IMPLANTS FOR CREATING CONNECTIONS TO TISSUE PARTS, IN PARTICULAR TO SKELETAL PARTS, AS WELL AS DEVICE AND METHOD FOR IMPLANTATION THEREOF

Abstract

A method for locating a material having thermoplastic properties in pores of bone tissue includes providing a pin having the material having thermoplastic properties and a core, wherein the material having thermoplastic properties is arranged on the circumferential surface of the core constituting an outer region of the pin. An opening is provided in the bone tissue, and the pin is positioned at least partly in the opening. The outer region of the pin is then impinged with mechanical vibration energy for a time sufficient for liquefying at least part of the material having thermoplastic properties, and, in a liquefied state, pressing it into the pores of the bone tissue surrounding the opening. The vibration energy is stopped for a time sufficient for re-solidification of the liquefied material, and then the core is removed.

Claims

1. A method for creating a positive-fit connection capable of load-bearing to a tissue part in a human or animal body, the tissue part comprising first and second surfaces, the method comprising the steps of: providing an implant comprising a support with a proximal end and a distal base plate, the support and the base plate not being liquefiable under implantation conditions, and the implant further comprising a second material, which is biocompatible, has thermoplastic properties, and is liquefiable by mechanical oscillation, providing a tissue opening reaching from the first surface to the second surface of the tissue part, the opening having a form which is adapted to a cross section of the implant, positioning the implant with the base plate facing forward from the first surface through the opening so that the base plate is positioned beyond the second surface of the tissue part and at least portions of the second material are positioned proximally of the base plate, impinging a proximal face of the second material with mechanical oscillation and simultaneously pressing it against the base plate for a time sufficient for liquefying at least a part of the second material and for pressing it out of a region between the proximal face of the second material and the base plate, so that at least portions of the liquefied material are distally of the second surface of the tissue, letting the second material to re-solidify and, in a re-solidified state, to constitute the positive-fit connection.

2. The method according to claim 1, wherein a cross section of the tissue opening is sufficiently smaller than a corresponding cross section of the second material, for achieving a friction-fit between the wall of the tissue opening and the implant.

3. The method according to claim 1, wherein the support is a central support and wherein after the step of positioning the implant, the second material is arranged around the support.

4. The method according to claim 3, wherein the second material is chosen to have a tubular shape.

5. The method according to claim 3, wherein the support is a rod.

6. The method according to claim 1, wherein the tissue-part is a tubular bone part, and wherein during the step of impinging the proximal face with mechanical oscillation and simultaneously pressing, the portions of the second material are pressed into the marrow space.

7. The method according to claim 1, comprising the step of fixing the positioned implant after the step of positioning the implant.

8. The method according to claim 1, wherein during the step of impinging and simultaneously pressing, further portions of the second material are pressed into surface unevennesses, cavities or pores of a wall of the tissue opening.

9. The method according to claim 8 and further comprising a step of mechanically creating the unevennessses, cavities or pores in the wall of the tissue opening.

10. The method according to claim 9, wherein the step of mechanically creating comprises roughening the wall of the tissue opening or creating a thread in the tissue opening.

11. The method according to claim 1, wherein the support is a sleeve with an open, proximal end, the base plate closing a distal end of the sleeve, the sleeve comprising a perforated circumferential wall, and wherein during the step of impinging a proximal face of the second material with mechanical oscillation and simultaneously pressing it against the base plate, at the liquefied part of the second material is pressed through the perforations.

12. The method according to claim 1, wherein the tissue part is a cortical bone.

13. The method according to claim 1, wherein the mechanical oscillation for impinging the second material has a predominantly same direction as the pressing of the implant against the base plate.

14. The method according to claim 1, wherein the step of letting the second material to re-solidify comprises stopping the impingement with mechanical oscillation, while still pressing the second material against the base plate.

15. The method according to claim 1, wherein the step of impinging and simultaneous pressing further comprises pressing the second material onto the second surface of the tissue part.

16. The method according to claim 1, wherein the mechanical oscillation has a frequency of between 2 and 200 kHz.

17. The method according to claim 1, wherein the step of impinging and simultaneous pressing comprises positioning a distal end of a resonator of an implantation device on the proximal face of the second material, wherein the resonator acts like a hammer thereon.

18. The method according to claim 1, wherein the base plate has a circular cross section and wherein the tissue opening is a bore in bone tissue.

19. The method according to claim 1, wherein the tissue part comprises living tissue.

20. The method according to claim 1, wherein said tissue part is a human or animal bone part, cartilage part, ligament part or tendon part.

21. The method according to claim 1, and further comprising a step of connecting another tissue part, a means for supporting or for replacing tissue, a suture, a cerclage wire or a therapeutic auxiliary device to the implant.

22. The method according to claim 21, wherein the means for supporting tissue is an external carrier beam.

23. The method according to claim 22, wherein the external carrier beam is connected with a plurality of implants.

24. The method according to claim 23, wherein the external carrier beam is positioned across a bone fracture or laceration.

25. The method according to claim 1, wherein the tissue part is a long bone and the opening reaches from an outside surface thereof into a marrow space thereof.

26. The method according to claim 1, wherein the step of positioning comprises positioning the implant through a tendon or ligament and through a bone part situated underneath the tendon or ligament.

27. The method according to claim 1, wherein the step of positioning and the step of impinging and simultaneous pressing comprise minimal invasive surgery.

28. The method according to claim 1, wherein the second material is a non-resorbable polymer.

29. The method according to claim 1, wherein the second material is a resorbable polymer.

30. The method according to claim 1, wherein the second material further contains foreign phases or additional substances suitable for reinforcing, swelling or making porous the second material, or for promotion of healing or regeneration, or for furthering x-ray visibility.

31. The method according to claim 1, wherein the additional substance is a growth factor, an antibiotic, an inflammation inhibitor or a buffer.

32. The method according to claim 1, wherein the support plate and the base plate consist of a metal, a ceramic material, a glass, a polymer or a composite material.

33. A method for unicortically anchoring a fixation device to human or animal bone tissue, the method comprising the steps of: providing the fixation device comprising a support with a proximal end and a distal base plate attached to a distal end of the support, the support and the base plate not being liquefiable under implantation conditions, and the fixation device further comprising a second material, which is biocompatible, has thermoplastic properties, and is liquefiable by mechanical oscillation, providing a tissue opening reaching from the first surface to the second surface of a cortical bone opening into an interior space of the bone tissue but not through the cortical bone tissue on an opposite side, the opening having a form which is adapted to a cross section of the fixation device, positioning the fixation device with the base plate facing forward from the first surface through the opening so that the base plate is positioned beyond the second surface of the cortical bone and at least portions of the second material are positioned proximally of the base plate, impinging a proximal face of the second material with mechanical oscillation and simultaneously pressing it against the base plate for a time sufficient for liquefying at least a part of the second material and for pressing it out of a region between the proximal face of the second material and the base plate into the interior space, letting the second material to re-solidify and, in a re-solidified state, to constitute a positive-fit connection of the fixation device to the bone tissue, the positive-fit connection constituting the unicortical anchoring of the fixation device, the anchoring in the bone tissue being secure against tilting.

34. The method according to claim 33, wherein the interior space is a marrow space.

35. The method according to claim 33, wherein the support is a central support and wherein after the step of positioning the implant, the second material is arranged around the support.

36. The method according to claim 33, wherein the support is a sleeve with an open, proximal end, the base plate closing a distal end of the sleeve, the sleeve comprising a perforated circumferential wall, and wherein during the step of impinging a proximal face of the second material with mechanical oscillation and simultaneously pressing it against the base plate, at the liquefied part of the second material is pressed through the perforations.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The invention is explained in more detail by way of the subsequent Figures, wherein:

[0031] FIG. 1 shows an exemplary embodiment of the device for implanting implants according to the invention, and its use;

[0032] FIG. 2 shows a fixation plate fastened on a bone by implants according to the invention;

[0033] FIGS. 3 and 4 show examples of implants according to the invention, to be used e.g. in the application according to FIG. 2, and connections between bone and plate created therewith;

[0034] FIGS. 5a to 5d show exemplary cross sections of pin-like implants according to the invention, wherein the implants comprise axially extending energy directors;

[0035] FIGS. 6 to 8 show longitudinal sections through two exemplary, pin-like implants according to the invention, wherein the implants comprise implant parts of a non-liquifiable material;

[0036] FIGS. 9 to 13 show exemplary embodiments of cooperating holding means on pin-like or dowel-like implants and resonators;

[0037] FIG. 14 shows applications of implants according to the invention on a human scull or jawbone;

[0038] FIGS. 15 to 17 show implants applicable e.g. in the scull region and exemplary connections between two scull parts created therewith;

[0039] FIG. 18 shows an exemplary resonator arrangement for applications as shown in FIGS. 16 and 17;

[0040] FIG. 19 shows a further application of implants according to the invention in the region of the human vertebral column;

[0041] FIG. 20 shows a further application of implants according to the invention for fixing a tooth replacement;

[0042] FIGS. 21 and 22 show in section two exemplary implants according to the invention suitable for the application as shown in FIG. 20;

[0043] FIG. 23 shows a fixation device fixed to a forearm bone by implants according to the invention;

[0044] FIG. 24 shows an example of a connection implant suitable for the application as shown in FIG. 23;

[0045] FIG. 25 shows in section the fixation device according to FIG. 23 being fastened on a bone by implants according to FIG. 24;

[0046] FIG. 26 shows a further example of a connection implant suitable for the application as shown in FIG. 23;

[0047] FIG. 27 shows a trochanter plate for fixing a broken neck of a joint, wherein the plate is fixed with the help of an implant according to the invention;

[0048] FIG. 28 shows a stem for an artificial joint ball, wherein the stem is fastened to a tubular bone with an implant according to the invention;

[0049] FIG. 29 shows a joint ligament being fastened to bones by implants according to the invention;

[0050] FIG. 30 shows a section through a tissue cavity, for example caused by a tumor, wherein the cavity is to be filled with an implant according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] Schematically, and in a very simplified manner, FIG. 1 shows an exemplary embodiment of an implantation device 1 applicable for implanting implants according to the invention.

[0052] The device 1 comprises a generator 2 and an oscillation unit 3 connected together via a cable 4. The oscillation unit 3, which is partly accommodated in a housing 5, is designed as a hand apparatus to be used like a hand drill, for example. The oscillation unit 3 comprises an oscillation element integrated in the housing 5 (not shown in detail) and actively connected to a resonator (sonotrode) 6. At least a distal resonator part projects out of the housing 5. The generator 2 supplies the oscillation element with energy. Excited by the oscillation element, the resonator oscillates at a predefined frequency or, as the case may be, with a predefined frequency pattern. Frequencies of 2 to 200 Hz and resonator amplitudes of 1 to 100 m in the direction (z-direction) indicated by the double arrow are particularly suitable. The frequencies may be set depending on the application, the materials to be liquefied and the shape of resonator and implant. It is also conceivable to superimpose additional mechanical oscillations, such as with a lower frequency and larger amplitude on the vibrations in the ultrasound region. In many cases, it is sufficient to design the device for a single oscillation frequency, for example for 20 or 40 kHz and for a resonator amplitude of approximately 20 or 30 m in the z-direction (direction in which an implant 7 is pressed by the resonator 6 against a tissue part). In order to control the power (supplied energy per unit of time), the excitation may be pulsed, wherein pulse distances and/or pulse lengths are set.

[0053] Advantageously, and in a per se known manner, the oscillation frequency and the resonator shape are matched to one another such that the resonator oscillates in a standing wave and such that its distal end, which is pressed against the implant, has a maximum amplitude in the z-direction. It is further advantageous to give pin-like implants a length that is matched to a predefined excitation frequency and predefined implant material.

[0054] The distal end of the resonator 6 may be designed for holding an implant 7, as is shown in FIG. 1. This simplifies positioning of the implant on a tissue part or in an opening of a tissue part, such as the bone of a leg 10. For positioning and implantation without an opening, it may also be advantageous to provide an implant guide that is supported on the housing 5 or on the tissue part. It is also possible to design the resonator with a planar end face like a hammer and to simply press it against an implant held in a tissue opening or held by way of a suitable separate mounting or guide means. The distal end face of such a resonator must not stick to the implant during implantation. This is achieved by a suitable, non-adhering end-face of the resonator or by an implant part adjoining the resonator part that consists of a non liquefiable material.

[0055] For applications in a sterile operation region, the device may be used in a sterile covering. Advantageously, the sterile covering comprises an opening for the distal part of the resonator, and the resonator or a distal resonator part can be removed for exchange and sterilization.

[0056] Other exemplary embodiments of the implantation device 1 according to the invention can be designed as hand-held apparatus comprising all components (including energy supply) or as completely stationary apparatus.

[0057] FIG. 2 shows a fixation or stabilization plate 21 being fastened by implants 7 according to the invention on a bone part in the region of a bone fracture or laceration, in order to stabilize the fracture or laceration. The bone part 20 in this case comprises a relatively thin, but relatively compact, outer cortical layer 22 disposed above cancellous bone tissue 23 which is porous. Other than shown in FIG. 2, the transition of the cortical bone to the cancellous bone in natural tissue is a gradual transition in which the tissue becomes more and more porous. The implants 7 extend through openings in the plate 2, through the cortical bone substance 22 and into the cancellous bone 23 and they are anchored at least in the cancellous bone 23.

[0058] FIGS. 3 and 4 in section and in an enlarged scale, show two examples of implants according to the invention that may be used for the application shown in FIG. 2. FIG. 3 shows an implant after implantation. FIG. 4 shows another implant that is positioned in an opening 24 of plate 21 and cortical bone substance 22 and is ready for impingement with oscillation energy.

[0059] For implantation, at least the cortical substance layer is to be opened, for example by drilling. A suitable bore may also continue into the cancellous bone 23 as a pocket hole. Since the cortical substance of the bone has no suitable pores for pressing in the liquefied material, such openings or surface irregularities may be created by cutting a thread 25 or by roughening the inner walls of the bore. The liquefied material is then pressed into such openings and re-solidified to form a positive-fit connection. The liquefied material of the implant is pressed into the pores of the cancellous bone 23, and, in this manner, the implant 7 is anchored in a depth-effective manner. It shows that hydrostatically pressing a liquid material into the tissue pores is significantly gentler on the tissue than mechanically introducing a solid material. For this reason, it is possible to create stable connections to tissue not having much mechanical strength, e.g., to osteoporotic bone tissue.

[0060] In order to connect the implant 7 to the plate 21, the implant may have a head that is like a mechanical screw, such as is shown in FIG. 2. As shown in FIG. 3, the opening in the metallic plate 21 may also comprise an inner thread that is like the thread created in the cortical substance 22 of the bone. The liquefied material penetrates and solidifies in these threads, thereby forming a positive fit. In this case, an implant head is not needed. The implant 7 is aligned flush to the plate 21 by driving a suitably dimensioned implant to the desired position, thereby avoiding undesirable trimming of a projecting implant part.

[0061] For a plate 2 consisting of a thermoplastic plastic, the connection between plate and implant (securement against loosening) may be accomplished as shown in FIG. 4, wherein a material-fit connection (welding or adhering) is formed at the same time the implant is anchored in the tissue. On driving in the implant, this material-fit connection begins to form at the connection location 26. In this case as well, the implant 7 is advantageously driven so far in that, in the end, it is flush with the outer side of the plate 21.

[0062] Since the implant 7 does not need to be rotated into the tissue, it does not need to include means for coupling in a relatively large torsional force, as is as required for known screws. Dimensioning of the implants can therefore be determined purely by their function in the implanted condition. As such, the implants are more streamline and the openings that need to be created in the tissue are smaller than is the case with conventional screws of the same material. Since the positive-fit is formed by liquefaction and resolidification of the material, it comprises less stress and notches, which further increases its strength and makes it less prone to material fatigue.

[0063] Implants according to the invention to be anchored in the tissue part in a depth-effective manner, as shown in FIGS. 2 to 4, are advantageously pin-like or dowel-like and comprise the liquefiable material for example at their distal end, as well as on further surface regions at which an anchoring is desirable (e.g. in a thread in plate 21 and cortical substance 2 of the bone). In fact, as shown in FIGS. 2 to 4, the implants may completely consist of the liquefiable material, wherein the distal end and the surface regions at which the material is to be liquefied in particular are advantageously provided with energy directors, or energy directors are provided at surfaces coming into contact with these regions. Such energy directors may be distal implant ends that are pointed or taper to one or more essentially point-like or linear tip regions. Further surface regions to be liquefied may include humps, tips or ribs whose height and widths are to be adapted to the anchoring being created. The energy directors project at least 10 m beyond the surface. They may also be significantly larger and may be designed as axially-running ribs rendering the pin cross section humped or cornered, as is shown in an exemplary way by FIGS. 5a to 5d. Pin-like implants have such cross sections over their entire length, or only over a part of their length.

[0064] For pin-like implants to be anchored in the region of their cylindrical surface only, or in addition to anchoring in the region of the distal end, tissue openings (e.g. bores) are provided such that introduction of the implant causes (at least locally) a friction fit between tissue and implant or energy directors respectively, i.e. the tissue openings are slightly narrower than the cross section of the implants.

[0065] For further functions, the liquefiable material may contain foreign phases or further substances. In particular, the material is mechanically strengthened by admixture of fibers or whiskers (e.g. calcium phosphate ceramics or glasses). The liquefiable material may further comprise in situ swelling or dissolvable, i.e. pore-form ing constituents (e.g. polyester, polysaccharides, hydrogels, sodium phosphate) and substances to be released in situ, e.g. growth factors, antibiotics, inflammation reducers or buffers (e.g. sodium phosphate) to combat the negative effects of an acidic breakdown. Admixtures for furthering visibility in x-ray pictures and similar functions are conceivable also.

[0066] It has been shown that when anchoring implants in cancellous bone (wherein the implants have a construction according to FIGS. 2 to 4, are composed of polymers such as PC or PLLA and have a diameter of 3 to 4 mm) forces in the region of 0.5 to 5 N per mm.sup.2 implant cross section are advantageously used for the pressing-in. Forces in the named range result in a driving-in speed greater than 5 mm/s.

[0067] FIGS. 6 to 8 show three further, exemplary pin-like implants 7, which, in addition to regions of liquefiable material, comprise a core 11 (FIGS. 6 and 7) or a sleeve 13 (FIG. 8) composed of a non-liquefiable material, such as metal, ceramic or glass, or a composite material.

[0068] The implants according to FIGS. 6 and 7 comprise at their distal end a cap 12 of the liquefiable material, which is more or less pointed (FIG. 6) or comprises a plurality of pointed or linear end regions (FIG. 7). The cylindrical surface of the core 11 is completely surrounded by liquefiable material (FIG. 6) or only in regions, wherein these regions extend axially, or annular (FIG. 7) or may be regularly or irregularly distributed over the core surface. These regions advantageously comprise energy directors as described above for implants consisting entirely of liquefiable material. The liquefiable material is to be thicker or thinner, depending on the desired penetration depth, but should not be thinner than approx. 10 m.

[0069] Step-like reductions in cross section as shown in FIG. 6 are suitable as energy directors. Implants with such steps are advantageously implanted in correspondingly stepped or narrowing tissue openings.

[0070] The impingement of a pin-like or dowel-like implant with a non-liquefiable core 11 may either concern the complete proximal end of the implant or only the annular outer region consisting of the liquefiable material.

[0071] The implant according to FIG. 8 comprises the liquefiable material in the inside of a non-liquefiable sleeve 13. The sleeve 13 is provided with openings arranged in places where anchoring is desired. Such an embodiment of the implant according to the invention is suitable in particular for the application of highly viscous, thixotropic materials as liquefiable material since such a material cannot withstand the mechanical loading caused by the resonator pressing on the implant. The openings in the sleeve are to be dimensioned in a manner such that the highly viscous material can only get through when liquefied. Sleeves 13 of porous sintered material are particularly suitable. An implant with a sleeve 13 is to be positioned in a tissue opening and the resonator is applied only on the liquefiable material, i.e. has a cross section adapted to the inner cross section of the sleeve.

[0072] At the proximal end of a pin-like or dowel-like implant there may be provided a head-like thickening, an artificial part replacing or fixing a further tissue part, a therapeutic auxiliary device, fastening means for such a device, or a fixation means for a suture or cerclage wire. The proximal end may also be equipped as a holding means cooperating with a corresponding holding means on the resonator (see FIGS. 9 to 11).

[0073] A metallic core 11, for example in a pin-like or dowel-like implant, usually serves as a mechanical reinforcement of the implant and is suitably dimensioned for this application. The core may, however, also be significantly thinner and easily removable from the implant. In this case, it provides visibility in an x-ray picture during minimally-invasive implantation, and may serve as a guide wire. The core is removed directly after implantation.

[0074] An implant comprising a metallic core and being anchored in the tissue according to the invention and comprising a liquefiable material that is resorbable has a good primary stability immediately after implantation. On resorption of the anchoring material, the anchoring loosens or is made dynamic, such that more and more load has to be carried by the tissue itself. This encourages the regeneration process and prevents the atrophy process in many cases. After decomposition of the liquefiable material, the core can be removed easily if its surface is designed such that the vital tissue does not grow together with it. If its surface, however, is designed in a manner such that tissue intergrowth is promoted (bioactive surface), this intergrowth constitutes an ideal, secondary stability for an implant or implant core remaining in the tissue (see also FIG. 28).

[0075] Implant cores as shown in FIGS. 6 and 7 may not only consist of metal (e.g. steels, titanium or cobalt-chrome alloys), but according to their application, may also consist of polymers (e.g. polyetheraryl ketone, polyfluoro- and/or polychloroethylene, polyetherimides, polyethersulphones, polyvinylchlorides, polyurethanes, polysulphones, polyester) or of ceramic or glass-like materials (e.g. aluminium oxide, zirconium oxide, silicates, calcium phosphate ceramics or glass) or of composite materials (e.g. carbon fibre reinforced high-temperature thermoplasts).

[0076] FIGS. 9 to 13 show various exemplary applications for holding a pin-like or dowel-like implant according to the invention in or at the distal part of the resonator 6 (sonotrode) of the implantation device 1 (FIG. 1). The holder may for example be a positive-fit holder as shown in FIGS. 9 and 10. The positive-fit for example is realized as a snap-closure (FIG. 9) of a resiliently designed proximal extension 14 of an implant core 11 or implant 7 which is introduced into a corresponding opening 15 at the distal end of the resonator 6. The positive-fit may also be realized by a suitably secured pin 16 extending through the resonator 6 and the proximal extension 14 of an implant core 11 or implant. Advantageously, the positive-fit is arranged at a distance d to the distal end of the resonator such that it lies in a node point of the oscillations in z-direction, i.e. in a position in which the amplitude in z-direction is essentially zero.

[0077] FIG. 11 shows a screwed connection 17 between resonator 6 and implant 7, i.e. a non-positive fit or force-fit connection. If this connection is biased in a manner such that the oscillations propagate uninterrupted from the resonator to the implant, the implant 7 becomes a part of the resonator 6 and is to be designed accordingly. This means that the distal end of the resonator does not necessarily require maximal amplitude in the z-direction, but may as well lie on a node point.

[0078] FIGS. 12 and 13 show advantageous implant holders on the resonator 6 for implants whose proximal end consists of the liquefiable material. In both cases, the proximal implant end is shaped by and bonded to the distal end of the resonator 6 due to the ultrasound effect and suitable energy directors arranged on the resonator. FIG. 12 shows a resonator 6 with a distal surface which is formed as the impact surface of a granulating hammer. FIG. 13 shows a resonator 6 with a central energy director. In both cases, the proximal end of the implant 7 is contacted by the energy directors of the resonator 6 and the resonator is set into oscillation. The liquefiable material in the region of the energy directors of the resonator is liquefied first and bonds to the resonator, wherein it assumes the shape of its distal surface and forms a head 18 in the case which is shown in FIG. 12.

[0079] Holding of the implant on the resonator as shown in FIGS. 9 to 13 is advantageously established before positioning the implant on or in the tissue part, and it is released after implantation, in the cases of FIGS. 12 and 13, by way of a force with which the resonator is bent away or rotated off the implant 7.

[0080] As an example of further fields of application for implants according to the invention, FIG. 14 shows the fixation of a cover plate 30 of bone or of a man-made material into an opening of the calvaria 29 and the fixation for example of an artificial fixation plate 31 on a broken or fractured jawbone 32. Similar applications are conceivable in reconstruction surgery in the facial region. The connections that are to be created between the cover plate 30 and the surrounding bone tissue are advantageously limited to selected locations of the gap 33 between the plate and the native bone. The fixation plate 31 is likewise connected to the jawbone at selected plate locations 31. The connections at the selected locations are realized in successive implantation steps using the implantation device 1.

[0081] In section and in an enlarged scale, FIGS. 15 to 17 show connections that may be created with implants 7 according to the invention and that, for example, are suitable for the applications shown in FIG. 14.

[0082] FIG. 15 shows an implant 7 according to the invention that may be used to provide at least a local connection between the scull 29 and the cover plate 30, which is to be fixed in an opening of the scull that may contain porous material (e.g. likewise scull bone). The implant 7 is positioned (above) and then implanted by way of ultrasound energy (double arrow) in order to connect the scull 29 and the cover plate 30 across the gap 33 (below).

[0083] The gap 33 is advantageously formed obliquely in a manner such that external pressure forces on the gap region are accommodated by the calvaria 29. On the outer side, the gap 33 is extended for positioning the implant 7. The implant, which for example, is spherical or sausage-like and consists of a thermoplastic or thixotropic material, is positioned in the extended outer gap region and is impinged with oscillation energy. As a result, the implant material is liquefied, and on the one side, is pressed into the pores of the calvaria 29, and on the other side, is pressed into corresponding pores of a cover plate 30 consisting of, for example, bone, or into correspondingly arranged artificially created openings (e.g. dot-dashed groove) in an artificial plate. A positive-fit anchoring is thereby created on both sides such connecting calvaria 29 and cover plate 30.

[0084] FIG. 16 shows a fixation foil 35 which may also have the form of a textile web and which may, for example, be applied for local fixation of the cover plate 30 in the opening of the scull 29. The foil 35 is, for example, tape-like and is advantageously flexible. It consists completely of a liquefiable thermoplast or is, for example, reinforced with a fiber mat, or with a similar structure. It is applied over the gap 33 and is excited on both sides (double arrows) with the help of an implantation device (FIG. 1) in a manner such that it adheres to the surface of the calvaria 29 and the surface of the cover plate 30 (larger-surfaced, less depth-effective connection which may be limited to a multitude or a pattern of individual fixation points). As the case may be, the surface regions, at which the implant is to be connected to the material lying therebelow, may be suitably pre-treated (e.g. roughened) or suitable surface structures (surface unevennesses, recesses, grooves etc.) are provided on the artificial plate 30. In order to connect the film 35 to a bone surface, a pressure on the order of 0.5 to 3 N per mm.sup.2 of resonator end face is sufficient.

[0085] FIG. 17 shows a fixation plate 36 that is fastened with the help of a fixation film 35 or corresponding textile web over the gap 33 and which, for accommodating accordingly larger forces, consists e.g. of metal. Therefore, in addition to being used in a skull application, the fixation plate 36 may also be used on the jaw as shown in FIG. 13 or in the application according to FIG. 2. The fixation plate 36 consists of a material that is not liquefiable in the context of the invention. On a surface directed towards the tissue to be fixed, the fixation plate 36 has a surface structure suitable for a positive fit. The film 35 is positioned between the plate 36 and the tissue or material to be fixed and through the plate 36 is impinged at least locally with oscillation energy and is thus connected to the surface of the calvaria 29 and to the cover plate 30. The positive-fit connection between film 35 and fixation plate 36 may be created during implantation, or the plate 36 with the film 35 already connected to it may be used as a finished implant. In such a two-layer implant the connection between the layers may also be of a material fit (adhesion or welding). The film 35 in such a two-layer implant may also be reduced to a coating of the plate, wherein the coating advantageously does not have a constant thickness, but has energy directors consisting of a pattern of humps, points or ribs that have a minimal height (coating thickness) of approx. 10 m.

[0086] The fixation plate 31 shown in FIG. 14 comprises film regions 31 arranged for example in suitable recesses and having an outer surface provided with energy directors. These film regions are connected to the jawbone regions lying thereunder.

[0087] It may be advantageous for the application shown in FIG. 16 to design the resonator to be used in a manner such that the oscillations transmitted to the implant are not aligned perpendicular (z-direction) to the connection plane to be created as indicated with double arrows, but parallel to this (x/y-direction). As the case may be, a transmission element 37 as shown in FIG. 18 is suitable. This transmission element 37 is connected to the resonator 6 with a non-positive fit and specifically at a location in which the wave in the z-direction has a node point (amplitude=0) and thus the wave in the x/y direction has a maximum amplitude. This oscillation in the x/y direction is transmitted to the film 35 by the transmission element 37.

[0088] Schematically and in a greatly simplified manner, FIG. 19 shows a further application of implants according to the invention, namely a support element for a human vertebral column region. The support element 40 is elastic and supports the vertebral column region in a lasting or possibly temporary manner. In the context of the invention, the support element 40 is fastened to vertebral bodies in that it consists of a correspondingly liquefiable material and is fastened without depth effectiveness (as shown in FIG. 16), in that it consists of a non-liquefiable material and is connected to the vertebral bodies through a film and without depth effectiveness (as shown in FIG. 17) or with predrilling and depth effectiveness (as shown in FIGS. 2 to 4). The pin-like implants 7 shown in FIG. 19 have, for example, a head projecting beyond the support element and are made according to FIG. 13. For a lasting support, connecting implants and support element are made of a non-resorbable material. For a temporary support, connecting implants and support elements are made of a resorbable material.

[0089] FIG. 20 shows the application of a dowel-like implant 7 according to the invention forming a basis for an artificial tooth 40 in a jawbone 32. The implant 7 consists, at least partly, of a thermoplastic or thixotropic material. On its end face, it comprises means for holding the artificial tooth 40, a bridge or prosthesis. The implant is positioned in the corresponding opening with or without the artificial tooth and is pressed in further under ultrasound vibration. Since at the same time at least a part of the implant liquefies, it not only fills gaps between implant and bone in a largely interstice-free manner, but is also pressed into the pores of the jawbone so that a depth-effective connection arises as is for example shown in section in FIG. 21.

[0090] FIG. 22 shows in section a further exemplary embodiment of an implant according to the invention. This implant is particularly suitable for the application shown in FIG. 20. The liquefiable material is not arranged on the outer surface of the implant, but within a sleeve 13 which is permeable to the liquefiable material when liquefied, as has already been described in connection with FIG. 8. The longitudinally sectioned implant is shown to the left of the middle line in a state before application of ultrasound and to the right of the middle line in a state after the application of ultrasound. The sleeve 13 consists, for example, of a metallic or ceramic sintered material with an open porosity, and assumes the bearing function of the implant. In the shown case, it comprises an opening with an inner thread suitable for fastening a tooth, bridge or tooth prosthesis. The implant comprises a further, annular opening 43 in which the liquefiable material is positioned, for example a cylindrical piece 44 of the liquefiable material. For a targeted liquefaction, energy directors 45 are provided in the inside of the annular opening 43 in contact with the liquefiable material.

[0091] The implant according to FIG. 22 is, for example, positioned in an opening of a jawbone (41, FIG. 20) and then the liquefiable material is impinged with mechanical energy using a resonator 6 with an annular distal end. As a result, this material is liquefied and pressed through the porous sleeve material, into the surrounding bone tissue, whereby the implant is anchored in this tissue.

[0092] For the application shown in FIGS. 19 to 20, it is particularly advantageous to select a resorbable material as the liquefiable material, whilst the bearing part consists of a material that is neither liquefiable nor resorbable and that has a sufficient mechanical strength for the fastening of a tooth, bridge or prosthesis. At the same time, at least the surface of the central part is bioactive (e.g. porous as described for the sleeve 13), that is to say, equipped in a manner such that it promotes an intergrowth with bone tissue. Immediately after implantation, such an implant has a primary stability that is adequate for fastening the tooth, bridge or prosthesis and for normal use thereof. Promoted by the bioactive surface of the central implant part, regenerated tissue then successively replaces the resorbable material and grows together with the central implant part. The implant according to the invention thus offers an immediate primary stability without the application of cement and, after a resorption and regeneration phase a permanent secondary stability, which is equal to the stability of known implants. In comparison to known implantation methods, however, there is no transition phase in which, according to the state of the art, the opening 41 is closed and one waits for regeneration of bone tissue before the tooth, the bridge or the prosthesis is fastened directly in the regenerated bone.

[0093] FIG. 23 shows an external fixation device 51 comprising supports 52 and a carrier 53 fastened on the supports 52, which device is for example fastened on a tubular bone 50 of a human arm according to the invention. The supports 52 are designed as implants according to the invention. The medial part of a tubular bone consists mainly of cortical bone substance and comprises only very little tissue regions that are porous in the context of the invention. For this reason, the marrow space 54 in the inside of the tubular bone 50 is used for the liquefied material to be pressed into. This is shown in FIGS. 24 and 25 in more detail. The supports are provided for example with base plates 55 since the marrow cannot counteract the hydrostatic pressure with sufficient resistance.

[0094] In order to fasten the fixation device, openings (with a thread 25 as the case may be) are drilled through the tubular bone 50 extending into the marrow space, wherein the bore diameter corresponds to the diameter of the implant 7 or the base plate 55 respectively. The implant 7 comprises a central support 52, a distal end fastened to the base plate 55, and an annular or tubular region 57 of the liquefiable material arranged around the support and essentially covering the base plate 55. The implant is introduced into the opening 56 and is held at a predefined depth with suitable means to be applied externally. Then the liquefiable material 57 around the support 52 is pressed against the base plate 55 under the effect of ultrasound, so that it is pressed between the bone 50 and the base plate 55 into the marrow space 54 and thus forms a positive-fit connection holding the support 52 in the opening 56. This anchoring permits a unicortical fastening of the support 52, wherein the fastening is secure against tilting. According to the state of the art, such fastening can be achieved only by a bicortical fastening.

[0095] FIG. 26 shows a further embodiment of the implant 7 according to the invention, wherein the is particularly suitable for the application shown in FIG. 23. The liquefiable material, which for example is a thixotropic cement, is arranged in the inside of the support 52, and openings 58 are provided above the base plate 55 and have a size such that the cement cannot exit in its highly viscous form, but exits in its liquefied form by the effect of the resonator 6. The end of the support 52 is designed as a sleeve in the sense of the sleeve according to FIG. 8. The cement pressed through the openings 58 with the help of the resonator secures the support in the marrow cavity, and as the case may be, in the adjacent bone tissue.

[0096] The implant according to the invention shown in FIG. 27 is a tension screw 60, which, for example, is used together with a trochanter plate to fix a broken femoral neck bone. The tension screw 60 (in the sense of an implant sleeve 13, FIG. 8) is hollow and at least in its distal end comprises openings through which a liquefied material can be pressed out in order to anchor this distal region better in osteoporotic bone tissue than is possible alone with the thread of the tension screw. The thread of the screw thus serves in particular for pulling together the tissue in the region of the fracture, until the distal screw end is anchored in the tissue by the liquefiable material.

[0097] FIG. 28 shows, in a very schematic sectional representation, a tubular bone 50 on which an artificial joint element 62 is fastened by way of an implant 7 according to the invention. The stem 63 of the joint element 62 and liquefiable material 57 arranged around the stem represent the implant according to the invention, which is pressed into the tubular bone 50 under the effect of ultrasound, wherein the material 57 is liquefied and is pressed into pores of the cancellous bone 23 and into unevennesses of the inner surface of the cortical substance 22 of the tubular bone. The stem 63 has a surface structure which is suitable for a positive fit connection to the liquefiable material 57, in the same manner as shown for plate 36 in FIG. 17.

[0098] A particularly advantageous embodiment of the stem 63 consists, for example, of titanium and has a porous surface that is thus bioactive and it is surrounded by resorbable liquefiable material. Such an implant has a primary stability directly after implantation, which permits at least partial loading. The primary stability is later taken over by a secondary stability effected by the intergrowth of vital bone tissue into the porous surface of the titanium stem 63. This means that the artificial joint element may be loaded essentially immediately after implantation, but without the use of cement. This early loading favors regeneration of the vital tissue and prevents atrophy (osteoporosis). All the same, in a further phase, vital tissue intergrows with the titanium stem.

[0099] FIG. 29 likewise very schematically shows a joint 70 in the region of which a ligament 71 connects the bones 72 and 73. The ligament 71 is naturally intergrown with the bone, wherein this connection may tear on overloading. Implants 7 according to the invention can be used for the repair, wherein implant embodiments according to FIGS. 2 to 4 may be used. For the repair, the cortical substance of the joint bone is opened and pin-like implants 7 are driven through the ligament 71 and secured externally with a head (e.g. according to FIG. 13). Embodiments with less depth effectiveness according to FIGS. 16 and 17 are also conceivable.

[0100] Concluding, FIG. 30 shows that the connection to be created with the implant 7 according to the invention need not necessarily serve the connection of two elements (two tissue parts or a tissue part and an artificial part). It is also conceivable to use an implant according to the invention for filling a tissue opening 80 being caused by a tumour for example. For such an application, an implant 7 of a highly viscous and thixotropic material 81 is used. With the aid of a guide 82 being positioned around the opening, this material is introduced into the opening 18 such that it projects beyond the opening. The resonator 6 used for this application has a cross section corresponding to the inner cross section of the guide 82 and presses the material 81 into the opening 80 like a piston. The opening 80 is thereby not only filled essentially without interstices, but the material 81 becoming liquid under the effect of ultrasound is also pressed into the tissue pores opening into the opening 80, and thereby forms a positive fit connection after solidification, which is shown below in FIG. 30. This positive-fit connection securely holds the implant 7 in its opening 80 even without the opening comprising undercuts, and without providing other retaining means (e.g. periosteum sutured above the implant).

[0101] Suitably, finely processed bone material of the patient may be admixed to the liquefiable material.

[0102] If in a case as shown in FIG. 30 a thermoplastic material is used instead of the thixotropic cement, the opening 80 may also be specially manufactured for accommodating a fixation element for a wire 84 or suture, as shown dot-dashed in FIG. 30 (only below). A therapeutic auxiliary device, such as a stimulator, may be fixed in the same manner.

Example 1

[0103] Pins of PLLA and polycarbonate manufactured by injection molding and having a round cross section of diameters between 3.5 and 4.25 mm, a length of 26 to 40 mm (ideal length at 20 kHz: 35 mm), obtusely tapered, distal ends and four grooves axially extending over 10 mm from the distal end were anchored with an excitation frequency of 20 kHz in cancellous bone (femur head) of freshly slaughtered cattle. For implantation, the thin cortical substance layer lying over the cancellous bone was opened, but the cancellous bone was not pre-drilled. On implantation, the implants were pressed against the tissue with pressures of 60 to 130 N and excited with the excitation frequency (sonotrode amplitude approx. 20 to 25 m). The advance was limited to 10 mm which was achieved in less than 2 s. The implants were then held without excitation for 5 seconds.

[0104] The resulting anchorage depths were in the order of 15 mm and the anchorage on tearing out proved to be stronger than the implants themselves (maximum tear-out forces over 500 N). Sensors being placed at 1 mm from the pre-bore in the cortical bone substance (1.5 mm below the bone surface) recorded temperatures of max. 44 C. (approx. 22 above room temperature) approx. 10 s after implantation. The temperature rise was reduced to half its value in approximately 30 seconds.

[0105] No molecular weight reduction was found in the implanted PLLA material when compared with the material before implantation.