DE112009005095B4 - Implantable force transmission system, in particular for adjusting a valve - Google Patents

Abstract

Implantable transmission system,
in particular for adjusting a valve, having an actuator (2) which is arranged together with at least one first permanent magnet (3) or body of soft magnetic material in a hermetically sealed housing (1),
characterized,
the actuator (2) can move the first permanent magnet (3) or body in a linear guide in the housing (1) in a controlled manner,
at least one encapsulated second permanent magnet (5) is arranged in a guide (7) outside the housing (1) at a distance from the first permanent magnet (3) or body, and that a magnetic force is applied between the first permanent magnet (3) or body and the second permanent magnet (5) acts.

Description

Technical application

The present invention relates to an implantable force transmission system which can be used in particular for active medical implants, for example for adjusting a hydrocephalus valve.

Active, electronically controlled medical implants typically require hermetic encapsulation on at least some of their components, preventing sensitive components from being attacked by aggressive bodily fluids or, conversely, toxic components entering the body. In pacemakers, for example, the battery and the electronics are housed in a hermetically sealed housing. Special feedthroughs provide electrical contact between the internal electronics and the outside electrodes.

In certain cases, for example, in an active valve implant, but not only electrical energy should be passed through the closed housing wall, but it is also a transfer of mechanical forces required. Such an implant must contain an actuator which - depending on the actuator principle and actuator design - usually also has to be hermetically encapsulated.

In such implants with a hermetically sealed actuator, the problem arises to transmit the mechanical force generated by the actuator out of the hermetic housing to the outside. In principle, a power transmission through flexible wall parts, for example. In the form of a bellows, take place. The disadvantage of such a solution, however, is the increased expenditure of energy and energy that goes along with it. The required actuators and energy storage require a lot of space, which is not available in an implant.

An example of a valve implant is the hydrocephalus valve. This usually has a spring that presses a closure body against an opening. At a certain differential pressure between the distal and proximal ends of the valve, the spring releases and releases a channel to drain cerebrospinal fluid. Simple hydrocephalus valves have a fixed opening pressure given by the design, which can not be changed. More sophisticated models can be subsequently adjusted with the aid of permanent magnets, so that the opening pressure can be adapted to the course of the disease even after implantation of the valve. For this purpose, a strong magnetic field is generated by means of an extracorporeally arranged programming device which exerts a force effect on permanent magnets integrated in the implant with which the opening characteristic of the valve can then be adjusted.

Also from the US 2006/0074371 A1 Such an adjustable hydrocephalus valve is known. In this valve, the spring pressure is adjusted to the closure body via a cam mechanism. The cam gear has permanent magnets of alternating polarity over the circumference of a rotor. An externally applied programming device, which generates a pulsed magnetic field via electromagnets, allows the rotor to be adjusted stepwise, thereby changing the spring pressure on the valve body.

However, such possibilities of intervention by the attending physician are inadequate, since the amount of cerebrospinal fluid formed and the physiological value of cerebrospinal pressure vary greatly during the course of the day and also depend on the activity of the patient. An active hydrocephalus valve, whose pressure-flow characteristic adapts itself autarkically over the course of the day to the physiological needs of the patient, would therefore be desirable. This requires an implantable actuator that can be used to automatically adjust the valve. Such a valve could be timed in the simplest case or work based on a suitable sensor. It should be non-invasively programmable after implantation to accommodate the individual needs of each patient.

The EP 1 523 635 B1 describes a valve with a compact shape memory alloy drive in which two shape memory wires acting in opposite directions are used as actuators to move a ball between two stable positions and thus to open and close a valve. When implanting such a valve, the shape memory material and the electrical contact must firstly be biocompatible. On the other hand, a long-term stable, biocompatible and flexible, thermally and electrically insulating encapsulation of the heated and moved shape memory wires is required. This is difficult to realize technically. Furthermore, an implantation requires special electrical feedthroughs from the electronics housing to the actuator through the hermetic housing wall, which additionally causes considerable costs.

The object of the present invention is to provide an implantable power transmission system which has a arranged in a hermetically sealed housing, compact and easy to control actuator whose force on the closed housing wall after outside, and which is particularly suitable for the adjustment of a hydrocephalus valve.

Presentation of the invention

The object is achieved with the implantable power transmission system according to claim 1 and 2. Advantageous embodiments of this power transmission system are the subject of the dependent claims or can be found in the following description and the exemplary embodiments.

The proposed power transmission system has an actuator which, together with at least one first permanent magnet or soft magnetic material body, is arranged in a hermetically sealed housing in such a way that the actuator can move and / or rotate the first permanent magnet or body in the housing in a controlled manner. Outside the housing, at least one encapsulated second permanent magnet is disposed at a distance from the first permanent magnet in a guide in which a magnetic force acts between the first permanent magnet or body and the second permanent magnet. In an alternative embodiment, the actuator is arranged together with at least one first permanent magnet in a hermetically sealed housing, that the actuator can move the first permanent magnet controlled and / or rotate. Outside the housing, in this alternative, at least one encapsulated body of soft magnetic material is spaced apart from the first permanent magnet in a guide in which a magnetic force acts between the first permanent magnet and the body.

In an advantageous embodiment, the actuator in both alternatives is formed by at least two shape memory elements, which are arranged with respect to a displacement direction of the first permanent magnet or body to the second permanent magnet or body in front of and behind the first permanent magnet or body. Under a shape memory element or shape memory wire is understood to be an elongated element of a shape memory alloy, as it is also known under the abbreviation SMA.

The two shape memory elements, preferably two shape memory wires, extend in a preferred embodiment perpendicular to the displacement direction of the first permanent magnet or soft magnetic body. They are in particular arranged so that the first permanent magnet or soft magnetic body is in the stretched state of the one element in a first position in the direction of displacement and in the stretched state of the other element in a second position. Therefore, the two shape memory elements extend perpendicular to the intended effective direction, so that with a small reduction of these elements when heating a maximum displacement of the permanent magnet or soft magnetic body can be achieved. The two elements are fixed at their ends and electrically contacted. The heating of these elements is carried out by a current flow through the respective element, in particular by a current pulse of suitable strength and length is passed through the respective element. This current pulse leads to the shortening and thus extension of the respective element, so that this shifts the permanent magnet or soft magnetic body with a corresponding arrangement of the two elements in the direction of the other element and this expands. By alternately loading the two elements with a current pulse, the permanent magnet or soft-magnetic body can thus be moved back and forth between two stable positions in the displacement direction.

The use of such a trained shape memory drive as an actuator has the advantage that the actuator is compact and easy to control. With such an actuator can be, for example, the opening state of a valve switch or vary the valve opening pressure in two stages. It is a similar actuator mechanism of action as in the above EP 1 523 635 B1 However, where serving as an actuator, counteracting shape memory elements are encapsulated in a hermetic housing. The force to open a valve is transmitted magnetically through the closed housing wall. As a result, the shape memory elements do not come into contact with the environment, for example a body fluid, and can be contacted by soldering without regard to biocompatibility requirements. Furthermore, they need not be long-term stable, flexible and biocompatible encapsulated. The thermal losses during energization are lower because the elements are surrounded by air rather than liquid, so energy consumption can be minimized. Also relevant for implant applications requirement for biocompatibility of the shape memory material is eliminated. Compared to a, technically also possible, electromagnetic actuation of the permanent magnets, the shape memory principle offers the advantage of lower energy consumption in a more compact design.

In the following, the proposed power transmission system will be explained in one embodiment with a combination of two permanent magnets. These explanations can be in the case of the use of attractive magnetic force Of course, also be transferred to embodiments in which a combination of a permanent magnet and a body of soft magnetic material is used.

By using such permanent magnets, high forces can be transmitted over relatively large distances. The actuator shifts and / or rotates the first permanent magnet, hereinafter also referred to as the inner magnet, in the hermetically sealed housing in a controlled manner, d. H. by an adjustable distance on a defined path or - in one rotation - by a defined angle. As a result of this movement of the inner magnet, the magnetic force action changes to the second permanent magnet arranged outside the housing, also referred to below as the outer magnet. The outer magnet is suitably coated to protect it from mechanical and chemical damage. The encapsulation or shell is preferably carried out biocompatible and corrosion resistant. As a result of the displacement and / or rotation of the inner magnet, the outer magnet experiences a force effect which it can transmit directly or indirectly to an object. In the case of a valve application, the outer magnet acts on a closure body, which controls the inflow or outflow of a liquid or a gas. By the movement of the inner magnet while the force on the outer magnet and thus on the closure body in response to the movement of the inner magnet is increased or decreased. In this way, for example, the required differential pressure in active hydrocephalus valves and thus the outflow of cerebrospinal fluid (cerebrospinal fluid) can be controlled.

The outer magnet is in this case arranged in a suitable guide, by means of which the force exerted by it on the object in the direction is controlled. This is preferably a linear guide.

The electrically operated actuator used in the hermetically sealed housing may be, for example, an electric motor, a solenoid, an ultrasonic motor, a piezomotor, a shape memory drive or the like, and operate in a rotary or linear manner. The actuator is controlled by intelligent electronics, either together with an implant self-sufficient power supply device, i. H. a battery, an accumulator or a capacitor, is also integrated in the hermetically sealed housing or housed in a separate, hermetically sealed housing which is connected via a cable connection to the actuator. Preferably, the electronics provide the capability of wireless telemetry communication with an off-implant programmer that can program the electronics. The techniques for telemetric transmission of control commands and signals are known to those skilled in the art. However, in a simple embodiment, the electronics may also have only a once-programmed control program which controls the force effect to be generated by the actuator throughout the day. In a preferred embodiment, the power transmission system also comprises a force measuring device which measures the force exerted by the actuator on the inner magnet and transmits to the outside via the intelligent electronics with a corresponding telemetry device. This allows an exact adjustment of the force exerted on the inner magnet and thus - in the case of a valve application - on the valve body force.

The hermetically sealed housing with the actuator and the inner magnet and the encapsulation of the outer magnet are biocompatible for implantation of the power transmission system in a living body or provided with a biocompatible coating.

In a preferred embodiment, both the inner magnet and the outer magnet are each arranged in a linear guide, wherein the linear guides are preferably on the same axis. By solid embedding of the magnets in suitably geometrically shaped guide body or by appropriate suitable geometric design of the magnets can be prevented that they can tilt in the linear guides with respect. Their pole axes. In this way, the power transmission can be realized both repulsive and attractive forces between the two magnets.

In a further advantageous embodiment, the two permanent magnets are freely rotatably arranged in their guides, in which case only an attractive force can be used for power transmission. This exploits that unlike poles align themselves automatically against each other. A possible tilting of the magnets or the guide body is prevented.

Alternatively, in this embodiment, one of the two permanent magnets can be replaced by a body of soft magnetic material.

The guide for the outer magnet is preferably rigidly connected to the hermetically sealed housing. In the case of a valve application, the valve may be firmly integrated in this arrangement.

The proposed implantable force transmission system makes it possible to use a variety of different actuators for implant applications, regardless of whether actuator components might be toxic or whether bodily fluids would be added to the actuator. This can be used in each case the most favorable for the application actuator principle. In addition to the application of active medical implants, such a power transmission system can also be used in other technical fields. This applies in particular to areas in which contamination can occur due to actuators or the functioning of the actuators would be impaired by the environment. Examples include vacuum technology, the food industry or the chemical industry.

Brief description of the drawings

The proposed implantable force transmission system will be explained in more detail below with reference to three exemplary embodiments in conjunction with the drawings. Hereby show:

1 a first example of an embodiment of the power transmission system for adjusting a valve;

2 a second example of an embodiment of the power transmission system for adjusting a valve; and

3 a third example of an embodiment of the power transmission system for adjusting a valve.

Ways to carry out the invention

In the following, three advantageous embodiments of the proposed power transmission system for valve applications, in particular for use in hydrocephalus valves, are shown. In these examples, the distance dependence of the force acting between the inner and outer permanent magnets is used to control the action of the outer magnet on the closure body of the valve. The force increases when the inner magnet is moved to the outer magnet, and decreases when the distance between the two magnets is reduced. This increases in the first two examples, the force with which the outer magnet presses on the closure body and thus the pressure required to open the valve. In the third example, the force with which the outer magnet presses on the closure body, due to the special structure with the additional spring element decreases.

1 shows an example of the embodiment of the power transmission system, in which the adjustment of the valve opening pressure is achieved by varying a repulsive force between the two permanent magnets. The repulsive force between the two magnets acts much like a mechanical spring in conventional differential pressure valves with the difference that this force effect can now be transmitted through a closed wall in contrast to the mechanical solution.

In the in 1 illustrated embodiment of a hydrocephalus valve with the proposed power transmission system causes a linear actuator 2 that together with the inner magnet 3 in a hermetic housing 1 is encapsulated, a linear movement of the inner magnet 3 , The outer magnet 5 will be in a leadership 7 outside the hermetic enclosure 1 guided by a corresponding external design of the hermetic housing 1 is formed. Through the linear actuator 2 thus becomes a linear relative movement of the inner magnet 3 to the outside magnet 5 in turn, for closing the valve opening against a spherical closure body 8th is pressed on the valve seat 9 of the valve rests. Both magnets are in such a way in guide bodies 4 . 6 integrated or encapsulated that poles of the same name are always facing each other and the magnets can not rotate against each other. An actuation of the linear actuator 2 shifts the inner magnet 3 relative to the outer magnet 5 , which causes the repulsive force 11 and thus the force on the closure body 8th changed.

Becomes the linear actuator 2 through intelligent electronics, which together with a power supply also in the hermetic housing 1 can be integrated, driven, so can be adjusted in this way continuously and independently the minimum required opening pressure of the valve. Below this pressure, the valve remains closed, above this pressure it begins to open, causing a cerebrospinal fluid flow 10 through the channels of the valve can use.

In a further exemplary embodiment of a power transmission system in conjunction with a hydrocephalus valve, as in 2 is shown, the attractive force 12 used between two permanent magnets for adjusting the valve opening pressure. In this case there are closure bodies 8th and valve seat 9 between the inner 3 and the outer permanent magnet 5 , The magnets 3 . 5 are aligned so that their unlike poles are facing each other.

An advantage of this embodiment is that the permanent magnets 3 . 5 must not be stored against rotation, since unlike poles align themselves against each other. This will cause a possible tilting of the guide body 4 . 6 prevented. Another advantage of such an embodiment is that the magnets 3 . 5 can be stored so that they can rotate in any direction. This can be achieved, for example, by integration into a freely movable ball or by using freely movable magnetic balls. You can thus align themselves in any externally applied magnetic field according to their polarization direction. A depolarization by very strong magnetic fields, as they can occur, for example, in magnetic resonance imaging for diagnosis and therapy control, for example. Hydrocephalus, characterized in contrast to the embodiment of the example 1 be safely excluded. As soon as no strong external field is present, the rotatably mounted magnets align themselves again in the desired manner and exert an attractive force on each other.

Also in the example of 2 is a variation of the valve opening pressure by a change in the distance between the inner 3 and outer magnet 5 causes. Again, the effective force and thus the valve opening pressure decreases when the two magnets by the action of the linear actuator 2 moved away from each other, and increases when approaching. Again, the linear actuator 2 be controlled by an intelligent electronics, which together with a power supply also in the hermetic housing 1 can be integrated.

A variant of in 2 illustrated embodiment is that one of the two permanent magnets ( 3 ) respectively. ( 5 ) is replaced by a soft magnetic body. Thus, the attractive force between a permanent magnet and a soft magnetic body is then used, which can also be controlled by changing the distance.

In both embodiments can be used for precise adjustment of the valve opening pressure and a force measuring device between the linear actuator 2 and inner magnet 3 is arranged. With it, the force can be accurately determined and read, which acts between the two magnets and thus on the closure body.

In the third example of the 3 The Hydrocephalus Valve is shown in the left part picture in the open and in the right part picture in the closed state. The inner magnet 3 Here, in turn, together with the actuator in a hermetic housing 1 arranged. The actuator is in this example by two shape memory wires 13 . 14 realized in the direction of displacement of the inner magnet 3 to the outside magnet 5 in front of and behind the inner magnet 3 are arranged. The two shape memory wires 13 . 14 are each fixed at their ends. The outer magnet 5 will be in a leadership 7 outside the hermetic enclosure 1 guided, so that when moving on a closure body 8th acts to close and open the valve on a valve seat on the valve inlet 15 is pressed or can stand out from it again to the flow between the valve inlet 15 and valve outlet 16 to block or release.

The closing of the valve is in this case by an elastic spring element 17 that supports the outer magnet 5 in the direction of the closure body 8th suppressed. Is the attraction between inner magnet 3 and outer magnet 5 sufficiently small, so outweighs this spring force, so that the closure body 8th is pressed against the valve seat with the differential force between spring force and magnetic attraction between the inner and outer magnets.

To close the valve is through the first shape memory wire 13 a current pulse passed so that it shortens and the inner magnet 3 in the direction of one in the housing 1 fixed additional magnets 18 shifts. In this position reaches the inner magnet 3 due to the now prevailing attraction between the two magnets 3 . 18 a stable condition. The additional magnet 18 is here in the direction of displacement of the inner to the outer magnet behind the inner magnet 3 so fixed in the case that he has an attractive force on the inner magnet 3 exercises. The additional magnet 18 only serves to achieve a stable position of the inner magnet 3 when the valve is closed. By the displacement of the inner magnet 3 in the direction of the additional magnet 18 in which the second shape memory wire 14 , which is de-energized at this time, correspondingly expands (see right partial illustration of 3 ), the attraction between the inner magnet decreases 3 and the outer magnet 5 rapidly, leaving the elastic spring element 17 barely compressed. This then presses the encapsulation of the outer magnet 5 against the closure body 8th and this against the valve seat.

To open the valve, the second shape memory wire 14 subjected to a current pulse. This shortens this wire and moves the inner magnet 3 in the direction of the outer magnet 5 , The first shape memory wire 13 , which is not energized at this time, it expands accordingly (see. 3 , left part illustration). By the approach between inner and outer magnet 3 . 5 outweighs the attractive magnetic force between these magnets against the restoring force of the elastic spring element 17 so that the outer magnet 5 in the direction of the inner magnet 3 is moved. A stable state is reached when the attraction between both magnets 3 . 5 the restoring force of the elastic spring element 17 equivalent. In this state, this no longer presses the outer magnet 5 against the closure body 8th and thus the closure body 8th against the valve seat so that the valve is open.

It goes without saying that the inner magnet 3 or its envelope so in a hermetically sealed housing 1 is led that he can not tilt during a shift.

LIST OF REFERENCE NUMBERS

1

hermetic housing

2

Linear Actuator

3

Inner magnet

4

guide body

5

Outer magnet

6

guide body

7

guide

8th

closure body

9

valve seat

10

CSF flow

11

Repulsive force

12

Attractive force

13

first shape memory wire

14

second shape memory wire

15

valve inlet

16

valve outlet

17

spring element

18

additional magnet

Claims (19)

Implantable force transmission system, in particular for adjusting a valve, with an actuator ( 2 ), which together with at least one first permanent magnet ( 3 ) or body of soft magnetic material in a hermetically sealed housing ( 1 ), characterized in that the actuator ( 2 ) the first, permanent magnet ( 3 ) or body in a linear guide in the housing ( 1 ) at least one encapsulated second permanent magnet ( 5 ) in a guided tour ( 7 ) outside the housing ( 1 ) at a distance from the first permanent magnet ( 3 ) or body is arranged, and that a magnetic force between the first permanent magnet ( 3 ) or body and the second permanent magnet ( 5 ) acts. Implantable force transmission system, in particular for adjusting a valve, with an actuator ( 2 ), which together with at least one first permanent magnet ( 3 ) in a hermetically sealed housing ( 1 ), characterized in that the actuator ( 2 ) the first permanent magnet ( 3 ) in a linear guide in the housing ( 1 ) in a controlled manner that at least one encapsulated body of soft magnetic material in a guide ( 7 ) outside the housing ( 1 ) at a distance from the first permanent magnet ( 3 ) is arranged, and that a magnetic force between the first permanent magnet ( 3 ) and the body works. Power transmission system according to claim 1, characterized in that the actuator ( 2 ) by at least two shape memory elements ( 13 . 14 ) is formed in a direction of displacement of the first permanent magnet ( 3 ) or body to the second permanent magnet ( 5 ) in front of and behind the first permanent magnet ( 3 ) or body are arranged. Power transmission system according to claim 2, characterized in that the actuator ( 2 ) by at least two shape memory elements ( 13 . 14 ) is formed in a direction of displacement of the first permanent magnet ( 3 ) to the encapsulated body of soft magnetic material in front of and behind the first permanent magnet ( 3 ) are arranged. Power transmission system according to claim 3 or 4, characterized in that the two shape memory elements ( 13 . 14 ) extend perpendicular to the direction of displacement and are fixed on both sides at their ends. Power transmission system according to claim 5, characterized in that the two shape memory elements ( 13 . 14 ) are arranged so that the first permanent magnet ( 3 ) or body in the stretched state of the one element ( 13 ) in a first position in the direction of displacement and in the extended state of the other element ( 14 ) is in a second position. Power transmission system according to one of claims 3 to 6, characterized in that the two shape memory elements ( 13 . 14 ) Are shape memory wires. Power transmission system according to one of claims 3 to 7, characterized in that in the direction of displacement behind the first permanent magnet ( 3 ) or body another permanent magnet ( 18 ) fixed on the first permanent magnet ( 3 ) or body exerts an attractive force. Power transmission system according to one of claims 1 to 8, characterized in that the guide ( 7 ) for the second permanent magnet ( 5 ) or body is a linear guide. Power transmission system according to claim 9, characterized in that the two linear guides lie on the same axis. Power transmission system according to claim 9 or 10, characterized in that the first permanent magnet ( 3 ) or body and / or the second permanent magnet ( 5 ) or body in a guide body ( 4 . 6 ) is firmly embedded, which is guided in the linear guide. Power transmission system according to claim 9 or 10, characterized in that the first permanent magnet ( 3 ) or body and the second permanent magnet ( 5 ) or body in the linear guide or in a guide body ( 4 . 6 ) are freely rotatably arranged, which is guided in the linear guide. Power transmission system according to one of claims 1 to 12, characterized in that the housing ( 1 ) rigid with the guide ( 7 ) for the second permanent magnet ( 5 ) or body is connected. Power transmission system according to one of claims 1 to 13, characterized in that between the actuator ( 2 ) and the first permanent magnet ( 3 ) or body is arranged a force measuring device. Power transmission system according to one of claims 1 to 14, characterized in that the actuator ( 2 ) is connected to control electronics through which the actuator ( 2 ) for moving the first permanent magnet ( 3 ) or body is controllable. Power transmission system according to claim 15, characterized in that the control electronics is programmable. Power transmission system according to claim 16, characterized in that the control electronics are connected to a telemetry device, via which the control electronics can be programmed wirelessly by an external programming device. Power transmission system according to one of claims 1 to 17, which additionally has a valve with a valve seat ( 9 ) and a valve body ( 8th ), the leadership ( 7 ) and the valve are arranged so that the second permanent magnet ( 5 ) or body by the magnetic force of the first permanent magnet ( 3 ) or body the closure body ( 8th ) directly or indirectly against the valve seat ( 9 ) presses. Power transmission system according to one of claims 1 to 17, which additionally has a valve with a valve seat ( 9 ) and a valve body ( 8th ) and a spring element ( 17 ), which on the second permanent magnet ( 5 ) or body exerts a force acting against the magnetic force spring force, wherein the guide ( 7 ) and the valve are arranged so that in dependence on a differential force between the magnetic force and the spring force of the closure body ( 8th ) by the second permanent magnet ( 5 ) or body directly or indirectly against the valve seat ( 9 ) or by the second permanent magnet ( 5 ) or body no force on the valve body ( 8th ) is exercised.

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