Implant for fixing a cranial bone flap in a cranial opening of an osseous skull

Abstract

The invention relates to an implant for fixing a cranial bone flap in a cranial opening of an osseous skull, comprising a flexible mesh structure having webs and openings formed between the webs, wherein the flexible mesh structure is made of a plastic material and is designed to be fastened to the bone flap and to the osseous skull.

Description

[0001] Implant for fixation of a cranial bone flap in a cranial opening of a bony skull

[0002] The invention relates to an implant for fixing a cranial bone flap in a cranial opening of a bony skull.

[0003] Neurosurgical interventions on the brain are usually performed through an opening in the bony skull. Creating such a cranial opening is also known as a craniotomy. During a craniotomy, a portion of the skull bone is removed from the bony skull by trepanation, usually with the aid of a craniotomy tool. The removed portion is also called a bone flap or fragment. After the procedure, the bone flap is repositioned and fixed in the previously created cranial opening.

[0004] Implants in the form of so-called staple systems are known for fixating the bone flap. For example, a staple system from Aesculap AG, Tuttlingen, Germany, is known under the name CranioFix®2. This well-known staple system has an upper plate element, a lower plate element, and a rod element that movably connects the two plate elements. To fix the bone flap, the lower plate element is first placed on the “lamina interna” of the skull, with the rod element aligned approximately parallel to the axial direction of the cranial opening. The bone flap is repositioned in the cranial opening, with its inner side being placed on the lower plate element. The rod element extends from the inner side of the skull through the craniotomy gap formed between the bone flap and the surrounding skull bone to the outer side of the skull.For final fixation, the upper plate element is brought closer to the lower plate element along the rod element using several snap elements and pressed into the final position with a defined force. In the final fixation state, the two plate elements are pressed firmly against the outer side and the inner side of the bone flap and the surrounding cranial bone in the axial direction of the cranial opening.

[0005] With regard to the known stapling system, various aspects can be considered disadvantageous: The arrangement of the lower plate element in the epidural space can, under certain circumstances, lead to irritation of the dura mater or even an epidural hematoma. The axial tensioning of the plate elements carries the risk of inadvertent pressure being applied to the dura mater. To prevent inadvertent application of compressive forces, a separate tool for holding the rod element is provided in the case of CranioFix®2. This additional tool can lead to difficult handling. Furthermore, the plate elements remain permanently on the patient's skull after fixation. This is particularly disadvantageous in the case of the upper plate element in cosmetically critical areas, for example, during a frontal craniotomy.Since the upper and lower plate elements must rest as flat as possible on the skull bone and bone flap for satisfactory fixation, fixation is often not possible or not satisfactory in cases of severe curvatures or thickness gradients. Furthermore, severe curvatures can cause the upper plate element to protrude from the outer surface of the skull, which can lead to unsatisfactory cosmetic results and / or scalp irritation.

[0006] The object of the invention is to provide an implant of the type mentioned above that offers advantages over the prior art. In particular, the disadvantages associated with the prior art are to be at least partially overcome or reduced.

[0007] This object is achieved by providing an implant having the features of claim 1. Advantageous embodiments are the subject of the subclaims. Their wording is incorporated into the description by express reference.

[0008] The implant according to the invention comprises a flexible mesh structure with webs and openings formed between the webs, wherein the flexible mesh structure is made of a plastic material and is designed for attachment to the bone flap and to the bony skull. The solution according to the invention enables improved medical and cosmetic results and also enables particularly simple application and revision. The flexible mesh structure extends over a large area and is therefore thinner than conventional staple systems or the like. This relatively thin thickness allows for improved cosmetic results, as the flexible mesh structure is less visible under the patient's scalp. As a result, the implant according to the invention is preferably used in cosmetically critical areas of the skull, for example, during a frontal craniotomy.Because the mesh structure is flexible, its shape can be easily adapted to the patient's specific skull geometry. Protrusion of the implant is prevented, even in more curved, convex or concave skull areas. The thin yet flexible design also prevents scalp irritation. This is advantageous from a medical perspective. The flexible and thin design, combined with its manufacture from the aforementioned plastic material, also allows for particularly simple application by the surgeon. For example, the flexible mesh structure can be easily cut to the size and geometry appropriate for the respective craniotomy using simple tools such as scissors or a scalpel, thus resulting in simplified and particularly versatile application.This is in contrast to known metal implants, which usually have to be provided in different sizes and / or geometries and do not allow easy size and / or geometry adjustment by the end user. The flexible mesh structure is designed for attachment to the bone flap and to the bony skull, whereby the attachment can be carried out in particular with a material fit using a suitable adhesive or with a form-fitting and / or force-fitting connection using suitable fastening elements. For attachment, the flexible mesh structure is applied and secured to the outer surface of the skull and / or an outer surface of the bone flap. Removal of the implant for revision purposes is accordingly simple. In particular, no special instrument is required for this purpose. If the flexible mesh structure is adhesively attached, it can be removed from the bone flap and the bony skull like a plaster for the purpose of revision.In one embodiment, the webs and / or openings of the mesh structure are arranged regularly, in particular at regular intervals and / or in a regular pattern. In a further embodiment, the webs and / or openings are arranged irregularly. In one embodiment, the openings have an opening width of 2 μm to 5 mm. In a further embodiment, the openings each have an opening width in the range of 2 μm to 1 mm. In a further embodiment, the openings each have an opening width in the range of 2 μm to 20 μm. In one embodiment, the plastic material is at least partially resorbable, preferably completely resorbable. In a further embodiment, the plastic material is not resorbable. The plastic material is biocompatible. Biocompatible plastics for medical applications are known to those skilled in the art. In one embodiment, the implant consists of the flexible mesh structure.In further embodiments, the implant has a multi-layer structure, wherein the flexible mesh structure forms one layer of the multi-layer structure.

[0009] In one embodiment of the invention, the flexible sheet-like structure is translucent. In other words, the flexible mesh structure is transparent. This avoids artifacts when using imaging techniques. If the flexible mesh structure is designed for adhesive bonding to the bone flap and the bony skull surrounding the cranial opening, the translucent properties allow the use of a radiation-induced curing adhesive. In a further embodiment of the invention, the flexible mesh structure has a thickness of 0.2 mm to 0.5 mm. This allows for particularly good cosmetic results, as the flexible mesh structure is not visible or practically undetectable under the patient's scalp due to its low thickness. On the other hand, a thickness in this range ensures sufficient mechanical properties.

[0010] In a further embodiment of the invention, the flexible mesh structure is isotropically elastic. Isotropically elastic means that the flexible mesh structure exhibits direction-independent elastic properties in its flat plane of extension. This allows the flexible mesh structure to be adapted even more effectively to the patient's given skull geometry during application.

[0011] In a further embodiment of the invention, the webs are arranged in a knotless, crossed arrangement, and the flexible mesh structure is designed in the form of a knitted or woven fabric. Knotless means that the webs of the flexible mesh structure do not have any firmly connected intersection points. This makes the flexible mesh structure particularly easy to adapt to the given shape of the bone flap and the surrounding bony skull. This further simplifies the application of the implant. In this embodiment, the flexible mesh structure is a knitted or woven fabric. Alternatively, production by electrospinning or additive manufacturing processes is conceivable. In an alternative embodiment, the webs are firmly connected to one another at their respective intersection points. This makes cutting particularly easy. The flexible mesh structure cannot fall apart.

[0012] In a further embodiment of the invention, the plastic material contains polypropylene and / or polyglycolic acid. The inventors have recognized that this can offer particular advantages. Due to their good biocompatibility, polypropylene and polyglycolic acid are already used for the production of medical suture material. This demonstrates their excellent suitability from a mechanical perspective. While polypropylene is not resorbable, polyglycolic acid can be hydrolytically absorbed by the body within approximately 60 to 90 days. In addition, polypropylene exhibits transparent properties, which can simplify implantation. The group of polylactic acids, especially those with transparent properties, can be an alternative or additional component of the plastic material.In further embodiments, plastics of natural origin, such as cellulose, silk, fibroin, gelatin, or collagen, in a mixture with polypropylene and / or polyglycolic acid are conceivable, particularly to promote biocompatible properties. In a further embodiment of the invention, the plastic material contains a non-metallic additive, preferably glass fibers and / or ceramic particles. These additives can increase mechanical strength and / or osteointegration.

[0013] In a further embodiment of the invention, the implant comprises at least one medicinal active ingredient, which is applied to the flexible mesh structure in the form of an active ingredient coating and / or introduced into the openings in the form of an active ingredient filling. Alternatively or additionally, the medicinal active ingredient can be applied to the mesh structure and / or introduced into the mesh structure. The medicinal active ingredient is, for example, an antibiotic, an analgesic, growth factors, or the like. The planar expansion of the flexible mesh structure prevents locally excessive active ingredient concentrations and enables a particularly advantageous release of the active ingredient. In particular, improved regeneration of the periosteum is enabled.In one embodiment, the medicinal active ingredient is applied to the flexible sheet structure, in particular to its underside and / or top side, in the form of said active ingredient coating. In another embodiment, the medicinal active ingredient is alternatively or additionally introduced into the openings of the flexible mesh structure in the form of an active ingredient filling.

[0014] In a further embodiment of the invention, the implant comprises an adhesive which is applied to the flexible mesh structure in the form of an adhesive layer and / or introduced into the openings in the form of an adhesive filling. With this embodiment of the invention, the use of a separate adhesive product and / or separate fastening elements can be dispensed with. The adhesive is a component of the implant in the form of the adhesive layer and / or the adhesive filling. In one embodiment, the adhesive is at least partially absorbable, preferably completely absorbable. In a further embodiment, the adhesive is not absorbable. All biocompatible adhesives suitable for medical applications can be used. Such adhesives are known to those skilled in the art.If the implant contains a medicinal agent according to the preceding embodiment, this agent can be integrated into the adhesive layer and / or adhesive filling. The adhesive serves, on the one hand, to attach the flexible mesh structure to the bone flap and the surrounding bony skull. On the other hand, the adhesive mechanically stabilizes the flexible mesh structure. The adhesive is preferably designed to cure using UV radiation. Alternatively or additionally, other curing mechanisms are conceivable, for example, through moisture, heat, or other physical and / or chemical mechanisms. In a further embodiment of the invention, the adhesive is a medical tissue adhesive that cures under the influence of UV radiation. The inventors have recognized that such an adhesive offers particular advantages in connection with the present application.

[0015] In a further embodiment of the invention, the implant has at least one removable first protective layer, which is applied at least indirectly to an underside of the flexible mesh structure, and / or a removable second protective layer, which is applied at least indirectly to an upper side of the flexible mesh structure. The first protective layer and / or the second protective layer is peeled off and thereby removed before implantation of the implant. The first protective layer serves to protect the underside of the flexible mesh structure. The second protective layer serves to protect the upper side of the flexible mesh structure. If the flexible mesh structure does not have an active ingredient layer, adhesive layer and / or other layer on its underside and / or upper side, the first protective layer and / or second protective layer is applied directly to the flexible mesh structure.Otherwise, the corresponding protective layer only indirectly covers the flexible mesh structure and is applied directly to one of the said layers. The first protective layer and / or second protective layer is preferably a protective film, in particular a smooth one. The protective film is preferably made of a suitable plastic material, for example, PTFE.

[0016] The invention further relates to a kit comprising an implant according to one of claims 1 to 8 and comprising an adhesive configured to bond the flexible mesh structure to the bone flap and the bony skull. In this embodiment of the invention, the adhesive is provided as a separate product and, together with said implant, forms a kit for securing a cranial bone flap. The adhesive is applied to the underside and / or top of the flexible mesh structure prior to its actual application for securing it. Suitable adhesives for this purpose are known to those skilled in the art. In one embodiment, the adhesive is a spray adhesive that can be sprayed onto the flexible mesh structure.

[0017] The invention further relates to a kit comprising an implant according to one of claims 1 to 8 and comprising a plurality of fastening elements configured for force-fitting and / or form-fitting fastening of the flexible mesh structure to the bone flap and to the bony skull. In one embodiment, the plurality of fastening elements are pins. Alternatively, the fastening elements can be screws, hooks, or the like. In one embodiment, the pins are degradable by pre-drilling. In a further embodiment, the pins are non-degradable and self-tapping. The fastening elements are inserted into the outer side of the bone flap and the bony skull surrounding the cranial opening prior to the actual application of the implant. The inserted fastening elements form anchor points for the flexible mesh structure, which can be hooked onto and tightened by means of its openings on the fastening elements.

[0018] Further advantages and features of the invention emerge from the claims and from the following description of preferred embodiments of the invention, which are illustrated with reference to the drawings.

[0019] Fig. 1 shows a schematically simplified perspective view of the head of a patient, whose bony skull has a cranial opening closed with a bone lid,

[0020] Fig. 2 shows the area of ​​the cranial opening in a schematic plan view, wherein the bone cover is fixed with an embodiment of an implant according to the invention,

[0021] Fig. 3 the area of ​​the cranial opening in a schematically simplified sectional view,

[0022] Fig. 4 shows a perspective exploded view of the implant according to Figs. 2 and 3 in a state provided with two protective films,

[0023] Fig. 5 shows a schematically simplified principle representation of a section through a layer structure of the implant according to Fig. 4,

[0024] Fig. 6 shows a schematic representation of an embodiment of a kit according to the invention,

[0025] Fig. 7 shows a schematic representation of another embodiment of a kit according to the invention and

[0026] Fig. 8 shows an exemplary application situation using the kit according to Fig. 7 in a representation corresponding to Fig. 3.

[0027] According to Fig. 1, a patient's head has a cranial opening B. The cranial opening B extends from an outer side of the skull CA through the patient's bony skull C to an inner side of the skull CI (see Fig. 3). The cranial opening B extends axially through the bony skull C and is bordered radially by it.

[0028] Cranial opening B can generally be caused by an accident or other trauma. In this case, cranial opening B is the result of a craniotomy and serves as a surgically created access point for a neurosurgical procedure on the patient's brain.

[0029] In such a craniotomy, the bony skull C is opened by mechanically removing a bone flap D. This can be done, for example, using a trepanation and a craniotomy. The bone flap D is separated from the bony skull C, forming an annular gap S. The annular gap S is also called the craniotomy gap. The bone flap D can also be referred to as a bone part, bone fragment, or bone segment.

[0030] After the bone flap D has been removed, it can be temporarily removed from the remaining bony skull C, forming the actual cranial opening B. After the brain surgery has been completed, the bone flap D is repositioned and fixed in the opening B.

[0031] According to Fig. 2, an implant 1 is provided for fixing the cranial bone flap D in the cranial opening B. The implant 1 comprises a flexible sheet-like structure 2 with webs 3 and openings 4 formed between the webs. Furthermore, the flexible sheet-like structure 2 is made of a plastic material K and is configured for attachment to the bone flap D and to the bony skull C bordering the opening B in a manner described in more detail below.

[0032] 2 and 3, the flexible mesh structure 2 spans the bone flap D, the annular gap S, and the area of ​​the bony skull C surrounding the opening B. The flexible mesh structure 2 rests on an outer side DA of the bone flap D and the outer side CA of the bony skull C. The attachment of the flexible mesh structure 2 to the bone flap D, on the one hand, and to the bony skull C, on the other hand, varies depending on the design and can, for example, be achieved by means of a material bond using a suitable adhesive and / or using suitable fastening elements. The arrangement of the webs 3 and / or the openings 4, shown in particular in Fig. 2, is exemplary. In embodiments not shown in the figures, the webs and / or openings are arranged differently for this purpose, wherein, in particular, an irregular arrangement can be provided.The same applies to the opening widths shown for openings 4. These are also purely exemplary.

[0033] In the present case, the flexible mesh structure 2 has a rectangular, specifically square, shape with outer edges 5, 6, 7, 8 arranged in pairs opposite one another. The shape shown is exemplary. In embodiments not shown in the figures, the flexible mesh structure is round, oval, or otherwise adapted to the geometry of the bone flap to be fixed.

[0034] As shown in particular in Fig. 3, the flexible mesh structure 2 is thin compared to the involved bone structures C, D. In the present case, the flexible mesh structure 2 has a thickness t of 0.4 mm. In embodiments not shown in the figures, the thickness of the flexible mesh structure ranges between 0.2 mm and 0.5 mm. Due to the low thickness and the manufacture from the plastic material K, the flexible mesh structure 2 can be easily cut to size and adapted to the bone flap D to be fixed. In addition, due to its properties, the shape of the mesh structure 2 can be easily adapted to a curvature or other geometry of the involved bone structures C, D.

[0035] In the embodiment shown, the flexible net structure 2 is a fabric G, with the webs 3 arranged in a knotless, crossed arrangement. In this respect, it can also be referred to as a knotless net. In an embodiment not shown in the figures, the webs are firmly connected to one another at their respective intersection points, in which case it can also be referred to as a knotted net.

[0036] In an embodiment not shown in the figures, the flexible mesh structure 2 is not in the form of a woven fabric, but instead is designed as a knitted fabric, a knitted fabric, a nonwoven fabric or the like.

[0037] As shown in particular in Fig. 2, the flexible mesh structure 2 has translucent properties. Consequently, the bone flap D, the annular gap S and the regions of the bony skull C arranged beneath the flexible mesh structure 2 can be viewed through the flexible mesh structure 2. This allows, in particular, precise positioning and is accompanied by further advantages that will be described in more detail. In the embodiment shown in Figs. 2 to 5, a material-to-material attachment of the flexible mesh structure 2 to the bone structures C, D is provided. For this purpose, the implant 1 comprises an adhesive A. The adhesive A is applied to the flexible mesh structure 2 in the form of an adhesive layer 9 and is additionally introduced into the openings 4 in the form of an adhesive filling 10 (see Fig. 5).In embodiments not shown in the figures, the adhesive A is provided either in the form of the adhesive layer or the adhesive filling. In this case, the adhesive A is a medical tissue adhesive H that cures under the influence of UV radiation. Due to the translucent properties of the flexible mesh structure 2, the tissue adhesive H can be cured particularly easily, since the UV radiation required for this can be transmitted through the flexible mesh structure 2.

[0038] In the embodiment shown, the implant 1 additionally comprises a medicinal active ingredient W. The medicinal active ingredient W is applied in the form of an active ingredient layer 13 to the flexible mesh structure 2 and is additionally introduced into the openings 4 in the form of an active ingredient filling 14. The shown provision of the implant 1 with the medicinal active ingredient W is optional and therefore not present in all embodiments. Furthermore, it is possible for the active ingredient layer 13 and the adhesive layer 9 to be combined into one layer. In other words, the active ingredient W can be a component of the adhesive layer 9 or vice versa. Against this background, the arrangement of the layers 13, 9 shown in Fig. 5 is to be regarded as schematically greatly simplified.

[0039] Furthermore, the implant 1 in the present case has a first protective layer 11 and a second protective layer 12. The first protective layer 11 is applied at least indirectly to an underside 21 of the flexible mesh structure 2. The second protective layer 12 is applied at least indirectly to an upper side 22 of the flexible mesh structure 2. Indirectly means that the respective protective layer 11, 12 can be applied to further layers, depending on the layer structure, and thus indirectly to the respective side of the flexible mesh structure 2. In the present case, the second protective layer 12 is applied directly to the upper side 22. The first protective layer 11 is applied directly to the adhesive layer 9 and thus indirectly to the underside 21.

[0040] Both protective layers 11, 12 are removable and are removed before application of the implant 1. In the present case, the protective layers 11, 12 are films made of a suitable plastic material. In the embodiment shown, the plastic material is PTFE. Fig. 5 shows schematically that the plastic material K is provided with a non-metallic additive Z1, Z2. The additive Z1, Z2 is a mixture of glass fibers Z1 and ceramic particles Z2. Providing the plastic material K with the said additive is optional and is intended to improve the mechanical properties and / or osteointegration of the flexible mesh structure 2.

[0041] The plastic material K is a composite of polypropylene P1 and polyglycolic acid P2.

[0042] To fix the bone flap D using the implant 1, the first protective layer 11 is removed. After this, the flexible mesh structure 2 is pressed with the adhesive layer 9 first onto the outer side DA of the bone flap D. Alternatively, the implant can

[0043] 1 with the second protective layer first on a flat surface. The bone flap D is then pressed with the outer side DA onto the underside 21 of the flexible mesh structure 2, more precisely onto the adhesive layer 9 arranged there. The assembly of implant 1 - without the first protective layer 11 - and bone flap D is then repositioned in the area of ​​the cranial opening B. After repositioning, the areas of the flexible mesh structure that protrude laterally beyond the bone flap D and the annular gap S are

[0044] 2 pressed onto the outer side CA of the surrounding bony skull C.

[0045] The tissue adhesive G is then cured, whereby the second protective layer 12 can be removed either before or after curing.

[0046] In the embodiment shown in Figs. 2 to 5, the adhesive A is a component of the implant 1. Alternatively, the adhesive A can be provided as a separate product.

[0047] Fig. 6 shows a kit 100 with a flexible mesh structure 2 and with the adhesive A, which is provided as a separate product 40. The separate product 40 can, for example, be a container in the form of a tube or the like filled with the adhesive A. The adhesive A is applied to the flexible mesh structure 2 before it is applied.

[0048] Fig. 7 shows another kit 200 with a flexible mesh structure 2 and several fastening elements 50. The fastening elements 50 are designed to fasten the flexible surface structure 2 to the bone structures C, D (see Fig. 8). In this case, the fastening elements 50 are pins that are inserted into the outer side DA of the bone flap D or into the outer side CA of the surrounding bony skull C. When inserted, the fastening elements 50 form anchoring points to which the flexible mesh structure 2 can be anchored.

[0049] With regard to further features of the flexible mesh structure 2 contained in the kits 100, 200, reference is made to the above and express reference is made.

Claims

Claims: An implant (1) for fixing a cranial bone flap (D) in a cranial opening (B) of a bony skull (C), comprising a flexible mesh structure (2) with struts (3) and openings (4) formed between the struts, wherein the flexible mesh structure (2) is made of a plastic material (K) and is designed for attachment to the bone flap (D) and to the bony skull (C). An implant (1) according to claim 1, characterized in that the flexible mesh structure (2) is translucent. An implant (1) according to claim 1 or 2, characterized in that the flexible mesh structure (2) has a thickness (t) of 0.2 mm to 0.5 mm. An implant (1) according to any one of the preceding claims, characterized in that the flexible mesh structure (2) is isotropically elastic.An implant (1) according to any one of the preceding claims, characterized in that the webs (3) are arranged in a knotless, crossed manner and the flexible mesh structure (2) is formed in the form of a knitted fabric or a woven fabric (G). An implant (1) according to any one of the preceding claims, characterized in that the plastic material (K) comprises polypropylene (P1) and / or polyglycolic acid (P2). An implant (1) according to any one of the preceding claims, characterized in that the plastic material (K) comprises a non-metallic additive (Z1, Z2), preferably glass fibers (Z1) and / or ceramic particles (Z2). An implant (1) according to any one of the preceding claims, characterized by at least one medicinal active ingredient (W), which is applied to the flexible mesh structure (2) in the form of an active ingredient coating (13) and / or introduced into the openings (4) in the form of an active ingredient filling (14). An implant (1) according to any one of the preceding claims, characterized by an adhesive (A) which is applied to the flexible mesh structure (2) in the form of an adhesive layer (9) and / or introduced into the openings (4) in the form of an adhesive filling (10). An implant (1) according to claim 9, characterized in that the adhesive (A) is a medical tissue adhesive (H) that cures under the influence of UV radiation. An implant (1) according to any one of the preceding claims, characterized by at least one removable first protective layer (11) which is applied at least indirectly to a bottom surface (21) of the flexible mesh structure (2), and / or a removable second protective layer (12) which is applied at least indirectly to a top surface (22) of the flexible mesh structure (2).Kit (100) comprising an implant (1) according to any one of claims 1 to 8 and an adhesive (A) configured for bonding the flexible mesh structure (2) to the bone flap (D) and the bony skull (C). Kit (200) comprising an implant (1) according to any one of claims 1 to 8 and several fastening elements (50) configured for force-fit and / or form-fit fastening of the flexible mesh structure (2) to the bone flap (D) and the bony skull (C).

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