DE102010044571A1 - base graft - Google Patents

Abstract

Disclosed is a basic implant (1) for attachment to a bone and as a base for a functional implant to be attached to the basic implant (1), with a holding structure (2) for connecting to the bone, which holding structure (2) has an open-pored structure (5) a metal or a metal alloy, and with a base structure (3) for fixing the functional implant, which is characterized in that the base structure (3) has a closed surface (4) without pores. This prevents the bone cement used to fix the functional implant from penetrating into the pores and closing them. An improved connection between the basic implant (1) and the functional implant can also be established, since air inclusions in the bone cement can be prevented more easily. A method is also disclosed for producing a basic implant for fixing to a bone and as a base for a functional implant to be fixed thereon, which basic implant has a holding structure for connecting to the bone and a basic structure for fixing the functional implant. The method is characterized in that at least the holding structure made of a metal or a metal alloy is formed with open pores by means of selective laser sintering and the surface in the area of the base structure is closed and formed without pores. Production by means of selective laser sintering allows, on the one hand, a very defined and thus precisely predeterminable formation of the pore or grid size and arrangement in the open-pored structure. On the other hand, it allows a fast and comparatively inexpensive production of implants individually adapted to a patient.

Description

The invention relates to a base implant for fixing to a bone and as a basis for a functional implant to be fixed to the base implant having the features of the preamble of claim 1. It further relates to a method for producing such a base implant.

It has long been known and possible in medicine to replace worn parts of the human skeletal apparatus, in particular joints or joint parts, completely or partially with implants. Already known for a long time z. As implants as a replacement for the natural femoral head of the femur, artificial joint shells on the hip bone and artificial knee joints.

In the corresponding implantation operation, the worn parts of the natural bone are removed in the region of the defective joints, and corresponding openings or comparable structures are introduced into the residual bone by drilling, milling or sawing, into which the implants containing the artificial joint element are inserted these are set. In other words, here a damage or a defect of the bone is brought about, such damage is unavoidable for the implantation operation.

In the course of such an operation, a replacement implant is normally used directly replacing the worn part of the bone, typically the joint part (joint head, joint socket, joint hinge), which here, because it replaces the actual bone function in the joint, is called a functional implant.

Such functional implants have limited durability for a variety of reasons. On the one hand, the functional elements of the implants, such as artificial joint sockets, artificial joint heads, artificial joint hinges and the like., Also wear, on the other hand it can be in the field of anchoring the implants in the natural bone stump to changes in the bone and thus to a loss of secure anchoring. Thus, it is not uncommon for a new implant replacing the first implant to be introduced in a revision operation at an already implanted site. Due to the phenomenon that joint wear and tear already affects younger people today and that, on the other hand, people are living longer and longer, there are already cases in which not only one but a second or even further revisions are required.

Since, of course, in the revision surgery, the surgeon finds the bone defect caused in the first operation, but he can not use the bone stump in unprocessed form for the anchoring of the revision implant, nowadays revision surgery usually other material devastating operations are made on residual bone, which is the natural Stability of the revision implant impaired and can lead to problems especially in repeated revision surgery, up to an impossibility of further revision, which ultimately causes the patient to lose the functionality of the affected skeletal section, z. B. an affected knee joint, means.

Accordingly, it is endeavored to operate as early as possible during initial surgery as bone-conserving as possible and accordingly to use undemanding implants in the anchoring with regard to processing of the residual bone. Furthermore, efforts are made to keep the further processing and material reduction of the bone stump as small as possible in revision operations.

In this context, there have recently been considerations, especially for revision surgery, not immediately determining a function implant containing the functional elements on the bone stump and having to perform corresponding manipulations of the defect site created by the predecessor operation, but rather the functional implant at one into the bone defect set and anchored there base implant. This approach has the advantage that the basic implant can be used without further processing in the existing bone defect, requires a maximum of minimal processing of the bone stump. In accordance with such basic implants, a holding structure is formed, which is introduced into the bone defect and anchored there. Already in today's concepts, this support structure consists of an open-pore, porous metal mesh or such a structure of metal alloy, which is roughly adapted in its outer shape to the shape of the bone defect and can be firmly connected by striking into the bone defect with the bone stump. In this case, the open-pore structure of the holding structure generates a high frictional or clamping force, so that a firm connection of the base implant with the bone can be achieved without further aids, such as bone cement. The porosity of the structure also allows osteointegration, i. H. an ingrowth of the bone stump into the support structure with calcine material.

On a side facing away from the holding section in the implantation position, such has one Basic implant on a basic structure on which then a the actual joint function taking over functional implant is determined.

One known material from which such base implants can be formed is known by Zimmer, Inc., and is sold under the trademark "Trabecular ^Metal® ". For this material, to the descriptions z. For example, on the website of this company, available at www.zimmer.com, it is an open-pore tantalum foam. This foam is a structure with pores in stochastic size distribution, the exact position, size and geometry of the production is not affected. In addition, known base implants made of this material are formed entirely from this tantalum foam and have an open pore over their entire surface, in particular also in the region of the basic structure. The known basic implants made of this material are spray-coated with a material that promotes osteointegration, namely with hydroxyapatite in a plasma process, wherein the hydroxyapatite only penetrates into the near-surface pores, without reaching the pores located there in the depth of the metal foam body or there to form a surface coating respectively.

This results in various problems now. As already mentioned, the manufacturing process does not allow an exact definition of the pore structure. This is always stochastic, even if the parameters are adapted to foam formation and thus other stochastic distributions can be achieved. For an exact design taking into account forces to be absorbed, a desired deformability in the region of the holding section and other aspects, this type of production is not, at best conditionally suitable. The fact that there is always an overall open-pore surface, in particular also in the region of the basic structure, in the mentioned production process always leads to a further disadvantage. Because at the base structure, the functional implant is fixed with an adhesive, usually bone cement. For this purpose, bone cement is applied to the base structure and the functional implant is attached to this structure, so when applying pressure, the bone cement deviates into the porous structure of the basic implant. This has two disadvantages. On the one hand, the bone cement in this area fills the pores, so that there is no longer an osteointegration, which promotes the hold of the base implant on the bone stump, is no longer possible. On the other hand, the pressure that can be applied to the layer of the bone cement by pressing the functional implant into the base implant is limited. This causes z. As air pockets remain in the bone cement and thus lead to a reduction in the binding force between the base implant and functional implant.

The object of the present invention is to address the above-mentioned disadvantages and problems existing in known basic implants, and in any case to address them in preferred embodiments. This object is achieved by a base implant with the features of claim 1. Advantageous developments of such a base implant are given in the dependent claims 2 to 8. In a further aspect, a solution to this problem in a method for producing a base implant having the features of claim 9. Advantageous developments of the method are given in claims 10 to 14.

A core idea of the invention is to form the basic structure with a closed surface without pores in the case of a base implant, which has an open-pored structure of a metal or a metal alloy at least in the region of the holding structure. This essential step or this essential modification compared to the known implants requires that bone cement applied to the base structure for fixing the functional implant when applying pressure for connecting the two implants no longer penetrate into the depth of the structure of the base implant and provided there for osteointegration. Can close pores. In addition, an increased amount of pressure can be applied to the bone cement so that possible air pockets between the functional implant and the base structure can be pushed out beyond the lateral edge of the base structure and brought out of the connection site. This ensures an even better hold of the functional implant in the basic structure of the basic implant.

In the production of a basic implant with the known method as a metal foam, the formation of a closed surface without pores in the region of the basic structure is not readily and simply possible, in particular not with the required dimensional accuracy. Accordingly, in the known basic implants so far no considerations have been made with regard to the formation of a closed surface of the basic structure.

The basic structure in the base implant to which the functional implant is fixed need not be even, nor is it limited to, one that is openly accessible only from one side of the base implant. You can z. B. also be a basic implant penetrating, tubular opening, which then has completely inside a closed surface without pores.

Advantageously, the base implant according to the invention as a whole is formed from an open-pored structure of a metal or a metal alloy and has a closed surface without pores only in the area of the basic structure. Such a design not only allows a structure modeled on the inside of the bone (the cancellous bone) over the vast majority of the base implant, it also allows almost complete osteointegration into the open pores of the base implant. Only in. Area of the base structure, where bone cement is applied to connect the functional implant with the base implant and forms an adhesive layer, the inventively provided closed surface is formed without pores.

In cases in which individual sections of the base implant, which have neither the bone nor with the functional implant contact before ingrown endogenous materials such. B. bone substance to be protected, it may be advantageous if such sections are also formed with a closed surface without pores.

For a very defined constructive design of the open-pore structure, it is proposed that it has a defined ordered arrangement of pores. In contrast to the stochastic and arbitrary arrangement of the pores in a conventional metal foam, in the base implant according to the invention, therefore, the pores are preferably formed and selected in their structure in a targeted and selected manner. This can be achieved, in particular, if the open-pored structure, as provided by an advantageous development of the invention, is formed by selective laser sintering. With the method of selective laser sintering, not only the open-pore structure but also the closed surface in the area of the basic structure can be formed and produced in one operation.

Advantageously, at least the open-pored structure, but preferably the base implant as a whole (including the closed surface in the region of the basic structure) is formed from titanium or a titanium alloy, in particular from pure titanium. This metal is ideal for selective laser sintering, it is also biocompatible.

In order to avoid possible problems that may arise when meeting the surface of the base structure with bone cement, in particular when the surface of the base structure is made of titanium, this surface may be coated with a ceramic material, in particular with titanium nitride. This coating also prevents the abrasion of titanium particles from the surface in the process of inserting the functional implant in a base implant having a closed surface of titanium in the basic structure.

In order to promote and accelerate the deliberate ingrowth of the base implant into the bone stump, the base implant may advantageously be provided with an osteointegration-promoting coating in the interior of the support structure in the pores, in which case the osteointegration-promoting material may contain one or more calcium and Phosphorus containing material (s) is / are, especially bruschite and / or hydroxyapatite.

The basic implant according to the invention can be formed both as a prefabricated standard part with one or more sizes and shapes of the holding sections adapted to typical bone defects. With particular advantage, which is given in particular by the manufacturing process by means of selective laser sintering, but the base implant can also be made individually, eg. B. by means of z. B. CT images created diagnostic images or calculated therefrom model specifications. Here, the selective laser sintering allows a quick and easy implementation of an individually predetermined geometry, without the need for the preparation of complicated and expensive molds or other forms for forming a correspondingly foamed base implant.

With regard to the method aspect, the solution to the problem mentioned at the outset is that the base implant is formed from a metal or a metal alloy by means of selective laser sintering, at least with its open-pored holding structure, and that the surface in the region of the base structure is made closed and without pores. As previously mentioned, the selective laser sintering fabrication method not only provides the advantage of cost effective and rapid fabrication of individual implant shapes, but also allows the fabrication of fully designed pores in the open cell structure in their dimensional and dimensional ratios.

Preferably, the base implant is produced as a whole by selective laser sintering from a metal or a metal alloy, titanium or a titanium alloy, in particular pure titanium, being preferably used as the metal or metal alloy, as stated above with the advantages mentioned there.

In the course of production, in the region of the basic structure, the closed surface can be provided with a ceramic coating, in particular a coating of titanium nitride, which leads to the effects and advantages already mentioned above.

In order to coat the surfaces of the pores in the interior, that is to say also of the internal pores, with one or more osteointegration-promoting material (s), it is preferable to use a dip-coating method which, for B. may be an electrolytic dipping process carried out. As coating materials it is preferred to use a material containing calcium and phosphorus, in particular bruschite and / or hydroxyapatite. Here, a system developed by the company DOT Thin Film and Surface Technology GmbH of Rostock and offered under the brand name "credit rating ^®" coating processes in particular comes for these extending into the depth of the open pore structure coating into consideration. In this method, an inner CaP phase of finely crystalline Hydroxilapatit is applied in a dipping process and on this inner CaP phase, a more soluble outer CaP phase of bruschite.

Further advantages and features of the invention will become apparent from the following description of embodiments with reference to the accompanying figures. Show here:

1 in three different representations and views a), b), c) an embodiment of a base implant according to the invention, here a base implant for insertion into the tibial end of the femur for anchoring the femoral component of a knee implant as a functional implant;

2 a schematic representation of a knee implant after a revision surgery with both femur and tiabia side used basic and functional implants;

3 in a slightly different perspective, a view of the femoral-end assembly with base implant and functional implant;

4 a view of the tibial base implant and functional implant.

Exemplary embodiments of basic implants according to the invention and their postoperative arrangement on the femur or tibia and interaction with corresponding functional implants for forming an artificial knee joint are illustrated in the figures. The illustrations are schematic and not necessarily true to scale. In addition, they do not show all the details, but are limited to the representation of the invention essential details and other features that facilitate the explanation and description of the invention.

In 1 is initially in three different views, a frontal view in 1a ), a side view in 1b ) and a view from the top in 1c ) A first embodiment of a base implant shown and with the reference numeral 1 quantified. The basic implant shown in this figure 1 is one for connecting to the lower side of a femur. It has a holding section 2 on, which is designed for insertion into the existing bone defect at the lower end of the femur. This holding section 2 is formed of a porous metal, namely a porous, grid-like titanium structure of pure titanium. The basic implant 1 also has a basic structure 3 on which serves to create a functional implant, here an implant forming the femurseitige articular surface of the knee. In the embodiment shown and in the base implant 1 is the basic structure 3 composed of a U-shaped opening, at the bottom of which is a tubular, open on both sides implementation by the support structure 2 connects through it. The basic structure 3 is on its surface, at which the functional implant comes to rest, with a closed surface 4 formed without pores.

In the embodiment shown, the base implant is 1 except for the closed surface 4 of the basic implant 3 from an open-pored structure 5 made of pure titanium.

Here is the open-pored structure 5 , in particular in the area of the support structure 2 , But also in other areas, formed from a defined order arrangement of pores or grid openings. This is the basic implant 1 formed by selective laser sintering of metal powder, wherein the defined and controlled pore or lattice structure is formed by the controlled guidance of the laser beam during the sintering process. In the same operation of the selective laser sintering becomes the closed surface 4 in the area of the basic structure 3 also made of pure titanium.

This in 1 shown basic implant 1 can be produced as a prefabricated standard part, but it can also be adapted to a previously diagnosed in a patient, z. For example, in a pre-surgery defect at the tibial end of the femur and thus individually designed and manufactured.

The open-pored structure 5 is particularly in the area of the support structure 2 , but preferably also in the adjacent areas to the depth of the base implant 1 coated with an osteointegration-promoting material, e.g. B. Hydroxilapatit and / or Bruschit. The coating in the open-pore structure 5 in particular by a dip coating method, for. B. achieved an electrolytic dip coating process. In the embodiment shown, a coating method of DOT Dünnschicht- und Oberflächentechnologie GmbH from Rostock, which offers this supplier under the brand name "Bonit ^® " and in a dipping process an inner CaP phase of finely crystalline hydroxilapatite and on this inner CaP phase a more easily soluble outer CaP phase is applied from Bruschit.

In 2 is shown schematically as using a as in 1 shown basic implant 1 and another basic implant adapted in shape to the structures in the area of the femoral tibial component 10 and corresponding functional implants 6 and 9 a knee joint is constructed.

Shown is the tibial-sided section of the femur F, into which the base implant 1 with the holding section 2 introduced and anchored there. This is the basic implant 1 with the holding section 2 into a defect existing there, as it exists in particular after removal of a primary implant, used and anchored there. The anchoring is done by driving in the base implant 1 , wherein the open-pore structure 5 in the area of the holding section 2 creates an excellent grip. This structure wedges itself when it is impacted with the bone remnants in the area of the defect, thus providing a frictional and positive grip.

In the thus anchored base implant 1 then becomes the functional implant 6 used. This comes with corresponding contact surfaces on the base structure 3 of the basic implant 1 to lie and is anchored there with bone cement. The functional implant 6 has a section with the articular surface 8th and a holding pin 7 on, which protrudes into the tube of the femur F and provides there for additional support. The retaining pin 7 protrudes through the tubular portion of the base structure 3 and is adapted in its dimension, ie its diameter, to the diameter of this tubular portion. For inserting the functional implant 6 into the base implant 1 gets on the base structure 3 of the basic implant 1 , ie applied to the area of the bottom open U and in the adjoining tubular section bone cement, then the functional implant 6 into the base implant 1 used and pressure applied in the direction of the femur F. It can now because of the closed surface of the basic structure 3 the bone cement is not in the open-pore structure 5 penetrate and close the pores. This in particular has the advantage that the open-pore structure as a whole is still permeated by bone substance brought about via the adjacent femur F and thus fused with the stump of the femur F at the defect site and can form an intimate connection. This ingrowth of the basic implant 1 is due to the coating of the open-pore structure 5 transported with the osteointegration-promoting material in terms of speed and efficiency.

In the in 2 also shown on the tibial side is a revision implant with a base implant 10 used. Evident is the femurseitige section of the tibia T, which has at its end caused by a primary implantation defect. This defect is a base implant (not shown in detail here) 10 used, which like the in 1 shown base implant in its support structure consists of an open-pore structure of pure titanium, and a basic structure to which the functional implant 9 , here the lower joint structure of the knee-imaging implant is attached and attached to this. Also this basic implant 10 is provided with a closed surface in the area of the basic structure. It's like the basic implant 1 , Wherein produced by selective laser sintering, wherein in this process, the defined order arrangement of pores or the grid is generated as well as the closed surface in the region of the base structure.

Also the basic implant 10 is penetrated by a tubular opening which is part of the basic structure and is bounded by a closed surface. Through this tubular section protrudes a retaining pin 12 of the functional implant 9 , who adhere to the functional section 11 connects to the lower articular surface of the knee so formed. This holding pin 12 protrudes into the tube of the tibia T and provides there for additional support.

The basic implant is also described in the same way as described above 10 coated with an osteointegration-promoting material in the area of the open-pored structure. So can this basic implant 10 , which initially finds its way into the tibia T by striking the defect, fused with this bone. At the base implant 10 becomes the functional implant 9 in the same way as before with respect to the functional implant by the base implant 1 described fixed by means of bone cement, which can not penetrate into the open pores of the remaining base implant because of the closed surface of the base structure and prevent osteointegration there.

In the 3 and 4 is here shown pulled apart and in slightly different views, each one representation of the femurseitigen components ( 3 ) and the tibial components ( 4 ) of the implant arrangement with the basic implants according to the invention 1 and 10 according to 2 shown.

From the illustration of the embodiments and the above description will be clear to the skilled person again, which advantages bring the inventive base implant and its use in particular for revision operations with it.

LIST OF REFERENCE NUMBERS

1

base graft

2

holding structure

3

base structure

4

closed surface without pores

5

open-pored structure

6

function implant

7

holding mandrel

8th

articular surface

9

function implant

10

base graft

11

function section

12

holding mandrel

F

femur

T

tibia

Claims (14)

Base implant for attachment to a bone (F, T) and as a base for attachment to the base implant ( 1 . 10 ) to be determined functional implant ( 6 . 9 ), with a holding structure ( 2 ) for connection to the bone (F, T), which holding structure ( 2 ) an open-pore structure ( 5 ) is made of a metal or a metal alloy, and having a basic structure ( 3 ) for determining the functional implant ( 6 . 9 ), characterized in that the basic structure ( 3 ) a closed surface ( 4 ) without pores. Basic implant according to claim 1, characterized in that it consists overall of an open-pored structure ( 5 ) is formed of a metal or a metal alloy and only in the region of the basic structure ( 3 ) a closed surface ( 4 ) without pores. Basic implant according to claim 1, characterized in that it is in between the support structure ( 2 ) and the basic structure ( 3 ), neither contact with the bone (T, F) nor with the functional implant ( 6 . 9 ) have, at least partially, a closed surface ( 4 ) without pores. Basic implant according to one of the preceding claims, characterized in that the open-pore structure ( 5 ) has a defined order arrangement of pores. Basic implant according to one of the preceding claims, characterized in that the open-pore structure ( 5 ) is formed by selective laser sintering. Basic implant according to one of the preceding claims, characterized in that it is at least in the open-pored structure ( 5 ) consists of titanium or a titanium alloy, in particular pure titanium. Basic implant according to one of the preceding claims, characterized in that the closed surface ( 4 ) in the area of the basic structure ( 3 ) is coated with a ceramic material, in particular with titanium nitride. Basic implant according to one of the preceding claims, characterized in that it is at least in the region of the support structure ( 2 ) in the pores also in the interior of the base implant ( 1 ) is coated with an osteointegration-promoting material, in particular with one or more calcium and phosphorus-containing material (s), preferably bruschite and / or hydroxyapatite. A method for producing a base implant for fixing to a bone and as a basis for a functional implant to be fixed thereon, which base implant has a holding structure for connecting to the bone and a base structure for fixing the functional implant, characterized in that at least the support structure is made of a metal or a metal alloy formed open porous by selective laser sintering and the surface is closed in the base structure and formed without pores. A method according to claim 9, characterized in that it is made entirely by selective laser sintering of a metal or a metal alloy. Method according to one of claims 9 or 10, characterized in that titanium or a titanium alloy, in particular pure titanium, for producing the structures formed by selective laser sintering is used. Method according to one of claims 9 to 11, characterized in that the closed surface is provided in the region of the base structure with a ceramic coating, in particular with a coating of titanium nitride. Method according to one of claims 9 to 12, characterized in that in the open-pore portion, the surface of the pores, including the inner pores, by a dip coating process with one or more osteointegration promoting material (s) is coated. A method according to claim 13, characterized in that as coating a calcium and phosphorus-containing material, in particular Bruschit and / or Hydroxilapatit is applied.

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