WO2008040408A1

WO2008040408A1 - Augmentation component for bone implants

Info

Publication number: WO2008040408A1
Application number: PCT/EP2007/006753
Authority: WO
Inventors: Wilhelm Blömer; Richard Zeller; Jens Schneider; Jens Beger; Patricia Graf
Original assignee: Aesculap Ag & Co. Kg
Priority date: 2006-09-29
Filing date: 2007-07-31
Publication date: 2008-04-10
Also published as: DE102006047663A1; DE202006015416U1

Abstract

The invention relates to an augmentation component (7) for bone implants, especially for femoral or tibial implants, comprising a metallic porous structure and at least one opening (8, 9, 10) for a securing element (11, 12) for securing the augmentation component (7) to the bone implant (1). The aim of the invention is to ensure the stability of said component and to allow for optimum in-growth of the bone material. For this purpose, the augmentation component (7) is constituted by a three-dimensional frame from interconnected webs that form communicating hollow spaces of between 0.5 mm and 6 mm in size. The invention also relates to a bone implant (4) which is connected to the augmentation component (7) according to the invention.

Description

AUGMENTATION COMPONENT FOR BONE IMPLANTS

The invention relates to an augmentation component for bone implants, in particular for femur or tibial implants, with a metallic, porous structure and with at least one opening for a fastening element which fixes the augmentation component to the bone implant.

In the implantation of bone implants, which are used in place of the natural bone in the body and to compensate for bone defects, there is often the problem that remain between the bone implant on the one hand and the natural bone on the other hand Defekt spaces that are not filled and replaced by the bone implant can. These remaining bone defects must be filled in order to achieve sufficient stability and to be able to apply the bone implant over the entire surface of the bone.

It is known to fill such defects between a bone implant and the bone by massive metallic moldings, so-called augmentation components. These can have a wide variety of shapes, for example in the form of plates, wedges, cylinders, etc., and they can have openings through which fastening means, for example screws, reach through which fixes these augmentation components to the corresponding implants. (US 6,387,131; Company catalog OSS FEMURAL / TIBIAL AUGMENTATION of Biomed Orthopedics, Inc. 2003; Company Prospectus Orthopedic Catalog, Reconstructive Surgery Knee Systems of Smith & Nephew, 2003). When using augmentation components consisting of a metallic solid material, no new bone formation can occur in the area they occupy. Osteolysis can even increase the size of the defect and this can have a critical effect on the long-term stability of the implant.

In addition to these metallic augmentation components made of solid material, bone replacement materials of biological or synthetic origin are also used to fill in bony defects. With the use of materials of biological origin, the poor availability of disadvantage, also with autologous implants, the additional burden on the patient by removing bone material from another part of the body. Therefore, increasingly synthetic, ceramic or metallic bone substitute materials are used, which have a porous structure (company prospectus The actipore.PLF system of Biorthex, Inc., 2002). In the case of the non-metallic augmentation components, the strength in the load-bearing area of the bone is often insufficient, and in the case of the metallic porous augmentation components there is the problem that, with sufficient strength, the size of the pores is small, since a relatively large wall thickness is necessary to ensure mechanical stability to ensure. There is therefore very little volume available for ingrowth of the bone.

It is an object of the invention to design a generic augmentation component in such a way that it is on the one hand highly load-tolerant and on the other hand provides large volumes for the ingrowth of bone substance. This object is achieved in an augmentation of the type described above according to the invention that the augmentation component is composed of a three-dimensional framework of interconnected webs forming interconnected cavities with a size between 0.5 mm and 6 mm.

The design of a three-dimensional framework of interconnected webs makes it possible to form a very stable framework at extremely low cost of the augmentation, which can also absorb high loads, but on the other hand by the absence of continuous walls and by the use of webs like a truss has very many openings and thus also forms relatively large cavities, which are interconnected. This truss-like, three-dimensional framework thus provides an optimal support structure for the filling of bone defects and thus forms a guide rail for the ingrowth of the bone material, which can fill most of the defect with bone, since the metallic webs of the support structure only a very small volume of the bone defect fill out.

The webs may for example have a thickness between 0.2 mm and 2.5 mm.

The relative density of the augmentation component can be between 0.05 and 0.5. By relative density is meant the density of the cellular material divided by the density of the solid from which the webs are made.

The augmentation component consists of a biocompatible metallic material, for example titanium, a titanium alloy or a cobalt alloy. In addition, it can be provided that the webs are provided with a coating, for example with a resorbable calcium phosphate layer that stimulates bone growth.

The size of the cavities within the augmentation component may be the same, but in a preferred embodiment it is contemplated that the size of the cavities will vary within the augmentation component.

In this case, cavities of different sizes can be uniformly distributed over the entire volume of the augmentation component, but it is also possible for the size of the cavities to change from one area of the augmentation component to another area of the augmentation component. This makes it possible, in particular, to vary the mechanical properties of the augmentation component over its volume, for example to adapt the mechanical properties to the mechanical properties of the adjacent bone material. By means of this adaptation, it is possible to prevent the adjacent bone material from being damaged by osteolysis due to excessive strength of the augmentation component.

The size of the cavities can thereby change gradually or even suddenly in the transition from one area to another area.

Furthermore, it is favorable if the augmentation component has no cavities in the region of the opening, but is made compact. In the region of the opening, which serves to fix the augmentation component to an implant, for example by a screw passing through the opening, this results in a particularly high strength of the augmentation device. tion component, which leads to a secure and unchangeable fixing of the augmentation component on the implant.

It is favorable if the augmentation component corresponds in its outer dimensions to the outer dimensions of the bone implant on which it is held by the fastening element. Thus, the augmentation component forms a continuation of the implant parts into the respective bone defect.

A lattice-like structure, as used in the described augmentation component, can be easily machined on its outer surfaces in any shape, so that the augmentation component can be adapted not only to the outer dimensions of the bone implant, but also to the exact structure of the bone defect to be filled ,

For example, according to a preferred embodiment, the augmentation component can be plate-shaped as a support for a tibial plateau of a tibial implant.

The invention also relates to a bone implant, in particular a femoral or tibial implant, which is connected to an augmentation component of the type described above.

The following description of preferred embodiments of the invention is used in conjunction with the drawings for further explanation. Show it: FIG. 1 shows a schematic view of a tibial implant with a plate-shaped augmentation component prior to assembly and placement on a tibial plateau;

FIG. 2 shows a cross-sectional view of the augmentation component of FIG. 1 in the direction of the arrow 2 in FIG. 1 and FIG

FIG. 3 shows an enlarged detailed view of the three-dimensional lattice structure of the augmentation component of FIG. 2 in region A of FIG. 2.

The invention is discussed below using the example of a tibial implant 1, which is placed on the tibial plateau 2 of a correspondingly resected tibia 3. It is understood, however, that the invention also applies to other bone implants that are placed on bone to bridge bone defects, particularly in joint prostheses in the area of the knee joint or hip joint. Also, in bone replacement implants, which are used to bridge defects of the femur or tibia, the invention may find application.

In the present exemplary embodiment, the tibial implant 1 comprises a plate-shaped tibial plateau 4 with a shaft 5 protruding vertically downwards. This shaft 5, in the case of a tibial implant 1 fixed to the tibia 3, enters and positions a shaft-shaped recess 6 incorporated in the tibia 3 Thereby, the tibial implant 1. On the tibial plateau 4 joint components are placed in a conventional manner and not shown in the drawing, take over the function of the meniscus, for example, a Gelenkflächenteil of ultra high molecular weight polyethylene (UHWM-PE) on which then the Condyle one at the femur Supported femur implant, which is also not shown in the drawing.

On the underside of the tibial plateau 4, a plate-shaped augmentation component 7 is arranged, which serves to bridge a bone defect between the underside of the tibial plateau 4 and the top of the tibial plateau 2 and the one hand flat on the underside of the tibial plateau 4 and on the other hand flat at the top of the tibia is applied. The augmentation component 7 has a central opening 8, through which the shaft 5 protrudes, and two through openings 9, 10, through which screws 11, 12 are inserted, which can be screwed into the tibial plateau 2 and thereby the augmentation component 7 firmly and permanently connect with the tibial plateau 4, for example by clamping the augmentation component 7 between the tibial plateau 4 and the tibial plateau 2.

The outer contour of the augmentation component 7 is adapted to the outer contour of the tibial plateau 4, that is to say the outer contour of the augmentation component 7 follows the outer contour of the tibial plateau 4 so that the augmentation component 7 does not protrude laterally beyond the tibial plateau 4, but the space between the tibial plateau 4 and the tibia 3 completely filled out.

The height of the augmentation component 7 depends on the size of the bone defect and can be chosen differently so that the tibial plateau 4 of the tibial implant 1 assumes the desired position relative to the tibia 3. For this purpose, different thickness augmentation components 7 are available. The augmentation component 7 consists of a metallic material, for example of titanium or a titanium alloy, in particular Ti6AI4V, or a cobalt alloy.

It is composed of a plurality of webs 13, which are connected to each other so that a three-dimensional lattice structure is formed with adjacent cavities 14, which communicate with each other.

The webs can have a diameter between 0.2 mm and 2.5 mm, their length is dimensioned so that the size of the cavities formed by them is between 0.5 mm and 6 mm. It is possible that the webs are all the same size and arranged regularly, so that there is a uniform distribution of cavities of the same size on the volume of the augmentation, but the webs 13 may also be arranged differently long and irregular, so that the size of the Cavities varies. This variation can be made so that different sized cavities are distributed uniformly over the entire volume of the augmentation component 7, but it is also possible that the size of the cavities from one area of the augmentation component 7 changed to another, either gradually or possibly also leaps and bounds , As a result, an adaptation of the strength properties can be achieved.

In the embodiment shown in Figure 3 webs 13 are provided of equal length and in a regular arrangement. In this structure, the webs form individual trusses 15, in each of which the same length of webs 13 alternately connected by 120 ° inclined to adjacent webs. In a traverse so the webs run alternately at an angle of 30 ° up and down. In a plane a plurality of such trusses 15 are arranged parallel to each other. Below this first level extending in a lower plane in the same way trusses perpendicular to the traverses of the top level, in such a way that their highest points in each case coincide with the lowest points of the traverses in the overlying level. In this area, the perpendicular to each other trusses are connected.

In the same way, including a level, in which again perpendicular to the overlying level extending trusses are arranged, which are also connected in the same way with the overlying trusses.

In this way, a complicated and regular three-dimensional structure is obtained, which, viewed at 45 ° to the respective trusses, has a honeycomb structure with continuous channels with a cross section in the form of a regular hexagon.

Such a very complicated structure gives the augmentation component a high strength and nevertheless allows a complete intergrowth with bone material, so that the bone augmentation augmented component consists for the most part of bone material, for example, the proportion of bone material is on the order of 50% to 95%. while the metallic material of the augmentation component is only 5% to 50%.

Such complex lattice structures can be built up in layers, for example, using an electron beam melting method in which metal powder is deposited in layers in a layer by means of a controlled electron beam. becomes molten, at which the lattice structure passes through the respective plane. The layered structure also makes it possible to produce very complicated progressions of the webs in the three-dimensional structure, and the shaped body produced in this way can also already be adapted to the outer contour of the implant.

In principle, however, it is also possible to rework such a molded body on the outside in order to achieve a corresponding outer contour.

While the augmentation component 7 in the illustrated embodiment has cavities in the entire region, it can be provided that in the edge region 16 of the openings 9, 10 no cavities are provided, but a compact design. As a result, a particularly high strength is achieved in the region of the openings 9, 10, so that the screws 11, 12 passing through the openings 9, 10 can securely and permanently fix the augmentation component 7 on the tibial implant 1.

By adapting the outer contour of the augmentation component to the outer contour of the tibial plateau, after the definition of the augmentation component 7 on the tibial plateau 4, a structural unit of an implant is obtained, in which a layered implant upper part is formed, which is formed from the compact tibial plateau 4 on the one hand and the lattice-shaped framework the augmentation component 7 on the other. This unit can be handled by the surgeon like a tibial implant with a tibial plateau 4 of greater strength, and he also has the ability to make an adjustment of the thickness of the upper part of the implant by connecting the tibial plateau 4 with augmentation 7 different thickness. The described complex three-dimensional lattice structure gives the augmentation component 7 such a high mechanical strength that all loads can be transferred from the tibial plateau 4 via the augmentation component 7 to the tibia 3, even if no bone has yet grown. On the other hand, after the full penetration of the augmentation component 7 by bone substance, the natural support function of the bone is restored and the lattice structure of the augmentation component 7 can be designed such that its mechanical strength corresponds to the strength of the incorporated bone substance, so that with regard to the mechanical properties a homogeneous Structure arises.

Claims

Augmentation component (7) for bone implants (1), in particular for femur or tibial implants, with a metallic, porous structure and with at least one opening (9, 10) for a augmentation component (7) on the bone implant (1) fixing fastener ( 11, 12), characterized in that the augmentation component (7) on the bone implant (1) of interconnected webs (13) is constructed, the interconnected cavities (14) form with a size between 0.5 mm and 6 mm.

2. augmentation component according to claim 1, characterized in that the webs (13) have a thickness between 0.2 mm and 2.5 mm.

3. Augmentation component according to one of claims 1 or 2, characterized in that the relative density of the augmentation component (7) is between 0.05 and 0.5.

4. augmentation component according to one of the preceding claims, characterized in that the augmentation component (7) consists of titanium, a titanium alloy or a cobalt alloy.

5. Augmentation component according to one of the preceding claims, characterized in that the webs (13) are provided with a coating device.

6. augmentation component according to one of the preceding claims, characterized in that the size of the cavities (14) within the augmentation component (7) varies.

7. Augmentation component according to claim 6, characterized in that the size of the cavities (14) changes from one area of the augmentation component (7) to another area of the augmentation component (7).

8. augmentation component according to claim 7, characterized in that the size of the cavities (14) gradually changes during the transition from one area to another area.

9. augmentation component according to claim 7, characterized in that the size of the cavities (14) changes abruptly during the transition from one area to another area.

10. augmentation component according to one of the preceding claims, characterized in that the augmentation component (7) in the region of the openings (9, 10) has no cavities, but is compact.

11. Augmentation component according to one of the preceding claims, characterized in that the augmentation component (7) in its outer dimensions corresponds to the outer dimensions of the bone implant (1) on which it is held by the fastening element (11, 12).

12. augmentation component according to one of the preceding claims, characterized in that the augmentation component (7) is plate-shaped as a pad for a tibial plateau (4) of a tibial implant (1).

13. Bone implant, in particular femur or tibial implant, characterized in that it is connected to an augmentation component (7) according to one of the preceding claims.