DE102005045070A1 - Femur implant, comprises magnetically operated mechanism for moving holding elements - Google Patents

Abstract

A mechanism causing the radial positioned holding elements (5) to move is accommodated inside the hollow shaft (3,4) of the implant (1). A magnetic element (7) is positioned above a transmission unit (8) acting on a shaft (9) with an oval cross section when the magnet (7) is activated by an exterior device. Two sets of radial positioned holding elements (5) are moved horizontally when the shaft (9) is rotated by the mechanism and pushed into the surrounding tissue for a better anchoring effect.

Description

The The invention relates to a bone implant, in particular a femoral neck prosthesis, with an elongated one Shaft with one or more, laterally protruding projections for Achievement of a frictional Connection to the adjacent bone.

Very often be hip joint prostheses, in particular in older Persons often suffer from osteoporosis and more often to femoral neck fractures comes, implanted. Also arthroses of the hip joint are due to excessive wear or genetically determined deformities of the hip bone is a common indication for implantation of a hip joint prosthesis or a femoral neck prosthesis. During implantation, the femoral neck becomes separated from the femur with the ball joint. In the remaining femurs a conical blind hole is milled, its contour of the shape of the shaft of the prosthesis to be used equivalent. This replaced outside of the femur the femoral neck with the ball joint. The shaft of the implant is coated with bone cement so that a force-fit Contact between the prosthesis and the bone arises. To support the force fit and thus the fixation of the prosthesis on or in the bone is the Shank with several laterally protruding, z. B. knob-like projections fitted, so that is an irregular, structured surface results, which offers a better grip.

A frequent Complication is solving the non-positive Connection between prosthesis shaft and bone, especially in the Case of osteoporosis disease. In such a case will be so far the prosthesis either surgically fixed again or replaced.

Also bone fractures often involve bone implants used to connect two broken bones, this means, Again, the implant is located in the bone and with this anchored. Also, such implants are mainly used by the elderly The problem here is that the healing process is relative is slowly going on and consequently a consistent immobilization is required. Again, there is the problem that the implant detach from the bone can.

Of the The invention is thus based on the problem of a bone implant specify that without additional If necessary, engage the bone again can.

to solution This problem is with a bone implant of the aforementioned Art provided according to the invention, that or the projections displaceable relative to the shaft and with at least one in the shaft movably received magnetic element, which over a with it interacting external magnetic field is movable, motion coupled is.

Different than in all known implants are in the bone implant according to the invention the laterally protruding, usually knob-like projections radially movable, can so be extended radially. This movement is via a magnetic Controlled element that with the or radially displaceably mounted projections is motion coupled. This magnetic element acts to move the projections with an external magnetic field that is used to move the magnetic Element is varied accordingly, so that the magnetic element the field movement or field variation follows. From this movement of the magnetic element results due to the motion coupling of the same to the tabs their movement.

This means that in case of solving the frictional Connecting, for example, the femoral neck implant to the bone the projections slightly further radially outwards moved and pushed back into or on the bone, therefore So the prosthesis is anchored again. Preference is given to several projections provided, facing each other lie so that the prosthesis in the bone again spreads well.

The bone implant according to the invention can So only by interaction of the magnetic element with the be re-anchored external magnetic field, a possible as usual so far operational Intervention is advantageously no longer necessary here. The patient will only a changing, exposed to moving magnetic field, which controls the movement of the projections becomes.

With regard to the movement coupling of the projection or projections, various embodiments are conceivable. The protrusion (s) may be motion coupled to a rotatably mounted actuator which in turn is motion coupled to the magnetic element. Here, therefore, the displacement of the projections is realized by a rotational movement of the actuating element, wherein this rotational movement of the actuating element is caused by the external magnetic field in connection with the magnetic element. Alternatively, it is conceivable vorzuse a linearly displaceable actuator hen, with which the projections are coupled, and this linearly displaceable actuator is coupled to the magnetic element and can be moved linearly via the external magnetic field.

in the Case of a rotatably mounted actuating element has this at least in the field of motion coupling to the one or more protrusions a non-circular Section on. The diameter or width of the rotatably mounted Stellelements thus varies, so therefore also the projections more or less far removed from the shaft, depending on how the position is the non-round actuator. The non-circular positioning element is included preferably as elongated Rod executed, the cross-section is at least partially out of round, or at the a radially projecting non-circular approach is provided, for example is designed as a disc or the like. "Out of round" in this case means, for example an oval cross section or a cross section with a substantially "G" shape but any cross-sectional shape that occurs during a rotation due to non-round shape the protrusion movement according to the invention allowed.

One linearly displaceable actuator can be at least in Range of motion coupling to the one or more projections in have its shape conically widening section. Here changes that is, the diameter or the shape of the actuating element substantially conical, so that also depending on the position of the conical Control element with respect the positionally fixed with respect to the linear actuator movement projections these can be pushed out more or less. there can the actuator as elongated, at least partially conical rod be executed, but it is conceivable also an execution as a rotatable threaded rod with a conical running on this Adjusting nut or adjusting sleeve. In general, therefore, every execution used in which a linear movement of the conical section for the projection movement according to the invention leads.

Of the or the projections are preferred with a guide bar in each case one substantially radially to the shaft longitudinal axis extending guide bore guided and over the web end preferably directly coupled to the adjusting element motion. A movement of the actuating element thus results directly in one Projection moving.

Farther can be provided that the driving a rotatable actuator magnetic element over the external magnetic field rotatable and the linearly displaceable Actuator driving magnetic element via the external magnetic field is mounted linearly displaceable. The movement of the magnetic Elements thus corresponds to that which also performs the actuator. A rotatably mounted magnetic element is thus connected to a rotating external magnetic field moves while moving to the linear movable magnetic element, the external magnetic field linear is moved. The magnetic element, which is a permanent magnet, preferably in rod form, follows the magnetic field movement that naturally relative to this application slowly.

Especially is appropriate it, when the magnetic element coupled to this reduction gear is downstream. About this is achieved that a movement of the magnetic element, caused through the varying external magnetic field, in comparison with the movement path of the magnetic element much shorter movement of the actuating element is implemented, whereby a correspondingly high torque can be achieved. In the case of a rotatably mounted magnetic element that over the transmission gear coupled with a cross-sectionally oval rod, for example is, the magnetic element is rotated several times 360 °, around the oval pole between its two extreme positions with respect to the projections or webs to twist, with the number of rotations of the element from the reduction ratio depends.

The Design becomes obvious made such that an adjustment fixed or locked is and is maintained, and an inadvertent return movement is excluded. It is thus avoided that, should the patient For some reason be exposed to an external magnetic field, this accidentally the extended projections moved back again, which is why, for example, correspondingly high field strengths are required for element movement are. It is also avoided that the protrusions pressed against the bone after Completion of the adjustment movement, the Stellele ment push back a bit and so the solid frictional Bone system is loosened a bit again. Also conceivable locking mechanisms, the for example about the external magnetic field only solved Need to become, to make a new adjustment.

Further Advantages, features and details of the invention will become apparent the embodiments described below and with reference to the Drawings. Showing:

1 1 is a schematic representation of a bone implant according to the invention in the form of a femoral neck implant of a first embodiment,

2A . 2 B two possible cross-sectional shapes of the rod-like actuating element,

3 the bone implant 1 with further extended projections,

4 a bone implant according to the invention of a second embodiment with retracted projections,

5 the bone implant 4 with protrusions pushed out,

6 a bone implant according to the invention of a third embodiment with retracted projections, and

7 the bone implant 6 with protrusions pushed out.

1 shows a bone implant according to the invention 1 in the form of a femoral neck implant 2 , which has an elongated shaft 3 has, in the an inner receptacle 4 for a moving mechanism for moving laterally projecting protrusions 5 is provided. The bone implant 1 is preferably implemented in two parts to insert this movement device, that is, the recording 4 can be opened.

The movement device comprises a magnetic element 6 in the form of a permanent magnet 7 which is rod-shaped here, and to which its two poles N and S are shown. This permanent magnet 7 is with a reduction gear 8th it is rotatably coupled, it is rotatable about the vertical axis V, to which an external magnetic field H is applied, which as shown by the arrow is also rotated accordingly.

About the reduction gear 8th is the rotational movement of the permanent magnet 7 converted accordingly, so that a much lower rotation of the coupled with the transmission gear rod-shaped actuating element 9 results. The rod-shaped actuator 9 has a non-circular cross section, this can, see 2A be oval or, see 2 B be essentially G-shaped.

The projections 5 each have a rod or pin-shaped web 10 on which they drill into appropriate holes 11 , Which extend substantially radially to the shaft longitudinal axis and into the receptacle 4 are guided. They lie with their bridge ends 12 in this embodiment, directly on the non-circular outer side of the actuating element 9 at.

Now, via the external magnetic field H, the permanent magnet 7 turned, this results from the reduction gear 8th controlled a rotational movement of the actuating element 9 , In 1 is the actuator 9 for example, as in 2A is hinted, so that the bridge ends 12 on the sides with a small diameter. Will now be the actuator 9 rotated by 90 °, for example, as a result of the oval or generally non-circular shape, the webs 10 pushed outward. The projections 5 are thus moved radially outwards, as in 3 is shown. In again 3 shown sectional view through the actuator 9 can be seen in the in 3 end position shown now the bridge ends 12 at the areas of widest diameter of the actuator 9 at. Due to the radial movement of the projections 5 so they can be pushed back to the bone, if the frictional connection to the bone, which is not shown here, has been released. In this adjustment position, the projections are fixed, unintentional reverse rotation or provision is excluded. The prosthesis can therefore be anchored again. It is expedient if the projections face each other so that they spread each other in the bone.

4 shows a further embodiment of a bone implant according to the invention 13 , which is also a magnetic element 14 in the form of a permanent magnet 15 having, with a reduction gear 16 is coupled. The reduction gear 16 in turn is with an actuator 17 connected, which is executed here in the manner of a cone, that is, the diameter changes conically. Again, the projections 18 via appropriate guide bars 19 in corresponding holes 20 in the prosthesis socket 21 that up in the recording 22 are guided, received radially displaceable.

In this embodiment, the radial Ausschiebebewegung the projections 18 by an over the external magnetic field H obtained linear displacement of the actuating element 17 , Unlike the embodiment according to 1 Here, the permanent magnet is also linear to the transmission gear 16 postponed. The relatively short, controlled by the external magnetic field H linear magnetic movement is converted into a correspondingly longer adjusting movement, that is, the travel of the actuating element 17 is significantly longer than the path of movement of the permanent magnet 15 ,

Due to the conical configuration of the actuating element 17 Now, in this linear movement, the projections 18 that cross the bridge 35 directly on the surface of the conical actuator 17 , abut, pushed outward. So here comes a linear motion of both the Per Manentmagneten and the actuating element used.

A third embodiment of a bone implant according to the invention 23 shows 6 , The magnetic element provided here 24 , also a permanent magnet here 25 , is rotatable via the external magnetic field H and with a reduction gear 26 coupled. This in turn is with a threaded rod 27 connected, on which a conical actuator 28 , which forms a conical adjusting nut or adjusting sleeve, runs. Upon rotation of the threaded rod 27 becomes the conical actuator 28 moved linearly. The projections 29 are about their leadership 30 that also here in corresponding holes 31 in the prosthesis socket 32 are guided, directly with the conical actuator 28 coupled, that is, the bridge ends 33 lie directly on the outside of the conical actuator 28 at. The threaded rod 27 is (the same applies to the rotatable actuator 9 out 1 ) With its lower end, for example via a plain bearing 34 superimposed.

If now the external magnetic field H is rotated slightly, this results in a rotation of the permanent magnet 25 , in a seen from the angle of rotation forth significantly greater rotational movement of the threaded rod 27 , defined by the reduction gear 26 , results. As a result of the rotation of the threaded rod 27 becomes the conical actuator 28 moved down. The bridge ends 33 run on the outside of the conical actuator 28 , resulting in the projections 29 also pushed radially outward here.

Claims (10)

A bone implant, in particular a femoral neck prosthesis, having an elongated shaft with one or more projections projecting laterally therefrom for effecting a frictional connection to the adjacent bone, characterized in that the projection or projections ( 5 . 18 . 29 ) relative to the shaft ( 3 . 21 . 32 ) slidably and with at least one in the shaft ( 3 . 21 . 32 ) movably received magnetic element ( 6 . 14 . 24 ), which is movable via an external magnetic field (H) interacting with it, are motion-coupled. Bone implant according to claim 1, characterized in that the projection or projections ( 5 . 18 . 29 ) with a rotatably mounted or linearly displaceable actuator ( 9 . 17 . 28 ) are in motion coupled, which in turn with the magnetic element ( 6 . 14 . 24 ) is motion coupled. Bone implant according to claim 2, characterized in that the rotatably mounted actuating element ( 9 ) at least in the region of the movement coupling to the projection or projections ( 5 ) has a non-circular section. Bone implant according to claim 3, characterized in that the actuating element ( 9 ) is listed as an elongated rod, which is at least partially non-circular in cross-section, or at which a radially protruding non-circular approach is provided. Bone implant according to claim 2, characterized in that the linearly displaceable actuating element ( 17 . 28 ) at least in the region of the movement coupling to the projection (s) ( 18 . 29 ) has a conically widening section in its shape. Bone implant according to claim 5, characterized in that the actuating element ( 17 ) as an elongated, at least partially conical rod, or as a rotatable threaded rod ( 27 ) running conical adjusting nut or adjusting sleeve ( 28 ) is listed. Bone implant according to one of the preceding claims, characterized in that the projection or projections ( 5 . 18 . 29 ) with a guide bar ( 10 . 19 . 30 ) in each case in a substantially radially to the shaft longitudinal axis extending guide bore ( 11 . 20 . 31 ) and over the bridge end ( 12 . 22 . 33 ) with the actuating element ( 9 . 17 . 28 ) are motion coupled. Bone implant according to one of the preceding claims, characterized in that the a linear or a rotatable threaded rod linearly displaceable actuator ( 9 . 28 ) driving magnetic element ( 6 . 24 ) via the external magnetic field (H) rotatable and a linearly displaceable actuator ( 17 ) driving magnetic element ( 14 ) is mounted linearly displaceable over the external magnetic field (H). Bone implant according to one of the preceding claims, characterized in that the magnetic element ( 6 . 14 . 24 ) a coupled with this reduction gear ( 8th . 16 . 26 ) is connected downstream. Bone implant according to one of the preceding claims, characterized in that the magnetic element ( 6 . 14 . 24 ) a preferably rod-shaped permanent magnet ( 7 . 15 . 25 ).