Extracorporeal length-adjustable implant system and length-adjustable implant component

Description

[0001] The invention relates to an externally (extracorporeally) adjustable implant component as part of an endoprosthesis and to an implant system comprising such an implant component and an adjustment device therefor.

[0002] The adjustment device is provided for a prosthesis stem of the implant component, which is designed for attachment to a bone to be lengthened, and comprises mutually displaceable attachment parts, each of which is to be arranged on a part of the bone to be lengthened, as well as an adjustment element driven by a drive element, which is designed to distract the two mutually displaceable attachment parts.

[0003] Intracorporeally adjustable prostheses are important for applications where the prosthesis is intended to grow with the patient. They are particularly indicated in cases where a correspondingly longer prosthesis is required due to natural processes, such as the growth of children, but also for applications where, for bone formation (osteogenesis), the bone is progressively stretched further along a separation or fracture site in order to continuously stimulate the formation of new cells. For example, in the latter application, the two bone pieces created by the separation site are successively moved away from each other, for example by 1 mm per day, in order to constantly stimulate the formation of new bone tissue. In this way, for example, an extremity such as a leg can be lengthened. This is important for creating a length equalization between a person's two legs.In a similar way, although usually much slower, by constantly increasing the length of a prosthesis, the bone fitted with the prosthesis can become longer in a similar way to what would happen during the natural growth process of children or adolescents.

[0004] It has long been known that external fixators are used in such cases. However, these have serious disadvantages, such as being cumbersome and hazardous to use, as well as carrying a high risk of infection.

[0005] To address these disadvantages, implantable prostheses have been developed that allow for desired length adjustment via an intracorporeally implanted prosthesis. The actual length adjustment can be performed invasively, particularly in the case of purely mechanical length adjustment, or via a drive implanted in the prosthesis that is remotely controlled externally (Mutars system from the German company Implantcast GmbH, Synoste system from the Finnish company Synoste Oy).

[0006] The latter offer the advantage that adjustment can be performed non-invasively from the outside. For this purpose, the prosthesis contains an electric motor or forms part of an electric motor that can be controlled externally (extracorporeally). If necessary, it can also be supplied with energy externally. Such a design with a so-called distributed electric motor is known, in which the prosthesis and its adjustment element form part of an electric motor (the rotor, so to speak), and the other part with the excitation (the stator, so to speak) is formed by an extracorporeal attachment (WO 01 / 786141). The actual electric motor is therefore essentially arranged partly intracorporeally (with its rotor) and partly extracorporeally (with its stator).

[0007] Such an electric motor-based system is easy to operate, but incorrect operation is also relatively easy. While sufficient extracorporeal adjustability can be achieved, the risk of operating errors—in which case the electric motor's high adjustment force could cause incorrect adjustment that is dangerous for the patient—requires skilled personnel to operate it. Approval of such a system is therefore complex and difficult. It can usually only be used by qualified personnel, which entails additional work. This leads to coordination problems with regard to the required appointment times at which the qualified personnel have time to treat (outpatient) patients, or leads to (overly) large adjustment units (in cm of adjustment range per appointment) in order to minimize the number of patient visits (albeit at the cost of adjusting units that may be medically questionable in terms of size per appointment).

[0008] US2011 / 230883 A1 discloses a length-adjustable IM nail system comprising a telescoping IM nail with a proximal and a distal body. An internal magnet in the proximal body is connected to a threaded rod, which in turn is connected to the distal body. The threaded rod passes through a threaded block connected to the proximal body. The position of the distal end of the threaded rod is fixed relative to the distal body, but can rotate freely within this fixed position. An actuator is also disclosed, comprising a pair of rotating magnets arranged in an angular relationship to each other and to the axis of the IM nail and the patient's limb. Rotation of these external magnets in the same direction results in rotation of the internal magnet and the threaded rod, as well as axial telescopic movement of the threaded block and the proximal body relative to the distal body.

[0009] CN 102 895 048 A relates to an artificial bone for a human body capable of lengthening through a non-surgical procedure. The artificial bone is characterized by comprising an upper bone, a lower bone, a rotating body, a protective cover, and a control portion. The lower end of the upper bone integrally forms a first spiral connecting portion, the upper end of the lower bone integrally forms a second spiral connecting portion, and the rotating body is connected to the first spiral connecting portion and the second spiral connecting portion and rotates to enable separation of the upper bone from the lower bone. Magnetic rings are regularly distributed around the circumference of the rotating body.The protective cover extends to completely enclose the rotated body along its longitudinal direction, preventing human body tissue from coming into contact with the outside. The control section enables rotation of the rotated body through magnetic force.

[0010] US Pat. No. 7,753,915 B1 discloses a system for adjusting bone length, comprising a two-part telescopic device connected to bone portions whose length is to be adjusted between the connection points. Each portion of the telescopic device is attached to a bone portion. A rod, with an embedded permanent magnet, is threadedly engaged at both ends with both portions of the telescopic device. The permanent magnet is excited by an external magnet assembly, so that a radial force is exerted on the rod, causing it to rotate. The rotation of the rod is converted via the threads at both ends into an axial movement of the telescopic portions relative to one another, thereby causing an increase or decrease in bone length depending on the direction of the axial movement between the telescopic portions.

[0011] US 2004 / 030395 A1 discloses a surgical distraction device for non-invasively applying a stretching or tensioning force to a patient's skeleton or to an implant, comprising anchoring means for securing a first and a second component of the device to a bone or adjacent bones, the components being connected by a linkage having an extendable length. The distraction device comprises a magnet connected to the linkage via a reduction gear and actuating means arranged externally of the patient for generating a moving or varying electromagnetic field, causing the magnet to rotate and the linkage to extend.

[0012] The invention is based on the object of creating an improved system that allows extracorporeal actuation and is easier to handle.

[0013] The inventive solution lies in the features of the independent claim. Advantageous further developments are the subject of the dependent claims.

[0014] The invention relates to an implant component in which the adjustment device is designed such that a drive element with a rotatably arranged permanent magnet acts via a gear on a spindle drive to convert a rotary movement of the permanent magnet into a distracting longitudinal movement, wherein the drive element is designed for actuation by means of a magnetic field of an extracorporeal drive unit, and with particular advantage a bending rod is provided for power transmission from the drive element to the spindle drive.

[0015] Thanks to the bending rod, which is elongated and designed to absorb or transmit shear forces, any bending of the implant component that occurs under load can be compensated. The bending rod makes it possible to compensate for an angular error between the drive element with the gear (reduction gear) on the one hand and the actual spindle drive on the other. Such an angular error arises in particular when the implant component bends under high load. The fastening parts that move relative to one another, typically the inner and outer tubes of a telescopic adjustment mechanism, are bent perpendicular to their central axis under load. There is then a risk that the actual drive element with the gear is no longer exactly aligned with the axis of the spindle drive.Such misalignments, which are usually only due to small angular differences, can lead to the mechanism jamming. The invention recognizes that this can be reliably prevented in an astonishingly simple way by means of a bending rod between the drive element and gear on the one hand, and the spindle drive on the other. This eliminates the risk of the adjustment element jamming, even under high load.

[0016] For this purpose, the drive spindle expediently has a central bore that is open on one side and into which the bending rod is inserted. This not only ensures that the bending rod is well guided, but also results in a relatively long bending rod with a compact design. This makes it possible to absorb even relatively large angular errors of up to + / - 5 degrees using the bending rod. For a force-locking connection between the bending rod on the one hand and the drive spindle on the other, a coupling between the free end of the bending rod and the drive spindle is preferably provided at the base of the central bore. For this purpose, it is further expediently provided that the bending rod has a length that preferably corresponds to at least one third, more preferably at least one half, of the length of the drive spindle, and is particularly designed to absorb an angular offset of up to + / - 5 degrees.It is advantageous to have a laterally constricted design along its main section. This facilitates the desired bending of the bending rod and also ensures the required clearance of the bending rod in the central bore.

[0017] In the case of an extracorporeally length-adjustable implant system, an implant component as previously described; and an extracorporeal drive unit for the drive element of the implant component, it is further provided that the extracorporeal drive unit has a rotatably mounted extracorporeal magnetic ring with an interior space which is designed to receive the bone to be lengthened with the adjustment device, and an actuating device which is designed to rotate the extracorporeal magnetic ring in its ring plane, wherein the extracorporeal magnetic ring is designed as a permanent magnet and has a directed static magnetic field in its interior space which is ring-fixed, and the extracorporeal magnetic ring is mechanically rotated by the actuating device.

[0018] Here are some of the terms used: "Ring-fixed" refers to an arrangement that is fixed in relation to the ring and rotates with the ring.

[0019] "Directional" refers to a typically uniform orientation of a magnetic field. In particular, the magnetic field should have the same direction at every point within the field. "Homogeneous" refers to a substantially uniform magnetic field in which local deviations in field strength in a central region comprising at least 80% of the total area amount to a maximum of + / - 10% of the mean value.

[0020] "Static" refers to a magnetic field of constant strength. It thus forms a contrast to the typically rapidly changing electromagnetic fields.

[0021] This embodiment of the invention is based on the idea of moving away from the electromotor-operated concept and instead providing mechanical actuation. The invention achieves this by providing a static magnetic field via the magnetic ring, which can be rotated mechanically (manually or by motor). Preferably, the magnetic ring as a whole is rotated by the actuating device. The permanent magnet acting as the drive element within the implant component always aligns itself according to the static magnetic field of the magnetic ring. The position of the permanent magnet acting as the drive element within the adjustment device therefore results from the position or the rotation of the static magnetic field. By switching to a mechanically rotated static magnetic field, the invention achieves significant simplification and precise position control over the position of the permanent magnet acting as the drive element.This means that a simple manual operation can be sufficient; electricity is no longer required for operation.

[0022] This also eliminates any risk of electric shock due to a malfunction. Furthermore, any risk of a malfunction resulting in the position adjustment running away, which could lead to excessive adjustment and thus injury to the bone itself and, in particular, to the surrounding soft tissues such as muscles or tendons, is eliminated. Furthermore, thanks to the constant static magnetic field, patient exposure to eddy currents, such as those generated by changing electromagnetic fields, is avoided.

[0023] The system, with its drive unit based on a static magnetic field, can thus be operated by assistants or laypersons, and in principle even by the patient themselves. This represents a significant advantage in medical practice, as the patient can operate the adjustment device at home if necessary. This makes it possible to perform adjustments more frequently and in shorter, gentler increments than was previously possible with the state of the art, especially when operation was only permitted by trained personnel.

[0024] Furthermore, this embodiment of the invention with the rotatable magnetic ring allows precise control over the orientation of the static magnetic field. This allows for fine adjustment of the angular position of the drive element of the adjustment device, enabling very precise adjustment of the achieved adjustment.

[0025] The invention thus achieves an astonishingly simple increase in adjustment reliability while simultaneously simplifying the drive unit, making it suitable for laypeople and patients.

[0026] The magnetic ring is preferably divisible into at least two segments in order to create openable and closable access to the interior of the magnetic ring for a body part provided with the prosthetic shaft, in particular a leg or arm. This allows the magnetic ring and thus the drive unit as a whole to be easily arranged at the location in the body where the implant component with the adjustment device is arranged. For example, by folding open the magnetic ring, the drive unit can be easily positioned in the area of a patient's thigh in order to adjust the shaft of an implant component arranged in the femur. This eliminates the need to thread the extremity to be treated through the magnetic ring. The remainder of the drive unit is preferably designed in such a way that folding open the magnetic ring allows free access to its interior.The application is made considerably easier thanks to the foldable magnetic ring.

[0027] It is also advantageously provided that the magnetic force of the magnets arranged in the magnetic ring neither prevents nor promotes the opening of the magnetic ring. For this purpose, the magnetic ring is designed so that it can be opened without magnetic force. "Free of magnetic force" here means that the force directed by the magnetic force against opening is either zero or so small that an operator can easily overcome it by hand, in particular without the use of tools. For this purpose, a parting plane between the segments is advantageously selected so that it extends in the direction of the directed static magnetic field. This ensures that components of the magnetic force running transversely to the parting plane are minimized.

[0028] Here, the segments are preferably connected by connecting means, at least one of which can be opened and reclosed, and at least one of which can be folded like a hinge. Thanks to these connecting means, the segments can be easily opened and closed again after placement of the affected extremity (that is, the body part in which the implant component with the adjustment device according to the invention is contained, in particular an arm or a leg). By enabling hinge-like folding, complete removal of the openable segment can be avoided (although this would also be possible in principle). This further facilitates handling.

[0029] In the open, unfolded state, the magnetic ring is preferably secured against (unwanted) movement. For this purpose, a locking device is expediently provided which fixes the magnetic ring with its segments in the open position so that they cannot twist. This effectively counteracts the risk of unplanned movement of the magnetic ring, which could also lead to unwanted folding shut. Furthermore, in the opposite sense, a securing device is preferably provided which is designed, in particular by means of a positive guide, to cause a coupling of the magnetic ring in the closed position. This blocks the magnetic ring from folding out of the open position. This reliably prevents unwanted opening of the magnetic ring, for example during normal operation.

[0030] The magnetic ring is constructed with permanent magnets. It is expediently formed by a plurality of sub-magnets arranged on the magnetic ring. This allows the use of commercially available and therefore inexpensive, typical permanent magnets as sub-magnets. This allows even relatively large magnetic rings to be manufactured efficiently and with relatively little weight. The individual sub-magnets, or individual magnets, are preferably of the same type, specifically designed as magnetic dipole bodies, preferably made of rare earth metals (so-called rare earth magnets). The sub-magnets are preferably regularly arranged along the magnetic ring with different field orientations at fixed angles. Due to the fixed angle arrangement, the sub-magnets in the magnetic ring always retain their field orientation.By using individual sub-magnets with different field orientations, it is possible to create a static magnetic field distribution such that the field is concentrated inside the magnetic ring and canceled outside. Furthermore, it is possible to generate a homogeneous magnetic field within the magnetic ring in this way. Ideally, this is achieved by using as many small sub-magnets as possible; however, a good approximation of a nearly homogeneous field within the magnetic ring can be achieved with as few as a dozen sub-magnets (10 to 20).

[0031] Furthermore, the sub-magnets are advantageously arranged such that their magnetic fields (more precisely, the stray fields outside the sub-magnets) are maximally compensated along a separation plane between segments of the magnetic ring. This allows the magnetic field perpendicular to the separation plane to be minimized. This is a particularly advantageous way to ensure that the segments can be opened without magnetic force in a simple and reliable manner, as already explained above.

[0032] Advantageously, a housing is provided for the drive unit, which surrounds the magnetic ring. The housing short-circuits magnetic fields outside the magnetic ring, especially stray fields, so that the external space surrounding the housing is largely free of magnetic fields ("external field-free"). For this purpose, the housing has one or more shields and / or is preferably made of soft magnetic material. Thus, there is no external influence from the magnetic field of the magnetic ring (which is quite strong inside). This significantly facilitates safe transport.

[0033] The drive unit is expediently equipped with a positioning device that acts on the magnetic ring, in particular a counter that indicates the rotations of the magnetic ring. This allows the position of the magnetic ring to be displayed, allowing the user to make fine and precise adjustments. This applies to both the angular position of the magnetic ring and the number of rotations of the magnetic ring. For example, a counter can provide the operator with clearly legible and reproducible information about the adjustment distance of the adjustment device achieved by the drive device.

[0034] Advantageously, an extracorporeal locking switch can also be provided, which is preferably arranged on the drive unit and acts on an adjustment locking device arranged on the prosthesis shaft. The adjustment locking device can thus be used to lock the adjustment element of the implant component against unintentional adjustment. If an adjustment is intended using the drive unit, the adjustment locking device is released using the locking switch, thus releasing the adjustment element again so that the desired adjustment can be carried out using the drive unit.

[0035] The drive unit is preferably provided with a base. This base holds the drive unit in an upright position and simultaneously acts as an anti-tilt device to ensure correct relative positioning of the drive unit to the implant component. To achieve initial correct positioning, the base is preferably further provided with a directionally oriented receptacle for the body part, in particular the arm or leg, into which the implant component with the adjustment device is implanted.

[0036] For further information on the interaction of the implant component with the drive device, please refer to the above description.

[0037] The invention is explained in more detail below with reference to advantageous embodiments of the invention and the accompanying drawings. They show: Fig. 1 is a schematic view of a bone with an inserted implant component and a drive unit arranged next to it; Fig. 2 is a schematic representation of a static magnetic field within a magnetic ring; Fig. 3a, b is a schematic representation of a sub-magnet and a physical representation of two adjacently arranged sub-magnets; Fig. 4 is a frontal view of a first embodiment of a drive unit with a magnetic ring; Fig. 5 is a frontal view of the first embodiment in a partially unfolded state; Fig. 6 is a perspective view of a second embodiment of a drive unit; Fig. 7 is a sectional view of the second embodiment with a section through the housing and a frontal view of the magnetic ring; Fig. 8a perspective view of the second embodiment in a partially unfolded state; Fig. 9 a perspective view of the second embodiment in a fully unfolded state; Fig. 10 a perspective view of the second embodiment with the upper housing part partially removed; Fig. 11 a front view as a section through the housing of the Figure 10 illustrated embodiment; Fig. 12a, b further perspective views of the second embodiment with the upper housing part attached and with a partially sectioned locking mechanism; Fig. 13a, b a front and a side view of a third embodiment with a pivoting protective cover; Fig. 14 a perspective view of the third embodiment; Fig. 15 representations of the shielding using the example of the first embodiment; Fig. 16a perspective view of an implant component with adjustment device; Fig. 17 a top view of the implant component with exposed interior; Fig. 18 a partially sectioned view of the implant component according to Figure 17 ; and Fig. 19 a sectional view of a spindle for an adjustment device of the implant component.

[0038] A system for adjusting the length of an implanted prosthesis and an adjusting device for this purpose is described in the form of a first embodiment in Figure 1schematically shown. One can see a lower extremity, a leg 9, which has a bone 90 to be lengthened, in the form of a femur. It is divided into two parts 91, 92, with the implant component 1 anchored in both parts and thus connecting the two parts 91, 92 of the femur 90. In particular, the implant component 1 can be a length-adjustable shaft of a prosthetic system, as is shown, for example, in Figure 16 is shown.

[0039] For connection to other implant components, the implant component 1 according to the invention has a conical connector at each of its two ends, preferably a male conical connector 11 at one end and a female conical connector 12 at the other end (it is understood that other connection forms are also possible, e.g. by means of threads, etc.). The implant component can in particular be part of a larger joint endoprosthesis, in particular for a total replacement of the femur bone 90. By means of the adjustment device 2 (in Figure 1not shown), the ends of the implant component 1 can be moved away from each other with the conical connectors 11, 12, ie the length of the implant component 1 can be changed, in particular increased. An extracorporeal drive unit 7 is provided to actuate the adjustment device 2. It comprises a magnetic ring 8, which is rotatably held and guided within a carrier 70. The magnetic ring 8 is designed such that a directed static magnetic field is created in its interior 80. Such a directed static magnetic field 88 is Figure 2 The magnetic ring 8 is not designed as a unitary solid body, but rather is discretely constructed, namely from a plurality of sub-magnets 85. The sub-magnets 85 are each designed as a magnetic dipole, which means that the actual magnetic body has a north pole "N" on one side and a south pole "S" on the other side (this is shown in Figure 3aby different shades of grey). If the magnetic body shown there is further formed into a cylindrical shape, the arrangement of the north pole and south pole remains basically unchanged (this is shown in Figure 3b (shown in the figure, with the direction of the remanent magnetization 87 highlighted by a black arrow). This further results in a specific magnetic orientation. Technically speaking, the sub-magnets 85 are dipole magnets 86, which have a directed magnetic field inside, as shown in Figure 3b is clearly shown.

[0040] The invention makes use of this characteristic of the sub-magnets 85 and thus creates a directed static magnetic field with a manageable number (namely 16) of sub-magnets 85, which is also largely homogeneous (see Figure 2). "Homogeneous" here means that, viewed across the surface of the interior space 80, there is a location-dependent deviation in the magnetic field strength that is no greater than + / - 15% of the actual mean magnetic field strength. This is achieved by a specific angular orientation of the sub-magnets 85 in the magnetic ring 8. Firstly, the sub-magnets 85 are arranged equidistant from the center, i.e., ideally, a uniform circle is formed. Secondly, the sub-magnets 85 are inserted into the magnetic ring 8 with different orientations.

[0041] To visualize this, Figure 2 (in a similar manner as in Figure 3b) the direction 87 of the remanent magnetization is drawn. It can be seen that the sub-magnets 85 in the middle are each parallel to the desired course of the magnetic field lines, but only there. The further a sub-magnet 85 is inserted to the side, the more it is twisted, as can be easily deduced from the position of the arrow indicating the direction 87 of the magnetization. It is in particular this special twisted arrangement of the sub-magnets 85 that produces a largely homogeneously directed static magnetic field in an interior space 80.

[0042] By actuating the magnetic ring 8, in particular by means of a manual actuating device 75, the magnetic ring 8, together with its sub-magnets 85, is set into a rotary motion in the ring plane, whereby the directed static magnetic field 88 also rotates accordingly. The manual actuating device 75 can, in the simplest case, be designed as a handle 75 or a handy coating on the outer surface of the magnetic ring 8; however, mechanization by means of a servo drive (not shown) can also be provided if necessary. With reference to a permanent magnet as the drive element 3, the angular position of the drive of the adjustment device 2 and the currently achieved adjustment path can be determined easily and reliably by slowly rotating the magnetic ring 8 with its static magnetic field 88.Thus, the drive unit 7 already enables simple yet precise control and monitoring of the actual position of the permanent magnet by means of the manual adjustment of the magnetic ring 8 by means of the actuating element 75, which in turn results in the current angular position of the drive of the adjustment device 2. Due to the strength of the magnetic field generated in the cavity 80 of the magnetic ring 8 and the design as a static, i.e. constantly strong (albeit possibly slowly rotating) magnetic field, slippage that would impair positioning accuracy practically does not occur thanks to this arrangement. In this regard, it can be made easier for the user to record the achieved adjustment path by optionally arranging a counter 66 on the drive unit 7, which counter monitors the number of revolutions of the magnetic ring 8 in the drive unit 7 and displays it to the user.Due to the precise transmission of the rotational movement of the magnetic ring 8 to the permanent magnet in the drive of the implant component 1, a clear measure is thus given for the adjustment distance effected by the adjustment device 2 of the implant component 1.

[0043] An example of a structural design of the drive unit 7 with magnetic ring 8 is described below with reference to the Figures 4 and 5explained using a first exemplary embodiment. The drive unit, designated as a whole by the reference numeral 7, comprises a carrier 70 in which the magnetic ring 8 is rotatably mounted. The inner side of the circular recess acts as a guide 78 for the magnetic ring 8. Furthermore, two indentations 75' are formed in the carrier 70 and are provided as handles for carrying. They enable problem-free movement and positioning of the drive unit 7. Two feet 6 are provided in the lower area of the drive unit 7. They serve to hold the drive unit 7 in an upright position so that it cannot tip over, so that the extremity (leg 9) with the implant component 1 can be guided through the interior 80 of the magnetic ring 8.

[0044] The magnetic ring 8 is divided into two segments 81, 82, each designed as a semicircular arc. The outer circumference of the magnetic ring 8 is mounted on an inner side of a complementarily shaped circular recess in the carrier 70.

[0045] The carrier 70 is divided into an upper and lower half along a horizontal dividing line. For this dividing line, a buckle closure 73 is provided on one lateral side of the carrier 70 and a hinge 74 is provided on its opposite lateral side. By opening the buckle closure 73, the upper half of the carrier 70 can be folded upwards, with the hinge 74 as the pivot point. When folded open, the segment 81 of the magnetic ring 8 remains on the upper half and the segment 82 of the magnetic ring 8 remains on the lower half of the carrier 70. To prevent the segments 81, 82 from falling out or twisting, a total of four locking closures 84 are provided to lock the magnetic ring 8 to the carrier 70, two for each of the segments 81, 82. In the closed state, the two segments 81, 82 are connected to one another by tension locks 83'.When closed, the two segments 81 and 82 form the single magnetic ring 8.

[0046] The magnetic ring 8 comprises a plurality (14 in the illustrated embodiments) of cylindrical sub-magnets 85 made of rare earth material. Suitable receptacles are provided on the magnetic ring 8 to hold them on the magnetic ring 8. The cylindrical sub-magnets 85 are inserted into these receptacles and secured so that they cannot twist or fall out. The anti-twist feature is important because the individual sub-magnets 85 are inserted and held with a precisely defined angular orientation. The angular orientation serves to specifically align the magnetic field generated by the respective sub-magnet 85 and is indicated by arrows in Figure 4 and 5 visualized (for the meaning of the arrows, see also the above explanation of Figure 2 and 3b). It can be seen that the angular orientation of the individual sub-magnets 85 is always different from the neighboring ones. The alignment is deliberately chosen so that the magnetic field is concentrated on the interior space 80 (the exterior space of the magnetic ring 8 is essentially field-free), thus creating an essentially homogeneous, directed static magnetic field in the interior space 80 (cf. Figure 2 and the explanation above).

[0047] By rotating the magnetic ring 8, in particular manually, the static magnetic field 88 thus generated can be rotated, whereby a permanent magnet located in the interior 80 rotates synchronously under the influence of the magnetic field. Such a permanent magnet is used as a drive element for the implant component, as will be explained later.

[0048] A second embodiment for a drive unit 7' is shown in the Figures 6 to 11It differs in its design, but is functionally essentially similar to the first embodiment described above. The same reference numerals are used for identical or similar parts; to avoid unnecessary repetition, reference is made to the above explanation, which applies accordingly.

[0049] The second embodiment of the drive unit 7' has a housing 71 surrounding the magnetic ring instead of the carrier 70.

[0050] It essentially completely encloses the magnetic ring 8, with the exception of a large opening 72 in the upper region of the housing 71. This opening is dimensioned to allow access extending over at least 30°, i.e. one twelfth of the circumference of the magnetic ring 8, so that the user can manually rotate the magnetic ring 8, in particular on the outer surface of the magnetic ring 8 designed for manual actuation (provided with a grip coating). It should be noted, however, that a manual drive is not mandatory. A coupling opening 76 is provided in the housing 71 for the possible flange-mounting of a drive motor. A drive motor (not shown) can be arranged here, which acts on the magnetic ring 8 and sets it in rotation.

[0051] It should be noted that such a motor drive may also be provided in the first embodiment.

[0052] The housing 71 is preferably made of soft magnetic material, for example, highly permeable iron, nickel, and / or cobalt alloys, in order to shield the exterior from the magnetic (residual) field of the magnetic ring 8. Low-alloy structural and free-cutting steels or electrical steel sheets are particularly suitable.

[0053] Preferably, at least the housing 71 is designed to be shielded in the area of the outer surface of the magnetic ring 8. The housing 71 is expediently dimensioned such that, in the area of the shielding (e.g., outer surface), it has a distance from the magnetic ring 8 that is at least as large as the diameter / height of the individual sub-magnets 85, preferably a multiple thereof. This allows a good shielding effect to be achieved even with relatively low material thicknesses (typically 0.5 mm or less) and thus low weight. If shielding is also optionally to be provided in the area of the end faces of the magnetic ring 8, the housing 71 would either have to be designed with a relatively great depth in order to achieve the above-mentionedDistance of the front housing wall of at least the diameter / height of the individual sub-magnets 85 to achieve, or the material thickness of the front housing wall would have to be chosen considerably higher than in the area of the shell surface, usually more than twice or even three times as thick (i.e. typically greater than 1 mm).

[0054] The housing 71 is further provided with a direction-oriented receptacle for an extremity, for example, a leg. However, this is not intended to accommodate the extremity provided with the implant component 1, but rather its contralateral counterpart, i.e., the other leg. For this purpose, the housing 71 is, as shown in Figure 6shown by way of example, in the area of its base 6' it is provided with a recess which is essentially V-shaped in cross-section and which forms a receptacle 61. In the illustrated embodiment, it is dimensioned such that the lower leg of the other leg (not shown) can be received in the area of the receptacle 61, or alternatively / additionally, it is dimensioned so much larger that the thigh of the other leg (not shown) can be received in the area of the receptacle 62. The receptacle 61, 62 is expediently shaped such that it only receives the extremity in a defined position. Accordingly, if the lower leg or thigh of the said other leg is placed in the receptacle 61, 62, the drive unit 7' is automatically correctly aligned for adjusting the implant component 1 to be adjusted (the same applies to other extremities, such as arms). This simplifies correct application and use for the user.Positioning of the drive unit 7' according to the invention. It should be noted that the receptacles 61, 62 can also be designed as individually adapted formations.

[0055] As in the first embodiment, the magnet ring 8 is provided with a plurality of sub-magnets 85, which in the partial sectional view are shown in Figure 7 Here again, the alignment of the sub-magnets 85, visualized by the arrows 87, can be seen to form the concentrated, directed static magnetic field in the interior 80. Here, too, the magnetic ring 8 is divided into two segments 81, 82, which can be opened together with the upper half of the housing 71 (see Figures 8 and 9 ). As in the first embodiment, a hinge 74 is provided on one side for this purpose. Figure 9shows the second embodiment with the housing 71 fully opened. The respective ends of the segments 81, 82 can be clearly seen on the separating surfaces, which in the folded state (see Figure 7 ) lie in the parting plane 83.

[0056] At the Figure 10 In the illustration shown, a portion of the upper portion of the housing 71 has been removed. In addition to the upper segment 81 of the magnetic ring 8, its sub-magnets 85, as described above, are clearly visible. Furthermore, a plurality of guide rollers 89 are shown on the magnetic ring 8, which interact with an arcuate guide rail 79 arranged in the lower portion of the housing 71 (see Figure 11). In this way, a secure, forced guidance of the magnetic ring 8 in the housing 71 is achieved. It is sufficient for the curved guide rail 79 to extend over the lower housing half, since - thanks to the connection of the segments 81, 82 in the folded normal state - this results in complete guidance of the magnetic ring 8. In the folded state, this does not apply to the upper segment 81, but thanks to its curved shape and a locking pin 84' in the likewise curved upper half of the housing 71, it is secured to the extent that it cannot fall out. When the housing 71 is folded shut and the segments 81, 82 subsequently lock together, the magnetic ring 8 is closed again, and the drive device 7' is then ready for use again without any further action.

[0057] To ensure correct relative positioning of the two segments 81, 82 in the closed (folded) state, guide elements 77 are provided. They are designed in a pawl-like manner and are arranged at both ends of the guide rail 79 in the area of the parting plane 83 on the segments 81, 82 (see Fig. 12 and 13 ). They are part of a spring-loaded locking mechanism that holds the segments 81, 82 together. In the closed state, this provides effective guidance and securing for the magnetic ring 8, namely by means of the guide rollers 89 guided on the guide rail 79 and the guide elements 77 at the ends of the guide rail 79.

[0058] For locking in the secured position, a locking pin 84' is provided, which can be inserted into corresponding receiving openings in the upper area of the housing 71 and in the upper segment 81 of the magnetic ring 8 (see Fig. 12 a, b). The position in which the magnetic ring 8 must be in order to insert the locking pin 84' is the one in which the parting plane 83 between the segments 81, 82 is aligned with the hinge 74 of the housing 71 - only in this basic position is opening possible. The correct position of the magnetic ring 8 in this basic position is indicated by a reference marking 74' arranged in the area of the housing opening 72, one half of which is attached to the housing 71 and the other half to the magnetic ring 8 (e.g. as a double arrow marking) - if both are aligned one above the other, the basic position is reached.

[0059] In this basic position, the receiving openings in housing 71 and segment 81 of the magnetic ring 8 are aligned, and the locking pin 84' can be inserted. This creates a positive guide by means of which the magnetic ring 8 is locked, while at the same time, by means of a mechanical combination, the spring locking mechanism is unlocked, so that the segments 81, 82 are decoupled and the magnetic ring 8 can be opened. The locking pin 84' also secures the upper segment 81 of the magnetic ring 8 against unwanted movement when opening or in the opened state.

[0060] A third embodiment for a drive unit 7" is shown in Fig. 13a, b and 14shown. It is based on the second embodiment, but in contrast to the latter, has a differently designed housing 71. It has an outer protective cover 72' in the upper area, which is hingedly mounted on the hinge 74 and, when opened, exposes the upper area of the magnetic ring 8. In the area of the hinge 74, an extension arm 71" is provided on the housing 71. On the one hand, it carries the handle 75' for transporting the drive unit 7" and, on the other hand, forms a stop for the protective cover 72' in order to limit its opening.

[0061] The boom 71" is further shaped such that its lateral contour provides a receptacle 61 for the contralateral extremity (the other leg). Otherwise, its functionality corresponds to that of the receptacle 61 in the second embodiment, so that reference is made thereto to avoid repetition. This also applies accordingly to the other components of the third embodiment, which bear the same or corresponding reference numbers as the corresponding components of the second embodiment.

[0062] As a special feature, the third embodiment further comprises a counterpart to the outer protective cover 72'. An inner protective cover 71' is provided inside the magnetic ring 8, which separates the interior 80 from the magnetic ring 8. It not only functions as a mechanical cover, but also serves to shield the surrounding area, in particular adjacent areas of the extremity to be recorded (especially leg 9), from unnecessary exposure to magnetic fields.

[0063] The magnetic ring 8 is mounted on guide rollers 89' fixed to the housing, on which the magnetic ring 8 rests with its outer surface in its lower area. This enables a compact design with a relatively low center of gravity. The risk of the drive unit 7" accidentally tipping over can thus be counteracted. Optionally, the guide rollers 89' are designed with an enlarged diameter on their front sides, creating a collar and providing lateral guidance for the magnetic ring 8. Additional guide rollers 89' can also be provided, particularly in the upper area of the housing.

[0064] Furthermore, in this third embodiment, the housing 71 has double feet 6". They provide the drive unit 7" with a wider support surface and thus further increase the safety against tipping over. Furthermore, to avoid repetition, reference is made to the above description of the second embodiment.

[0065] Magnetic shielding can be provided on the magnetic ring 8 or the surrounding housing 71 and its components 71', 72', preferably made of magnetically highly conductive (highly permeable) material, in particular soft magnetic (ferromagnetic) materials such as iron, nickel, and cobalt alloys. For the sake of clarity, various shieldings are explained below with reference to Fig. 15based on the first embodiment, with the same applying to the other embodiments. An outer shield 67 can be provided at a relatively large distance, which is understood to be a multiple of the diameter or height of the submagnets 85. With such a spaced shield, shielding material thicknesses of only a few tenths of a millimeter are sufficient and advantageous.

[0066] For shielding on the magnetic wheel 8, a directly adjacent shielding jacket 68 is expediently provided. Typically, the shielding distance is approximately equal to the diameter or height of the submagnets 85, so that material thicknesses of at least half a millimeter, preferably up to one millimeter, are expedient. Such a shielding jacket can also be expedient on the inside, for example, on the inner protective cover 71' of the third embodiment to protect surrounding areas of the affected leg 9.

[0067] Furthermore, shielding can also be provided on the end faces of the magnetic wheel, as near-field shielding 69. The distance is typically smaller than the diameter or height of the submagnets 85, resulting in a strong magnetic modulation of the soft iron. Therefore, quite thick material of at least one, usually several millimeters, is required.

[0068] An embodiment of an implant component 1 is shown in the Fig. 17 to 19 shown. Figure 17 shows a partial section through the implant component 1 with its adjustment device 2. In the illustrated embodiment, the implant component 1 is shaped like a shaft and thus forms part of a prosthesis shaft, in particular for a modular prosthesis system.

[0069] At each of its two ends, it has a coupling element to adjacent prosthesis modules of a preferably standardized prosthesis system, for example, another shaft or a connection to a joint component. Thus, the implant component 1 has Fig. 17 at the end shown on the right, a male cone 11 as a coupling element and at the end shown on the left, a coupling element designed as a female cone 12 for connecting further prosthesis modules (not shown); it is understood that other types of connection than cone connectors can also be provided.

[0070] The actual shaft body between the coupling elements 11, 12 is designed with an outer tube 21 and an inner tube 22 guided longitudinally therein. They are part of an adjustment device 2 and interact telescopically to enable the setting of different lengths for the implant component 1. The outer tube 21 and the inner tube 22 are connected to one another via two sliding guides, of which one sliding guide 28 is arranged at the free end of the inner tube 22 and is movable within the outer tube 21, while the other sliding guide 29 is fixedly arranged at the end of the outer tube 21 in the region of the transition to the inner tube 22. Furthermore, a guide groove is arranged on the inside wall of the outer tube 21 to prevent mutual rotation of the inner tube 22 relative to the outer tube 21.An axial bearing 25, which is also arranged at the end of the outer tube 21, serves as a bearing for the longitudinal adjustment and to which a pair of sealing rings 24 is assigned in order to seal off the interior of the outer tube 21 from surrounding body tissue or fluids.

[0071] The adjustment device 2 for adjusting the length of the implant component 1 further comprises a drive element 3, which has a permanent magnet arranged for rotation about a central axis of the inner tube. It is arranged and configured with such an orientation that its polarization direction (direction from the north pole to the south pole) is orthogonal to the central axis. A sub-magnet 85, as described above, is also expediently used for this purpose. A gear 4 as a reduction gear is arranged downstream of the drive element 3. In the illustrated embodiment, it is designed as a two-stage planetary gear with a reduction ratio of approximately 1 to 20.

[0072] The gear 4 acts on a spindle drive 5, which converts a rotary movement of the gear 4 into a linear movement for length adjustment. A bending rod 35 is provided for torque transmission between the gear 4 and the spindle drive 5. The gear 4 acts on a driven end 34 of the bending rod 35, which is arranged coaxially to the central axis 27 of the inner tube 22. The bending rod 35 further has a collar 36, which is arranged in the area of the sealing rings 24, and adjoining it has an elongated, constricted shaft region 32, which ends at the free end of the bending rod 35 at a coupling piece 37. The elongated, constricted shaft region 32 is inserted into a central bore 51, open on one side, of the drive spindle 50, wherein the coupling piece 37 is connected to the drive spindle 50 at the base of the central bore 51.The drive spindle 50, which is set in rotational motion by the bending rod 35, rotates about a central axis 26 of the outer tube 21, thus causing a longitudinal movement of an adjustment slide 52 arranged on the drive spindle 50, which is firmly connected to the inner tube 22. As a result, a rotation of the drive magnet 3—via the reduction gear 4 and the spindle drive 5—causes a longitudinal adjustment of the implant component 1.

[0073] Reference is now made to Figures 18 and 19 During operation, bending stress occurs in the adjustment device 2 under load. A significant load resulting from the length adjustment of the implant component 1 is a buckling load, which causes the essentially shaft-like implant component 1 to bend. This stress is indicated by an elongated arrow in Figure 18symbolized. As a result of this stress, angular errors can occur between the central axis 26 of the outer tube 21 and the central axis 27 of the inner tube 22, ie under load the two central axes 26, 27 are no longer aligned, but have an alignment error angle of several degrees.

[0074] The sensitive torque transmission from the drive magnet 3 to the spindle drive 5 can be significantly disrupted, which can lead to undesired blocking. The bending rod 35, which, thanks to its bending, can absorb the misalignment (symbolized by the arrow in Fig. 19). It enables the compensation of misalignment errors in the range of up to + / - 5 degrees, preferably up to + / - 2 degrees. It thus increases the drive train's tolerance to bending stress and thus increases the load capacity and reliability of the adjustment device 2 of the implant component 1.

[0075] The implant component 1 is adjusted with its adjustment device 2 by placing the extremity (leg 9) with the implant component 1 in the interior 80 of the drive unit 7, 7' such that the adjustment device 2 with its drive magnet 3 lies in the plane of the magnetic ring 8. By actuating the drive unit 7, 7', namely by rotating the magnetic ring 8, usually by hand, the magnetic field 88, which rotates synchronously with the magnetic ring 8, acts on the drive magnet 3, which then also rotates synchronously. The static magnetic field, which, unlike a typical electromagnetically generated field (especially that of an electric motor winding), is not modulated in strength but has a constant strength, reliably prevents slippage between the drive magnet 3 and the magnetic ring 8. Thus, the angular position as well as the number of revolutions of the magnetic ring 8 is the same as that of the drive magnet 3.This allows for precise length adjustment in a simple manner. The number of revolutions performed (and thus the achieved adjustment distance) is displayed to the user on counter 66.

Claims

1. An implant component with an adjusting device (2) for an implantable prosthesis, which is designed for fastening to a bone (90) to be extended, comprising two fastening parts (21, 22) which are displaceable relative to one another, which are displaced relative to one another by means of the adjusting device (2) for longitudinal expansion, wherein the adjusting device (2) comprises a drive element (3) with a permanent magnet which is arranged so as to be rotatable and which acts via a gear (4) on a spindle drive (5) for converting a rotary movement of the permanent magnet into a distracting longitudinal movement, wherein the drive element (3) is designed for actuation by means of a magnetic field of an extracorporeal drive unit (7, 7', 7"), characterized in that a bending rod (35) is provided for force transmission from the drive element (3) to the spindle drive (5).

2. The implant component with an adjusting device according to claim 1, characterized in that a spindle (50) of the spindle drive (5) has a central bore (51) which is open on one side and into which the bending rod (35) is inserted.

3. The implant component with an adjusting device according to claim 2, characterized in that the bending rod (35) is coupled at its free end remote from the drive element (3) to a coupling piece (32) at the base of the central bore and the bending rod (35) preferably has a constricted shank.

4. The implant component with an adjusting device according to any one of claims 1 to 3, characterized in that the bending rod (35) has a length which is preferably at least one third, more preferably at least one half, of the length of the drive spindle (50), and is designed in particular to accommodate an angular offset of up to + / - 5 degrees.

5. The implant component with an adjusting device according to any one of claims 1 to 4, characterized in that the bending rod (35) consists of a TiA16V4 titanium alloy.

6. An extracorporeally length-adjustable implant system, comprising - an implant component (1) according to any one of the preceding claims; and - an extracorporeal drive unit (7, 7', 7") for actuating the drive element (3) by means of a magnetic field, wherein the extracorporeal drive unit (7, 7', 7") has a rotatably mounted extracorporeal magnetic ring (8) with an interior space (80) which is designed to receive the bone (90) to be extended with the adjusting device (2), and an actuating device (75) which is designed to rotate the extracorporeal magnetic ring (8) in its ring plane, wherein the extracorporeal magnetic ring (8) is embodied in a permanent magnet design and has a directed static magnetic field in its interior space which is fixed in the ring, and the extracorporeal magnet ring (8) is rotated mechanically by the actuating device (75).

7. The implant system according to claim 6, characterized in that - the magnetic field is concentrated on the interior space (80), and / or - the directed static magnetic field in the central interior space is unidirectional and / or homogeneous.

8. The implant system according to claim 6 or claim 7, characterized in that the magnetic ring can be divided into at least two segments (81, 82) so as to create an openable and closable access for a body part provided with the implant component (1), in particular a leg or arm, to the interior space of the magnetic ring (8), wherein the segments (81, 82) can be folded open in an open position of the magnetic ring (8), wherein preferably: - the segments (81, 82) can be folded open, preferably without magnetic force, in an open position of the magnetic ring (8); and / or - a separation plane (83) between the segments is selected to extend parallel to the directed static magnetic field; and / or - the segments are connected to connecting means, of which at least one (73) can be opened and closed again and at least one (74) can be folded in the manner of a hinge; and / or - a locking device (84) is provided which fixes the magnetic ring (8) with its segments (81, 82) in an opening position in a rotationally secure manner; and / or - a safety device is provided on the magnetic ring (8), which is designed, in particular by means of a locking bolt (84'), to prevent the magnetic ring (8) from folding open outside the opening position.

9. The implant system according to any one of claims 6 to 8, characterized in that the magnetic ring (8) is formed by means of a plurality of preferably identical sub-magnets (85), wherein preferably the sub-magnets are identical magnetic dipole bodies (86), in particular formed from rare earth magnets.

10. The implant system according to claim 9, characterized in that the sub-magnets (85) are inserted along the magnetic ring (8) in a regular manner with different orientation (87) of the magnetization in an angularly fixed manner.

11. The implant system according to claim 10, characterized in that the sub-magnets (85) are arranged so that their magnetic stray fields each maximally compensate for one another along a separating plane (83) between segments (81, 82) of the magnetic ring (8), wherein the sub-magnets (85) are preferably arranged so that their magnetic stray field is equal to zero along a separating plane (83) between segments (81, 82) of the magnetic ring (8).

12. The implant system according to any one of claims 6 to 11, characterized in that a housing (71) is provided for the drive unit (7, 7', 7"), which is preferably provided with one or more shieldings (67, 68, 69) and in particular surrounds the magnetic ring (8) free of external fields.

13. The implant system according to any one of claims 6 to 12, characterized in that the drive unit (7, 7', 7") is provided with a positioning device which acts on the magnetic ring (8), in particular a counter (66) indicating revolutions of the magnetic ring.

14. The implant system according to any one of claims 6 to 13, characterized in that the drive unit is provided with a standing foot (6) as tilting protection, which is preferably provided with a directionally-oriented receptacle (61, 62) for a body part (9) provided with the prosthesis, in particular an arm or a leg.