DE102004045410A1 - Bone replacement implant for human and veterinary applications - Google Patents

Abstract

The invention relates to bone replacement implants for human and veterinary applications, wherein the implants can be formed in principle for a variety of areas of bodies and skeletons. It is an object of the invention to provide such implants available that take into account the properties of the bone or bone part to be replaced from a physiological and biomechanical point of view and also achieve a permanently improved ingrowth behavior. For this purpose, the bone replacement implants according to the invention are formed from interconnected metallic and / or ceramic hollow spheres, which have different outside loads, shell thicknesses and / or strengths locally differentiated from the load.

Description

The This invention relates to bone replacement implants for human and veterinary use Applications, where the implants in principle for a variety of areas of bodies and skeletons can be formed. So it is easy the possibility only areas of a bone, e.g. as a result of tumor removal to replace the removed bone area, to replicate accordingly. It can but also bone replacement implants for medical applications to disposal The whole parts of bones, even complete bones can replace. So is surprisingly also the possibility full To reproduce vertebral bones whose properties are the natural ones to be replaced at least very close to vertebral bone.

That's the way it is DE 101 21 936 A1 in principle be known to provide medical prostheses for animal or human body of interconnected metallic hollow balls. A further specification of this general idea, however, can not be deduced from the corresponding disclosure content. There, only options for the connection of such metallic hollow spheres to each other, in the production of corresponding prostheses, which can be achieved by adhesive or sintered connections.

Such Prostheses can but, if any, only limited use as a bone substitute, since the of the respective Patients actually expected properties after implantation and a healing process can not always be achieved. Also a later one Replacement of such prostheses may be required as these result damaged or overstressed if necessary even destroyed could become.

A consideration physiological demands on the respective bone part, by Such a prosthesis has been replaced, can only by the reduced own mass such produced from metallic hollow spheres Prosthesis done. A specific consideration of different Loads on different volume or surface areas of prostheses or implants act, as in particular in vertebral bones the case can not be considered.

Even though the known from interconnected metallic hollow spheres prepared prostheses, opposite the hitherto conventional Full material available prostheses presented an improved on wax behavior in the body's own Enable tissue, but there are still deficits and especially in the healing process on.

It It is therefore an object of the invention to provide bone replacement implants in particular, the properties of the bone to be replaced or bone part from a physiological and biomechanical point of view consider and also achieve a permanently improved ingrowth behavior.

According to the invention this Task with bone replacement implants that have the characteristics of the claim 1, solved. Advantageous embodiments and developments of the invention can with designated in the subordinate claims Characteristics can be achieved.

The bone replacement implants according to the invention for human and veterinary Applications are with interconnected metallic and / or ceramic hollow spheres, where they are completely or can be made only partially from such hollow spheres.

The Arrangement of such hollow balls takes place but locally differentiated considering certain parameters that may have the hollow spheres. So are hollow spheres with different outer diameters, different Shell thickness and also different strengths in a given Design within the total volume of bone replacement implant arranged and connected with each other. This can be done locally differentiates also the possible ones mechanical properties at the respective locally differentiated Areas of such a bone replacement implant according to the invention targeted influence. Certain areas of such bone replacement implant can increased or have degraded skills and e-modules, so that a correspondingly different elasticity and deformability over the Volume of a bone replacement implant according to the invention can be achieved. So should at least areas of an implant an elasticity of at least 3%.

In particular, for an improved ingrowth behavior into the endogenous tissue, by which a permanently increased bond strength can be achieved even after implantation, it is advantageous at the edge of the implant, which has immediate tissue contact with the body's own tissue, smaller outer diameter for such hollow spheres, ge if necessary, but also solid balls, which will have to come back to the latter, to arrange, than in internal areas. As a result, a very favorable surface contouring of bone replacement implants can be achieved and smaller spaces between hollow spheres or spheres can remain, into which tissue can then grow in, or even provided by the provided contoured surface, which also also has an increased specific surface area, improved fixation Such bone replacement implants in the respective human or animal body can be reached. At least a portion of the spaces led to the outer surface should not be greater than 1 mm, preferably less than 0.5 mm, for a favorable ingrowth behavior of tissue.

The bone replacement implants according to the invention can permanently in the body remain and must in certain circumstances not be removed or replaced.

The Balls or preferably hollow spheres in edge regions, the immediate Tissue contact, should not exceed a maximum outer diameter of 3 mm.

The Metallic hollow spheres should be made of a metal or a metal Metal alloy have been produced in the respective body no Allergies or rejections of the tissue. For this are beside Stainless steel alloys, in particular titanium or tantalum optionally Also suitable alloys of these metals.

The for the bone replacement implants according to the invention can be used on metallic or ceramic hollow spheres known per se a coating process in which preferably a suspension of the respective ceramic or metal powder to a polymeric body, preferably Polystyrene applied, optionally after drying a Undergo pyrolysis, in which the hydrocarbons of the polymeric Kernes and optionally expelled binder shares of the suspension become. The following are the greenest Hollow balls then subjected to a sintering process in which for the respective Metal or ceramic required and favorable parameters met In particular, the sintering of hollow spheres made of titanium be carried out in an inert or reducing atmosphere.

The However, bone replacement implants can already be made done so that selected different parameters and dimensions having hollow balls, as a green body in one for the respective bone replacement implant favorable arrangement to each other be positioned and held in an appropriate form. Then in a subsequent sintering process the actual sintering of Hollow balls performed and each in direct contact with each other Hollow balls over each other sintered bridges be sintered, so that a cohesive of the bone replacement implant forming hollow balls can be achieved.

By suitable selection of the sintering conditions of the respective outer diameter of hollow spheres in green Form as well as the coating thickness with the suspension is the Possibility of Influence on the respective size of the sintered bridges or sinter necks between the respectively interconnected hollow balls, so that also certain cavity sizes between the hollow balls can be maintained and so a certain Measure permeability can be adjusted.

In addition, can it may be advantageous to use hollow spheres with a certain porosity. So should be arranged in particular in the outer edge areas Hollow balls, which are also in direct contact with the body's own Have tissue, have a minimum porosity, the possible should be at least 5%, but preferably at least 10%. This also makes the ingrowth behavior of the body's own tissue positive to be influenced. Of course, such porosity also has an influence on the mechanical properties, in particular strength, deformability and elasticity, so that the porosity Another parameter is local to bone replacement implants differentiated to be able to adapt to the respective requirements, so that a certain selected porosity of hollow spheres also in other internal areas of bone replacement implants can be used accordingly.

There is also the possibility, the inner area of bone replacement implants completely form metallic hollow balls and the outer edge areas, in direct contact with the body's own Tissue, then with elements of a biocompatible ceramic to provide. Therefor suitable elements are for example balls, hollow spheres or also porous Structures such as e.g. open-pored foams.

With suitable ceramics can be stimulated bone growth, so that an ingrowth of tissue into free cavities on the surface of a Implants supported and the ceramic dissolves later in the body.

Examples of such biocompatible ceramics are Al ₂ O ₃ , hydroxyapatite or a calcium phosphate, preferably tri-calcium phosphate.

Al ₂ O _{3 has} a completely inert Ver hold against the body's own tissue and the other two previously mentioned biocompatible ceramics are particularly similar to the natural bone structure and the corresponding bone structure, so they also do not lead to allergies or rejection reactions.

In particular, when balls or hollow spheres of Al ₂ O _{3 are to be used} in those edge regions which are in direct contact with the body's own tissue after implantation, it is possible to proceed as follows in the production of bone replacement implants according to the invention. Thus, such balls or hollow spheres can be brought into the desired shape, which corresponds to the outer contour of the respective bone replacement implant, which is possible, for example, with a correspondingly formed in negative contour shape. Subsequently, these Al ₂ O ₃ spheres or hollow spheres are bonded to one another in a material-locking manner and thus virtually form an outer shape / shell / shell for the respective bone replacement implant. The cohesive connection can be achieved so that the respective balls or hollow spheres are used in the greenest form and then the cohesive connection is made by sintering.

Subsequently, in the greenest form, the metallic hollow spheres in a predetermined arrangement, which corresponds to the respective load of the bone replacement implant, can then preferably be arranged therein. Subsequently, a sintering process for the finished sintering of the hollow spheres and for the cohesive connection of the outer shell of Al ₂ O ₃ elements can then be carried out.

In this case, the different sintering temperatures of Al ₂ O ₃ and the respective suitable metal can advantageously be utilized.

in the Trap of others mentioned biocompatible ceramics, namely Hydroxylapatite or a calcium phosphate can be treated so that by appropriate arrangement of metallic hollow spheres in the greenest Shape and subsequent sintering of one of the metallic hollow spheres formed nuclees for a bone replacement implant, either immediately upon cooling or a subsequent thermal treatment elements of such biocompatible ceramic on the respective outer surfaces of a Kernel formed from metallic hollow spheres for a bone replacement implant be launched and at a respective required holding time a cohesive connection can be produced between ceramic and metal, after cooling a permanent connection allows.

The bone replacement implants according to the invention can provided in various shapes and dimensions become. In this case, an adaptation to the respective shape of a to be replaced bone or bone part already in the production respectively. There is the possibility to use a method of image processing known per se, in which a three-dimensional detection of surface coordinates a bone or bone part to be replaced and the captured digital data then for the control of machine tools to use with which either a negative form for one in it made bone replacement implant produced or a mechanical Shaping be carried out by machining or forming can. It can but also used with a computer tomograph collected data become.

Especially subsequent to a machining, shells of hollow spheres can be destroyed, so that then at least on surface areas an open structure exists.

By such a design can but also within a bone replacement implant cavities or continuous channels be formed. In particular, channels can also be border areas represent after implantation with endogenous tissue in contact can stand.

Of Further there is the possibility an influence on the mechanical properties of a bone replacement implant by taking an extra support structure is provided. Such a support structure For example, a metal grid, frame or a or several support ring or support rings be around or on which hollow balls may be arranged.

One Bone replacement implant according to the invention but can also be formed from at least two separate parts be connected by means of connecting elements form or cohesively with each other are. Several parts of a bone replacement implant can do so for example by means of nails or Screws are connected, which then a releasable connection represent.

A cohesive Connection can be through this suitable technologies, for example by sintering, soldering, welding or also gluing done.

On a bone replacement implant according to the invention, however, only one part, as already explained extensively, must be formed with hollow spheres. A second part to be connected with such a part may be in another form, for example as a plate, Rod or even be designed in the form of a curved shell, while a smooth, in contrast to the interconnected hollow spheres, have a lower surface roughness surface. In particular, such a curved shell can represent a region of a bone replacement implant suitable for a joint part.

In According to a further advantageous embodiment, bone replacement implants according to the invention also be used in conjunction with drug formulations, for example, to influence the healing process in a favorable manner or possibilities for one to achieve subsequent further therapy.

So In particular, biodegradable blood plasma proteins should be included in a drug formulation be included. Especially advantageous should be trombinin and fibrinogen be included, which then form a so-called fibrin glue, which has a very beneficial effect on the wound healing process. It can but also other biodegradable proteins that are at least similar to or similar to the body's own are identical, additionally contained in such a drug formulation be. An example of this is albumin.

Next these proteins can but also for the most diverse indications suitable therapeutic agents be used in such a drug formulation. So can for example, antibiotics, corticosteroids, antifungals, neuroleptics, Antiepileptic drugs, steroid hormones, cancer-inhibiting hormones, cytotoxic drugs, Hormone modulators, narcotics, analgesics, peptide hormones, anti-inflammatory drugs, Vaccines, antibodies, monoclonal antibodies, amino acid sequences (DNA), peptides, proteins for a gene therapy, biological cells for gene therapy, biotechnological produced growth factors or corresponding cells in one be included in such drug formulation.

A such suitable drug formulation may simply be on the surface, the should be in direct contact with the body's own tissue, applied and deposited there accordingly. This is special relatively easy, when used as blood plasma proteins trombinin and fibrinogen, in the form of a Fibrin adhesives are included, since such a fibrin glue a corresponding adequate adhesion reached.

Especially then, if over a longer one Period the effect of such a drug formulation exploited should be, so to speak, a retarding drug delivery or Effect can be achieved, a correspondingly suitable and selected drug formulation also introduced into shells or even in the inner cavity of hollow spheres become. This is an infiltration of a corresponding drug formulation very cheap.

A Infiltration is possible whenever the shells of hollow spheres have sufficient porosity and the pores with the respective drug formulation at least partially filled can be. An infiltration can, for example, by using a negative pressure respectively. It can prepared bone replacement implants inserted into a vacuum chamber and subsequently the surface with a corresponding yet liquid Be sprayed drug formulation. Thereby can the pores or even the inside of hollow spheres with the drug formulation at least partially filled and subsequently drying before the final Implantation performed becomes.

One possibility, the bone replacement implants according to the invention in the respective stress-specific form, which simulate an actual bone is in the pictorial representation of 1 shown.

In 1 It can clearly be seen that metallic hollow spheres with significantly smaller outside diameters have been used on outer marginal areas, which are then in direct contact with endogenous tissue later on after implantation, than is the case in the interior of the bone replacement implant shown. In this example, a corresponding graded transition was chosen, which was done in several outer diameter gradations of metallic hollow spheres.

Of Further, it also becomes clear that the inner core of such Bone replacement implant can also be hollow, as is the case with Bone is the case. These cavities can subsequently at a Implantation again with the body's own Filled with bone marrow become.

This in 1 Example shown has a cylindrical outer contour. It can be made available and kept in a variety of outer diameters. Such a blank can then, as needed, cut to the appropriate length and then implanted in the respective dimensions.

Of course, there is but also the possibility other than to realize the cylindrical outer contour shown, wherein Such contouring also below by means of a mechanical, e.g. Machining or even a transformation is achievable.

Claims (21)

Bone replacement implant for human and veterinary applications, which is formed with interconnected metallic and / or ceramic hollow balls, characterized in that the hollow balls have locally differentiated specific load different outer diameter, shell thickness and / or skills. Bone replacement implant according to claim 1, characterized in that that hollow spheres, which are at the edge of the implant, the immediate tissue contact has, smaller outside diameter as the hollow spheres are arranged in inner regions, have. Bone replacement implant according to claim 1 or 2, characterized characterized in that the smaller hollow balls have a maximum outer diameter of 3 mm. Bone replacement implant according to one of the preceding Claims, characterized in that the hollow balls of steel, ceramic, Titanium, tantalum or an alloy thereof have been produced. Bone replacement implant according to one of the preceding Claims, characterized in that at least arranged in the outer edge regions Hollow spheres, which are in direct contact with the body's own tissue, a porosity of Shells of hollow balls of at least 5 is respected. Bone replacement implant according to one of the preceding Claims, characterized in that at outer in direct contact with the body's own Tissue-standing areas spheres, hollow spheres or a porous structure a biocompatible ceramic is / are arranged. Bone replacement implant according to claim 6, characterized in that the biocompatible ceramic is Al ₂ O ₃ , hydroxyapatite or a calcium phosphate. Bone replacement implant according to one of the preceding Claims, characterized in that on the surface of the implant in the Shells and / or the interior of hollow spheres a biodegradable blood plasma proteins containing or infiltrated therein containing drug formulation is. Bone replacement implant according to the preceding claim, characterized in that as biodegradable blood plasma proteins Contain trombinin and fibrinogen in the drug formulation are. Bone replacement implant after the two previous ones claims, characterized in that in the drug formulation additionally albumin is included. Bone replacement implant after the previous three claims, characterized in that in the drug formulation at least another medical drug is included. Bone replacement implant according to one of the preceding Claims, characterized in that the hollow spheres are differentiated by locally Arrangement with different outside diameters, shell thicknesses and / or strengths the natural structure of bones. Bone replacement implant according to one of the preceding Claims, characterized in that at outer edges of the Implant a larger modulus of elasticity than in internal Regions of the implant is present. Bone replacement implant according to one of the preceding Claims, characterized in that the hollow balls cohesively with each other are connected. Bone replacement implant according to one of the preceding Claims, characterized in that the hollow spheres sintered together are. Bone replacement implant according to one of the preceding Claims, characterized in that metallic hollow balls and balls or porous Structures of a biocompatible ceramic are sintered together. Bone replacement implant according to one of the preceding Claims, characterized in that it consists of at least two together is formed connected or connectable parts. Bone replacement implant according to claim 17, characterized characterized in that at least one part in the form of a plate or domed Shell is formed. Bone replacement implant according to claim 17 or 18, characterized in that the parts by means of connecting elements, positive or cohesive with each other are connected. Bone replacement implant according to one of the preceding Claims, characterized in that the hollow balls arranged around or on a support contour are. Bone replacement implant according to one of the preceding claims, characterized in that at least portions of the Knochenersatzimplan tats have an elasticity of at least 3%.