DE102014114163A1 - implant - Google Patents

Abstract

An implant (13) for replacement or supplementation of bone parts has an implant body (21) of i. w. solid material, such as metal, and with an open-pore, the bone (12) facing interface (14). Adjoining the interface (14) is a transition region (22) between the bone (12) and the implant body (21), the elasticity of which is variable as a function of its distance from the implant body (21). The elasticity of the transition region (22) from the implant body (21) to the bone (12) decreases. The transition region (22) thus forms an i. w. smooth transition of elasticity between the implant body (21) and bone (12). The implant incl. The transition region is preferably generative, z. B. by selective laser melting (SLM).

Description

The invention relates to an implant for replacement or supplementation of bone parts with an implant body of i. w. solid material, such as metal, and with an open-pore, bone-facing interface.

Replacement or supplementation of bone parts is often necessary for endoprosthetic care for improving or restoring joint function and thus increasing the patient's quality of life. If it comes to the wear of articulating joint partners or to a loosening of the implant, a revision must be carried out. Since it usually comes to the loss of bone material at the affected site, the use of larger revision implants is required. If the revision has to be repeated, massive segmental bone defects can occur.

The second most common cause of bone defects is bone tumors, some of which occur on the pelvis. When removing them surgically, a long resection should be sought, so that the margins are definitely in healthy tissue.

Due to their excellent biocompatibility and high mechanical stability, titanium and its alloys have proven their worth as implant material in everyday clinical practice in a wide variety of osteosynthesis or endoprosthetics applications. Furthermore, the ingrowth of bone cells into porous titanium structures could be detected. ( Lopez-Heredia M a, Goyenvalle E, Aguado E, Pilet P, Leroux C, Dorget M, et al. "Bone growth in rapid prototyped porous titanium implants". Internet June 1, 2008 [cited January 16, 2014]; http://www.ncbi.nlm.nih.gov/pubmed/17876801 ).

The possibility of using generative manufacturing techniques such as Electron Beam Melting (EBM) or Selective Laser Melting (SLM) allows individual prostheses to be developed and manufactured for each affected patient ([ Warnke PH, Douglas T, Wollny P, Sherry E, Steiner M, Galonska S, et al. "Rapid prototyping: porous titanium alloy scaffolds produced by selective laser melting for bone tissue engineering." Tissue Eng Part C Methods Internet June 15, 2009. http://www.ncbi.nlm.nih.gov/pubmed/19072196 ).

For sufficient stability, the surrounding bone must be able to grow into or into the implant. However, two major mechanisms can prevent this. On the one hand, there are micro-movements between the bone and the implant. Even with relative movements of 100 μm, connective tissue formation at the interface can occur, thereby preventing bone growth on or in the implant. On the other hand, the flow of force in the bone can be changed by the implant, thereby relieving the bone in places. This so-called stress shielding leads to atrophy of the affected bone tissue and to aseptic loosening of the implant.

Task and solution

The object of the invention is therefore to provide an implant of the type mentioned, in which the disadvantages described do not occur and in particular the ingrowth of the bone is promoted in the implant.

This object is achieved in that adjoins the boundary surface, a transition region between bone and implant body whose elasticity is variable depending on its distance from the implant body.

In this way, despite the use of a very strong and compatible material for the implant body, such as titanium, a transition between the low elasticity (modulus of elasticity of titanium 110 gigapascals [GPa]) and the larger of the bone (elastic modulus of cortical bone 10-20 GPa and much lower for cancellous bone). Elasticity here means the resulting elastic properties, ie also the flexibility, of the part of material considered, that is to say both of the implant body and of the transition region in its individual regions. The flexibility is usually within the limits given by the materials involved (bone and implant body).

The transition region advantageously creates a fairly fluid transition of the elasticity between the implant body and the bone. In the transition region pores are formed, which communicate with each other and shrink towards the implant body. This promotes the ingrowth of the bone into the implant. The ingrowing bone cells rejuvenate towards the implant and find many undercuts for a good grip.

The transition region may be formed of structures of a less flexible material compared to bone, preferably the same material as the implant body and integral therewith. The fluid transition between the implant body, for example made of solid titanium, and the bone is achieved by a perforated structure, which due to the material cross sections and the shape of a transition in the Flexibility creates despite the different moduli of elasticity of the materials.

These structures are preferably geometrically determined figures, which are connected to each other and have the same basic shape over the transition region, but optionally have changed dimensions of the structure elements forming the structure. They may preferably be nested multi-webs of webs. In contrast to random structures, optimized design and generative fabrication can create optimally smooth transition properties and avoid sharp edges that are detrimental to bone ingrowth.

The transition region is advantageously produced by selective laser melting (SLM), electron beam melting (EBM) or in a comparable manner. In this process, numerous powder layers of the implant material are successively melted onto the implant body by program-controlled laser beams, thus forming a structure which allows a virtually unlimited variety of shapes. Also undercuts etc. are possible.

The dimensions, structure, pore size, etc. of the transition region are adapted to the particular site of use, the size of the implant and the transition area to the bone. Preferably, however, the thickness is between 5 and 10 mm, the pore size can be between 0.5 and 2.5 mm and the web diameter of the structures can be dimensioned between 0.2 and 2 mm.

Such an implant ensures, in particular in highly stressed bones, which must be replaced, for example, when placing an artificial acetabulum on the pelvic bone in a pelvic bone replacement after a bone tumor or a mechanical injury, best opportunities for a permanent symptom-free care. It provides an improvement in stability through good primary stability, d. H. Prevention of relative movement due to comparable flexibility between bone and transition area, an open-pored, deep structure for osseointegration and adaptation of the mechanical properties of the implant to the adjacent bone tissue. The structures can be designed optimized so that both in the transverse direction, ie parallel to the interface, as well as in the printing direction, ie perpendicular thereto, sufficient flexibility is available. Thus, shifts in the area between the bone and the implant can be avoided, where load-related displacements of tenths of a millimeter would result in ingrowth of connective tissue, which would then prevent the ingrowth of bone cells. In addition, despite exact measurement and production existing form deviations of the interface between bone and implant could be flexibly collected.

The foregoing and other features will become apparent from the claims and from the description and drawings, wherein the individual features each alone or more in the form of sub-combinations in an embodiment of the invention and in other fields be realized and advantageous as well protectable versions. The subdivision of the application into individual sections and subheadings does not limit the statements made thereunder in their generality.

Brief description of the drawings

An embodiment of the invention is shown schematically in the drawing and will be explained in more detail below. Show it:

1 in a schematic perspective partial view, a provided with an implant for the acetabular pelvic bone,

2 a schematic partial cross-section through bone and implant with transition region, and

3 a basic structure from which the cells of the transition area can exist.

Detailed Description of a Preferred Embodiment

1 shows parts of a basin 11 , which has a large bony defect in the region of the ilium, z. B. due to a bone tumor or other causes. Since the natural acetabulum is affected, this and a subsequent part of the bone must be 12 through an implant 13 be replaced. For this purpose, the bone becomes an interface 14 worked out, radiologically measured exactly and then with a computer program the exact shape of the implant 13 established. This is made of a suitable material, preferably titanium, according to the specification of the computer program.

As you also look 1 , in which the bone is shown translucently, can see, the implant is with a pin 15 and a fastening strap 16 provided over it with cones 17 , Screws o. The like. Is attached to the healthy bone part. The pin 15 engages in a corresponding recess 18 one on the bone 12 is worked out. In addition, for lateral support and accurate centering is an iliac spike 19 through the ground the acetabular cup 20 of the implant inserted into a corresponding bore of the bone.

To the interface 14 closes in the direction of the implant body 21 a transition area 22 at. During the implant body 21 is made of solid metal, is the transition area 22 through geometric interconnected cellular structures 23 formed, of which, for example, a in 3 is shown. In the example shown, its basic form consists of nested triangles 24 from round bars 25 from the material of the implant body. They are integral with the implant body 21 connected, so that the first layer out of this "outgrow". They are z. B. generated generatively by selective laser melting (SLM) by first applied to the implant body in the region of the interface a fine titanium powder and this, controlled by the computer program, partially melted. This is repeated in very fine layers until the transition region is finished. Since the pattern painted by the laser can be changed from layer to layer, it is an arbitrary shape design, that is also a multiplicity of interconnected and partially undercut structures 23 to 3 manufacture. In the 3 The structure shown is one of many possible geometrically determined structures, which may be the same or different in shape and variable in their dimensions. However, it is also possible to design and dimension the structures differently depending on the distance to the implant body and, if there are special conditions on the bone, in different areas of the interface. It can also be used other cross sections instead of the illustrated round cross section of the webs.

In the schematic representation after 2 is hinted that the transition area 22 one from the implant body 21 to the bone 12 Increasing flexibility, ie decreasing stiffness, by the structures 23 have lower material cross-sections and / or number of webs in this direction. Inside and between the structures 23 , so at 3 between the bridges 24 are pores 26 formed due to the decreasing material cross-sections towards the bone 12 to enlarge.

It can be seen that this implant design offers the best opportunities for mechanical and biological integration. Due to the limited and essentially seamless flexibility between the implant and the bone, it adapts well to the bone interface when it is inserted. Under load, no or only insignificant movements between the bone and the implant, which are trapped in the flexible transition region and thus do not interfere with the interface, occur. The open to the bone, partially undercut and tapering in the direction of the implant pore structure creates the best conditions for the ingrowth of bone cells and thus a complete and lasting integration of the implant.

LIST OF REFERENCE NUMBERS

11

pelvic bones

12

bone

13

implant

14

interface

15

spigot

16

mounting tab

17

spigot

18

recess

19

Iliac pins

20

acetabulum

21

implant body

22

Transition area

23

structures

24

triangles

25

Stege

26

pore

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited non-patent literature

• Lopez-Heredia M a, Goyenvalle E, Aguado E, Pilet P, Leroux C, Dorget M, et al. "Bone growth in rapid prototyped porous titanium implants". Internet June 1, 2008 [cited January 16, 2014]; http://www.ncbi.nlm.nih.gov/pubmed/17876801 [0004]
• Warnke PH, Douglas T, Wollny P, Sherry E, Steiner M, Galonska S, et al. Rapid Prototyping: porous titanium alloy scaffolds produced by selective laser melting for bone tissue engineering. "Tissue Eng Part C Methods Internet June 15, 2009. http://www.ncbi.nlm.nih.gov/pubmed/19072196 [0005]

Claims (10)

Implant ( 13 ) for replacement or supplementation of bone parts with an implant body ( 21 ) made of solid material, such as metal, and with an open-pored, bone ( 12 ) facing interface ( 14 ), characterized in that at the interface ( 14 ) a transition area ( 22 ) between bones ( 12 ) and implant body ( 21 ) whose elasticity depends on its distance from the implant body ( 21 ) is changeable. Implant according to claim 1, characterized in that the elasticity of the transition region ( 22 ) from the implant body ( 21 ) to the bone ( 12 ) decreases. Implant according to claim 1 or 2, characterized in that the transition region ( 22 ) iw a smooth transition of elasticity between implant body ( 21 ) and bones ( 12 ). Implant according to one or more of the preceding claims, characterized in that in the transition region pores ( 26 ) are formed, which communicate with each other and the implant body ( 21 ) down. Implant according to one or more of the preceding claims, characterized in that the transition region ( 22 ) from structures ( 23 ) one compared to the bone ( 12 ) of less flexible material, preferably of the same material as the implant body ( 21 ) and formed integrally therewith. Implant according to one or more of the preceding claims, characterized in that the structures ( 23 ) in or between themselves the pores ( 26 ) and also structural elements, such as webs ( 25 ), which have different elasticity by changing the diameter, wall thickness, arrangement or distances. Implant according to claim 5 or 6, characterized in that the structures ( 23 ) are geometrically determined figures which are connected to each other and via the transition region the same basic shape, but possibly with changed dimensions of the structure ( 23 ) forming structural elements. Implant according to claim 7, characterized in that the structures ( 23 ) by interleaved mehrecke from webs ( 25 ) are formed. Implant according to one or more of the preceding claims, characterized in that the structures ( 23 ) of the transition area ( 22 ) made of metal, preferably titanium, and are produced generatively, for example by selective laser melting (SLM) or electron beam melting (EBM). Implant according to one or more of the preceding claims, characterized in that the transition region ( 22 ) has at least one of the following features: - its thickness is a few millimeters, preferably 5-10 mm, - the web diameter of its structures ( 23 ) is between 0.2 and 2 mm, - the size of the pores ( 26 ) is between 0.5 and 2.5 mm.

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