' 
to fluid flow. The diaphragms 82 move away from the seating surfaces 80, 
however, in response to a minimal level of positive fluid pressure within 
the SCD reservoir 76 to permit passage of fluid from the valve outlet 
fluid passageway 50 to the outlet flow channel 52. The diaphragms 82 close 
and seal upon the seating surfaces 80 once again in the absence of such 
positive upstream fluid pressure, or in response to negative downstream 
hydrostatic pressure in the SCD outlet chamber 78. The siphon control 
device 38 thus minimizes the undesirable consequences attendant to 
excessive overdrainage of fluid due to the siphoning effect of hydrostatic 
pressure. 
With reference now to FIGS. 1-14, the valve mechanism of the first 
illustrated embodiment of the fluid flow control device 20 will be 
described in detail. 
As illustrated best, initially, in FIGS. 2 and 3, the valve mechanism 
within the valve housing 36 provides means for controlling fluid flow from 
the inlet connector 22 to the outlet connector 24 and, more particularly, 
from the flushing reservoir 40 to the valve outlet fluid passageway 50. 
The valve housing 36 includes a central threaded aperture 86 through an 
upper section thereof into which is threaded a flow regulator insert 88 
(See FIG. 14) which defines a fluid passageway 90 therethrough. The lower 
end of the flow regulator insert 88 surrounding the fluid passageway 90 
forms a valve seat 92 against which a valve element in the form of a ruby 
ball 94 seats, to control the flow of fluid through the fluid passageway 
90. Of course, to accomplish this the diameter of the ruby ball 94 must be 
larger than the diameter of the valve seat 92. 
A pressure spring 96 is disposed immediately below and in contact with the 
ruby ball 94, to bias the ruby ball against the valve seat 92 to keep the 
fluid passageway 90 closed until a fluid pressure differential between the 
inlet and the outlet exceeds a selected valve opening pressure. The 
pressure spring 96 is supported at an end opposite the ruby ball 94 by a 
first surface 98 of a rotor assembly 100 which will be described in 
greater detail below. 
The fluid flow control device 20 of the present invention advantageously 
provides means for adjusting the amount of bias applied to the ruby ball 
94 by the pressure spring 96 in order to vary the selected valve opening 
pressure. Such adjusting means includes a fixed dual concentric stair-step 
array 102 (see FIGS. 7 and 8) and an overlying rotor assembly 100 (see 
FIGS. 9-11). A second surface 104 of the rotor assembly 100 is supported 
by the dual concentric stair-step array 102, and the rotor assembly is 
rotatable in response to an applied magnetic field to permit magnetic 
induction adjustments of the valve mechanism. 
The dual concentric stair-step array 102 includes a central rotor pivot 
106, a plurality of inner steps 108 which surround the rotor pivot, and a 
corresponding plurality of outer steps 110 which extend peripherally about 
the inner steps. The inner and outer steps 108 and 110 are constructed so 
that those steps opposite to one another with respect to the central rotor 
pivot 106 subtend the same arch and are located at the same level. The 
stair-step array 102 further includes an outer ring 112 which serves to 
capture a portion of the rotor assembly 100 therein, a supporting bracket 
114 and a lock lever pivot holder 116 which are utilized in connection 
with a pin actuating mechanism 118 to be described in greater detail 
below. 
The rotor assembly 100, shown best in FIGS. 9-14, includes a magnet 120 
embedded within a base 122. A rotor cap 124 is fixed to an upper surface 
of the base 122 over the magnet 120 to seal the magnet therebetween and to 
also provide the first surface 98 on which the pressure spring 96 rests. 
The rotor cap 124 includes a central aperture 126 surrounded by a 
cylindrical pressure spring-guide flange 128, and a peripheral compression 
spring-retaining flange 130 which is utilized to help retain a compression 
spring 132 in a proper position upon the first surface 98. The lower 
surface of the base 122 defines the second surface 104 of the rotor 
assembly 100. This portion of the base 122 includes an inner leg 134 which 
is adapted to bear against a selected one of the plurality of inner steps 
108, and an outer leg 136 which is disposed diametrically opposite the 
inner leg and is adapted to bear against a selected one of the plurality 
of outer steps 110. The inner and outer legs 134 and 136 extend the same 
distance downwardly from the base 122. Further, a base central aperture 
138 extends centrally through the base 122 and in alignment with the 
central aperture 126 of the rotor cap, which apertures are configured to 
permit passage of the central rotor pivot 106 therethrough. 
When the rotor assembly 100 is assembled to the stair-step array 102 such 
that the inner and outer legs 134 and 136 bearing against the 
diametrically opposite and corresponding inner and outer steps 108 and 110 
of the stair-step array, the first surface 98 of the rotor assembly 100, 
provided by the rotor cap 124, provides a lower seating surface for both 
the small pressure spring 96 and the much larger compression spring 132. 
As noted previously, the pressure spring urges the ruby ball 94 into 
engagement with the valve seat 92 to control the flow of fluid through the 
fluid passageway 90 of the flow regulator insert 88. The compression 
spring 132 bears against the rotor cap 124 at one end, and against a 
portion of the valve housing 36 surrounding the threaded aperture 86 so as 
to constantly urge the rotor assembly 100 into contact with the stair-step 
array 102. 
The pressure applied by the pressure spring 96 to the ruby ball 92 may be 
adjusted by rotating the rotor assembly 100 relative to the stair-step 
array 102. It will be understood that by simply rotating the rotor 
assembly 100, the vertical height of the rotor assembly relative to the 
stair-step array 102 may be varied. Positioning the inner and outer legs 
134 and 136 on higher inner and outer steps 108 and 110 tends to compress 
the pressure spring 96, thereby increasing the valve opening pressure in 
contrast with the positioning of the legs on lower steps. 
In order to adjust the rotational position of the rotor assembly 100 
relative to the stair-step array 102 when the fluid flow control device 20 
is subcutaneously implanted, an external magnetic tool 140 having 
diametrically opposite north and south magnetic poles (see FIG. 1). When 
the magnetic tool 140 is placed over the valve housing 136 such that 
magnetic flux coupling occurs between the magnet 120 and the magnetic 
tool, the rotor assembly 100 will be lifted vertically upwardly away from 
the stair-step array 102 against the force of the compression spring 132, 
thereby disengaging the inner and outer legs 134 and 136 from the inner 
and outer steps 108 and 110. The rotor assembly 100 may then be freely 
rotated about the central rotor pivot 106 to place the inner and outer 
legs 134 and 136 on a desired corresponding pair of inner and outer steps 
108 and 110 of the stair-step array 102 to provide the fluid flow control 
device 20, and specifically the valve mechanism, with a desired valve 
opening pressure. When the magnetic tool 40 is removed from proximity with 
the magnet 120, the magnetic flux coupling between the two is broken, 
thereby allowing the compression spring 132 to again force the rotor 
assembly 100 downwardly into contact with the stair-step array 102. 
It is sometimes desirable to provide a positive locking mechanism which 
will make it impossible to rotate the rotor assembly 100 relative to the 
stair-step array 102 even in the presence of magnetic field or flux 
coupling between the magnet 120 and the magnetic tool 140, unless an 
additional "unlocking" step is performed. To accomplish this, the pin 
activating mechanism 118 briefly mentioned above is provided. More 
specifically, a pin 142 is provided which has a first blunt end designed 
to engage vertical slots or detents 146 provided in the base 122 of the 
rotor assembly 100, and a second end 148 which is configured to provide an 
eyelet. The valve housing 36 and the supporting bracket 114 of the 
stair-step array 102 cooperate to provide a slot 150 through which the pin 
142 may reciprocate, and an internal cavity 152 into which an O-ring 154 
is positioned. The O-ring 154 engages the pin 142 and adjacent portions of 
the valve housing 136 and the supporting bracket 114 to prevent fluid 
leakage from the flushing reservoir 40 into the valve housing 36. The 
detents 146 provided in the outer periphery of the base 122 are arranged 
such that when any one of such detents is aligned with the first end 144 
of the pin 142, the inner and outer legs 134 and 136 of the rotor assembly 
100 are properly positioned over a corresponding set of inner and outer 
steps 108 and 110 of the stair-step array. When the pin 142 extends 
sufficiently through the slot 150 so that the first end thereof 144 
extends into one of the detents 146, the rotor assembly 100 cannot rotate 
relative to the stair-step array 102. 
To control the position of the pin 142, a lever assembly 156 is provided 
which includes a cylindrical pivot 158, an eyelet-engaging shaft 160 which 
extends from the pivot 158 to engage the second end 148 of the pin 142, a 
lock-paddle lever 162 which extends from the pivot 158 into the flushing 
reservoir 40, and a biasing lever 164 which extends from a portion of the 
lock-paddle lever angularly downwardly to engage the bottom plate 46 
underlying the flushing reservoir. The biasing lever 164 effectively 
causes the lever assembly to be normally pivoted such that the pin 142 is 
urged through the slot 150 into engagement with a selected one of the 
detents 146. However, the pin 142 can be withdrawn through the slot 150 by 
pressing downwardly on the dome 60 overlying the flushing reservoir 40 so 
as to also press downwardly on the lock-paddle lever 162, thus overcoming 
the force of the biasing lever 164. When the lock-paddle lever 162 is 
pressed downwardly, the lever assembly 156 pivots so that the shaft 160 
pulls on the second end 148 of the pin 142 to withdraw the pin partially 
through the slot 150 a sufficient distance to disengage the first end 144 
of the pin from an adjacent detent 146. Of course, when the downward 
pressure on the lock-paddle lever 162 is removed, the biasing lever 164 
automatically pivots the lever assembly 156 to once again cause the first 
end 144 of the pin 142 to seek to engage a selected detent 146. 
Accordingly, once the fluid flow control device 20 has been properly 
subcutaneously implanted, the valve opening pressure of the valve 
mechanism can be adjusted utilizing a two-step procedure. First, 
percutaneous pressure must be applied to the dome 60 sufficiently to press 
the lock-paddle lever 162 downwardly so as to pivot the lever assembly in 
a manner causing the first end 144 of the pin 142 to disengage an adjacent 
detent 146 in the periphery of the base 122 of the rotor assembly 100 (see 
FIGS. 5 and 6). Next, the external magnetic tool 140 is brought into close 
proximity with the magnet 120 embedded within the base 122 to permit the 
rotational position of the rotor assembly 100 to be varied, as desired, 
relative to the stair-step array 102, through magnetic induction coupling 
between the external magnetic tool 140 and the magnet 120. When the rotor 
assembly 100 is properly positioned relative to the stair-step array 102, 
the percutaneous pressure applied to the dome 60 is removed, thus 
permitting the biasing lever 164 to urge the lever assembly 156 in a 
direction causing the first end 144 of the pin 142 to seek to engage an 
adjacent one of the detents 146 (see FIG. 4). With the pin 142 so 
positioned, the rotor 100 is incapable of rotating relative to the 
stair-step array 102, regardless of the presence or absence of the 
magnetic tool 140 in proximity with the magnet 120. When the magnetic tool 
140 is removed from the vicinity of the magnet 120, the compression spring 
132 urges the rotor assembly 100 downwardly into positive contact with the 
stair-step array, thus ensuring proper performance of the fluid flow 
control device. 
FIGS. 15-18 illustrate an alternative embodiment of the fluid flow control 
device 20', wherein functional equivalent elements of the device 20' 
similar to those described above in connection with the fluid flow control 
device 20 having the same reference numbers. In this embodiment of the 
fluid flow control device 20', the pin actuating mechanism 118 has been 
removed. This is the only substantive change between the two embodiments. 
Other small changes include the configuration of the inner and outer legs 
134' and 136' which, it will be noted, are in the form of nubs which 
depend from the base 122' Further, the rotor cap 124' is integrally molded 
with the base 122, and is provided a lock-step tab 166 which interacts 
with a portion of the valve housing 36 to function as a stop to limit 
rotation of the rotor assembly 100 relative to the stair-step array to 
less than 360.degree.. Further, it will be noted that a shape of the flow 
regulator insert 88' is slightly different from the flow regulator insert 
88 illustrated in FIG. 14. Otherwise, the fluid flow control device 20' 
functions the same as the fluid flow control device 20 of FIGS. 1-14. 
Again, the primary difference lying in the fact that there is no pin 
actuating mechanism 118 that must be disengaged in order to rotate the 
rotor assembly 100 relative to the stair-step array 102 through magnetic 
induction coupling between the external magnetic tool 140 and the magnet 
120. 
From the foregoing it is to be appreciated that the present invention 
provides a flow control device 20 or 20' for use in a subcutaneously 
implanted physiological shunt system, wherein the valve opening pressure 
may be selectively adjusted when subcutaneously implanted. The 
construction of the flow control devices 20 and 20' of the present 
invention permits selective distal and proximal flushing of the devices 
through the application of manual percutaneous pressure. The present 
invention provides devices by which the flow of cerebrospinal fluid out of 
a brain ventricle can be controlled while preventing the backflow of fluid 
into the brain ventricle, and inhibiting excessive drainage through the 
physiological shunt in the presence of excessive downstream suction. 
Although two particular embodiments of the invention have been described in 
detail for purposes of illustration, various modifications may be made 
without departing from the spirit and scope of the invention. Accordingly, 
the invention is to be limited, except as by the appended claims.