DE102009050576A1 - Device for testing endurance limit of medical device, has two fixing devices at end cross sections of medical device, and two actuators which are coupled with fixing devices - Google Patents

Abstract

The device (1) has two fixing devices (3,4) at the end cross sections of a medical device, and two actuators which are coupled with the fixing devices. The device has a guiding element (10) at which the medical device is formed or shaped. A deformation kinematic of the medical device is recreated at a certain application site by rotational movement of the guiding element. An independent claim is also included for a method for testing the endurance limit of a medical device.

Description

The invention relates to a device for testing the fatigue strength of a medical device. Furthermore, the invention relates to a method for testing the fatigue strength of a medical device.

To demonstrate the functional safety of implantable, dynamically stressed medical devices, in particular of stents, devices for testing the fatigue strength are required. This proof is an indispensable prerequisite for obtaining CE- or FDA-compliant certification.

The materials used in stents include both purely metallic or purely polymeric materials as well as combinations of a metallic material with resorbable and permanent implant materials and constructions made therefrom for temporary or permanent retention in the human body.

With regard to the medical-technological background, it must be stated that mechanical testing of medical devices under defined alternating stress as well as taking into account the specific requirements of the respective implantation site continues to gain importance.

On the website of the company Bose http://www.boseelectroforce.com/product.cfm?pid=47 the device is "ElektroForce ^® 9400 Multiaxial Peripheral Stent Test Instrument" disclosed. The corresponding product information is under http://www.bose-electroforce.com/products/specs/MAPS_9400.pdf disclosed (cf. US 7472604 B2 ). The device is used for testing peripheral stents and simulates multi-axial loading of the stents. The stents are stressed by uniaxial dynamic bending in conjunction with radial cross-sectional deformations and tensile / compressive stress. The contact with an electrolyte (isotonic NaCl solution) is realized by a mass inertial volume flow.

In this device, the stresses applied to the stent are determined for various types of arteries and body movements. The stents are axially fixed at their end cross-sections and symmetrically bent by a centrally applied transverse stress (transverse force bending). This test regime is the same for all types of arteries and is based on a defined path- or force-controlled transverse stress regardless of the predominant shape changes and flexible rescue properties typical for the site of application.

The invention is therefore based on the object to provide a device for testing the fatigue strength of a medical device with which the shape changes or stresses of the medical device as a function of the specific strain kinematic and its flexible embedding are simulated realistically at the implantation.

This object is achieved with a device for testing the fatigue strength of medical devices according to claim 1. Furthermore, the object is achieved with a method for testing the fatigue strength of medical devices according to claim 14. Advantageous embodiments of the invention are contained in the subclaims.

According to the invention, the solution of the object in a device for testing the fatigue strength of at least one medical device with at least two fixing devices on the end sections of the medical device, at least two drives that are coupled to the fixation devices and by the different types of stress that form a test regime on the medical device can be applied, and with at least one medical device.

The device has at least one guide element to which the medical device can be molded and whose rotational movement imitates a deformation kinematic of the medical device at a specific application site. With the design of the guide element made of materials of different stiffness, the flexible embedding of the medical device at the application site can be taken into account.

The advantages of this test regime are an increase in the functional reliability of the medical device under continuous stress, a shortening of the test times of implants subjected to alternating stress, eg. As stents, and thus an improvement in patient safety and medical care.

Preferably, the guide element has at least one circular and / or involute-shaped spatial trajectory or partial segments of a trajectory for generating a path-controlled one- or two-axis rotational bend of the medical device. The path-defined rotation of the guide element can be used in conjunction with the likewise path-controlled, axially effective and rotatable fixings of the end cross-sections of the medical device to generate superimposed multiaxial shape changes / stresses on the medical device.

In an expedient embodiment, the radii of the guide element are infinitely adjustable. This allows customizing the Guide element for achieving changes in shape of the medical device equivalent to the use at different application sites.

Alternatively, the guide member may be interchangeable with another guide member having at least one other trajectory and / or other material rigidity. Again, an adjustment of the guide element for changing the shape of the medical device depending on the site of application is possible.

In a preferred embodiment, different types of stress can be applied to the medical device by means of the drives in accordance with a test regime at the application site and can be combined with one another. This allows adaptation of the stresses according to a specific application site.

In a further preferred embodiment, the drives can be operated independently of one another and different test regimes with freely selectable phase shifts of the individual types of stress on the medical device can be simulated on the device. Hereby, the test regimes can be further approximated to the real conditions in the body.

In particular, the types of stress include tensile, compressive, uniaxial or biaxial rotational bending, along with radial cross-sectional deformations, and / or torsion. A test regime in the body has complicated superpositions of different types of stress, so that for the realistic testing of a medical device, the generation of biomechanically relevant load combinations is indispensable.

The medical device may be formed of a metallic or polymeric material. The medical device can also be formed from a combination of a metallic material with resorbable and permanent implant materials. The medical device can be clamped directly or by a polyetherurethane or polysiloxane elastomer.

The device according to the invention is suitable for testing all of the named materials and therefore can be used flexibly.

The medical device ( 2 ) may be embedded in a transparent polyether urethane or polysiloxane elastomer tube.

The device preferably comprises an endoscope for an inspection in the interior of the medical device. This makes it possible to control the resistance of the medical device from within during testing.

Additionally or alternatively, the device includes a video camera for inspection of the medical device from the outside. This can z. B. in transparent medical devices also the interior are checked during testing. For non-transparent medical devices, the behavior of the component can be documented externally.

In a particular embodiment, the medical device is a stent, which is traversed by an electrolyte spray. The electrolyte spray produces a higher corrosive attack on the stent than a liquid electrolyte and does not cause any moving masses. This allows a stent to be tested more efficiently in terms of materials.

Furthermore, the solution of the problem in a method for testing the fatigue strength of a medical device with a device according to the invention. During a rotational movement of the guide element, the medical device attaches itself to the guide element, and a deformation kinematic of the medical device at a specific application location is simulated.

In this way, a test regime can be generated, which comes closer to the real stress of the medical device in the body as stresses that can be generated with conventional test equipment. The testing time of life-relevant implants (stents) can be shortened and functional reliability can be increased within a planned lifetime.

Preferably, with the help of the drives different types of stress can be applied to the medical device according to a test regime at the application site and combined with each other.

Furthermore, the drives can be operated independently of one another and different test regimes with freely selectable phase shifts of the individual types of stress on the medical device can be simulated on the device. The stresses can thus be more precisely approximated to real conditions.

As types of stress, tensile, compressive, single or biaxial rotational bending in conjunction with radial cross-sectional deformations and / or torsion will be applied to the medical device. These types of stress are the typical types of stress occurring at an application site.

In a preferred embodiment, an endoscopic inspection takes place in the interior of the medical device. The monitoring of the material behavior of the medical device can therefore also by done inside. Furthermore, a documentation of the inspection process is possible.

In a further preferred embodiment, an inspection of a medical device takes place from the outside by means of a video camera. Thus, the material behavior of the medical device product during the testing process can also be documented.

As a decisive parameter, the fatigue test method comprises more than 10 ⁷ alternating stresses of a test regime. This number of stresses ensures certifiable and according to the state of the art at the same time reliable test results.

In particular, the medical device is a stent, which is traversed by an electrolyte spray. The electrolyte spray causes a higher corrosive attack on the medical device and has no moving masses that could affect the measurement result. This results in reliable measured values.

In the following an embodiment of the invention will be explained in more detail with reference to two figures. Show it:

1 a plan view of the inventive device and

2 a sectional view of the device according to the invention.

The 1 and 2 show the device according to the invention 1 with a stent 2 as a medical device. The device 1 mainly comprises two rails 7 , a sled 8th , a first drive rod 9 and a guide element 10 with a second drive rod 12 ,

The rails 7 are arranged parallel to each other in the x-direction of the coordinate system. On the rails 7 is the sled 8th arranged transversely.

At the sled 8th is a first end 2a of the stent 2 in a first fixing device 3 attached. The first end 2a of the stent 2 is about the first fixing device 3 with a first hose 5 connected. The first fixing device 3 is with a first drive rod 9 coupled, the hinged on the outer periphery of the first fixing device 3 attached and parallel to the slide 8th is arranged.

A second end 2 B of the stent 2 is in a second fixing device 4 attached to the guide element 10 is coupled. The second end 2 B of the stent 2 is about the second fixing device 4 with a second hose 6 connected.

The guide element 10 includes in the illustration a plane curved trajectory 11 and is stuck to the second drive rod 12 connected (cf. 2 ). The second drive rod 12 is parallel to the slide 8th arranged and forms the axis of rotation for the guide element 10 , The guide element may have a variable material rigidity.

For testing the stent 2 becomes the stent 2 first with his first end 2a in the first fixing device 3 and with its second end 2 B in the second fixing device 4 attached. An electrolyte spray E is continuously passed through the first tube during the entire testing process 5 in the stent 2 passed and over the second hose 6 from the stent 2 dissipated. As an alternative to the electrolyte spray E, water or a liquid electrolyte can also be used.

On the stent 2 A test regime is applied that captures the strain, compression, torsion, and rotational bending stresses associated with radial cross-sectional deformations. The train or pressure is with the help of the carriage 8th on the stent 2 applied. The sled 8th is moved by means of a drive, not shown, depending on the conditions at the planned application site in the body in the pulling direction X1 or in the printing direction X2 or alternately in the pulling direction X1 and the pressure direction X2 and the stent 2 while stretched or compressed.

The first drive rod 9 serves to generate a torsional movement of the stent 2 about its longitudinal axis L3, which runs in the x-direction of the coordinate system. The torsional motion is generated by the first drive rod 9 is moved by a drive, not shown in the longitudinal direction L1. This turns the first drive rod 9 the first fixing device 3 in the torsion direction T. The torsion may be in a direction about the longitudinal axis L3 of the stent 2 be done or be back and forth. The resulting torsional motion superimposes the tensile pressure movement in the stent 2 ,

The tensile-pressure movement and the torsional movement are combined with a rotation bend in the stent 2 combined. The rotation bend is generated by the second drive rod 12 is rotated by a drive, not shown, in the bending direction B about its longitudinal axis L2. This is the guide element 12 with turned. The second fixing device 4 on the guide element 10 attached, causes the stent 2 to the trajectory 11 of the guide element 10 applies and according to the trajectory 11 is bent. When turning back the second drive rod 12 becomes the stent 2 relieved again and returns to its original form.

The stress types tension, compression, torsion and bending are combined with each other and superimposed on each other so that they come close to the given stresses at the planned application site. Each type of stress is applied periodically, the phase shifts and frequencies being freely selectable.

The effects of the specific rescue properties of the application site on the shape changes of the medical device are modeled by an adapted interpretation of the material stiffness of the guide element.

The device allows the simultaneous testing of multiple medical devices with the same testing regime.

LIST OF REFERENCE NUMBERS

1

contraption

2

stent

2a

First end

2 B

Second end

3

First fixing device

4

Second fixing device

5

First hose

6

Second hose

7

rail

8th

carriage

9

First drive rod

10

guide element

11

trajectory

12

Second drive rod

e

electrolyte spray

X1

tensile direction

X2

print direction

T

torsional

B

bending direction

L1

longitudinal axis

L2

longitudinal axis

L3

longitudinal axis

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 7472604 B2 [0005]

Cited non-patent literature

• http://www.boseelectroforce.com/product.cfm?pid=47 [0005]
• http://www.bose-electroforce.com/products/specs/MAPS_9400.pdf [0005]

Claims (21)

Contraption ( 1 ) for testing the fatigue strength of at least one medical device ( 2 ) with at least two fixing devices ( 3 . 4 ) at the end cross sections of the medical device ( 2 ), at least two drives connected to the fixing devices ( 3 . 4 ) and by the different types of stress, which form a test regime, on the medical device ( 2 ) and with at least one medical device ( 2 ), characterized in that the device ( 1 ) at least one guide element ( 10 ) to which the medical device ( 2 ) is anformbar and by its rotational movement a deformation kinematic of the medical device ( 2 ) can be imitated at a specific application location. Contraption ( 1 ) according to claim 1, characterized in that the guide element ( 10 ) at least one circular and / or involute-shaped spatial trajectory ( 11 ) or subsegments of a trajectory ( 11 ) for generating a path-controlled one- or two-axis rotation bend of the medical device ( 2 ) having. Contraption ( 1 ) according to claim 2, characterized in that the radii of the guide element ( 10 ) are infinitely adjustable. Contraption ( 1 ) according to claim 1 or 2, characterized in that the guide element ( 10 ) against another guide element ( 10 ) with at least one other trajectory ( 11 ) and / or other material stiffness is interchangeable. Contraption ( 1 ) according to one of claims 1 to 4, characterized in that by means of the drives different types of stress corresponding to a test regime at the site of application to the medical device ( 2 ) can be applied and combined with each other. Contraption ( 1 ) according to claim 5, characterized in that the drives are operated independently of each other and on the device ( 1 ) different test regimes with freely selectable phase shifts of the individual types of stress on the medical device ( 2 ) are simulated. Contraption ( 1 ) according to one of claims 1 to 6, characterized in that the types of stress comprise tension, pressure, one or two-axis rotational bending, accompanied by radial cross-sectional deformations, and / or torsion. Contraption ( 1 ) according to one of claims 1 to 7, characterized in that the medical device ( 2 ) is formed of a metallic or polymeric material. Contraption ( 1 ) according to one of claims 1 to 7, characterized in that the medical device ( 2 ) is formed from a combination of a metallic material with resorbable and permanent implant materials. Contraption ( 1 ) according to one of claims 1 to 7, characterized in that the medical device ( 2 ) is embedded in a transparent polyether urethane or polysiloxane elastomer tube. Contraption ( 1 ) according to one of claims 1 to 10, characterized in that the device ( 1 ) an endoscope for an inspection in the interior of the medical device ( 2 ). Contraption ( 1 ) according to one of claims 1 to 11, characterized in that the device ( 1 ) a video camera for an inspection of the medical device ( 2 ) from the outside. Contraption ( 1 ) according to one of claims 1 to 12, characterized in that the medical device ( 2 ) a stent ( 2 ), which is traversed by an electrolyte spray (E). Method for testing the fatigue strength of a medical device ( 2 ) with a device ( 1 ) according to claims 1 to 14, characterized in that during a rotational movement of the guide element ( 10 ) the medical device ( 2 ) to the guide element 10 applies and a deformation kinematic of the medical device ( 2 ) is simulated at a certain application location. A method according to claim 14, characterized in that with the help of the drives different types of stress corresponding to a test regime at the site of application to the medical device ( 2 ) are applied and combined with each other. A method according to claim 14 or 15, characterized in that the drives are operated independently of each other and on the device ( 1 ) different test regimes with freely selectable phase shifts of the individual types of stress on the medical device ( 2 ) are simulated. Method according to one of claims 14 to 16, characterized in that the types of stress train, pressure, one- or two-axis rotational bending and / or torsion on the medical device ( 2 ) are applied. Method according to one of claims 14 to 17, characterized in that an endoscopic inspection in the interior of the medical device ( 2 ) he follows. Method according to one of claims 14 to 18, characterized in that an inspection of a medical device ( 2 ) from the outside by means of a video camera. Method according to one of claims 14 to 19, characterized in that the method for fatigue testing comprises more than 107 alternating stresses of a test regime. Method according to one of claims 14 to 20, characterized in that the medical device ( 2 ) a stent ( 2 ), which is traversed by an electrolyte spray (E).

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