Implant for fixing a skull flap to a cranial opening in the femoral skull

Abstract

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

Description

[Technical field]

[0001] The present invention relates to an implant for securing a skull flap to a cranial opening in a bony skull. [Background technology]

[0002] Neurosurgical procedures on the brain are generally performed through an opening in the bony skull. The creation of such a cranial opening is also called a craniotomy. In a craniotomy, a portion of the bony skull is usually separated from the bony skull by a burr technique using a craniotomy. The separated portion is also called a bone flap or bone fragment. After the procedure is completed, the bone flap is repositioned and fixed into the created cranial opening.

[0003] For fixing the bone flap, implants in the form of clamping systems are known. For example, a clamping system named CranioFix®2 from Aesculap AG (Tuttlingen, Germany) is known. This known clamping system has an upper disk element, a lower disk element and a rod element that movably connects the two disk elements to each other. To fix the bone flap, the lower disk element is first placed on the inner layer of the cranial vault and the rod element is aligned approximately parallel to the axial direction of the cranial opening. The bone flap is repositioned in the cranial opening so that its inner surface is placed on the lower disk element. The rod element then extends from the inner cranial surface through the cranial opening gap between the bone flap and the surrounding skull to the outer cranial surface. For final fixation, the upper disk element is moved toward the lower disk element along the rod element by means of a number of snap elements and pressed with a defined force towards the end position. In the final fixation state, the two disc elements are firmly pressed against both the outer and inner surfaces of the bone flap and the surrounding skull in the axial direction of the cranial opening.

[0004] The known clamping system is considered to be disadvantageous in various respects. The placement of the lower disc element in the epidural space may, under certain conditions, cause dura inflammation or epidural hematoma. There is a risk of unintentional pressure being applied to the dura by axial clamping of the disc element. In the case of CranioFix® 2, a special tool is provided to hold the rod element in order to avoid unintentional compression. The need for additional tools can make handling difficult. Furthermore, the disc element remains permanently on the patient's skull after fixation. This is particularly disadvantageous when the upper disc element is placed in cosmetically important areas, for example in frontal craniotomy. Since in order to achieve a sufficient fixation, the upper and lower disc elements must be placed as flat as possible on the skull and bone flap, fixation may not be possible or may not be sufficient in the case of large curvatures or thickness gradients. Furthermore, large curvatures may cause the upper disc element to protrude from the outer surface of the skull, which may result in an unsatisfactory cosmetic result or scalp irritation. Summary of the Invention

[0005] The object of the present invention is to provide an implant of the type mentioned in the opening paragraph, which offers advantages over the prior art, and in particular is intended to at least partially overcome or mitigate the disadvantages associated with the prior art.

[0006] This object is achieved by providing an implant having the features of claim 1. The dependent claims relate to advantageous embodiments, the language of which is incorporated into the present specification by express reference.

[0007] The implant according to the invention has a flexible mesh structure with webs and openings formed between the webs, which is made of a plastic material and is arranged to be fixed to the bone flap and the bony skull. The solution according to the invention allows for improved medical and cosmetic results and is particularly easy to apply and modify. The flexible mesh structure extends in a plane and therefore has a small thickness compared to conventional clamping systems and the like. Thanks to its relatively small thickness, the flexible mesh structure is less noticeable under the patient's scalp, which allows for improved cosmetic results. The implant according to the invention is therefore preferably applied in cosmetically important skull areas, for example in frontal craniotomies. Due to the flexibility of the mesh structure, its shape can be very easily adapted to the given skull shape of the patient. Protrusion of the implant is avoided even in convexly or concavely curved areas of the skull. Thanks to the thin and flexible design, it is also possible to avoid irritation of the scalp, which is also beneficial from a medical point of view. The flexible and thin design, together with being made from the aforementioned plastic material, also allows the surgeon to apply it very easily. For example, the flexible mesh structure can be cut into the size and shape suitable for the respective craniotomy with simple tools such as scissors or a scalpel without much effort, thus achieving a simple and particularly versatile use. This is in contrast to known metal implants, which usually have to be prepared in various sizes and / or shapes and cannot be easily adjusted in size and / or shape by the end user. The flexible mesh structure is designed to be fixed to the bone flap and the bony skull, in particular to be integrally glued with a suitable adhesive or to be form-fitted and / or force-fitted with a suitable fixing element. During fixation, the flexible mesh structure is applied to the outer surface of the skull and / or to the outer surface of the bone flap and fixed. The implant can therefore be easily removed for modification purposes. In particular, no special instruments are required for this purpose.If the flexible mesh structure is glued, it can be removed from the bone flap and the bone skull in the manner of a bandage for correction purposes. 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, each opening has an opening width in the range of 2 μm to 1 mm. In a further embodiment, each opening has an opening width in the range of 2 μm to 20 μm. The plastic material is in one embodiment at least partially resorbable, preferably entirely resorbable. In a further embodiment, the plastic material is not resorbable. The plastic material is biocompatible. Biocompatible plastics for medical applications are known to the skilled person. In one embodiment, the implant consists of a flexible mesh structure. In a further embodiment, the implant has a multi-layer construction, the flexible mesh structure forming one layer of the multi-layer construction.

[0008] In one embodiment, the flexible sheet-like structure has optical transparency. In other words, the flexible mesh structure is transparent. In this way, artifacts are avoided when using imaging techniques. If the flexible mesh structure is provided to be integrally bonded to the bone flap and the bony skull around the cranial opening, a radiation-curable adhesive can be used because of its optical transparency.

[0009] In a further embodiment, the flexible mesh structure has a thickness of 0.2 mm to 0.5 mm. On the one hand, thanks to the small thickness, particularly good cosmetic results are obtained, since the flexible mesh structure is unnoticeable or barely noticeable under the patient's scalp. On the other hand, a thickness within the aforementioned value range ensures sufficient mechanical properties.

[0010] In a further embodiment, the flexible mesh structure has isotropic elasticity, meaning that the flexible mesh structure has direction-independent elastic properties in the plane of its extension, which allows the flexible mesh structure to better adapt to a given skull shape of the patient during application.

[0011] In a further embodiment, the webs are arranged crosswise without knots, and the flexible mesh structure is in the form of a knitted or woven fabric. The absence of knots means that the webs of the flexible mesh structure do not have nodes that are firmly connected to each other. It is therefore very easy to adapt the flexible mesh structure to the given shape of the bone flap and the surrounding bone skull. This makes the application of the implant even easier. In this embodiment, the flexible mesh structure is a knitted or woven fabric. Alternatively, it is conceivable to manufacture it by electrospinning or additive manufacturing. In another embodiment, the webs are firmly connected to each other at their respective nodes. In particular, this allows it to be easily cut to size. The flexible mesh structure is prevented from falling apart.

[0012] In a further embodiment, the plastic material comprises polypropylene and / or polyglycolic acid. The inventors have found that this is particularly advantageous. Polypropylene and polyglycolic acid are already used for the manufacture of medical sutures thanks to their good biocompatibility. This shows that they are also suitable from a mechanical point of view. Polypropylene is not absorbed, whereas polyglycolic acid is hydrolyzed and absorbed in the body within about 60-90 days. Furthermore, polypropylene has transparent properties, which facilitates implantation. The group of polylactic acids, which have particularly transparent properties, may alternatively or additionally be a component of the plastic material. In a further embodiment, it is conceivable to mix plastics of natural origin, such as cellulose, silk, fibroin, gelatin or collagen, with polypropylene and / or polyglycolic acid, in order to particularly increase the biocompatibility properties.

[0013] In a further embodiment, the plastic material comprises non-metallic additives, preferably glass fibres and / or ceramic particles, which can increase mechanical strength and / or bone bonding.

[0014] In a further embodiment, the implant has at least one medically active substance, which is applied to the flexible mesh structure in the form of an active substance coating and / or introduced into the openings in the form of an active substance filling. Alternatively or additionally, it can be said that the medically active substance is applied to the mesh structure and / or introduced into the mesh structure. The medically active substance is, for example, an antibiotic, an analgesic, a growth factor, etc. The flexible mesh structure spreads in a sheet-like shape, which avoids high local concentrations of the active substance and in particular allows for an advantageous release of the active substance. In particular, the regeneration of the periosteum can be improved. In one embodiment, the medically active substance in the form of the aforementioned active substance coating is applied to the flexible sheet-like structure, in particular its lower and / or upper surface. In a further embodiment, the medically active substance is alternatively or additionally introduced into the openings of the flexible mesh structure in the form of an active substance filling.

[0015] In a further embodiment, 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 filler. In this embodiment of the invention, the use of a separate adhesive product and / or separate fixing elements can be dispensed with. The adhesive in the form of an adhesive layer and / or an adhesive filler constitutes part of the implant. In one embodiment, the adhesive is at least partially absorbent, preferably entirely absorbent. In a further embodiment, the adhesive is not absorbent. All biocompatible adhesives suitable for medical applications are suitable for use. Such adhesives are known to the skilled person. If the implant comprises a medically active substance according to the aforementioned embodiment, this substance may be contained in the adhesive layer and / or the adhesive filler. On the one hand, the adhesive serves to fix the flexible mesh structure to the bone flap and the surrounding bone cranial cavity. On the other hand, the adhesive serves to mechanically stabilize the flexible mesh structure. The adhesive is preferably designed to be cured by ultraviolet radiation. Alternatively or additionally, further curing mechanisms are conceivable, for example by moisture, heat or other physical and / or chemical action mechanisms.

[0016] In a further embodiment, the adhesive is a medical tissue adhesive which cures under the influence of ultraviolet radiation. The inventors have found that such adhesives offer particular advantages for this use.

[0017] In a further embodiment, the implant has at least one peelable first protective layer applied at least indirectly to the lower surface of the flexible mesh structure and / or a peelable second protective layer applied at least indirectly to the upper surface of the flexible mesh structure. The first protective layer and / or the second protective layer are peeled off before the implant is implanted. The first protective layer serves to protect the lower surface of the flexible mesh structure. The second protective layer serves to protect the upper surface of the flexible mesh structure. If there is no active substance layer, adhesive layer and / or other layer on the lower surface and / or on the upper surface of the flexible mesh structure, the first protective layer and / or the second protective layer are applied directly to the flexible mesh structure. Otherwise, the protective layer only indirectly covers the flexible mesh structure and is applied directly to one of the aforementioned layers. The first protective layer and / or the second protective layer are preferably protective films, particularly smooth. The protective film is preferably made of a suitable plastic material, such as PTFE.

[0018] The invention also relates to a kit comprising an implant according to any one of claims 1 to 8 and an adhesive for bonding the flexible mesh structure to the bone flap and the bony skull. In this embodiment, the adhesive is available as a separate product and forms a kit for fixing the skull flap together with said implant. To fix the flexible mesh structure, the adhesive is applied to the lower and / or upper surface of the flexible mesh structure before the latter is actually applied. Adhesives suitable for this purpose are known to the skilled person. In one embodiment, the adhesive is a spray adhesive that can be sprayed onto the flexible mesh structure.

[0019] The invention also relates to a kit comprising an implant according to any one of claims 1 to 8 and a number of fixation elements for force-fit and / or form-fit fixation of the flexible mesh structure to the bone flap and the bone cranium. In one embodiment, the fixation elements are pins. Alternatively, the fixation elements may be screws, hooks, etc. In one embodiment, the pins are dismantled and require pilot holes. In another embodiment, the pins are non-dismantled and self-cutting. The fixation elements are inserted into the outer surface of the bone flap and the bone cranium around the cranial opening before the actual application of the implant. The fixation elements used form the fixation points for the flexible mesh structure, which is hooked and fixed in its opening on the fixation elements.

[0020] Further advantages and features of the present invention will become apparent from the following description of preferred exemplary embodiments of the invention, as illustrated by the claims and the drawings. [Brief description of the drawings]

[0021] [Figure 1] 1 is a highly simplified schematic perspective view of a patient's head, the patient's bony skull having a cranial opening closed by a bone flap; [Diagram 2] 1 shows a schematic plan view of the area of ​​a cranial opening, with a bone flap fixed thereto using an embodiment of an implant according to the invention; [Diagram 3] 1 shows a simplified schematic cross-sectional view of the region of the cranial opening. [Figure 4] FIG. 4 shows a perspective exploded view of the implant according to FIGS. 2 and 3 with two protective films. [Diagram 5] FIG. 5 shows a highly simplified schematic cross-sectional view through the layer structure of the implant according to FIG. 4. [Figure 6] 1 shows a schematic diagram of one embodiment of a kit according to the present invention. [Figure 7] FIG. 2 shows a schematic diagram of a further embodiment of a kit according to the present invention. [Figure 8] An example of an application situation using the kit according to FIG. 7 is shown in the diagram according to FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] According to Figure 1, the patient's head has a cranial opening B. The cranial opening B extends from an outer skull surface CA through the patient's bony cranium C to an inner skull surface CI (see Figure 3). The cranial opening B passes axially through the bony cranium C and is surrounded radially by the bony cranium C.

[0023] Cranial opening B may in principle result from an accident or other trauma. In this example, cranial opening B results from a craniotomy and serves as a surgically created access for neurosurgical procedures on the patient's brain.

[0024] In such a craniotomy, the bone flap D is mechanically separated to open the bony skull C. This can be done, for example, by burr hole and craniotomy. In this case, the bone flap D is separated from the bony skull C to form an annular gap S. The annular gap S is also called a craniotomy gap. The bone flap D is also called a bone part, bone fragment, or bone segment.

[0025] After the bone flap D has been cut, it is temporarily separated from the remainder of the bony skull to create the actual cranial opening B. After the procedure on the brain is completed, the bone flap D is replaced in the opening B and secured thereto.

[0026] According to Fig. 2, an implant 1 for fixing a skull flap D to a cranial opening B is provided. The implant 1 comprises a flexible sheet-like structure 2 having 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 to be fixed to the bone flap D and to a bony skull C surrounding the opening B, as will be explained in more detail below.

[0027] In the situation shown with reference to Figures 2 and 3, the flexible mesh structure 2 spans the bone flap D, the annular gap S and the area of ​​the bone skull C around the opening B. The flexible mesh structure 2 rests on the outer surface DA of the bone flap D and on the outer surface CA of the bone skull C. The fixation of the flexible mesh structure 2 to the bone flap D on the one hand and to the bone skull C on the other hand varies depending on the embodiment and may for example be fixed by adhesive bonding with a suitable adhesive and / or fixed using a suitable fixation element.

[0028] The arrangement of the webs 3 and / or apertures 4 specifically shown in Figure 2 is by way of example. In embodiments not shown, the webs and / or apertures may be arranged differently, in particular irregularly, as may the aperture widths of the apertures 4 shown. Again, these are given by way of example only.

[0029] In this example, the flexible mesh structure 2 has a rectangular, particularly square, shape with pairs of opposing outer edges 5, 6, 7, 8. The illustrated configuration is by way of example only. In embodiments not shown, the flexible mesh structure is circular, oval, or conforms to the shape of the bone flap to which it is to be fixed.

[0030] As particularly shown in FIG. 3, the flexible mesh structure 2 is thin compared to the associated bone structures C, D. In the present example, the flexible mesh structure 2 has a thickness t of 0.4 mm. In a not shown embodiment, the thickness of the flexible mesh structure ranges from 0.2 mm to 0.5 mm. Thanks to its small thickness and being made from a plastic material K, the flexible mesh structure 2 can be easily cut to size and its dimensions can be adapted to the bone flap D to be fixed. Furthermore, thanks to its properties, the mesh structure 2 can easily be shaped to the curvature or other dimensions of the associated bone structures C, D.

[0031] In the illustrated embodiment, the flexible mesh structure 2 is a woven fabric G, and the webs 3 are arranged crosswise without knots. In this respect, the flexible mesh structure 2 may also be referred to as a knotless mesh. In an embodiment not illustrated, the webs are firmly connected to each other at their intersections, in which case the flexible mesh structure 2 may also be referred to as a knotted mesh.

[0032] In embodiments not shown, the flexible mesh structure 2 is not in the form of a woven fabric, but instead is in the form of a knitted fabric, non-woven fabric, or the like.

[0033] As shown particularly in Figure 2, the flexible mesh structure 2 is translucent, and therefore the bone flap D, the annular gap S, and the area of ​​the bone cranial cavity C underneath the flexible sheet-like structure 2 can be viewed through the flexible sheet-like structure 2. This allows, among other things, precise positioning and provides further advantages that will be explained in more detail below.

[0034] In the embodiment shown in Figures 2 to 5, the flexible sheet-like structure 2 is fixed to the bone structures C, D by adhesive bonding. For this purpose, the implant 1 has an adhesive A, which is applied to the flexible sheet-like structure 2 in the form of an adhesive layer 9 and is further introduced into the openings 4 in the form of an adhesive filling 10 (see Figure 5). In a not shown embodiment, the adhesive A is provided either in the form of an adhesive layer or an adhesive filling. In this example, the adhesive A is a medical tissue adhesive H which hardens under the influence of ultraviolet radiation. Due to the translucency of the flexible mesh structure 2, the ultraviolet radiation required for this purpose can be irradiated through the flexible mesh structure 2, so that the tissue adhesive H can be hardened particularly easily.

[0035] In the illustrated embodiment, the implant 1 also comprises a medical active substance W. The medical active substance W is present in the form of an active substance layer 13 on the flexible mesh structure 2 and is further introduced into the openings 4 in the form of an active substance filler 14. The provision of the medical active substance W on the implant 1 is optional and does not apply to all embodiments. Furthermore, the active substance layer 13 and the adhesive layer 9 can also be combined into one layer. In other words, the active substance W can be part of the adhesive layer 9 or vice versa. Against this background, the arrangement of the layers 13, 9 shown in FIG. 5 should also be considered as schematic and highly simplified.

[0036] Furthermore, the implant 1 of this example has a first protective layer 11 and a second protective layer 12. The first protective layer 11 is applied at least indirectly to the lower surface 21 of the flexible mesh structure 2. The second protective layer 12 is applied at least indirectly to the upper surface 22 of the flexible mesh structure 2. Indirectly means that, depending on the layer structure, each of the protective layers 11, 12 may be applied in further layers and thus indirectly applied to the respective faces of the flexible mesh structure 2. In this example, the second protective layer 12 is applied directly to the upper surface 22. The first protective layer 11 of this example is applied directly to the adhesive layer 9 and indirectly to the lower surface 21.

[0037] Both protective layers 11, 12 are peelable and are removed before application of the implant 1. In the present example, the protective layers 11, 12 are films made of a plastic material suitable for this purpose. In the embodiment shown, this plastic material is PTFE.

[0038] 5 shows a schematic diagram of the plastic material K of the present example containing non-metallic additives Z1 and Z2. The additives Z1 and Z2 in the present example are a mixture of glass fibers Z1 and ceramic particles Z2. The inclusion of the aforementioned additives in the plastic material K is optional and is intended to improve the mechanical properties and / or bone bonding of the flexible mesh structure 2.

[0039] The plastic material K in this example is a composite material of polypropylene P1 and polyglycolic acid P2.

[0040] When fixing the bone flap D by the implant 1, first the first protective layer 11 is peeled off. The flexible mesh structure 2 is then pressed against the outer surface DA of the bone flap D, with the adhesive layer 9 in front. Alternatively, the implant 1 can be placed on a flat base, with the second protective layer in front. The bone flap D is then pressed so that its outer surface DA is pressed against the underside 21 of the flexible mesh structure 2, more precisely against the adhesive layer 9 arranged on the flexible mesh structure 2. The implant 1 (without the first protective layer 11) and the bone flap D are then repositioned in the area of ​​the cranial opening B. Once repositioned, the bone flap D and the part of the flexible mesh structure 2 protruding laterally from the annular gap S are pressed against the outer surface CA of the surrounding bony skull C.

[0041] The tissue adhesive G is then allowed to harden, and the second protective layer 12 may be removed either before or after hardening.

[0042] In the embodiment shown in Figures 2 to 5, adhesive A is part of the implant 1. Alternatively, adhesive A may be provided as a separate product.

[0043] 6 shows a kit 100 having a flexible mesh structure 2 and adhesive A, where adhesive A is provided as a separate product 40. Separate product 40 may be, for example, a container in the form of a tube or the like filled with adhesive A. Adhesive A is applied to the flexible mesh structure 2 prior to application of the flexible mesh structure 2.

[0044] Fig. 7 shows a further kit 200 with a flexible mesh structure 2 and a number of fixation elements 50. The fixation elements 50 are configured to fix the flexible sheet-like structure 2 to bone structures C, D (see Fig. 8). The fixation elements 50 in this example are pins, each of which is inserted into the outer surface DA of the bone flap D or into the outer surface CA of the surrounding bony skull C. In the inserted state, the fixation elements 50 form, so to speak, fixation points at which the flexible mesh structure 2 can be fixed.

[0045] Regarding further features of the flexible mesh structure 2 contained in the kits 100, 200, explicit reference is made to the above description.

Claims

1. An implant (1) for fixing a skull flap (D) to a cranial opening (B) in a bony skull (C), comprising: a flexible mesh structure (2) having webs (3) and openings (4) formed between said webs; The flexible mesh structure (2) is made of a plastic material (K) and is designed to be fixed to the bone flap (D) and the bony skull (C), implant (1).

2. 2. The implant (1) according to claim 1, characterized in that the flexible mesh structure (2) is optically translucent.

3. An implant (1) according to claim 1 or 2, characterized in that the flexible mesh structure (2) has a thickness (t) of between 0.2 mm and 0.5 mm.

4. An implant (1) according to any one of claims 1 to 3, characterized in that the flexible mesh structure (2) has isotropic elasticity.

5. The webs (3) are arranged crosswise without knots, 5. An implant (1) according to any one of claims 1 to 4, characterized in that the flexible mesh structure (2) is in the form of a knitted or woven fabric (G).

6. 6. Implant (1) according to any one of claims 1 to 5, characterized in that the plastic material (K) comprises polypropylene (P1) and / or polyglycolic acid (P2).

7. 7. Implant (1) according to any one of claims 1 to 6, characterized in that the plastic material (K) comprises non-metallic additives (Z1, Z2), preferably glass fibres (Z1) and / or ceramic particles (Z2).

8. 8. An implant (1) according to any one of claims 1 to 7, characterized by at least one medically active substance (W) applied to the flexible mesh structure (2) in the form of an active substance coating (13) and / or introduced into the openings (4) in the form of an active substance filling (14).

9. An implant (1) according to any one of claims 1 to 8, characterized by an adhesive (A) applied in the form of an adhesive layer (9) to the flexible mesh structure (2) and / or introduced in the form of an adhesive filler (10) into the openings (4).

10. 10. Implant (1) according to claim 9, characterized in that the adhesive (A) is a medical tissue adhesive (H) which hardens under the influence of ultraviolet radiation.

11. An implant (1) according to any one of claims 1 to 10, characterized by at least one peelable first protective layer (11) applied at least indirectly to the underside (21) of the flexible mesh structure (2) and / or a peelable second protective layer (12) applied at least indirectly to the upper side (22) of the flexible mesh structure (2).

12. An implant (1) according to any one of claims 1 to 8, and an adhesive (A) provided for adhering said flexible mesh structure (2) to said bone flap (D) and said bony skull (C).

13. An implant (1) according to any one of claims 1 to 8, and a plurality of fixation elements (50) provided for force-fit and / or form-fit fixation of the flexible mesh structure (2) to the bone flap (D) and the bony skull (C).

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