DE102024102123A1 - Elbow arthrodesis implant with improved anatomical adaptability - Google Patents

Abstract

The present invention relates to an implant for arthrodesis of an elbow comprising at least a humeral section, an ulnar section and a transition region connecting the humeral and the ulnar section, wherein the implant has a specific surface relationship between the ulnar and humeral sections and a specific orientation of these surfaces to one another.

Description

The present invention relates to an implant for arthrodesis of an elbow comprising at least a humeral section, an ulnar section and a transition region connecting the humeral and the ulnar section, wherein the implant has a specific surface relationship between the ulnar and humeral sections and a specific orientation of these surfaces to one another.

Elbow arthrodesis is a rare indication for complications following elbow surgery. During arthrodesis, the elbow joint is temporarily or permanently mechanically stiffened using an implant, thus significantly restricting the mobility of the affected joint. This fusion may be indicated when primary injuries such as trauma or fractures (diacondylar C3 fractures, Monteggia injuries), dislocations, dislocation fractures (“Monteggia-like fractures”), burns, or surgical procedures (osteosynthesis) preclude other options or make the successful completion of these “conservative” treatments unlikely. Furthermore, this therapy can be used in cases of failed prosthetic treatments or as an alternative to a prosthesis. To date, there is a lack of a functional implant for elbow arthrodesis that is anatomically adapted and offers high stability while simultaneously protecting soft tissue. In the past, in addition to the use of intraoperatively shaped osteosynthesis plates, arthrodesis attempts using screws were also made.

The patent and scientific literature also contains a wide variety of solutions for constructing joint endoprostheses and arthrodesis implants for a wide range of applications.

This is how Kamineni, S. et al in Journal of Shoulder and Elbow Arthroplasty, 3. 1-7, Elbow Arthrodesis -A Review, 10.1177/2471549219870347 , an overview of possible arthrodesis treatment options for the elbow.

In the DE 3 940 728 A1 An elbow endoprosthesis is described with a humeral component, an ulnar component, and a radial component, as well as a pivot bearing that guides the ulnar component in the area of the humeral component. The elbow endoprosthesis is characterized by the fact that a bearing that acts on the radial component is arranged in the area of the ulnar component.

In the DE 69 818 001 T2 A system for osteosynthesis for vertebral arthrodesis of the spine is described. The system comprises at least one rod for vertebral extension or compression, suitable for extending over at least part of the spine; at least one orientable vertebral anchoring element with a head with a spherical surface and a vertebral anchoring part; the spherical head of the anchoring element forming the end opposite the anchoring part; a common support for receiving, coupling, and locking the vertebral anchoring element and the rod, this common support comprising a first concave seat for receiving the rod and open upwards opposite the anchoring part, and a second concave seat for receiving the spherical head, this second seat being arranged so that the spherical head can assume any adjustable angular position about its center relative to the support, the first seat being laterally displaced with respect to the second seat. and threaded means for locking the rod and the anchoring element to the support, said locking means comprising at least one nut, characterized in that the nut is screwed onto a threaded part, the threaded part belonging to the support, at least a part of the first seat is located laterally outside the threaded part, this first seat being laterally open, and the concave recess of the two seats is directed axially opposite to the anchoring part of the anchoring element, the unit being constructed in such a way that the nut, when screwed onto the threaded part of the support, axially locks the rod in its seat.

Such state-of-the-art solutions offer further potential for improvement. This particularly relates to improved adaptability and improved stabilization of the elbow joint.

The object of the present invention is therefore to at least partially overcome the disadvantages known from the prior art. In particular, the object of the present invention is to provide an elbow implant that enables both temporary and permanent treatment of pathologies involving significant joint destruction at the elbow, while maintaining both pronation and supination.

The object is achieved by the features of the independent claim, directed to the implant according to the invention. Preferred embodiments of the invention are specified in the subclaims, in the description or in the figures, with further features being specified in the subclaims, Features described or shown in the description or the figures may, individually or in any combination, constitute an object of the invention, unless the context clearly indicates the opposite.

According to the invention, an implant for arthrodesis of an elbow comprises at least a humeral section, an ulnar section and a transition region connecting the humeral and the ulnar section, wherein a quotient of a surface of the humeral section relative to a surface of the ulnar section, calculated as the surface of the humeral section divided by the surface of the ulnar section, is greater than or equal to 1.1 and less than or equal to 5 and the amount of an angular difference of a surface vector of the humeral section relative to a surface vector of the ulnar section is greater than or equal to 75° and less than or equal to 180°.

Surprisingly, it was found that the above-defined implant improved the possibility of elbow arthrodesis. Based on the surface ratios of the humeral and ulnar sections, combined with a specific rotation of both sections relative to each other within the implant, improved contact of the implant with the dorsal humerus and posteroradial ulna is achieved. Furthermore, the implant enables a penetrating screw to be safely guided and positioned through the implant, thus achieving both angular-stable fixation of the joint and the ability to build compression. This also significantly improves the stabilization of the radius of the joint. Furthermore, the angular alignment of the sections allows for additional functionalities such as elongated holes to be integrated better and more precisely, which contributes to improved implant positioning. Overall, this results in a secure temporary and definitive treatment of the elbow, with both pronation and supination of the joint being largely preserved.

The implant according to the invention is an implant for elbow arthrodesis. Human elbows can be treated using the implant according to the invention. In contrast to conventional elbow endoprostheses, which incorporate artificial, functional means to increase joint mobility, an arthrodesis implant essentially aims to stabilize and fix the joint. This is intended to prevent further destruction of the elbow and provide the body with time to rebuild an improved joint environment.

The implant comprises at least one humeral section. The humeral section of the implant is the section that is applied to the humerus by mechanical means and mechanically fastened to it. The humeral section of the implant is preferably elongated and approximately rectangular in its base area, whereby, for example, the end pointing towards the upper arm can be rounded. This humeral section can be curved or uncurved, and this section can have a constant or varying width along the section. Width here is understood to be the spatial extent perpendicular to the bone's axis of symmetry. The humeral section can preferably have a length of greater than or equal to 5 cm and less than or equal to 20 cm, a width of greater than or equal to 1 cm and less than or equal to 5 cm, and a thickness of greater than or equal to 0.5 cm and less than or equal to 3 cm. This section can be made, for example, from titanium, medical steel, high-strength polymers, carbon, or mixtures of these components. The humeral segment does not have any mechanical means that would allow significant mobility or deflection of the segment.

The implant further comprises an ulnar section. The ulnar section of the implant is the section that is mechanically attached to the forearm bone, specifically the ulna, and mechanically secured thereto. The ulnar section of the implant is preferably elongated and approximately rectangular in its base area, whereby, for example, the end pointing towards the forearm can have a rectangular shape. This section can have a constant or varying width. Preferably, the ulnar section can have a length of greater than or equal to 5 cm and less than or equal to 20 cm, a width of greater than or equal to 0.5 cm and less than or equal to 3 cm, and a thickness of greater than or equal to 0.2 cm and less than or equal to 2 cm. This section can be made, for example, from titanium, medical steel, high-strength polymers, carbon, or mixtures of these components. The ulnar section does not have any mechanical means that would allow significant mobility or deflection of the section.

The humeral and ulnar segments are connected by a transition region. The transition region connects the upper humeral segment with the lower ulnar segment and has no mechanical means that would allow significant mobility or deflection of the humeral or ulnar segments. The transition region allows for mechanical coupling. between the humeral and ulnar sections and, in the case of implantation, this area encloses the direct elbow area of the patient. Depending on the desired fixation geometry, the area can be straight or angled. This section is preferably angled. This transition area generally has a variable width and thus ensures the transition between the different dimensions of the humeral and ulnar sections. The transition area can preferably have a length of greater than or equal to 2 cm and less than or equal to 9 cm, a width of greater than or equal to 0.5 cm and less than or equal to 5 cm, and a thickness of greater than or equal to 0.5 cm and less than or equal to 4 cm. The transition area can be made, for example, from titanium, medical steel, high-strength polymers, carbon, or mixtures of these components.

A quotient of a surface area of the humeral section in relation to a surface area of the ulnar section, calculated as the surface area of the humeral section divided by the surface area of the ulnar section, is greater than or equal to 1.1 and less than or equal to 5. The surface area of the two sections is defined as the area that can rest on the respective bone. Thus, it is not the thickness of the sections that is meant, but the surface areas that extend towards or away from the bone. The entire surface area for each section is used for the calculation, regardless of whether the surface is full-surface or has holes or recesses. This relationship implies that the humeral section is at least 30% larger than the ulnar section. This can ensure improved fixation of the implant to the bone. Preferably, the ratio can be greater than or equal to 1.25 and less than or equal to 4, further preferably greater than or equal to 1.5 and less than or equal to 3.5. In these relationships, there is sufficient surface area for mechanical fastening of the section as well as improved fixation of the joint.

The magnitude of an angular difference of a surface vector of the humeral section relative to a surface vector of the ulnar section is greater than or equal to 75° and less than or equal to 180°. The implant according to the invention has an angled design, whereby the surfaces of the two attachment sections do not point in the same direction. The surface vectors of the humeral and ulnar sections, which are perpendicular to the surfaces of the sections, are therefore not aligned parallel to each other, but exhibit an angular offset. The offset can be determined by determining the corresponding surface vectors, combining their base points, and determining the angular difference between the two vectors in a plane. In the case of curved or bent surfaces, the surface vector of the center of gravity of the respective area is used for the determination. Overall, the angular arrangement means that the two sections are not fixed to the bone with the same lateral orientation. The implant therefore encompasses the joint from at least two sides and leads to greater mechanical stabilization through the intervention. Preferably, the angulation can result in the humeral segment being aligned with the dorsal portion at a defined angle to the posterior surface of the ulna. This arrangement of the segments leads to significantly improved fixation of the joint and a higher healing success rate.

In a preferred embodiment of the implant, the transition region can have a humeral connection surface to the humeral section, an ulnar connection surface to the ulnar section, and a central connection region connecting these two surfaces, wherein the magnitude of an angular difference of a surface vector of the humeral connection surface relative to a surface vector of the ulnar connection surface is greater than or equal to 75° and less than or equal to 180°. The transition region has a connection surface to each of the humeral and ulnar sections.

These areas arise from the transition area towards the humeral and ulnar sections, with the respective connection surfaces being located in areas where the cross-section of the respective sections no longer changes and remains constant until the end of the respective section. Excluded from these changes are drill holes, recesses, or rounding of the end area of the respective section. Alternatively, the surfaces can be located at points where the area is ultimately rotated and the subsequent sections have a constant surface orientation. The changes in the angular orientation mean that the angulation of the implant does not occur through a rotation within the sections, but rather through a rotation in the transition area. The transition area as such ensures that the sections are attached to the respective bone with different orientations. The surface vector of the humeral connection surface and the ulnar connection surface is therefore on the boundary line between the respective sections and the transition area. In some cases, it may be advisable to manufacture the individual parts separately and join them together at these points. However, it is also possible to manufacture the entire implant additively manufactured, for example, via 3D printing. In these cases, the connection surfaces are as defined above. Preferably, the angle in the transition area can be greater than or equal to 90° and less than or equal to 160°, and more preferably, greater than or equal to 100° and less than or equal to 140°.

In a further preferred embodiment of the implant, the transition region can have a non-constant cross-section. For improved mechanical stabilization of the elbow and to create a connection between the two sections that is as inelastic as possible, it has proven particularly suitable for the cross-section of the transition region to vary from the connection to the humeral section to the ulnar section. The width of the transition therefore changes. The change in width of the transition region can preferably occur continuously. Preferably, the cross-section can change by greater than or equal to 50% and less than or equal to 150%, more preferably by greater than or equal to 70% and less than or equal to 125%.

Within a further preferred aspect of the implant, a quotient of a width of the humeral connection surface relative to a width of the ulnar connection surface, calculated as the width of the humeral connection surface divided by the width of the ulnar connection surface, can be greater than or equal to 2 and less than or equal to 6. The above-specified ratio of the widths has proven particularly suitable for providing improved mechanical holding forces for the two sections. This means that the connection to the humeral part is significantly wider than the ulnar part. Preferably, the ratio can be greater than or equal to 2.2 and less than or equal to 5, and more preferably greater than or equal to 2.5 and less than or equal to 4.5.

According to a preferred characteristic of the implant, a quotient of the length of the humeral segment relative to the length of the ulnar segment, calculated as the length of the humeral segment divided by the length of the ulnar segment, can be greater than or equal to 1.2 and less than or equal to 3. Particularly effective stabilization of the joint can result in cases where a specific relationship between the lengths of the two segments is maintained. Higher ratios can be disadvantageous, as in this case, excessive asymmetry develops between the two segments and there is a risk that one of the segments can no longer be evenly attached to the bone, at least in part. Smaller ratios, on the other hand, can be disadvantageous, as in these cases, impaired stabilization is accepted. Preferably, the ratio can be greater than or equal to 1.45 and less than or equal to 2.8, and further preferably greater than or equal to 1.5 and less than or equal to 2.5.

In a further preferred embodiment of the implant, the thickness of the transition region can be greater than or equal to 5 mm and less than or equal to 15 mm. For improved stabilization of the elbow with sufficient mechanical stabilization of the humeral and ulnar sections, it has proven particularly suitable for the thickness of the transition region to be in the above-specified range. The mechanical strength and the necessary adaptability to the existing elbow situation are met. The thickness of the region results from the extent of the transition region from the bone to the surface facing away from the bone. In the case of a transition region with varying thicknesses, the average thickness counts. Preferably, the thickness can be greater than or equal to 7.5 mm and less than or equal to 13 mm, further preferably greater than or equal to 8 mm and less than or equal to 11 mm.

In a preferred aspect of the implant, the ulnar section can have a width of greater than or equal to 4 mm and less than or equal to 12 mm. The width range specified above has proven particularly suitable for secure attachment of the ulnar section and fixation of the joint. This is particularly the case with an angled design of the implant. Smaller widths can be disadvantageous because they provide too small a contact surface with the bone. Larger surfaces can be disadvantageous because in these cases the entire section does not lie evenly against the bone. Preferably, the width can be greater than or equal to 5 mm and less than or equal to 10 mm, and more preferably greater than or equal to 6 mm and less than or equal to 9 mm.

In a further preferred embodiment of the implant, both the humeral section and the ulnar section can each have one or more concentric holes and at least one elongated hole. For secure and movement-free attachment of the implant to the bone, it has proven advantageous for both the humeral section and the ulnar section to be attached to the bone by means of holes. The holes can preferably be arranged over the entire length of the respective section. The implant can preferably have several screw holes in the upper humeral section, which fulfil different functions. Depending on the design, there can be 2 to 6 holes with a diameter of 2-4 mm in this section. The holes in this section can be filled with either angle-stable screws with a Threaded head or with non-angle-stable screws, for example lens screws or countersunk head without threaded head, of different lengths. The screws serve to firmly connect the implant to the humerus. In the middle area of the upper (humeral) part of the section there can be an oval, 5-30 mm long oblong hole with a width of 2-5 mm. Screws without a threaded head can be inserted into this oblong hole to pull the implant onto the bone and, after loosening the screw, to move the implant proximally (upwards) or distally (downwards). The latter can particularly improve the fit of the implant on the bone. Analogous to the humeral section, the ulnar section can have several holes, for example 2 to 10 holes, which enable angle-stable screw connection. In addition, this section can also have an oblong hole for the insertion of a lag screw. The oblong hole in the ulnar section can preferably be 5 to 30 mm long and 2 to 5 mm wide.

In a further embodiment of the implant, the oblong hole of the humeral section can be located axially centrally within the humeral section. For improved adaptation of the implant to the bone, it has proven particularly suitable for the oblong hole to be located centrally within the humeral section. This arrangement is achieved in cases where the center of the oblong hole is greater than or equal to 40% from the outer ends of the humeral section. The reference basis for the percentage specification is the total length of the humeral section.

Within the scope of a further preferred embodiment of the implant, the humeral section can have a bore, wherein the bore is angled relative to the surface vector of the humeral section and is designed to guide a screw into the humeroulnar joint. This bore can be arranged in particular in the part of the humeral section adjacent to the transition region. This region can preferably extend from 5% to 20% of the total length of the humeral section from the transition region into the humeral section. In this region, a bore can enable an angle-stable screw connection with an angle of 100° to 160°, which securely fixes the joint and transmits only moderate mechanical forces to the implant. More preferably, this region can extend from 7% to 17% of the total length of the humeral section and further preferably from 8% to 15% of the total length of the humeral section.

Further advantages and advantageous embodiments of the inventive objects are illustrated by the figures and explained in the following examples. It should be noted that the figures are for descriptive purposes only and are not intended to limit the invention in any way.

• 1 schematisch den Aufbau eines erfindungsgemäßen Implantats in der Aufsicht auf den humeralen Abschnitt;
• 2 schematisch den Aufbau eines erfindungsgemäßen Implantats in der Aufsicht auf den Übergangsbereich;
• 3 schematisch den Aufbau eines erfindungsgemäßen Implantats in der Aufsicht auf den ulnaren Abschnitt;
• 4 schematisch den Aufbau eines erfindungsgemäßen Implantats in einer weiteren Aufsicht auf den ulnaren Abschnitt;
• 5 schematisch den Aufbau eines erfindungsgemäßen Implantats in einer weiteren Aufsicht auf den ulnaren Abschnitt.
• 6 schematisch die Definition der Winkelbeziehung zwischen den Oberflächenvektoren des humeralen und des ulnaren Abschnitts.

The

• 1 schematically shows the structure of an implant according to the invention in a top view of the humeral section;
• 2 schematically shows the structure of an implant according to the invention in a top view of the transition area;
• 3 schematically shows the structure of an implant according to the invention in a top view of the ulnar section;
• 4 schematically shows the structure of an implant according to the invention in a further plan view of the ulnar section;
• 5 schematically shows the structure of an implant according to the invention in a further plan view of the ulnar section.
• 6 schematically the definition of the angular relationship between the surface vectors of the humeral and ulnar sections.

The 1 shows a schematic view of the structure of an implant 1 according to the invention, viewed from above onto the humeral section 2. The implant is divided into three parts, with the humeral section 2, which lies against the upper arm, lying against the transition region 3, which is arranged on both the humeral section 2 and the ulnar section 4. The humeral section 2 and the ulnar section 4 have a specific surface area ratio to one another, which is responsible for the improved stabilization of the elbow joint by the implant. The figure also shows that the surface of the humeral section 2 has a different orientation than the surface of the ulnar section 4. If one considers the orientation of the surface vectors (not shown) that are perpendicular to the surfaces of sections 2, 4, they are not aligned parallel to one another, but rather form an angle of approximately 90° to one another. This orientation of the surfaces of sections 2, 4 relative to each other can contribute to improved attachment of the implant to the bone and thus to improved stabilization of the joint through arthrodesis. In this embodiment, the humeral 2 and the ulnar section 4 are designed to be more rectangular in surface shape, with the ends of sections 2, 4 pointing away from the transition area 3 being rounded. These ends could optionally also not be rounded. Preferably, the entire implant 1 can have the following dimensions: height 25 cm, width 2.5 cm, average thickness 1 cm, whereby in particular the humeral section can have a height of 10 cm, a width of 2.5 cm, a thickness of 1 cm, the ulnar section can have a height of 10 cm, a width of 2 cm, a thickness of 0.8 cm and the transition region can have a height of 5 cm, a width of 1.5 cm and a thickness of 0.9 cm.

The 2 shows schematically the structure of an implant 1 according to the invention in a top view of the transition area 3. This figure has the same functional components as for the 1 listed. It should also be emphasized at this point that both the humeral section 2 and the ulnar section 4 can accommodate additional functional components. For example, both the humeral section 2 and the ulnar section 4 have several holes 5 and one elongated hole 6 each. The holes 5 serve to permanently attach the implant 1 to the respective bone, whereas the elongated hole 6 allows the implant 1 to be positioned and moved on the bone. Preferably, the implant 1 is first optimally attached to the bone using a screw that can be moved through the elongated hole 6, and then the entire implant 1 is detachably connected to the bone using additional fastening devices, such as screws, through the holes 5. It is also possible for only the humeral section 2 or the ulnar section 2 to have elongated holes 6. Additionally, the bore 13 in the humeral section 2 is shown; this is angled and allows a screw to be inserted directly into the elbow joint.

The 3 shows schematically the structure of an implant according to the invention in a top view of the ulnar section 2. The 3 shows the three-part structure of the implant 1 consisting of the humeral section 2, the transition area 3 and the ulnar section 4. This figure also shows the humeral connection surface 7 and the ulnar connection surface 8. The two connection surfaces 7, 8 are the surfaces in which the respective section 2, 4 transitions into the transition area 3. They each represent the surface of the transition area 3 which has the same cross-section as the adjacent section 2, 4. The further transition area 3 then has a correspondingly different cross-section and forms the connecting area 14. In summary, this means that in the transition area 3 not only the rotation of the sections 2, 4 against each other takes place, but also an adaptation or adjustment of the individual cross-sectional surfaces of the humeral section 2 and the ulnar section 4.

The 4 shows schematically the structure of an implant 1 according to the invention in a further plan view of the ulnar section 2. The 4 shows the three-part structure of implant 1, consisting of humeral section 2, transition area 3, and ulnar section 4. This figure also shows the width 10 of the ulnar connection surface 4 and the length 12 of the humeral section 2. The length 12 results from the longest distance between the humeral connection surface 7 and the end of the humeral section 2.

The 5 shows schematically the structure of an implant 1 according to the invention in a further plan view of the ulnar section 4. The 5 shows the three-part structure of implant 1, consisting of humeral section 2, transition area 3, and ulnar section 4. This figure also shows the length 12 of the ulnar section 4. The length 12 results from the longest distance between the ulnar connection surface 8 and the end of the ulnar section 4.

The 6 shows a schematic definition of the angular relationship between the surface vectors of the humeral section 2 and the ulnar section 4. The surface vectors, which are perpendicular to the surfaces, are shown on the individual surfaces. The foot points of the surface vectors are combined to determine the angle, and the rotation of the surfaces is determined from the difference in the orientation of the two vectors in degrees. In this example, the angular difference between the two vectors is approximately 90°. Furthermore, the implant can have a valgus angle, i.e. an angular deviation that describes the lateral deviation of the forearm from the longitudinal axis of the upper arm, of greater than or equal to 0° and less than or equal to 20°, furthermore of greater than or equal to 2.5° and less than or equal to 15°, and more preferably of greater than or equal to 5° and less than or equal to 10°. In addition, the flexion angle caused by the implant, ie the angle which is spanned between the humerus and the forearm bone after the implant has been applied, can be greater than or equal to 30° and less than or equal to 90°, furthermore greater than or equal to 40° and less than or equal to 80° and more preferably greater than or equal to 60° and less than or equal to 90°.

List of reference symbols

1

Implant

2

humeral section

3

Transition area

4

ulnar section

5

Hole

6

slot

7

humeral attachment surface

8

ulnar attachment surface

9

Width of the humeral attachment surface

10

Width of the ulnar connection surface

11

Length of the humeral section

12

Length of the ulnar segment

13

drilling

14

Connection area

QUOTES CONTAINED IN THE DESCRIPTION

This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 3 940 728 A1 [0005]
• DE 69 818 001 T2 [0006]

Cited non-patent literature

• Kamineni, S. et al in the Journal of Shoulder and Elbow Arthroplasty, 3. 1-7, Elbow Arthrodesis -A Review, 10.1177/2471549219870347 [0004]

Claims (10)

Implant (1) for arthrodesis of an elbow, comprising at least a humeral section (2), an ulnar section (4), and a transition region (3) connecting the humeral section (2) and the ulnar section (4), characterized in that a quotient of a surface area of the humeral section (2) relative to a surface area of the ulnar section (4), calculated as the surface area of the humeral section (2) divided by the surface area of the ulnar section (4), is greater than or equal to 1.2 and less than or equal to 5, and in that the absolute value of an angular difference of a surface vector of the humeral section (2) relative to a surface vector of the ulnar section (4) is greater than or equal to 75° and less than or equal to 180°. Implant after Claim 1 , wherein the transition region (3) has a humeral connection surface (7) to the humeral section (2), an ulnar connection surface (8) to the ulnar section (4) and a central connection region (14) connecting these two surfaces to one another, wherein the amount of an angular difference of a surface vector of the humeral connection surface (2) relative to a surface vector of the ulnar connection surface (4) is greater than or equal to 20° and less than or equal to 90°. Implant after Claim 2 , wherein the transition region (3) has a non-constant cross-section. Implant according to one of the Claims 2 or 3 , wherein a quotient of a width (9) of the humeral connection surface (2) relative to a width (10) of the ulnar connection surface (4), calculated according to width (9) of the humeral connection surface (2) divided by width (10) of the ulnar connection surface (4), is greater than or equal to 2 and less than or equal to 6. Implant according to one of the preceding claims, wherein a quotient of length (11) of the humeral section (2) relative to a length (12) of the ulnar section (4), calculated as length (11) of the humeral section (2) divided by length (12) of the ulnar section (4), is greater than or equal to 1.2 and less than or equal to 3. Implant according to one of the preceding claims, wherein a thickness of the transition region (3) is greater than or equal to 5 mm and less than or equal to 15 mm. Implant according to one of the preceding claims, wherein the ulnar portion (4) has a width of greater than or equal to 4 mm and less than or equal to 12 mm. Implant according to one of the preceding claims, wherein both the humeral section (2) and the ulnar section (4) each have one or more concentric holes (5) and each have at least one elongated hole (6). Implant after Claim 8 , wherein the elongated hole (6) of the humeral section (2) is arranged axially centrally in the humeral section (2). Implant according to one of the preceding claims, wherein the humeral portion (2) has a bore (13), wherein the bore (13) is angled relative to the surface vector of the humeral portion (2) and is designed to guide a screw into the humeroulnar joint.