EP1601301A1

EP1601301A1 - Bone implant that can be screwed in

Info

Publication number: EP1601301A1
Application number: EP03732311A
Authority: EP
Inventors: Wolfgang Dinkelacker
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-05-03
Filing date: 2003-05-03
Publication date: 2005-12-07
Also published as: WO2004098442A1; AU2003242247A1

Abstract

The bone implant (10) having a screw thread (11) on the periphery thereof for screwing the implant into the bone comprises groove-like recesses (16) that are made in the screw thread. The size of the groove-like recesses (16) correspond to the size of the osteons of the bone tissue that attach to the groove-like recesses. The groove-like recesses extend preferably in a direction that essentially corresponds to the direction of the pitch (15) of the screw thread. They form a micro-thread, which overlaps the screw thread and which enlarges the contact surface between the implant and the bone tissue. The matching of the groove size to the osteon size promotes the attachment of the osteons to the implant surface.

Description

SCREW-IN BONE IMPLANT

Field of the invention

The invention relates to a bone implant with an implant body, which has a screw thread on its periphery for screwing the implant body into the human bone and the surface of which is equipped with a biocompatible structure.

State of the art

Bone implants with helical implant bodies are known which are screwed into a correspondingly dimensioned hole in human bone. The hole is dimensioned according to the core diameter of the screw thread, so that when the implant is screwed in, it is securely anchored in the bone. Screwing in is made easier if the screw thread is self-tapping. For this purpose, cutting edges are incorporated into the screw thread, so that it acts like a tap. Such implants can preferably be designed as jaw implants (e.g. EP 1 234 550 AI).

Bone implants usually consist of a material that is well tolerated by the tissue of human bone. Titanium is particularly suitable and titanium alloys or tantalum and tantalum alloys. In order to promote rapid and permanent ingrowth of the implant in the bone, the known implants in the surface areas that come into contact with bone tissue are provided with a surface roughness which improves the attachment of the bone cells to the implant surface. A jaw implant with different surface roughness along its circumference is disclosed in US Patent 5,989,027. A central part of the implant, which is made of titanium, is provided with a porous metal layer, which is produced by sintering on a powder of titanium or a titanium alloy. Adjacent to this part is an area in which the implant has a lower roughness and which is produced by sandblasting the titanium surface. This area is followed by a further area which is essentially smooth and in which the biocompatible properties of the titanium come into effect. The implant can be designed as a screw, in which the part of the implant surface provided with the porous metal layer is located above the thread or is superimposed on the thread.

Summary of the invention

The invention proposes a screw-in bone implant that has increased biocompatibility through improved adaptation of the implant surface to the structure of the bone tissue.

As defined in the claims, the screw thread on the circumference of the implant has a number of groove-shaped depressions, the size of which corresponds to the size of the osteons of the bone tissue which attach to the groove-shaped depressions. The groove-shaped depressions preferably run in a direction which corresponds essentially to the direction of the threads of the screw thread. According to a preferred embodiment, the groove-shaped depressions only extend over part of a circumferential line, and a plurality of groove-shaped depressions are arranged one behind the other along the same circumferential line and have a variable width and depth over their length.

The groove-shaped depressions form a micro thread superimposed on the screw thread, which does not hinder the screwing-in process and increases the contact area between the implant and the bone tissue. Due to the groove-shaped depressions, the bone tissue is preformed when the implant is screwed in, which prepares its attachment to the implant body. The adjustment of the groove size to the size of the osteons favors the attachment of the osteons to the implant surface. The osteons align themselves with the groove-shaped depressions and attach themselves to the implant surface along these depressions.

According to a further aspect of the invention, the implant has a self-tapping thread, in which the groove-shaped depressions extend over the threads that are interrupted by the cutting edges.

Description of the drawings

Various embodiments of the invention are shown below with reference to drawings. Show it:

FIG. 1 shows a side view of a jaw implant designed according to the invention; Figure 2 is an enlarged partial view of the profile of a

Thread on the circumference of the implant according to Figure 1;

Figures 3a-c is a plan view of a flat development of part of a thread on the circumference of the implant according to Figure 1 and the cross section and the longitudinal profile of the groove-shaped depressions arranged in the thread;

FIG. 4 shows a side view of a further embodiment of a jaw implant according to the invention;

5a-c a plan view of a flat development of a part of a thread on the circumference of the implant according to FIG. 4 and the cross section and the longitudinal profile of the groove-shaped depressions arranged in the thread;

FIGS. 6a-c show schematic sectional representations of the profile of various embodiments of the thread turns on the circumference of implants designed according to the invention;

FIG. 7 shows a side view of a further embodiment of a jaw implant according to the invention; and

FIGS. 9-10 are side views of various implant shapes to which the invention can be applied.

Detailed description of the embodiments of the invention shown in the drawings

Figure 1 shows a jaw implant with a cylindrical implant body 10, the one around its circumference Has screw thread 11, with which the implant body is screwed into a pre-drilled hole in the jawbone. The implant body 10 has a central threaded bore 12, which serves to connect an implant attachment (not shown) to the implant body. The implant body 10 is preferably made of titanium or a titanium alloy. The screw thread 11 is designed in a manner known per se as a self-tapping thread, for which purpose the implant body 10 has four recesses 13 running in the axial direction and preferably offset by 90 degrees, only two of which are shown in FIG. 1. Each of the recesses 13 is delimited on one side by a cutting edge 14, while on the opposite side it runs out into the circumference of the implant body. ^ ^λ

In the threads 15 of the screw thread 11 there are groove-shaped depressions 16 which run in the direction of the threads 15 or parallel to these. In the illustrated embodiment, the groove-shaped depressions 16 are only in the concave part of the threads. However, the design can be modified such that corresponding groove-shaped depressions are also arranged in the rounded comb between the threads. The dimensioning of the groove-shaped depressions 16 is adapted to the order of magnitude of the osteons of the jaw bone tissue, which attach to the groove-shaped depressions 16. The groove-shaped depressions 16, also referred to herein briefly as "grooves", preferably have a concave profile 21 which is delimited at its edges by combs 22 at the level of the circumference of the thread 15 (FIG. 2). FIG. 3a shows a plan view of the grooves 16 in a flat development of part of the thread turn 15. The groove cross section 32 and a longitudinal profile 33 of the grooves 16 are shown in FIGS. 3b and 3c. The grooves 16 have a width which is preferably in the range between 10 and 300 micrometers, and a depth between 10 and preferably up to 150 micrometers. They form a micro thread superimposed on the screw thread 11, which does not hinder the screwing-in process and increases the contact area between the implant and the bone tissue. In addition, when the implant is screwed in, a preforming of the bone tissue is effected, which prepares its attachment to the implant body 10.

The function of the groove-shaped depressions for connecting the implant to the bone tissue is described in EP 1 013 236 AI. The groove-shaped depressions 16 promote quick and permanent anchoring of the implant in the bone. The adaptation of the groove size to the size of the osteons promotes the attachment of the osteons to the implant surface. The osteons align with the grooves 16 and attach themselves along the grooves to the implant surface.

Grooves 17 of the type disclosed in EP 1 013 236 AI are arranged on the head 18 of the implant body 10. The width and depth of the grooves 17 are adapted to the order of magnitude of the osteons and run in a crosswise spiral on the cylindrical circumference of the implant head 18. Only a narrow area 19 between the grooves 17 and the upper end of the implant body 10 can have a smooth surface.

The surface of the screw thread 11 with the threads 15 and the groove-shaped depressions 16 can be provided with a micro-roughness which is produced by acid etching or sandblasting and can additionally be covered by a sputter layer, which preferably consists of titanium. This surface treatment can also be extended to the implant head 18 and the area 19. A modified embodiment of the implant from FIG. 1 is shown in FIGS. 4 and 5a-c. The implant of FIG. 4 is a jaw implant with a cylindrical implant body 40 which has a screw thread on its circumference

41, which is screwed into a predrilled hole in the jawbone. The implant body corresponds to the implant body 11 from FIG. 1. In its head region, it can have cross-shaped grooves in the manner of the grooves 17 described in relation to FIG. In the embodiment of Figure 4, the screw thread 41 is not designed as a self-tapping thread. Grooved depressions 43 are arranged in the thread 42 of the screw thread 41, which run in the direction of the threads 42 or parallel to them and over the circumference of the thread

42 are distributed so that a plurality of groove-shaped depressions 43 are arranged one behind the other on each circumferential line of the thread 42. The groove-shaped depressions 43 of adjacent circumferential lines are mutually offset in their longitudinal extent. FIG. 5a shows a top view of the grooves 43 in a flat development of part of the thread turn 42. The groove cross section 44 and a longitudinal profile 45 of the groove-shaped depressions 43 are shown in FIGS. 5b and 5c.

The groove-shaped depressions 43 have a variable width and depth over their length. The groove-shaped depressions 43 have their greatest width and depth in the middle 46 of their longitudinal extent and are flat and narrow at their ends 47. In the top view of FIG. 5a, the contour lines of the grooves 43 have the shape of narrow segments 48.

Figures 6a-c show different embodiments for the profile of the threads of the screw threads 11, 41 in the form of schematic sectional views. Execution of Figure 6a has a thread 61 with a triangular cross-sectional profile and an acute-angled ridge 62 for lateral limitation of the thread. Grooves 65, which have a triangular profile, are arranged at a distance from one another in the flanks 63, 64 of the thread 61. In the embodiment of FIG. 6b, the grooves 66 have a semicircular profile. Otherwise, the embodiment of FIG. 6b corresponds to that of FIG. 6a. The embodiment of Figure 6c shows threads 67 with a trapezoidal cross-sectional profile and an acute-angled ridge 68 for lateral limitation of the threads. At the base 69 and the two adjacent flanks 70, 71 there are two grooves 72 with a semicircular profile at a distance from one another.

Another embodiment of the implant according to the invention is shown in FIG. 7. The implant of FIG. 7 is a jaw implant with a cylindrical implant body 74, which has a screw thread 75 on its circumference, which is screwed into the jaw bone. The implant body 74 corresponds to the implant body 10 from FIG. 1. In its head region, it can comprise cross-wound grooves which correspond to the grooves 17 in the implant head 18. Grooved depressions 77 are arranged in threads 76 of the screw thread 75 and run approximately at right angles to the direction of the threads 76. The groove-shaped depressions 77 can have a shape which corresponds to the shape of the grooves 43 shown in FIGS. 5a-c, so that they have a variable width and depth over their length in a planar development of a thread turn, the greatest in the center of the groove Have width and depth and their flat and narrow ends end in an acute-angled comb 78, which delimits the threads 76 on both sides. The groove-shaped depressions 77 of the implant body 74 are designed differently over the length of the screw thread 75. The width and depth of the groove-shaped depressions and / or their distance from one another increase in the direction of the foot-side end of the implant body 74. The distance between adjacent grooves 79 in the upper threads 76 is smaller than the distance of the grooves 77 in the lower threads. This takes into account the different bone densities of the compact in the area of the alveolar ridge and the cancellous bone in the lower areas of the alveolar bone. A non-illustrated modification of the embodiment according to FIG. 7 consists in that the groove-shaped depressions 77, 79 which run approximately at right angles to the direction of the thread turns 76 of the screw thread are overlaid by groove-shaped depressions extending in the direction of the thread turns of the screw thread in the manner of the groove-shaped depressions 16 shown in FIG. 1 and cross with them. An advantage of the embodiment according to FIG. 7 and the modifications of this embodiment is an improved introduction of pressure.

FIGS. 8-10 show various forms of jaw implants to which the invention can be applied. FIG. 8 shows a conical implant body 80 which has a thread 81 on its conical surface. The thread 81 is designed to be self-tapping, for which purpose four cutting edges 82 distributed uniformly over the circumference are arranged in the lower part of the implant body 80. The self-tapping thread 80 enables the implant to be screwed into a correspondingly predrilled hole in the jawbone. Grooves 83 are embedded in the threads of the thread 81, and their arrangement and design correspond to the groove-shaped depressions 16 or 43 from FIGS. 1 and 4. FIG. 9 shows an implant body 90 which is cylindrical in an upper part 91 and conical in a lower part 92. The circumference of the implant body 90 has a thread 93 which extends over both parts 91 and 92 and which is designed to be self-tapping in the lower part 92. Grooved depressions 94 are arranged in the thread 93, and their arrangement and design correspond to the grooved depressions 16 or 43 from FIGS. 1 and 4.

FIG. 10 shows a stepped implant body 100 which comprises three cylindrical sections 101, 102, 103, the diameters of which are stepped towards the end on the foot side. Each of these sections 101, 102, 103 has a screw thread 104, 105, 106 on its circumference, which is self-tapping in the lower sections 105, 106 and serves to screw the implant into a correspondingly predrilled hole in the jawbone. Grooved depressions 107 are arranged in the threads of the screw threads 104, 105, 106, and their arrangement and design correspond to the grooved depressions 16 or 43 of FIGS. 1 and 4.

Although the invention has been described with the aid of jaw implants, its principles can also be applied to other bone implants which have a screw thread on their circumference for screwing the implant into the bone. The exemplary embodiments shown and described can be modified and other embodiments can be realized without thereby leaving the scope of the invention defined in the claims.

Claims

PATEN CLAIMS

1. bone implant with an implant body (10) which has a screw thread (11) on its circumference for screwing the implant body into human bone and the surface of which is equipped with a biocompatible structure,

characterized,

that a plurality of groove-shaped depressions (16) are embedded in the screw thread (11), the size of which corresponds to the size of the osteons of the bone tissue, which attach to the groove-shaped depressions.

2. Implant according to claim 1, characterized in that the groove-shaped depressions (16) extend essentially in the direction of threads (15) of the screw thread (11).

3. Implant according to claim 2, characterized in that the groove-shaped depressions (43) only extend over part of the screw circumference.

4. Implant according to claim 2, characterized in that the groove-shaped depressions (43) have interruptions.

5. Implant according to claim 3, characterized in that a plurality of the groove-shaped depressions (43) are arranged one behind the other along a circumferential line running parallel to the threads (42).

6. Implant according to claim 5, characterized in that the groove-shaped depressions (43) have a variable width and depth over their length.

7. Implant according to claim 5, characterized in that the groove-shaped depressions (43) their greatest width and depth approximately in the middle (46) of their

Have longitudinal expansion and are flat and narrow at their ends (47).

8. Implant according to claim 1, characterized in that the screw thread (11) is designed as a self-tapping thread.

9. The implant according to claim 8, characterized in that recesses (13) are formed in the screw thread (11) in the direction of the longitudinal axis of the implant body (10) and form the cutting edges (14), and that the groove-shaped recesses (16) are embedded in the remaining part of the threads (15).

10. Implant according to claim 1, characterized in that the groove-shaped depressions (77) run approximately at right angles to the direction of the threads (76) of the screw thread (75).

11. The implant according to claim 10, characterized in that the groove-shaped depressions (77) have a variable width and depth over their length.

12. The implant according to claim 10, characterized in that the width and depth of the groove-shaped depressions (77, 79) and / or their distance from one another over the length of the screw thread (75) in the direction of the longitudinal axis of the implant body (74) are different.

13. Implant according to claim 10, characterized in that the groove-shaped extending approximately at right angles to the direction of the threads (76) of the screw thread

Recesses (77) are superimposed by the groove-shaped depressions (16) which run essentially in the direction of the threads of the screw thread and intersect with them.

14. Implant according to claim 1, characterized in that in a head region (18) of the implant body (10) grooves (17) are arranged, the width and depth of which are adapted to the order of magnitude of the osteons and are crisscrossed on the circumference of the head region ,

15. Implant according to claim 1, characterized in that the groove-shaped depressions (83) in the screw thread (81) are arranged on the circumference of a conical implant body (80).

16. The implant according to claim 1, characterized in that the groove-shaped depressions (94) in the screw thread (93) are arranged on the circumference of an implant body (90) which consists of a cylindrical part (91) and a conical part (92).

17. The implant according to claim 1, characterized in that the groove-shaped depressions (107) are arranged in the screw thread (104, 105, 106) on the circumference (101, 102, 103) of a stepped implant body (100).

18. Implant according to one of claims 1 to 17, characterized in that the implant is a jaw implant.