WO2023006566A1

WO2023006566A1 - Fixing means for a prosthesis

Info

Publication number: WO2023006566A1
Application number: PCT/EP2022/070467
Authority: WO
Inventors: Norbert Meier
Original assignee: mechamed GmbH
Priority date: 2021-07-28
Filing date: 2022-07-21
Publication date: 2023-02-02
Also published as: DE102021119574B4; DE102021119574A1

Abstract

The invention relates to a fixing means (2) which is designed for a prosthesis, in particular for a femoral prosthesis, and which is equipped with a prosthesis anchor. The fixing means has at least two contact surfaces which can be moved relative to each other and which are radially deflected by means of a tensioning shaft (5) and are thus fixed in a recess in the bone (1). The aim of the invention is to achieve a reliable and load-bearing seat of the fixing means within the spongy structure (6) of the bone. This is achieved in that the contact surfaces are circumferentially surrounded by a tubular holder (7) which extends in the axial direction coaxially to the tensioning shaft. Thus, the tubular holder is not wedge-shaped, as is the case with known bone dowels, but rather spreads out over the entire longitudinal extension thereof in a synchronous and concentric manner with respect to the tensioning shaft, whereby an optimal introduction a force into the spongy structures is achieved.

Description

Fixing agent for a prosthesis

The invention relates to a fixation means for a prosthesis, in particular for a thigh prosthesis, equipped with a prosthesis anchor and having at least one peripheral contact surface, by means of which the fixation means can be fixed in a recess of a bone. Furthermore, the invention relates to a prosthesis with such a fixation means.

Fixing means of this type for fixing a prosthesis in a bone, for example the femur, are already widely used and are therefore part of the prior art.

Histologically, human bone is made up of two types of bone: a compact, solid outer layer (compact bone) and a spongy inner zone (spongiosa). The spongiosa consists of bone trabeculae between which the blood-forming marrow tissue is embedded. At the ends of the long bones (epiphyses) the spongiosa dominates, in the middle (diaphysis) the compact bone.

At the proximal end of the femur, the bone trabeculae of the spongiosa show an arrangement that corresponds to the course of the main stress lines that occur in the bone during compressive and tensile loads. Similar to a three-dimensional framework, a maximum of strength is achieved with a minimum of substance.

Femoral components can be anchored according to various principles. Intramedullary stem anchoring is used most frequently, in which the prosthesis stem is cemented or cement-free in the medullary cavity of the femoral stem.

To anchor the prosthesis shaft in the medullary cavity of the femur, however, extensive removal of the spongiosa is necessary. Using scraping or rasp instruments After the resection in the proximal region of a thigh bone (femur), a recess is produced in the spongy part of the bone by rasping out the spongiosa in order to place the prosthesis body in this recess. Known prosthesis bodies often have a large volume, so that a correspondingly large amount of spongiosa has to be removed for implantation.

However, the removal of the spongiosa is to be regarded as a non-physiological local disturbance in the sense of the formation of a defect, which impairs the ability to adapt to loads and, above all, to age-related factors.

A cementless hip joint endoprosthesis with a hollow shaft has become known under the designation spongiosa hip joint endoprosthesis, the interior of which is permeable via openings to the medullary cavity. The interior is filled with spongy bone before implantation and then the prosthesis shaft is driven into the medullary cavity of the femur. Improved integration of the implant is to be achieved through the ingrowth of bone into the interior of the prosthesis or through reorganization of the introduced spongiosa.

When fixing the prosthesis with cement, the load-bearing capacity depends on the cementing technique, although research has shown that aseptic loosening of such prostheses, which occurs between cement and bone and/or between cement and prosthesis, is more common with conventional long-stem prostheses and mostly on the femoral side appear.

Another method is anchoring the artificial femoral head through the neck of the femur according to the tension screw principle. This form of anchoring is particularly favored in younger patients, since the medullary cavity of the femoral shaft is not affected and subsequent intramedullary shaft anchoring when changing a prosthesis is possible without any problems.

EP 1 168988 B1 discloses a prosthesis with a shaft which penetrates the bone and is exposed on the outside of the bone.

EP 0270863 A1 relates to a hip joint prosthesis for cementless implantation in the medullary cavity of the femur, the shaft being designed as a single or multi-threaded spiral. This is intended to reduce the tension introduced into the bone in the shaft area physiologically favorable values and the shear forces and relative movements at the interface between shaft and bone are minimized.

EP 0547354 A1 discloses an adjustable prosthesis head that carries the joint ball and is adjustable by means of a link element, a supporting body and a threaded bolt and is connected to a shaft fixed in the femur. In order to avoid overloading, a limiting element is provided that absorbs the forces and is reset after they occur.

DE 10308338 B4 relates to a bone dowel that can be inserted into a bore in the bone and into which a screw can be screwed. On the outer surface, the dowel jacket has a longitudinal slot and three longitudinal ribs arranged at an angle of 90° to prevent rotation.

Furthermore, DE 20305713 U1 also relates to a bone dowel with a longitudinal slot for fixing a screw in the bone, which has longitudinal ribs and circumferential ribs which are designed with sharp edges or barb-like and can dig into the bone tissue.

In addition, RU 2661 019 C1 describes a dental prosthesis which, in the use position, is spread and clamped over its entire length in the recess of the bone.

The permanent and stable anchoring of the prosthesis components has not yet been satisfactorily solved in the field of endoprosthetics. Studies show for cemented components that there is an increasing number of loosening over time.

The invention is based on the object of creating an endoprosthesis of the type mentioned at the outset, which ensures that the physiology of the bone marrow space including the spongiosa is preserved and thus favorable anatomical conditions during revision operations and optimal adaptation options to age-related bone changes and an optimal physiological introduction of force as well as an enlarged contact surface for the Growth of bone material and an individual adjustment in terms of orientation and position in the bone allows. This object is achieved according to the invention with a fixation means of a prosthesis according to the features of claim 1. The further development of the invention can be found in the dependent claims.

According to the invention, a fixing means is therefore provided which has a socket that encloses the contact surface at least in sections and is in particular elastically or flexibly deformable, which extends parallel to the main extension of the fixing means in the axial direction, with the socket in the use position extending uniformly over its entire length in opposite radial directions Directions with a matching or nearly matching amount concentric to the clamping axis is expanded or spread.

The fixing agent according to the invention enables an endoprosthesis to be introduced while preserving the spongy structures, so that the metabolic biology is not disturbed and the blood flow conditions are not significantly changed. By preserving the physiology of the bone marrow space, including the intertrochanteric spongiosa, favorable anatomical conditions are created for revision operations and optimal adaptation options to age-related bone changes.

The fixing means achieves secure anchoring of the contact surface provided with the peripheral quiver, so that the surfaces of the quiver that are supported on the spongiosa are significantly enlarged and, in particular, do not develop a wedge effect during fixation. With the quiver according to the invention, the relative axial movement of different contact surfaces is not transmitted to the surrounding cancellous structure. Rather, the contact surfaces slide on the inside of the quiver without displacing it relative to the cancellous structures. Since the quiver also has sufficient inherent rigidity, the peripheral radial displacement always takes place over the entire axial extent of the quiver due to the spreading effect, namely synchronously in opposite directions. Thus, the quiver not only achieves a far better, in particular almost homogeneous distribution of the compressive forces introduced into the spongy structures, but at the same time a transverse displacement or a tilting movement of the entire fixation means and consequently the prosthesis is reliably avoided. Inaccuracies in the orientation and position of the prosthesis are thus significantly reduced. It has been shown that in many cases pre-cutting or rasping is not necessary. Rather, the fixative can be driven directly into the bone without any major preliminary work.

This procedure offers decisive surgical advantages, in particular a considerable time saving and a reduction in the risk of infection.

Since the surface structure of the quiver as well as its outer cross-sectional shape can be adjusted as desired, in particular to the patient, an enlarged contact surface for the growth of bone material and, on the other hand, the prerequisite for an individual adaptability of the endoprosthesis to the respective bone shape are made possible with little means .

The solution according to the invention is based on the knowledge that, contrary to the prejudice in the professional world, the fixing agent finds sufficient support in the spongy structure and can easily meet the requirements for the holding forces. The prerequisite for this is the parallelism of the spread of the quiver over the entire length and synchronously with the central longitudinal axis of the fixing means.

The attachment of the prosthesis to the femur of a patient, which is possible due to the shape of the endoprosthesis according to the invention while largely sparing the spongiosa, creates a secure physiological, ie proximal, force application, with the spongy structures offering an extremely firm hold and allowing the transmission of high compressive forces.

A particularly advantageous embodiment of the invention is also achieved in that the quiver has a slotted sleeve with an area in which a fold, a fold, a deformable insert and/or a slot is provided, which preferably extends parallel to the slotted sleeve over the entire extent of the clamping axis, so that the quiver can be either perforated or closed on the circumference. Due to the spreading effect of the fixing means, which is equipped, for example, with wedge sleeves, the quiver is thus expanded radially along its longitudinal extent, with a concentric cross-sectional shape being retained in every phase of the spreading process.

The quiver could, at least in sections, consist of a perforated material, for example a perforated metal sheet or a lattice, in order to encourage ingrowth. Another, likewise particularly advantageous embodiment is also achieved in that the quiver is made of a plastic material, at least in sections consists, which facilitates the introduction of the fixative into the bone by a low frictional resistance.

Another, particularly promising embodiment of the invention is achieved in that the holder has a rib-like and/or groove-like shape running at least in sections parallel to the longitudinal axis. The longitudinal formations are driven into the cancellous structures during the introduction of the fixative and wedge there without disturbing the cancellous tissue. Rather, the formations displace the spongy tissue, which can then continue to fulfill its physiological function. The formations thereby prevent an undesired rotation about the central longitudinal axis and thus an undesired deflection from the predetermined angular position.

A plurality of the in particular rib-shaped formations are preferably arranged evenly distributed on the circumference of the quiver or the slotted sleeve, so that torques acting on the prosthesis can be effectively absorbed.

The rib-shaped formations preferably have a cross-sectional shape in the cross-sectional plane of the slotted sleeve, which becomes narrower or tapers in the course of the radial extension and in particular tapers to a point and thus promotes the penetration of the formations into the cancellous tissue. By providing a peripheral edge with serrations or corrugations in sections, the resistance to an axial tensile load on the fixing means and thus the holding force can be increased in a simple manner.

In addition, it has already proven to be practical if the quiver extends in the axial direction with its distal end area beyond the length of the wedge sleeves with a projection. This avoids direct contact of the wedge sleeves with the spongy tissue, even in the end area of the contact surface. Because the quiver has a flexible surface, for example, the material of the quiver is optimally suited as a contact surface with the cancellous tissue, with wedge effects, in particular due to edges or projections, being avoided in contact with the cancellous tissue.

The quiver can be closed at its distal end section, which is surrounded by the spongy structure, in order to create a closed cover for the contact surface by means of a bottom surface. This means that the connection can be released again if necessary because the spongy tissue does not grow into the contact surface. To separate, the tension is released and the fixative off taken from the quiver. This is then removed from the spongy structures, possibly destructively.

In order to achieve the best possible transfer of force from the quiver to the spongy structures, it has already proven to be particularly promising if the quiver is made of a flexible material and can therefore optimally mold to the existing structures. If necessary, this effect can also be supported by a suitable, for example knob-like surface structure.

The invention permits various embodiments. To further clarify its basic principle, one of them is shown in the drawing and is described below. This shows in

1 shows a side view of a fixing means according to the invention;

Figure 2 is a sectional side view of the fixture shown in Figure 1;

Fig. 3 is a perspective view of the fixing means;

Fig. 4 is a sectional side view of the fixative used in a femur.

A fixing means 2 according to the invention intended for fixing a prosthesis in a bone 1 is explained in more detail below with reference to FIGS. The fixing means 2 has a prosthesis anchor 3 for coupling to a functional section (not shown) of an artificial joint and at least two wedge sleeves 4 that are movable relative to one another and form the contact surfaces of Figure 2 can be seen. In order to achieve a reliable fit of the fixing means 2 within the spongy structures 6 of the bone 1, which are only shown in outline in Figure 4, the wedge sleeves 4 are enclosed on the peripheral side by a quiver 7, which extends coaxially to the clamping axis 5 in the axial direction over both wedge sleeves 4 . For fixing, the quiver 7 is spread synchronously over its entire length in opposite radial directions concentrically to the clamping axis 5, so that the undesirable wedge effect known from bone dowels is avoided. This achieves a sufficient holding force in the bone 1 without extensive removal of the spongy structures 6 . The fixing means 2 has this one than one Slot sleeve 8 running quiver 7 with a continuous longitudinal slot 9 and consists of a plastic material. Rib-shaped formations 10 running parallel to the clamping axis 5 can only be seen in outline in FIG.

Applicant: mechamed GmbH Gerstenstiege 15 30938 Burgwedel

Our reference: MEI-54-PCT July 21, 2022

REFERENCE NUMBER LIST

1 bone

2 fixatives

3 prosthesis anchors

4 wedge sleeve

5 clamping axis

6 structure

7 quiver

8 slotted sleeve

9 longitudinal slit

10 shape

Claims

PATENT CLAIMS

1. A fixing means (2) intended for a prosthesis and equipped with a prosthesis anchor (3) for fixing the prosthesis in a recess of a bone (1) which has at least one peripheral contact surface, characterized in that the fixing means (2) has a die has at least one contact surface peripherally enclosing the socket (7) at least in sections, the socket (7) being spread and/or clamped in the position of use, in particular over its entire length concentrically to an axis in the recess of the bone (1).

2. Fixing means (2) according to claim 1, characterized in that the holder (7) has a slit sleeve (8) with an area in which a fold, a fold, a deformable insert and/or a longitudinal slit (9) is provided , which in particular runs parallel to the clamping axis (5) over the entire extent of the slotted sleeve (8).

3. Fixing means (2) according to claim 1 or 2, characterized in that the quiver (7) consists at least in sections of a plastic material.

4. Fixing means (2) according to at least one of the preceding claims, characterized in that the holder (7) has a rib-shaped and/or groove-shaped formation (10) running at least in sections parallel to the clamping axis (5).

5. Fixing means (2) according to at least one of the preceding claims, characterized in that several of the particular rib-shaped formations (10) are arranged evenly distributed on the circumference of the quiver (7).

6. Fixing means (2) according to at least one of the preceding claims, characterized in that the at least one rib-shaped formation (10). Has a cross-sectional shape in the cross-sectional plane of the slotted sleeve (8), which is tapered in the direction of the radially outer extent.

7. Fixing means (2) according to at least one of the preceding claims, characterized in that the quiver (7) extends in the axial direction with its distal end area over the length of the wedge sleeves (4).

8. Fixing means (2) according to at least one of the preceding claims, characterized in that the quiver (7) is designed to be closed at its distal end section surrounded by the cancellous structure (6).

9. Fixing means (2) according to at least one of the preceding claims, characterized in that the quiver (7) consists of a flexible material.

10. Fixing means (2) according to at least one of the preceding claims, characterized in that the fixing means (2) has at least two wedge sleeves (4) that are movable relative to one another and can be radially deflected by means of an axis designed as a clamping axis (5), and that the The holder (7) encloses several wedge sleeves (4) on the circumference at least in sections and extends parallel to the clamping axis (5) over several wedge sleeves (4), the holder (7) being concentric to the clamping axis (5) over its entire length in the use position. is spread.

11. Prosthesis with a fixing means (2) according to at least one of the preceding claims.