NL2036988B1

NL2036988B1 - Intramedullary implant

Info

Publication number: NL2036988B1
Application number: NL2036988A
Authority: NL
Inventors: Theodorus Peter Verhaegh Franciscus
Original assignee: Nemevo 3 B V
Priority date: 2024-02-08
Filing date: 2024-02-08
Publication date: 2025-08-20
Also published as: WO2025170464A1

Abstract

An intramedullary implant (1) for connection to a prosthetic device (E), comprising a main stem (2) having a proximal end (3) for insertion into a medullary cavity ofa bone stump (B) and a distal end (4) for engagement with the prosthetic device (E). The main stem (2) comprises a medullar section (5) extending from the proximal end (3) in distal direction (D), and a coupling section (6) extending from the distal end (4) in proximal direction (P). The medullar section (5) and coupling section (6) meet at an insertion point (S) along the main stem (2) between the proximal end (3) and the distal end (4), wherein the insertion point (S) designates a maximum insertion depth (Di) into the medullar cavity. The coupling section (6) has a constant coupling diameter (d1) extending from the insertion point (S) to the distal end (4). [Figure 1]

Description

Intramedullary implant

Field of the invention

The present invention relates to an intramedullary implant, in particular an intramedullary implant for connection to an extracorporeal coupling device, prosthetic device and the like, such as a prosthetic limb.

Background

German patent application DE102009027255 A1 discloses a femoral stump implant comprising a stem part intramedullary anchored in a hollow bone and a coupling part provided for an extracorporeal coupling device. The coupling part is attached extracorporeally in a direction to the stem part, where the implant is segmented into a proximal area, areas with different surface characteristics regarding swelling, ingrowing and outgrowing characteristics of surrounding tissues. In an embodiment, the stem part is distally provided with a circumferential collar which is distally followed by an enlarged coupling part.

US patent application US 2004/068324 A1 discloses a subcutaneous, intramuscular support for a rigid transcutaneous implant, which can be anchored intracorporeally in a bone stump and which has an intermediate piece between the part to be intracorporeally anchored and an extracorporeal coupling device, which can be coupled to it. The intermediate piece is preferably constructed as a double cone receivable in the implant and extracorporeal coupling device.

Prior art intramedullary and transcutaneous implants of the type described above may cause soft tissue and stoma complications near or along enlarged distal coupling part of the implant. Furthermore, such prior art implants often utilize an intermediate piece between the implant and extracorporeal coupling device and wherein the intermediate piece is shaped as a double cone congruently receivable in the implant and the extracorporeal coupling device. Making use of such a double cone intermediate piece results in a mechanically complex implant which is prone to material fatigue and damage. Consequently, preventive replacement or repair of the intermediate piece, as well as removal of these prior art implants, can be difficult due to a tightly wedged double cone engagement of the intermediate piece with the implant and extracorporeal coupling device.

Summary

It is an object of the present invention to provide an improved intramedullary implant, particularly an intramedullary implant for connection to an extracorporeal coupling device, prosthetic device and the like. The intramedullary implant addresses the aforementioned problems by reducing soft tissue and stoma problems, as well as problems related to bone resorption. Furthermore, the intramedullary implant exhibits reduced mechanical complexity, improved strength and durability, and facilitates attachment and removal of the extracorporeal coupling device or prosthetic device, and wherein the implant is easier to remove when required.

According to the present invention, an intramedullary implant of the type described above is provided and comprises a main stem having a proximal end for insertion into a medullary cavity of a bone stump and a distal end for engagement with a prosthetic device, extracorporeal coupling device and the like. The main stem comprises a medullar section that extends from the proximal end in distal direction, and a coupling section that extends from the distal end in proximal direction. The medullar section and the coupling section meet at an insertion point along the main stem between the proximal end and the distal end, wherein the insertion point designates a maximum insertion depth of the intramedullary implant into the medullar cavity of the bone stump.

The coupling section has a constant or uniform coupling diameter extending from the insertion point to the distal end and wherein the coupling section is configured to cooperatively connect to the prosthetic device or extracorporeal coupling device.

According to the present invention, the constant or uniform coupling diameter of the coupling section allows soft tissue to move freely and smoothly along the coupling section and as such significantly reduces soft tissue and stoma problems, such as tissue inflammation and potentially infection. Furthermore, providing a uniform and constant coupling diameter to the coupling section eliminates the need for a double cone intermediate piece to be received by the distal and tightly wedges therein. Avoiding the use of such an intermediate piece greatly simplifies attachment and removal of the prosthetic device or extracorporeal coupling device from the intramedullary implant.

Short description of drawings

The present invention will be discussed in more detail below, with reference to the attached drawings, in which

Figure 1 shows a side view of an intramedullary implant according to an embodiment of the present invention;

Figure 2 shows a side view of an intramedullary implant according to another embodiment of the present invention;

Figure 3 shows a side view of an intramedullary implant placed inside a bone stump and connected to a prosthetic device according to an embodiment of the present invention;

Figure 4 shows a cross section of a prosthetic device connected to a coupling section of the intramedullary implant according to an embodiment of the present invention.

Detailed description of embodiments

Figure 1 and 2 each show an embodiment of an intramedullary implant 1 according to the present invention, wherein Figure 3 shows an example of the intramedullary implant 1 placed inside a bone stump B and connected to a prosthetic device E. In an embodiment, the bone stump B may be a femur or tibia for example.

As depicted, the intramedullary implant 1 comprises a main stem 2 having a proximal end 3 for insertion into a medullary cavity of the bone stump B and a distal end 4 for engagement with a prosthetic device E or extracorporeal coupling device E. In particular applications the prosthetic device E may have an integrated extracorporeal coupling device E or the prosthetic device E and extracorporeal coupling device E may be provided as separate parts to be assembled and connected to the intramedullary implant 1. For the present invention there will be no particular distinction made between the prosthetic device E or extracorporeal coupling device E and as such these terms can be used interchangeably.

The main stem 2 comprises a medullar section 5 extending from the proximal end 3 in distal direction D, and a coupling section 6 extending from the distal end 4 in proximal direction P, wherein the distal direction D and the proximal direction P are clearly indicated in the figures. For ease of understanding, the main stem 2 may be seen as an elongated rod and which in an exemplary embodiment may be made of titanium or any other metal/alloy suitable for implant.

The medullar section 5 and the coupling section 6 meet at an insertion point S along the main stem 2 between the proximal end 3 and the distal end 4. The insertion point S designates or represents a maximum insertion depth Di of the intramedullary implant 1 into the medullar cavity of the bone stump B as measured from the proximal end 3 to the insertion point S. It will be understood that the location of the insertion point S along the main stem 2 will vary depending on a specific design of the intramedullary implant 1 and its application.

In Figure 1 and 2 it is further shown that the coupling section 6 has a constant or uniform coupling diameter d1 that extends from the insertion point S to the distal end 4, and wherein the coupling section 6 is configured to cooperatively connect to the prosthetic device E. Here, the constant coupling diameter d1 must be understood as completely extending uniformly between the insertion point S to the distal end 4. Note that the length L by which the coupling section 6 extends from the insertion point S to the distal end 4 depends on specific requirements of the intermedullary implant 1.

According to the present invention, the constant or uniform coupling diameter d1 of the coupling section 6 allows soft tissue T as depicted in Figure 3 to move freely and smoothly along the main stem 2, i.e. the coupling section 6, as indicated by a range of movement Z. Free and smooth movement of the soft tissue T along the coupling section 6 significantly reduces soft tissue and stoma problems. So in contrast to prior art implants, soft tissue T as schematically depicted in Figure 3 does not need to move along, e.g., conically shaped enlargements of the main stem 2 or any surface irregularities between the insertion point S and the prosthetic device

E, thereby reducing soft tissue and stoma problems. Furthermore, providing a uniform and constant coupling diameter d1 along the coupling section 6 between the distal end 4 and the insertion point S eliminates the need for a double cone intermediate piece congruently received by the distal end 4 of the intramedullary implant 1 and prosthetic device E. That is, the prosthetic device E as depicted can be connected to intramedullary implant 1 without using a double cone intermediate piece in wedged engagement with the distal end 4, thereby avoiding soft tissue and stoma problems.

The medullar section 5 may be given a medullar diameter d2 to meet requirements of a particular application. For example, in an embodiment the medullar diameter d2 may be constant or uniform and extends from the insertion point S in proximal direction P along at least a part of the main stem 2, and wherein the medullar diameter d2 is substantially equal to the coupling diameter d1. In this embodiment, at least a part of the medullar section 5 that extends from the insertion point S toward the proximal end 3 exhibits a substantially constant or uniform diameter d2 equal to the coupling diameter d1. This embodiment reduces the mechanical manufacturing complexity of the intramedullary implant 1.

In an alternative embodiment it may the case that the medullar section 5 has a medullar diameter d2 that extends from the insertion point S in proximal direction P along at least a part of the main stem 2, and wherein the medullar diameter d2 tapers in the proximal direction P. That is, the medullar diameter d2 decreases in proximal direction P as measured from the insertion point

S. This embodiment may be more complex to manufacture but provides a stronger and durable anchoring of intramedullary implant 1 into the bone stump B. Note that at the insertion point S, the medullar diameter d2 may equal the coupling diameter d1 and tapers to a smaller diameter in proximal direction P.

In the embodiments of Figure 1 and 2 it is shown that the of intramedullary implant 1, or main stem 2 in particular, may be arcuate or curved between the proximal end 3 and the distal end 4. Such an arcuate or curved shape of the intramedullary implant 1 may be advantageous for a femoral bone stump B for example. However, in an alternative embodiment the intramedullary implant 1, or main stem 2, may be straight and without curvature. Such a straight intramedullary implant 1 may be advantageous for a tibial bone stump B for example.

To improve anchoring of the intramedullary implant 1 there is provided an embodiment wherein the medullar section 5 comprises a first medullar part 7 extending from the insertion point

S in proximal direction P toward a first intermediate point M1 along the main stem 2, and a second medullar part 8 extending from the first intermediate point M1 in proximal direction P toward a second intermediate point M2 along the main stem 2, wherein the second medullar part 8 comprises a circumferentially arranged surface pattern 8, e.g. a regular surface pattern 9. The surface pattern 9 allows the intramedullary implant 1 to be tightly integrated into the bone stump B and in engagement with bone tissue for strong and durable anchoring. In exemplary embodiments the surface pattern 9 may be a machined or moulded pattern comprising regularly arranged elongated grooves, ridges and the like. A regular pattern of point-like protrusions and/or indents along the main stem 2 to enhance anchoring may also be considered as the surface pattern 9.

Additional or alternative ways to improve anchoring of the intramedullary implant 1 may be provided by an embodiment wherein the first medullar part 7 comprises a course/rough first bone engaging surface 11 and/or the second medullar part 8 comprises a course/rough second bone engaging surface 12. In this embodiment, the course/rough first and second bone engaging surface 11, 12 provide a particular surface roughness and/or porosity on a smaller scale than regularly machined or moulded grooves, ridges, protrusion and the like. In an exemplary embodiment, the course/rough first and/or second bone engaging surfaces 11, 12 may comprise distributed surface irregularities by means of a plasma coating (e.g. titanium, hydroxyapatite) arranged along the first and/or second medullar part 7, 8.

Note that in particular cases it may be needed that a further prosthetic device (not shown) is to be connected to the proximal end 3 of the intramedullary implant 1. For such an scenario there is provided an embodiment wherein the medullar section 5 comprises a third medullar part that extends from the second intermediate point M2 in proximal direction P toward the proximal 5 end 3, wherein the third medullar part 10 is configured for connection to a further prosthetic device. The further prosthetic device may, e.g, be a prosthetic femoral head to be connected to the proximal end 3. As depicted, in an embodiment the third medullar part 10 has a frusto-conical shape for congruent conical engagement with the further prosthetic device.

From Figure 1 and 2 it follows that different embodiments of the medullar section 5 are 10 conceivable. For example, in contrast to Figure 1, in Figure 2 there is depicted an embodiment wherein the medullar section 5 comprises a first medullar zone 5a with a first zone diameter d2 extending from the insertion point S in proximal direction P and having a press length Lp along the main stem 2. That is, the first medullar zone 5a extends from the insertion point S to a third intermediate point M3 in proximal direction P over a press length Lp. Further, a second medullar zone 5b is provided and extends from the first medullar zone 5a in proximal direction P toward the distal end 3. That is, the second medullar zone 5b extends from the third intermediate point M3 in proximal direction P toward the distal end 3. The second medullar zone 5b has a second zone diameter d3 extending from the first medullar zone 5a in proximal direction P along at least a part of the main stem 2, and wherein the first zone diameter d2 is larger than the second zone diameter d3. In this embodiment the first medullar zone 5a has a larger diameter than the diameter of the second medullar zone 5b, thereby allowing the first medullar zone 5a to be in a tighter press fit engagement with the bone stump B. Therefore, the first medullar zone 5a with press length Lp may be advantageous to provide enhanced anchoring durability should bone resorption develop slowly, for example.

In a further embodiment as depicted in Figure 2, the first zone diameter d2 may be substantially equal to the coupling diameter d1, so that there are no sudden changes in diameter at the insertion point S that could cause soft tissue and stoma problems. Note that the second zone diameter d3 may taper in the proximal direction P. By tapering the second medullar zone 5b in proximal direction P allows for improved anchoring inside the bone stump B.

Like the embodiment depicted in Figure 1, in Figure 2 there is shown an embodiment that improves anchoring of the intramedullary implant 1, wherein the medullar section 5 comprises a first medullar part 7 extending from the insertion point S in proximal direction P toward a first intermediate point M1 along the main stem 2, and a second medullar part 8 extending from the first intermediate point M1 in proximal direction P toward a second intermediate point M2 along the main stem 2. The second medullar part 8 comprises a circumferentially arranged surface pattern 9, e.g. a regular surface pattern 9. As mentioned earlier, the surface pattern 9 allows the intramedullary implant 1 to be tightly integrated into the bone stump B and in engagement therewith for strong and durable anchoring. The surface pattern 9 may also be provided as a machined or moulded pattern of regularly arranged elongated grooves, ridges, point-like protrusions and/or indents.

Improved anchoring of the intramedullary implant 1 shown in Figure 2 may be similarly achieved by an embodiment wherein the first medullar part 7 comprises a course/rough first bone engaging surface 11 and/or the second medullar part 8 comprises a course/rough second bone engaging surface 12. Like the embodiment of Figure 1, the course first and second bone engaging surfaces 11, 12 shown in Figure 2 provide surface roughness and/or porosity on a smaller scale than machined or moulded grooves, ridges, protrusion, indents and the like. In an exemplary embodiment, the course/rough first and second bone engaging surfaces 11, 12 comprise distributed surface irregularities by means of a plasma coating (e.g. titanium, hydroxyapatite) arranged along the first and/or second medullar part 7, 8.

It is important to note that the first medullar part 7 in Figure 2 comprises the first medullar zone 5a and as such the course/rough first bone engaging surface 11 extends from the insertion point S along the first medullar zone 5a to the third intermediate point M3. The second medullar zone 5b is in part comprised by the first medullar part 7 as depicted.

In correspondence with Figure 1, the embodiment of Figure 2 shows that the medullar section 5 may also comprise a third medullar part 10 extending from the second intermediate point M2 in proximal direction P toward the proximal end 3, wherein the third medullar part 10 is configured for connection to a further prosthetic device (not shown), such as a prosthetic femoral head to be connected to the proximal end 3, wherein third medullar part 10 may be shaped in frusto-conical manner.

It was explained above that the coupling section 6 provides a constant and uniform coupling diameter d1 that extends from the insertion point S to the distal end 4 and wherein the coupling section 8 is configured to cooperatively connect to the prosthetic device E. The uniform and constant coupling diameter d1 allows soft tissue T to move freely and smoothly along the coupling section 6, thereby significantly reducing soft tissue and stoma problems. At the same time the coupling section 6 eliminates the need for a double cone intermediate piece to be congruently received by the distal end 4 of intramedullary implant 1 and the prosthetic device E.

Figure 1 and 2 show that in an embodiment the coupling section 6 may comprise a smooth coupling surface 13 that extends from the insertion point S to the distal end 4. Such a smooth coupling surface 13 allows soft tissue T to smoothly move along the coupling section 6 for reducing soft tissue and stoma problems. Furthermore, the smooth coupling surface 13 allows smooth insertion of the distal end 4 into the prosthetic device E for example, thereby facilitating controlled and accurate placement of the prosthetic device E.

In an alternative embodiment the coupling section 6 may comprise a tissue engaging zone 6a extending from the insertion point S in distal direction D and spanning at least in part the coupling section 6, and wherein the tissue engaging zone 6a comprises a smooth surface coating.

In particular, the tissue engaging zone 8a extends from the insertion point S in distal direction D to a fourth intermediate point M4 from which a coupling engaging zone 6b extends in distal direction

D to the distal end 4. The smooth surface coating of the tissue engaging zone 6a can be any suitable coating of choice (e.g. titanium nitride). In this embodiment it is not needed to have identical surface qualities of the tissue engaging zone 6a and the coupling engaging zone 6b.

That is, surface properties of the tissue engaging zone 6a and the coupling engaging zone 6b can be separately optimized. For example, in an embodiment the coupling section 6 may be made of titanium and wherein the tissue engaging zone 6a may be provided with a smooth surface coating. However, the coupling engaging zone 6b may not benefit from the smooth surface coating as it may be too smooth for durable and reliable attachment of the prosthetic device E to the intramedullary implant 1. In such a case the coupling engaging zone 6b may be given surface properties that are optimized for attaching the prosthetic device E to the intramedullary implant 1.

For example, the coupling engaging zone 6b may remain untreated and as such the surface properties thereof may be those of titanium.

Securing the prosthetic device E to the coupling section 6 is schematically depicted in

Figure 3 and 4, wherein Figure 4 shows a cross section of a prosthetic device E connected to the coupling section 6 of the intramedullary implant 1.

As shown in the figures, in an embodiment the coupling section 6 comprises one or more surface recesses 14, 15. These surface recesses allow the prosthetic device E to be secured in place along the coupling section 6, e.g. along the coupling engaging zone 6b. For example, the one or more surface recesses 14, 15 may be configured to receive an end portion of a suitable fastener 16 (e.g. bolt) that extends through an aperture 17 of the prosthetic device E.

Furthermore, the one or more surface recesses 14, 15 will not interfere with the a prosthetic device E as is moved along te coupling section 6 in proximal direction P, thereby allowing controlled and accurate positioning.

In a further embodiment, the one or more recesses 14, 15 may comprise one or more circumferential grooves 14 extending around the coupling section 6, e.g. the coupling engaging zone 6b. Such circumferential grooves 14 allow the prosthetic device E to be rotated around the coupling section 6 until a desired orientation is achieved. Suitable fasteners 16 can be used to secure the prosthetic device E in place. From Figure 1 and 2 it also follows that the one or more recesses 14, 15 may comprise one or more longitudinal grooves 15. Providing a combination of circumferential and longitudinal grooves 14, 15 to the coupling section 6 is possible as well.

The prosthetic device E to be connected to the intramedullary implant 1 may be a passive prosthetic device E or an active prosthetic device E comprising electronics for example. To allow an active prosthetic device E with electronic wires to be connected to the intramedullary implant 1 and a human subject, an embodiment is conceivable wherein the main stem 2 comprises a through bore or lumen 18 extending from the proximal end 3 to the distal end 4. The through bore 18 allows electronic wires to be efficiently routed from the prosthetic device E to the human body.

In view of the above, the present invention can now be summarized by a number of embodiments:

Embodiment 1. An intramedullary implant (1) for connection to a prosthetic device (E), comprising a main stem (2) having a proximal end (3) for insertion into a medullary cavity of a bone stump (B) and a distal end (4) for engagement with the prosthetic device (E);

wherein the main stem (2) comprises a medullar section (5) extending from the proximal end (3) in distal direction (D), and a coupling section (6) extending from the distal end (4) in proximal direction (P), wherein the medullar section (5) and the coupling section (6) meet at an insertion point (S) along the main stem (2) between the proximal end (3) and the distal end (4), wherein the insertion point (S) designates a maximum insertion depth (Di) of the intramedullary implant (1) into the medullar cavity of the bone stump {B}; and wherein the coupling section (6) has a constant coupling diameter (d1) extending from the insertion point (S) to the distal end (4) and wherein the coupling section (6) is configured to cooperatively connect to the prosthetic device (E).

Embodiment 2. The intramedullary implant (1) according to embodiment 1, wherein the medullar section (5) has a constant medullar diameter (d2) extending from the insertion point (S) in proximal direction (P) along at least a part of the main stem (2), and wherein the medullar diameter (d2) is substantially equal to the coupling diameter (d1).

Embodiment 3. The intramedullary implant (1) according to embodiment 1, wherein the medullar section (5) has a medullar diameter (d2) extending from the insertion point (S) in proximal direction (P) along at least a part of the main stem (2), and wherein the medullar diameter (d2) tapers in the proximal direction (P).

Embodiment 4. The intramedullary implant (1) according to any of embodiments 1-3, wherein the medullar section (5) comprises a first medullar part (7) extending from the insertion point (S) in proximal direction (P) toward a first intermediate point (M1) along the main stem (2), and a second medullar part (8) extending from the first intermediate point (M1) in proximal direction (P) toward a second intermediate point (M2) along the main stem (2), wherein the second medullar part (8) comprises a circumferentially arranged surface pattern (9).

Embodiment 5. The intramedullary implant (1) according to embodiment 4, wherein the medullar section (5) further comprises a third medullar part (10) extending from the second intermediate point (M2) in proximal direction (P) toward the proximal end (3), wherein the third medullar part (10) is configured for connection to a further prosthetic device.

Embodiment 6. The intramedullary implant (1) according to embodiment 4 or 5, wherein the first medullar part (7) comprises a course first bone engaging surface (11) and/or the second medullar part (8) comprises a course second bone engaging surface (12).

Embodiment 7. The intramedullary implant (1) according to embodiment 1, wherein the medullar section (5) comprises a first medullar zone (5a) with a first zone diameter (d2) extending from the insertion point (S) in proximal direction (P) and having a press length (Lp) along the main stem (2), and a second medullar zone (5b) extending from the first medullar zone (5a) in proximal direction (P) toward the distal end (3), wherein the second medullar zone (5b) has a second zone diameter (d3) extending from the first medullar zone (5a) in proximal direction (P) along at least a part of the main stem (2), and wherein the first zone diameter (d2) is larger than the second zone diameter (d3).

Embodiment 8. The intramedullary implant (1) according to embodiment 7, wherein the first zone diameter (d2) is substantially equal to the coupling diameter (d1).

Embodiment 9. The intramedullary implant (1) according to embodiment 7 or 8, wherein the second zone diameter (d3) tapers in the proximal direction (P).

Embodiment 10. The intramedullary implant (1) according to any of embodiments 7-9, wherein the medullar section (5) comprises a first medullar part (7) extending from the insertion point (S) in proximal direction (P) toward a first intermediate point (M1) along the main stem (2), and a second medullar part (8) extending from the first intermediate point (M1) in proximal direction (P) toward a second intermediate point (M2) along the main stem (2), wherein the second medullar part {8) comprises a circumferentially arranged surface pattern (9).

Embodiment 11. The intramedullary implant (1) according to embodiment 10, wherein the medullar section (5) further comprises a third medullar part (10) extending from the second intermediate point (M2) in proximal direction (P) toward the proximal end (3), wherein the third medullar part (10) is configured for connection to a further prosthetic device.

Embodiment 12. The intramedullary implant (1) according to embodiment 10 or 11, wherein the first medullar part (7) comprises a course first bone engaging surface (11) and/or the second medullar part (8) comprises a course second bone engaging surface (12).

Embodiment 13. The intramedullary implant (1) according to any of embodiments 1-12, wherein the coupling section (6) comprises a tissue engaging zone (6a) extending from the insertion point (8) in distal direction (D) and spanning at least in part the coupling section (6), and wherein the tissue engaging zone (6a) comprises a smooth surface coating.

Embodiment 14. The intramedullary implant (1) according to any of embodiments 1-13, wherein the coupling section (6) comprises one or more surface recesses (14, 15).

Embodiment 15. The intramedullary implant (1) according to any of embodiments 1-14, comprising a through bore (18) extending from the proximal end (3) and the distal end (4).

The present invention has been described above with reference to a number of exemplary embodiments as shown in the drawings.

Modifications and alternative implementations of some parts or elements are possible, and are included in the scope of protection as defined in the appended claims.

Claims

CONCLUSIONS

1. An intramedullary implant (1) for connection to a prosthetic device (E), comprising a main stem (2) with a proximal end (3) for insertion into a medullary cavity of a bone stump (B) and a distal end (4) for connection to the prosthetic device (E); wherein the main stem (2) comprises a medullary portion (5) extending from the proximal end (3) in a distal direction (D), and a coupling portion (6) extending from the distal end (4) in a proximal direction (P), the medullary portion (5) and the coupling portion (6) meeting at an insertion point (S) along the main stem (2) between the proximal end (3) and the distal end (4), the insertion point (S) defining a maximum insertion depth (D1) of the intramedullary implant (1) into the medullary cavity of the bone stump (B); and wherein the coupling portion (6) has a constant coupling diameter (d1) extending from the insertion point (S) to the distal end (4) and wherein the coupling portion (6) is configured to cooperate with the prosthetic device (E).

The intramedullary implant (1) according to claim 1, wherein the medullary portion (5) has a constant medullary diameter (d2) extending from the insertion point (S) in a proximal direction (P) along at least a portion of the main stem (2), and wherein the medullary diameter (d2) is substantially equal to the coupling diameter (d1).

The intramedullary implant (1) according to claim 1, wherein the medullary portion (5) has a medullary diameter (d2) extending from the insertion point (S) in a proximal direction (P) along at least a portion of the main stem (2), and wherein the medullary diameter (d2) tapers in the proximal direction (P).

The intramedullary implant (1) according to any one of claims 1 to 3, wherein the medullary portion (5) comprises a first medullary portion (7) extending from the insertion point (S) in a proximal direction (P) to a first intermediate point (M1) along the main stem (2), and a second medullary portion (8) extending from the first intermediate point (M1) in a proximal direction (P) to a second intermediate point (M2) along the main stem (2), the second medullary portion (8) comprising a circumferential surface pattern (9).

The intramedullary implant (1) of claim 4, wherein the medullary portion (5) further comprises a third medullary portion (10) extending from the second intermediate point (M2) in a proximal direction (P) toward the proximal end (3), the third medullary portion (10) being configured for connection to a further prosthetic device.

The intramedullary implant (1) according to claim 4 or 5, wherein the first medullary portion (7) comprises a coarse first bone engaging surface (11) and/or the second medullary portion (8) comprises a coarse second bone engaging surface (12).

The intramedullary implant (1) according to claim 1, wherein the medullary portion (5) comprises a first medullary zone (5a) having a first zone diameter (d2) extending from the insertion point (S) in a proximal direction (P) with a pressing length (Lp) along the main stem (2), and a second medullary zone (5b) extending from the first medullary zone (5a) in a proximal direction (P) towards the distal end (3), the second medullary zone (5b) having a second zone diameter (d3) extending from the first medullary zone (5a) in a proximal direction (P) along at least a portion of the main stem (2), and wherein the first zone diameter (d2) is larger than the second zone diameter (d3).

The intramedullary implant (1) according to claim 7, wherein the first zone diameter (d2) is substantially equal to the coupling diameter (d1).

The intramedullary implant (1) according to claim 7 or 8, wherein the second zone diameter (d3) tapers in the proximal direction (P).

The intramedullary implant (1) according to any of claims 7 to 9, wherein the medullary portion (5) comprises a first medullary portion (7) extending from the insertion point (S) in a proximal direction (P) to a first intermediate point (M1) along the main stem (2), and a second medullary portion (8) extending from the first intermediate point (M1) in a proximal direction (P) to a second intermediate point (M2) along the main stem (2), the second medullary portion (8) comprising a circumferential surface pattern (9).

The intramedullary implant (1) of claim 10, wherein the medullary portion (5) further comprises a third medullary portion (10) extending from the second intermediate point (M2) in a proximal direction (P) toward the proximal end (3), the third medullary portion (10) being configured for connection to a further prosthetic device.

The intramedullary implant (1) according to claim 10 or 11, wherein the first medullary portion (7) comprises a coarse first bone engaging surface (11) and/or the second medullary portion (8) comprises a coarse second bone engaging surface (12).

The intramedullary implant (1) according to any of claims 1 to 12, wherein the coupling portion (6) comprises a tissue engaging zone (6a) extending from the insertion point (S) in a distal direction (D) and at least partially spanning the coupling portion (6), and wherein the tissue engaging zone (6a) comprises a smooth surface coating.

The intramedullary implant (1) according to any of claims 1 to 13, wherein the coupling portion (6) comprises one or more surface recesses (14, 15).

The intramedullary implant (1) according to any one of claims 1 to 14, comprising a through bore (18) extending from the proximal end (3) and the distal end

(4).