Implant for replacing or filling a defect in a flat bone and method for producing such an implant

Abstract

To provide an implant for replacing or filling a defect of a flat bone of a human or animal body.SOLUTION: The invention relates to an implant (X) for replacing or filling a defect in a flat bone, wherein the implant (X) has a flat shape with a first side (X1) and an opposite second side (X2), wherein the implant (X) comprises a first layer (S1) consisting of non-porous polyetheretherketone or polyethylene, wherein the first layer (S1) has a layer thickness such that the shape of the implant (X) is set by the shape of the first layer (S1), implant (X) relates to an implant (X) comprising a second layer (S2) consisting of a porous polymer which is not a polyaryletherketone or a polyetheretherketone in at least some parts of the first surface (X1) and to a method for manufacturing such an implant (X).SELECTED DRAWING: Figure 1

Description

Detailed Description of the Invention

[0001] The present invention relates to an implant for replacing or filling defects in flat bones of the human or animal body. The present invention further relates to a method for producing such an implant.

[0002] Implants are known in the prior art that are intended to completely replace flat bones or fill defects in such bones. Flat bones include, for example, the skull, ribs, scapula, or pelvic bone. For example, International Publication No. 2015 / 144772 teaches an orbital covering lattice for replacing part of the eye socket. Such implants must be mechanically stable, and therefore are often made from biocompatible metals, such as titanium. Because human anatomy is unique, such implants are often patient-specific and / or manually bent to the correct shape during surgery. However, the use of metal implants adversely affects the selectivity of X-ray or MRI diagnostics of the implant site.

[0003] U.S. Patent Application Publication No. 2019069984 describes a polymer-based implant for bone replacement, in which a porous body is bonded to a non-porous material, resulting in an implant with a porous and non-porous surface. The materials and layer thicknesses used are selected to allow the implant to be shaped as desired during surgery and to eliminate the need for a metal support structure. Such polymer-based implants allow for the use of X-rays or MRI to diagnose the implant site.

[0004] However, intraoperative adaptation of the implant geometry limits the mechanical strength of the implant. Therefore, a first problem addressed by the present invention is to provide an implant that has minimal adverse effects on the use of X-rays or MRI for diagnosis of the implant site and is distinguished by high mechanical strength. A further problem addressed by the present invention is to provide a method for manufacturing such an implant.

[0005] The first problem is solved by the features of claim 1. The further problem is solved by the features of claim 16. Advantageous embodiments can be gathered from the dependent claims, the description and the drawings.

[0006] As a solution to the first problem, the present invention relates to an implant for replacing or filling a defect in a flat bone. The implant has a flat shape with a first surface and an opposite second surface. "Flat shape" is understood to mean both flat and curved surfaces. The implant has at least a first layer and a second layer. The first layer is composed entirely or mainly of non-porous polyetheretherketone (PEEK) or polyethylene (PE) and has a thickness such that the shape of the implant is set by the shape of the first layer. "Set shape" is understood to mean that the implant cannot be plastically deformed without being damaged. Therefore, the shape of the implant cannot be adapted by bending during surgery. The second layer is composed entirely or mainly of a porous polymer that is neither polyaryletherketone nor polyetheretherketone. The second layer is disposed on the first surface of the implant.

[0007] If the first layer consists entirely or mainly of non-porous polyethylene, preferably ultra-high molecular weight polyethylene (UHMWPE) is the material of choice for this purpose.

[0008] The layered structure of the implant according to the invention allows for high mechanical strength, essentially provided by the non-porous layer. The second layer, made of a porous polymer, ensures the implant's ingrowth behavior into the surrounding tissue. The dimensionally stable first layer eliminates the risk of mechanical overload during the implantation process damaging the porous second layer.

[0009] Preferably, the implant has no metal support structure. By completely omitting such metal support structures, diagnosis of the implant site by X-ray or MRI is not affected at all.

[0010] Preferably, the second layer consists entirely or mainly of one of the following materials: polyethylene, polyphenylene sulfone or polypropylene, particularly preferably ultra-high molecular weight polyethylene (UHMWPE), which are distinguished by their high biocompatibility and, in porous form, offer good ingrowth behavior to the surrounding tissue.

[0011] Preferably, the second layer is in a pressed and fused granular form. As a result, a homogeneous porosity is achieved combined with high resistance to surface damage of the second layer. Such a pressed and fused granular form can be obtained, for example, by using a mixture of starting particles, 10% by weight of which has a particle size of less than 1000 micrometers, 50% by weight of which has a particle size of less than 500 micrometers, and 90% by weight of which has a particle size of less than 450 micrometers.

[0012] According to a first preferred embodiment, no additional layer is disposed on the second surface of the implant, so that the first layer of non-porous polyetheretherketone (PEEK) is completely exposed. This embodiment is particularly advantageous when tissue does not grow onto the second surface of the implant. This may be necessary, for example, in the case of cranial implants. In such cranial implants, the second surface of the implant therefore forms the proximal surface.

[0013] According to a second preferred embodiment, the implant has a third layer on the second side made of the same material as the second layer disposed on the first side of the implant. In other words, the implant of this embodiment has an intermediate first layer made of non-porous polyetheretherketone (PEEK) or polyethylene (PE), on which a porous layer is disposed on at least some portions of each side. This embodiment is advantageous when tissue ingrowth is desired on both sides of the implant, for example, in the case of an orbital floor implant.

[0014] Preferably, the porosity and / or surface roughness of the third layer are different from those of the second layer. This allows for targeted tissue ingrowth into the second and third layers. Thus, a microporous structure improves connective tissue ingrowth, while a macroporous structure promotes hard tissue ingrowth, such as bone cells. Different porosities can be achieved, for example, by selecting starting particle sizes. For example, the second layer can be manufactured using a starting particle size of up to 1000 micrometers, and the third layer can be manufactured using a starting particle size of up to 700 micrometers. Alternatively, the second and third layers can have the same porosity and / or surface roughness. For example, if the implant is in the form of an orbital floor implant, a coarser granular material can be used for the third layer, which forms the lower surface of the implant, than for the second layer, which forms the upper surface of the implant facing the eye.

[0015] Preferably, at least a portion of the first layer is not covered by a further layer, in other words the non-porous polyetheretherketone (PEEK) or polyethylene (PE) is partially exposed, thus intentionally preventing tissue ingrowth in this exposed area.

[0016] The first layer, made of non-porous polyetheretherketone (PEEK) or polyethylene (PE), is preferably formed from multiple strips that are interconnected across the entire surface or that are separated from one another in some areas. Thus, the first layer can have, for example, a periphery surrounding the separated strips, with the strips and periphery being integrally formed. In such an embodiment, the second layer of porous polymer can also extend across the intermediate spaces between the strips, resulting in portions of the second layer being exposed on both sides. Such an embodiment allows the implant to be designed so that soft tissue can grow onto the implant on both sides, at least at certain points, without the need to apply a porous layer to both sides of the first layer. This can reduce the amount of foreign material implanted in the body.

[0017] Preferably, the first layer of non-porous polyetheretherketone has at least one passage opening, allowing fluid exchange and pressure compensation between the first and second surfaces while implanted.

[0018] Preferably, the implant has at least one recess for accommodating a fixation element. The recess is formed in the first layer and / or the second layer. The fixation element can be formed, for example, by a metal plate, preferably made of titanium or stainless steel. In such an embodiment, the implant can be fixed to the surrounding anatomical structure by a screw. Alternatively or additionally, the fixation element can be designed as a suture anchor, so that the implant can be sutured to the surrounding anatomical structure.

[0019] Preferably, at least one of the layers is enriched with at least one of the following materials: silver, strontium, magnesium, tricalcium phosphate, hydroxyapatite, molybdenum, calcium carbonate, whose antibacterial and bioactive properties reduce the likelihood of inflammation after the implantation process and improve ingrowth behavior into the surrounding tissue.

[0020] According to a preferred embodiment, the implant is a cranial implant. In such an embodiment, it is advantageous if the second surface of the implant is the proximal surface, i.e., the surface facing the dura mater in the implanted state. In such an embodiment, it is also advantageous if the first surface, except for the recesses for accommodating the fixation elements (if any), is covered over the entire surface with a layer of porous polymer. In such an embodiment, the second surface facing the dura mater is preferably not covered with an additional layer, so that the non-porous polyetheretherketone is exposed at the second surface of the implant.

[0021] According to a further preferred embodiment, the implant is an eye socket implant (Augenhohlen-Implantat), also called an orbital implant (Orbita-Implantat). In such an embodiment, it is advantageous if the second surface of the implant is the surface that faces the eyeball when implanted. The part of the implant along which the eyeball glides is either exposed to non-porous polyetheretherketone or polyethylene or is provided with a third microporous layer. A second layer of porous polymer is applied to at least some parts of the first surface of the implant, so that tissue can grow into the implant on this surface.

[0022] As a solution to a further problem, the present invention relates to a method for producing an implant that, in the manufactured state, has at least the features of claim 1. The method is characterized by the following steps: providing a fully formed first layer made of non-porous polyetheretherketone (PEEK) or polyethylene (PE), activating at least a part of the surface of the first layer with low-pressure plasma, and subsequently applying a second layer onto the correspondingly activated surface of the first layer by pressing and fusing a granular material.

[0023] The surface activation step of the first layer significantly improves the adhesion of the second layer to the first layer. The specific configuration of the low-pressure plasma depends on the geometry of the first layer, with a maximum applied power of 100 to 400 watts proven effective in testing. The process of pressing the second layer is preferably carried out immediately after surface activation of the first layer, preferably using a die and punch, the shape of which defines the geometry of the implant. The pressing process preferably defines a pressure and temperature curve over time, resulting in a reproducible process. The specific values ​​of pressure and temperature over time depend on the geometry of the implant.

[0024] Exemplary embodiments of the invention will now be described in detail with reference to the drawings. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a diagram of an implant according to a first exemplary embodiment. [Figure 2] 1 is a diagram of an implant according to a first exemplary embodiment. [Figure 3] FIG. 2 is a detailed view of an implant according to a first exemplary embodiment. [Figure 4] FIG. 2 is a detailed view of an implant according to a first exemplary embodiment. [Figure 5] FIG. 2 is a schematic side view of an implant according to a second exemplary embodiment. [Figure 6] FIG. 10 is a schematic isometric view of an implant according to a third exemplary embodiment. [Figure 7] FIG. 10 is a schematic top view of an implant according to a fourth exemplary embodiment. [Figure 8] FIG. 10 is a schematic top view of an implant according to a fifth exemplary embodiment. [Figure 9] FIG. 10 is a schematic top view of an implant according to a sixth exemplary embodiment.

[0026] 1 and 2 are diagrams of a first exemplary embodiment of implant X. Implant X is suitable for replacing or filling defects in flat bone. The first exemplary embodiment of implant X shown in FIGS. 1 and 2 is intended for use in the skull, for example, as cranial implant CX. Implant X has a flat, curved shape with a first side X1 and an opposite second side X2. Implant X has a first layer S1 made of non-porous polyetheretherketone or non-porous polyethylene, preferably ultra-high molecular weight polyethylene. On the first side X1, implant X has a second layer S2 made of a porous polymer attached to the first layer S1. The second layer S2 is made entirely or primarily of polyethylene, polyphenylene sulfone, or polypropylene, particularly preferably ultra-high molecular weight polyethylene (UHMWPE). Because the first layer S1 is so thick, implant X cannot be shaped during surgery. In other words, the first non-porous layer S1 is so thick that it is dimensionally stable and cannot plastically deform to conform to the implant's geometry without damaging the second porous layer S2. The minimum wall thickness of the first layer S1 required for this mechanical behavior depends on the size and shape of the implant X. In the example shown in Figure 1, the implant X is approximately 10 centimeters long and 10 centimeters wide and has a curved shape. If the first layer S1 is made of polyetheretherketone or ultra-high molecular weight polyethylene, the wall thickness of the first layer S1 will average 2 to 4 millimeters, given this geometry. Depending on the mechanical load on the implant X, the first layer S1 can also have a larger average wall thickness, for example, 6 millimeters.

[0027] The second layer S2 is present in a pressed and fused granular form, resulting in a homogeneous porosity of the second layer S2 combined with high resistance to surface damage. The homogeneous porosity allows tissue ingrowth into the second layer S2, while the non-porous design of the first layer S1 prevents tissue ingrowth into the first layer S1.

[0028] 3 and 4 are detailed views of an implant X according to a first exemplary embodiment. To manufacture such an implant X, a first layer S1 is first produced, for example, by a molding press or by a generative manufacturing process, also known as 3D printing. In particular, by using a generative manufacturing process, the first layer S1 can be precisely manufactured according to the patient's individual needs. Next, the first layer S1 is reworked as needed to remove burrs or support structures from the previous manufacturing step. Subsequently, at least a portion of the first layer S1 is activated using low-pressure plasma to create a particularly adhesive surface. Immediately thereafter, a second layer S2 is applied onto the previously activated surface of the first layer S1, specifically by pressing and fusing a granular material. In this way, the second layer S2 can be reliably applied onto the first layer S1 without the need for additional adhesives or the like.

[0029] The illustration in FIG. 3 makes clear that the second layer S2 can be significantly thinner than the first layer S1. FIG. 4 shows an embodiment in which the second layer S2 is the same thickness as the first layer S1. The specific thickness of the porous second layer S2 can be selected depending on the intended application and the specific needs of the patient. The second layer S2 can have a non-uniform thickness, such that the second layer S2 is thicker at some points on the implant X than at other points. A second layer S2 thickness of 1 to 6 millimeters has proven advantageous in testing. A typical overall thickness of an implant X having a two-layer structure consisting of a first layer S1 and a second layer S2 is 4 to 8 millimeters.

[0030] The representation of the porous second layer S2 in the drawings is abstracted because the representation of actual porosity in patent drawings is not reliably recognizable and reproducible.

[0031] FIG. 5 is a schematic side view of an implant X according to a second embodiment. In this embodiment, the implant X has porous layers on both the first side X1 and the opposite second side X2. To this end, a second layer S2 is disposed on the first side X1, and a third layer S3 is disposed on the second side X2. The third layer S3 is made of the same material as the second layer S2. However, the third layer S3 has a different porosity than the second layer S2, as shown in the illustration in FIG. 5. The different porosity is achieved by using different granule sizes. The first layer S1 is located between the second layer S2 and the third layer S3, so that the implant X has a three-layer sandwich structure.

[0032] FIG. 6 is a schematic isometric view of an implant X according to a third exemplary embodiment. In this embodiment, portions of the first layer S1 are not covered by additional layers, so that portions of the first layer S1 are exposed on both sides X1 and X2 of the implant X. On the first side X1, only two strips of the second layer S2 are applied over the first layer S1. The strip-like second layer S2 has thin walls, e.g., a thickness of only 1 millimeter. The uncovered portions of the first layer S1 on either side are provided with through-openings A. The through-openings allow fluid exchange and pressure compensation between the first side X1 and the second side X2 in the implanted state. The implant X can have multiple such through-openings A.

[0033] FIG. 7 is a schematic top view of the second surface X2 of an implant X according to a fourth exemplary embodiment. In this embodiment, the first layer S1 has a peripheral edge S1R and multiple interconnected strips S1B. The first layer S1 has multiple voids between the strips S1B. Thus, in contrast to the exemplary embodiments shown in FIGS. 1-6, the first layer S1 is not formed across the entire surface. The second layer S2 is disposed on the first surface X1 (not visible in FIG. 7) of the implant X and is visible from the second surface X2 through the voids in the first layer S1. Thus, in this embodiment, the second layer S2 is accessible from both sides in some portions. In such an embodiment, a third layer S3 made of a porous polymer can be disposed on at least some portions of the second surface X2, as shown schematically in FIG. 5. For clarity, such variations are not explicitly shown in the figures.

[0034] 8 is a schematic top view of an implant X according to a fifth exemplary embodiment. The edge of the implant X is provided with recesses Z designed to accommodate fixation elements MP. The fixation elements MP can be, for example, metal plates with holes for accommodating fastening screws or a single suture. The implant X can have multiple such fixation elements MP arranged in multiple recesses Z distributed over the edge of the implant X.

[0035] 9 is a schematic top view of the second surface X2 of an implant X according to a sixth exemplary embodiment. The implant X is in the form of an orbital implant OX. A third layer S3 made of a porous polymer is disposed on a portion of the second surface X2. The non-porous first layer S1 is exposed at the edge region of the implant X, i.e., is not covered by the porous layer. A second layer S2 is formed on at least a portion of the first surface X1 (not visible in FIG. 9). [Explanation of symbols]

[0036] X...implant, CX...cranial implant, OX...orbital implant, X1...first surface, X2...second surface, S1...first layer, S1B...strip, S1R...edge, S2...second layer, S3...third layer, A...through opening, Z...recess, MP...fixation element.

Claims

1. The implant (X) has a flattened shape with a first surface (X1) and an opposite second surface (X2), the implant (X) comprises a first layer (S1) made of non-porous polyetheretherketone or polyethylene, the first layer (S1) having a thickness such that the shape of the implant (X) is determined by the shape of the first layer (S1); The implant (X) comprises, on at least some portions of the first surface (X1), a second layer (S2) made of a porous polymer other than polyaryletherketone or polyetheretherketone, Implants (X) for replacing or filling defects in flat bone.

2. 2. The implant (X) according to claim 1, characterized in that said implant (X) does not comprise a metal support structure.

3. 3. An implant (X) according to claim 1 or 2, characterized in that the second layer (S2) consists entirely or mainly of one of the following materials: polyethylene, polyphenylene sulfone or polypropylene.

4. 4. An implant (X) according to claim 3, characterized in that the first layer (S1) and / or the second layer (S2) consist of ultra-high molecular weight polyethylene.

5. 5. An implant (X) according to any one of claims 1 to 4, characterized in that the second layer (S2) is present in pressed and fused granular form.

6. 6. An implant (X) according to any one of claims 1 to 5, characterized in that no further layer is arranged on the second face (X2) of the implant (X), thus leaving the first layer (S1) completely exposed.

7. 6. An implant (X) according to any one of claims 1 to 5, characterized in that the implant (X) has, on the second face (X2), a third layer (S3) made of the same material as the second layer (S2).

8. 8. Implant (X) according to claim 7, characterized in that the porosity and / or surface roughness of the third layer (S3) is different from the porosity and / or surface roughness of the second layer (S2).

9. Implant (X) according to any one of claims 1 to 8, characterized in that at least a part of the first layer (S1) is not covered by further layers (S2, S3).

10. 10. An implant (X) according to any one of claims 1 to 9, characterized in that the first layer (S1) is formed over the entire surface or by interconnected strips (S1B).

11. Implant (X) according to any one of claims 1 to 10, characterized in that the first layer (S1) has at least one through opening (A).

12. 12. An implant (X) according to any one of claims 1 to 11, characterized in that at least one recess (Z) for accommodating a fixation element (MP) is formed in the first layer (S1) and / or the second layer (S2).

13. 13. Implant (X) according to any one of claims 1 to 12, characterized in that at least one of the layers (S1, S2, S3) is enriched with elements consisting of at least one of the following materials: silver, strontium, magnesium, tricalcium phosphate, hydroxyapatite, molybdenum, calcium carbonate.

14. Cranial implant (CX) characterized by the features according to any one of claims 1 to 13.

15. Orbital implant (OX) characterized by the features according to any one of claims 1 to 13.

16. providing said fully formed first layer (S1); activating at least a portion of the surface of the first layer (S1) with low-pressure plasma; applying said second layer (S2) onto said activated surface of said first layer (S1) by pressing and fusing particulate material; It is characterized by 16. A method for manufacturing an implant (X, CX, OX) according to any one of claims 1 to 15.

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