FR2804331A1 - Implanted valve, for draining cephalo-rachidien liquid from cerebral cavity for treatment of hydrocephaly, includes shutter, and pressure regulator with alloy drives and stepping gear wheel - Google Patents

Abstract

The valve has a shutter (2), fitted to a drain pipe between a zone containing excess cephalo-rachidien liquid and a drain zone, and a pressure regulator for the shutter. The shutter regulator includes NITONOL alloy drives (6) which modify their mechanical properties and shape under the effect of temperature changes. The regulator has a stepping gear wheel (4) which modifies the shutter opening pressure in response to deformation of the drives. The drives includes a NITONOL spring which cooperates with the transmission wheel against the action of an elastomer cushion (19). The gear wheel cooperates with another spring (10) pressing against the shutter closing bearing (9) on a valve seat (7). The transmission has a ratchet wheel (11), fixed to a cam (12). which is rotated by the NITONOL drives. An actuating rod (21) has an end which cooperates with the cam (12) so as to compress the spring (10) between its other end and the shutter closing bearing. The valve also includes drive cooling and heating systems as well as an aerial for exciting these systems.

Description

The present invention relates to a valve for the treatment of hydrocephalus, and more particularly to such a valve comprising a valve disposed on a drainage line between a zone containing an excess of hydrocephalus. cerebrospinal fluid and a drainage zone, and means for adjusting the opening pressure of the valve.

Various types of valves used for the treatment of hydrocephalus are known, and more particularly for draining cerebrospinal fluid from a cerebral cavity to a drainage site. The fluid can be drained from various locations such as the cerebral ventricles or medullary canal, but the current preferred drainage site is very typically the peritoneal cavity.

It is known, however, that the drainage of cerebrospinal fluid into the peritoneal cavity has a number of disadvantages related to the "siphon" effect. In fact, the hydrostatic pressure due to the presence of the drainage line can under certain circumstances lead to overdrainage.

A number of valves have been proposed to overcome these disadvantages. Thus, valve mechanisms, or more complex systems such as systems known as "anti-siphon" or needle valves, have been used to prevent overdraining.

It has also been proposed more recently valves that can be adjusted after implantation, non-invasively. This solution allows the surgeon to adapt the operating pressure to the patient. The devices used generally comprise more or less complex magnetic micromotors.

The tools used for the external adjustment of these types of valves can be constituted by a simple magnet or include complex generators of magnetic field. The main disadvantage of this type of valve is their sensitivity to external magnetic fields to which the patient may be subjected at any time, and which are likely to disrupt the device. Another disadvantage of these devices is their sensitivity to magnetic resonance imaging techniques. The valves must be reset after each session.

The present invention aims to overcome these disadvantages.

More particularly, the invention aims to provide a valve for the treatment of hydrocephalus that can be adjusted non-invasively after implantation.

It is another object of the invention to provide such a valve which is insensitive to external magnetic fields and which is not out of adjustment when the patient wearing it is subjected to magnetic resonance imaging examination.

For this purpose, the invention relates to a valve for the treatment of hydrocephalus comprising a valve disposed on a drainage line between an area containing an excess of cerebrospinal fluid and a drainage zone, and control means of the opening pressure of the valve, characterized in that said adjustment means comprise shape memory alloy motor means, made for example of nickel-titanium alloy, capable of undergoing a modification of their mechanical properties under the effect of a temperature change, said motor means being arranged to deform during said modification of their mechanical properties, and that said adjusting means further comprise transmission means for modifying the opening pressure of said valve in response to a deformation of the motor means.

Shape memory alloys, such as certain nickel-titanium alloys, are known to have "memory" and "superelasticity" properties that depend on the alloy's composition and the heat treatment it has undergone. . Some of these alloys are known as NITINOL.

More particularly known are such alloys which can be packaged in a memorized form determined by their temperature. In this condition, the alloy can undergo during a change in temperature, a phase transition during which it passes at a certain temperature of a state with a very low coefficient of elasticity where it is totally " soft ", in a state where it is" rigid "and has a very high coefficient of elasticity, and vice versa.

The invention therefore uses this property of these alloys to provide a motor for adjusting the valve. This adjustment is obtained by heating or cooling the motor means.

This property is independent of the ambient magnetic field and therefore allows in particular to overcome any magnetic disturbance, especially in case of magnetic resonance imaging examination.

In a particular embodiment, said motor means comprise a shape memory alloy spring arranged to cooperate with said transmission means against the action of first elastic means.

It is understood that one can in this case achieve a stepping motor. Indeed, when the spring is in its state of high elasticity, the force it exerts on the first elastic means is greater than the reaction that they can oppose it, and it takes the form "stored". When, as a result of a phase change due to a temperature change, it is in its state of low coefficient of elasticity, the force exerted by the first elastic means carries it away, and the spring is deformed. It returns to its original shape during the next phase change. These successive deformations can then be used to actuate the transmission means and thus change step by step the opening pressure of the valve.

 Also in a particular embodiment, said transmission means comprise a cam arranged to cooperate with second elastic means pressing a valve closure member on a valve seat.

The aforementioned cam, actuated by the motor means, thus more or less constrains the second elastic means which determine the opening pressure of the valve. More particularly, said transmission means may further comprise a ratchet wheel integral with said cam, said motor means being arranged to drive said ratchet wheel in rotation.

The ratchet wheel rotates at an angle equal to one pitch of its teeth at each cycle of the motor means, and thus drives the cam which, with a suitable profile, applies the desired stress to the second elastic means.

Said transmission means may further comprise an actuating rod whose one end is arranged to cooperate with said cam to compress said second elastic means disposed between its other end and said valve closure member.

Said shape-memory alloy spring may more particularly consist of a pin spring, a first branch of which is held fixed and whose second branch is movable under the action of its own variable elasticity and the elasticity of said first elastic means, the end of the second branch forming a pawl for cooperating with said ratchet wheel.

The valve according to the invention may comprise cooling means for cooling said motor means.

This case is where the shape memory alloy has a transition temperature close to the human body temperature or slightly lower. The motor means is then used by cooling them below this transition temperature. These cooling means may simply consist of a cold object that is applied to the skin of the patient near the valve. They can also use the Peltier effect in a known manner.

Alternatively, the valve according to the invention comprises heating means for heating said motor means.

This case is where the shape memory alloy has a transition temperature higher than the temperature of the human body. The motor means are then implemented by heating them above this transition temperature. The heating means may consist of a resistive element. In either case, the valve according to the invention may comprise an antenna for the excitation of said cooling means and said heating means.

Two particular embodiments of the invention will now be described, by way of nonlimiting example, with reference to the appended diagrammatic drawings in which: FIG. 1 represents a first embodiment of the invention; and - Figure 2 is a partial view of a second embodiment.

FIG. 1 shows a valve for the treatment of hydrocephalus comprising, integral with a fixed housing, not shown, a valve body 1, an axis of rotation 3 of rotation assembly 4, and a motor spring block 6 of the shape memory alloy 6, and consequently variable elasticity depending on the temperature.

The body 1 of the casing 2 has, in a known manner, a partially closed tubular shape at one of its ends by a valve seat 7 comprising a fluid passage orifice 8. A closure member 9, constituted here by a ball, is housed in the body 1 and pressed against the seat 7 by a helical spring 10 also housed in the body 1.

An inlet catheter is mounted in known manner on the orifice 8 to connect the valve 2 to the area to be drained. Similarly, an outlet catheter is mounted at the end of the body 1 opposite the orifice 8 to connect the valve 2 to the drainage zone.

The drainage pressure is adjusted, as will be described hereinafter, by the compression of the spring 10.

The rotation assembly 4 is composed of a ratchet wheel 11 and a cam 12 mounted for free rotation on the axis 3. The ratchet wheel 11 and the cam 12 are integral.

The ratchet wheel 11 comprises in a known manner a set of asymmetric teeth all oriented in the same direction at its periphery. These teeth have a substantially radial face 13 with respect to the axis 3 and an inclined face 14. The cam 12 has at its periphery a succession of recesses 15 separated by bumps 16. The recesses 15 have, on a cam turn 12, distances to the axis 3 variables, for example increasing.

The mainspring 6 is here a pinned spring comprising a branch 17 fixed to the block 5, and a free branch 18 bearing against a cushion 19 of silicone elastomer which pushes it towards the fixed branch 17 against the variable elasticity of the spring.

The branch 18 of the spring 6 forms a ratchet wing 20, in contact with the teeth of the ratchet wheel 11 and oriented so that it can abut against the faces 13 of these teeth.

Finally, the connection between the stepwise rotation assembly 4 and the spring 10 is achieved by means of a rod 21 applied to the cam 12 by the spring 10. This rod is slidably mounted in a bearing 22 integral with the valve body 1.

The embodiment shown in FIG. 1 is that in which the transition temperature of the alloy of the spring 6 is lower than the temperature of the human body. In its normal state of operation, the spring 6 has a high coefficient of elasticity which brings it to its position shown in solid lines where it compresses the silicone cushion 19.

In this position, the flange 20 of the spring is in abutment against a face 13 of a tooth of the ratchet wheel 11. The rod 21 is supported at the bottom of one of the recesses 15 of the cam 12, the pressure of closing the ball 8 on the valve seat 7 being determined by the distance of this hollow to the axis 3.

If the spring 3 is cooled in any suitable manner below its transition temperature, its coefficient of elasticity drops so that the silicone pad 19 pushes its branch 18 towards the fixed branch 17 in the position shown in phantom. In this movement, the end of the flange 20 of the spring 6 slides on the face 14 of the tooth of the ratchet wheel 11 until it engages behind the face 13 of the next tooth, the ratchet wheel 11 and the cam 12 being held by the rod 21.

When the spring 6 is brought back to the ambient temperature of the human body, it resumes its rigidity and compresses the cushion 19 to return to the stored position shown in solid lines. In this movement, the end of its flange 20 pushes the face 13 of the tooth on which it is bearing causing the ratchet wheel 11 and the cam 12 to rotate by a rotation step.

During this rotation, the rod 21 is pushed back by the corresponding hump 16 of the cam 12, then falls into the next hollow 15. This hollow has, for example, a distance to the axis 3 greater than that of the preceding hollow, so that the rotation of the cam 12 has increased the opening pressure of the valve 2.

If it is desired on the contrary to reduce this opening pressure, the cam is rotated as before by a succession of cooling / heating cycles until the rod 21 is engaged in the deepest recess, corresponding to the pressure minimum opening, then the rotation is optionally continued to increase this pressure again to the desired value.

The embodiment shown in FIG. 2 will now be described.

This figure shows only the lower part of the valve according to the second embodiment, with the support block 30 and the spring 31 of shape memory alloy. In fact, this second embodiment is practically identical to the previous one, in particular with regard to the set of stepwise rotation and the flap.

However, in this case, the transition temperature of the alloy is chosen slightly higher than that of the human body. At room temperature, the spring 31 is therefore in its low-elastic state where it is pushed back by the silicone cushion 32. The configuration of the valve is therefore identical to that shown in dashed lines in FIG.

In the present embodiment, the free branch 33 of the spring 31 is surrounded by a resistor capable of heating the spring above its transition temperature.

When such heating is applied, the alloy of the spring resumes its high coefficient of elasticity so that the spring pushes the cushion 32 to come to its stored position shown in Figure 2. In this movement, it drives all rotary rotation step and changes as in the first embodiment the adjustment of the opening pressure of the valve.

When the resistor 34 stops being energized, the spring cools and returns to the original position where the heating / cooling cycle can resume to change the setting again.

In the embodiment of Figure 2, the resistor 34 is fed by an antenna 35 mounted in the housing of the valve. This antenna can be excited by an external magnetic field generator of any known type.

Such an antenna could also be used in a device of the type of that of Figure 1 in which one would use for example the Peltier effect to cool the spring.

The two devices above can be made of non-ferrous materials, therefore not susceptible to be affected by magnetic resonance imaging examinations.

Claims (1)

1 - Valve for the treatment of hydrocephalus comprising a valve (2) disposed on a drainage line between an area containing an excess of cerebrospinal fluid and a drainage zone, and means for adjusting the opening pressure of the valve, characterized in that said adjusting means comprise drive means (6; 31) of shape memory alloy, which may undergo a modification of their mechanical properties under the effect of a temperature change, said motor means being arranged to deform during said modification of their mechanical properties, and that said adjusting means further comprise transmission means (4) for modifying the opening pressure of said valve (2 ) in response to deformation of the motor means. 2 - Valve according to claim 1, wherein said motor means are made of nickel-titanium alloy shape memory. 3 - Valve according to any one of claims 1 and 2, wherein said motor means (6; 31) comprise a shape memory alloy spring arranged to cooperate with said transmission means against the action of first elastic means ( 19; 32). 4 - Valve according to any one of claims 1 to 3, wherein said transmission means (4) comprise a cam (12) arranged to cooperate with second elastic means (10) pressing a valve closure member (9) on a valve seat (7). 5 - Valve according to claim 4, wherein said transmission means (4) further comprises a ratchet wheel (11) integral with said cam (12), said motor means (6; 31) being arranged to drive said wheel to ratchet rotation. 6 - Valve according to any one of claims 4 and 5, wherein said transmission means (4) further comprises an actuating rod (21) whose end is arranged to cooperate with said cam (12) for compressing said second resilient means (10) disposed between its other end and said valve closure member (9). 7 - Valve according to the set of claims 3 and 6, wherein said shape memory alloy spring (6; 31) is a pin spring, a first branch (17) is held fixed and whose second limb ( 18; 33) is movable under the action of its own variable elasticity and the elasticity of said first elastic means (19; 32), the end of the second branch forming a pawl (20) for cooperating with said ratchet wheel (11). 8 - Valve according to any one of claims 1 to 7, comprising cooling means for cooling said motor means. 9 - Valve according to any one of claims 1 to 7, comprising heating means (34) for heating said motor means. 10 - Valve according to any one of claims 8 and 9 comprising an antenna (35) for the excitation of said cooling means and said heating means.