3D printed prosthetic socket with reinforced distal end

Abstract

A 3D printed prosthetic socket with a reinforced distal end comprises a shell (1) formed by 3D printing using a method of material extrusion, wherein the shell (1) comprises a proximal end of the shell (1) with an opening for inserting a residual limb of a lower extremity and a distal end of the shell (1). The prosthetic socket further comprises a reinforcing member (2) fixed to the distal end of the shell (1) by means of a connecting interlayer (3), wherein the reinforcing member (2) comprises a hollow part (4) of the reinforcing member (2) surrounding the lateral wall of the distal end of the shell (1) on all sides.

Description

[0001] 3D Printed Prosthetic Socket with Reinforced Distal End

[0002] Technical Field

[0003] The present invention relates to a 3D printed prosthetic socket with a reinforced distal end. Specifically, the invention relates to a prosthetic socket with a shell formed by 3D printing using a method of material extrusion, which in practice has the problem of cracking in the distal end region.

[0004] Background of the Invention

[0005] In the current state of the art, methods of 3D printing based on the principle of material extrusion, such as, e.g., FDM (Fused Deposition Modeling), FFF (Fused Filament Fabrication), FGF (Fused Granulate Fabrication), or MEX (Material Extrusion), are used for fast and inexpensive production of prosthetic sockets. In these methods, the material, whether in the form of filament or pellets, is melted and deposited by a print head in layers. In the case of the so-called vase mode, the print head additionally moves around and prints continuously. In the field of prosthetics, these methods of 3D printing have been used only for the last few years, mainly due to the fact that prosthetic sockets produced in this way suffer from insufficient strength due to limited design possibilities. A critical area is particularly the distal end of the prosthetic socket, near which cracking often occurs due to load. Better mechanical properties are provided by high-quality 3D printing, e.g., using the MJF (Multi Jet Fusion) or SLS (Selective Laser Sintering) methods, which essentially do not suffer from the above-mentioned problem. These methods, however, are significantly more expensive compared to 3D printing using the method of material extrusion. The problem of cracking of the distal end in the case of inexpensive 3D printing is most often addressed by means of reinforcing ribs that are integrally formed in the region of the distal end of the prosthetic socket, as described, e.g., in the article Structural integrity of custom-designed additive manufactured prosthetic sockets compared to traditional sockets (Kim, S. et al., 2024). However, increasing the strength of the distal end by means of reinforcing ribs is not sufficient, and in some tests it has even been shown to potentially lead to even faster cracking.

[0006] Another known method consists in wrapping the distal end with a reinforcing tape, which only slightly increases the force at which the prosthetic socket cracks at the distal end, but even this solution is not sufficient.

[0007] There are also solutions in which the distal end of the prosthetic socket is reinforced by means of metal or composite rods that pass directly through the material of the socket, as described, e.g., in the patent document WO2024 / 168342 A2. To accommodate these rod reinforcements, it is therefore necessary to create channels in the distal end, which complicates and prolongs the production.

[0008] Therefore, it would be desirable to come up with a solution that would reliably prevent cracking of the distal end of the prosthetic socket formed inexpensively and quickly by 3D printing using the method of material extrusion.

[0009] Summary of the Invention

[0010] The shortcomings of the solutions known from the state of the art are eliminated to a certain extent by a 3D printed prosthetic socket with a reinforced distal end comprising a shell formed by 3D printing using a method of material extrusion, wherein the shell comprises a proximal end of the shell with an opening for inserting the residual limb of the lower extremity and a distal end of the shell. The essence of the 3D printed prosthetic socket according to the present invention lies in the fact that the prosthetic socket further comprises a reinforcing member fixed to the distal end of the shell by means of a connecting interlayer, wherein the reinforcing member comprises a hollow part of the reinforcing member surrounding the lateral wall of the distal end of the shell on all sides.

[0011] Thus, the reinforcement of the distal end of the 3D printed socket is implemented by fixing a separate reinforcing member to the distal end of the shell. Essentially, fixing the reinforcing member effectively increases the thickness of the prosthetic socket and increases the intralaminar strength by means of the connecting interlayer, which very effectively prevents cracking, delamination, fracture, or other structural failures of the shell. Simultaneously, it is not necessary to modify the design of the shell itself or interfere with its production in any way. In addition, the reinforcing member itself can be produced serially as a standardized component for the given shell.

[0012] The production of the shell of the prosthetic socket is performed by one of the well- known, fast, and inexpensive 3D printing methods based on the principle of material extrusion, such as, e.g., FDM, FFF, FGF, or MEX. 3D printing is preferably customized based on a digital model of the prosthetic socket that is created based on a model of the residual limb of the specific user. The model of the residual limb may be acquired, e.g., based on a 3D scan of the residual limb, a 3D scan of a physical cast of the residual limb, or measurements of the residual limb.

[0013] The reinforcing member may be implemented in various shapes, as long as it comprises at least the hollow part surrounding the lateral wall of the distal end of the shell on all sides. The specific shape of the reinforcing member can thus be designed with respect to the shape of the shell, specifically such that the inner wall of the hollow part of the reinforcing member follows the outer shape of the distal end of the shell. The distal end of the shell means not only the distal edge of the shell but the wider region located in the vicinity of this distal edge. The region of the distal end of the shell (or also the prosthetic socket, since the shell is a basic component thereof) also includes a part of the shell in which the shell begins to gradually widen at a certain distance from the distal edge and the cylindrical shape of the shell becomes essentially conical. The reinforcing member may also have different heights depending on how large a region of the distal end of the shell it is desired to reinforce.

[0014] In addition to the hollow part that surrounds the distal end of the shell, the reinforcing member may also comprise other parts, e.g., a connecting part adapted for connecting a modular coupling adapter, as will be further described below. Some of the preferred shapes of the hollow part of the reinforcing member, whether or not this hollow part forms the whole reinforcing member, are described below. These shapes can be combined where possible.

[0015] Preferably, the hollow part of the reinforcing member has the shape of a hollow cylinder. This shape is the simplest to produce, wherein it also requires little material, as even a relatively small thickness of the wall of this hollow cylinder is sufficient to reinforce the distal end of the shell. The thickness of the wall of the hollow cylinder is preferably selected from the range of 1 to 10 mm, more preferably 2 to 5 mm.

[0016] However, the thickness of the hollow part of the reinforcing member wall does not have to be constant throughout the height.

[0017] Preferably the thickness of the wall of the hollow part of the reinforcing member increases gradually from the proximal end of the reinforcing member to the distal end of the reinforcing member. This allows an even higher strength to be achieved directly at the distal edge of the shell. The gradual increase of the wall thickness of the hollow part of the reinforcing member may be implemented in different ways. The thickness may increase, e.g., linearly, which means that the outer wall of the hollow part of the reinforcing member is straight but inclined with respect to the inner wall of the hollow part of the reinforcing member. Alternatively, however, the thickness may increase non-linearly and the outer wall of the hollow part of the reinforcing member may be curved.

[0018] Preferably, the inner diameter of the hollow part of the reinforcing member increases gradually from the distal end of the reinforcing member to the proximal end of the reinforcing member and follows the outer shape of the shell. Thus, this design of the reinforcing member makes it possible to accommodate the widening of the distal end of the shell at a certain distance from the distal edge of the shell and provide a hollow part of the reinforcing member that increases the strength in a larger region of the distal end of the prosthetic socket, not just in the immediate vicinity of the distal edge of the shell. The hollow part of the reinforcing member may have a constant thickness of the wall along the entire height, or this thickness may vary, e.g., it may increase from the proximal end of the reinforcing member to the distal end of the reinforcing member.

[0019] The proximal edge of the hollow part of the reinforcing member is preferably chamfered on the inner side. This chamfering results in a higher strength of the connection provided by the connecting interlayer and prevents the connecting interlayer from peeling between the proximal edge of the reinforcing member and the shell. In this way, the proximal edge of the reinforcing member may be chamfered, regardless of the shape it is implemented in, e.g., in any of the shapes described in the exemplary embodiments and shown in the figures.

[0020] The distal end of the hollow part of the reinforcing member preferably comprises a bottom. Openings may be created in this bottom for the connection of the adapter of the socket, to which the modular coupling adapter may subsequently be attached. The adapter of the socket does not need to be attached directly to the lower wall of the shell. Preferably, through openings are formed in the bottom that pass through both the bottom of the reinforcing member and the base of the shell.

[0021] The reinforcing member further preferably comprises a connecting part of the reinforcing member adapted for connection of the modular coupling adapter. This adaptation may consist, e.g., in the fact that the connecting part comprises a connecting plate integrated into the reinforcing member. This connecting plate comprises openings for the connection of the adapter of the socket, to which the modular coupling adapter is subsequently attached. The connection of the connecting plate, the adapter of the socket and the modular coupling adapter may be provided, e.g., by means of bolts, nuts, threaded inserts or other connecting elements. To form the complete prosthesis of the lower extremity, a modular tubular adapter is then connected to the distal end of the modular coupling adapter. It replaces the long bones of the lower extremity and a prosthetic foot is connected to its distal end.

[0022] In other embodiments of the reinforcing member, e.g., in the form of a hollow cylinder, the adapter of the socket may be attached directly to the lower wall of the shell.

[0023] The connecting part of the reinforcing member preferably lies outside the neutral axis of the prosthetic socket, which allows the adapter of the socket to be offset relative to the neutral axis of the prosthetic socket. This offset may mean either translation or rotation relative to the neutral axis of the prosthetic socket, or a combination of both, to achieve the arrangement that is most suitable for the patient. The neutral axis of the prosthetic socket means the vertical axis of the prosthetic socket, which is the line connecting the center of the cross-section of the proximal part of the socket, wherein this cross-section is formed by a horizontal plane passing through the center of the patellar ligament and the center of the cross-section of the distal end of the socket, wherein this cross-section is formed by a horizontal plane passing at a minimum height from the distal edge of the socket.

[0024] The connecting interlayer is preferably an adhesive layer or a laminating resin layer. These materials are widely available and easy to apply. Preferably, e.g., a quicksetting adhesive can be used that is compatible with both the material of the shell and of the reinforcing member and that, after setting, strengthens the distal end of the shell together with the reinforcing member. Alternatively, another material can be used for the connecting interlayer as long as it provides a reliable connection between the two separate components, i.e., the shell and the reinforcing member. To ensure a good mechanical bond between the reinforcing member and the connecting interlayer, it is also possible to modify the inner wall of the reinforcing member, specifically its hollow part surrounding the lateral wall of the distal end of the shell on all sides. The inner wall of the hollow part of the reinforcing member may be smooth but alternatively may comprise, e.g., a thread, circumferential grooves (recesses), a grid, through openings, etc.

[0025] The reinforcing member is preferably 3D printed. Therefore, similarly to the shell, it may be produced, e.g., by a fast and inexpensive method of material extrusion. Both the shell and the reinforcing member may thus also be printed in a single printing process, which saves time. In the case of printing in the vase mode, however, such combined printing is not possible. However, even with combined printing, the reinforcing member still represents a separate component that is not formed integrally with the shell and that is only subsequently attached to the shell by means of the connecting interlayer. The reinforcing member is preferably made of plastic, but alternatively it may also be made of another material, e.g., metal or composite, and by a production method other than 3D printing, e.g., injection molding, casting, machining, etc.

[0026] Description of Drawings

[0027] A summary of the invention is further clarified using exemplary embodiments thereof, which are described with reference to the accompanying drawings, in which: fig. 1 shows a 3D printed prosthetic socket in the first exemplary embodiment according to the present invention with the reinforcing member shown in section separate from the shell, fig. 2 shows the 3D printed prosthetic socket in the first exemplary embodiment according to the present invention in section with the reinforcing member fixed to the distal end of the shell, fig. 3 shows the 3D printed prosthetic socket in the first exemplary embodiment according to the present invention with the reinforcing member fixed to the distal end of the shell, fig. 4 shows the 3D printed prosthetic socket in the second exemplary embodiment according to the present invention with the reinforcing member shown in section separate from the shell, fig. 5 shows the 3D printed prosthetic socket in the third exemplary embodiment according to the present invention with the reinforcing member shown in section separate from the shell, fig. 6 shows the 3D printed prosthetic socket in the fourth exemplary embodiment according to the present invention with the reinforcing member shown in section separate from the shell, and fig. 7 shows a transtibial prosthesis comprising the 3D printed prosthetic socket in the fifth exemplary embodiment according to the present invention with the reinforcing member shown in section separate from the shell.

[0028] Exemplary Embodiments of the Invention

[0029] The invention will be further clarified using exemplary embodiments with reference to the respective drawings.

[0030] Example 1 : In the first exemplary embodiment according to fig. 1 to fig. 3, the 3D printed prosthetic socket comprises a 3D printed shell 1_, a reinforcing member 2, and a connecting interlayer 3 for fixing the reinforcing member 2 to the shell 1_.

[0031] For example, the shell 1. is produced from a plastic material by 3D printing using a method of material extrusion, e.g., using the FDM method. Specifically, first a horizontal base is printed using the conventional mode, and then the so-called vase mode is used to print a circumferential part of the shell 1_, in which the print head moves around and prints continuously. The 3D printing is performed based on a digital model of the prosthetic socket that is created based on a model of the residual limb of the specific user. For example, the model of the residual limb is acquired based on a 3D scan of the residual limb, a 3D scan of a physical cast of the residual limb, or measurements of the residual limb. Said method is known in the state of the art and allows the 3D printed prosthetic socket to be custom-produced for the specific user.

[0032] The shell 1_ formed in this way comprises a proximal end of the shell 1_ with an opening for inserting the residual limb of the lower extremity and also a distal end of the shell 1_, which is adapted for connection of a modular coupling adapter 8. This adaptation consist, for example, in the fact that an adapter of the socket is attached to the lower wall of the shell 1_, to which the modular coupling adapter 8 is subsequently attached. For example, the adapter of the socket is fixed in openings formed in the base of the shell 1_. However, neither the adapter of the socket nor the modular coupling adapter 8 are shown in fig. 1 to fig. 3 (nor in fig. 4 to fig. 6, which refer to other exemplary embodiments) for the sake of clarity. They are components known and conventionally used in the state of the art.

[0033] The reinforcing member 2 is fixed to the distal end of the shell 1., which is formed in the shape of a hollow thin-walled cylinder, which means that it is entirely formed by a hollow part 4 of the reinforcing member 2. The inner diameter of the hollow part 4 of the reinforcing member 2 corresponds to the outer diameter of the distal end of the shell 1_, or is slightly larger to allow the hollow part 4 of the reinforcing member 2 to be slid onto the distal end of the shell 1. over the connecting interlayer 3. For example, the connecting interlayer 3 is an adhesive layer by which the reinforcing member 2 is bonded to the distal end of the shell 1_. Therefore, it is clear that the distal end of the shell 1_ also has a cylindrical shape to allow the cylindrical hollow part 4 of the reinforcing member 2 to be slid on. However, especially in fig. 1 or fig. 2, it can be seen that the cylindrical shape is only maintained at the distal end of the shell 1. up to a certain distance from the distal edge of the shell 1_, specifically in the region of the horizontal base printed using the conventional mode and the cylindrical circumferential part composed of only the lateral wall printed using the vase mode. Then, however, the shell 1. begins to gradually widen to provide sufficient space for the accommodation of the residual limb. With respect to this widening, the height of the hollow part 4 of the reinforcing member 2 is chosen, i.e. , the dimension from the distal edge of the hollow part 4 of the reinforcing member 2 to the proximal edge of the hollow part 4 of the reinforcing member 2. The height of the hollow part 4 of the reinforcing member 2 is chosen, for example, such that the hollow part 4 of the reinforcing member 2 surrounds in particular the cylindrical circumferential part composed of only the lateral wall, as can be seen in fig. 2.

[0034] It is further apparent from fig. 1 to fig. 2 that in this exemplary embodiment, the proximal edge of the hollow part 4 of the reinforcing member 2 is chamfered from the inner side. This chamfering 5, which is best seen in detail in fig. 1 , results in a higher strength of the bonded connection at the proximal end of the reinforcing member 2 by means of the connecting interlayer 3 In fig. 3, it is most clearly visible that the hollow part 4 of the reinforcing member 2 surrounds the lateral wall of the distal end of the shell 1. on all sides, resulting in the desired increase in strength and elimination of cracking, fracture, delamination, or other structural failures of the distal end of the shell 1_.

[0035] Fig. 1 also shows that the reinforcing member 2 represents a separately produced component that is attached to the shell 1. only subsequently. For example, the reinforcing member 2 is made of a plastic material, e.g., by 3D printing using a method of material extrusion, in the same way like the shell 1_.

[0036] Example 2:

[0037] The second exemplary embodiment differs from the first exemplary embodiment only in the design of the reinforcing member 2.

[0038] As shown in fig. 4, in this embodiment, the thickness of the wall of the hollow part 4 of the reinforcing member 2 gradually increases from the proximal end of the reinforcing member 2 to the distal end of the reinforcing member 2. Specifically, this gradual increase in the thickness of the wall is implemented such that the outer wall of the hollow part 4 of the reinforcing member 2 is inclined relative to the inner wall of the hollow part 4 of the reinforcing member. In other words, it can be said that the outer wall of the hollow part 4 of the reinforcing member 2 has a conical shape, while the inner wall of the hollow part 4 of the reinforcing member 2 has a cylindrical shape. This increase in thickness provides the reinforcing member 2 with even greater strength of the distal end of the prosthetic socket, especially in the immediate vicinity of the distal edge of the shell 1_.

[0039] Example 3:

[0040] The third exemplary embodiment differs from the first exemplary embodiment only in the design of the reinforcing member 2.

[0041] As shown in fig. 5, the inner diameter of the hollow part 4 of the reinforcing member 2 gradually increases from the distal end of the reinforcing member 2 to the proximal end of the reinforcing member 2. Specifically, this gradual increase of the inner diameter is implemented such that the reinforcing member 2 follows the outer shape of the shell 1. along its entire height. Therefore, the hollow part 4 of the reinforcing member 2 begins to widen at a certain distance from the distal end just like the shell 1_ widens at a certain distance from the distal edge. As in the first exemplary embodiment (and unlike the second exemplary embodiment), the hollow part 4 of the reinforcing member 2 also has a constant thickness of the wall. The reinforcing member 2 according to this third exemplary embodiment is higher than the horizontal base of the shell 1_, and thus provides higher strength in a larger region of the distal end, not only in the immediate vicinity of the distal edge of the shell 1_ but also further away from it, e.g., in the region where the shell 1. begins to widen.

[0042] Example 4:

[0043] The fourth exemplary embodiment differs from the first exemplary embodiment mainly in the design of the reinforcing member 2.

[0044] As can be seen in fig. 6, the difference from the first exemplary embodiment lies in the fact that the distal end of the hollow part 4 of the reinforcing member 2 comprises a bottom 6. Therefore, the reinforcing member 2 has the shape of a thin-walled cylinder, which is, however, open only at the proximal end while its distal end is closed by said bottom 6. In this bottom 6, openings are formed for fixing the adapter of the socket, to which the modular coupling adapter 8 is subsequently attached.

[0045] Example 5: The fifth exemplary embodiment is a modification of the fourth exemplary embodiment, from which it differs in the design of the reinforcing member 2.

[0046] As can be seen in fig. 7, the difference from the fourth exemplary embodiment and from the other described examples lies in the fact that the reinforcing member 2 according to the fifth exemplary embodiment is not entirely composed of only the hollow part 4 of the reinforcing member 2. In addition to the hollow part 4 of the reinforcing member 2, the reinforcing member 2 further comprises a connecting part 7 of the reinforcing member 2, which extends from the lateral side of the hollow part 4 of the reinforcing member 2, specifically from the lateral side of its bottom 6. For this purpose, the bottom 6 is higher than in the fourth exemplary embodiment. The connecting part 7 is implemented as a connecting plate integrated directly into the reinforcing member 2, wherein the adapter of the socket is attached to this connecting plate (not shown in the simplified drawing according to fig. 7). Subsequently, the modular coupling adapter 8 is attached to the adapter of the socket.

[0047] Further, a modular tubular adapter 9 is attached to the distal end of the modular coupling adapter s, i.e., an elongated member that replaces the long bones of the missing extremity and that connects the modular coupling adapter 8 to a prosthetic foot 10 fixed at the distal end of the modular tubular adapter 9. This creates the whole prosthesis of the lower extremity, for example a transtibial prosthesis or a transfemoral prosthesis.

[0048] As can also be seen in fig. 7, the connecting part 7 of the reinforcing member lies outside the neutral axis 11 of the prosthetic socket. In other words, an offset and rotation of the adapter of the socket, and thus also of the modular coupling adapter 8 relative to the neutral axis 11 of the prosthetic socket is achieved.

[0049] Further, the 3D printed prosthetic socket according to the present invention may be implemented in many other alternative embodiments, which arise, e.g., from the alternatives mentioned in the section "Summary of the Invention".

[0050] In one alternative exemplary embodiment, e.g., the reinforcing member 2 is implemented such that the inner diameter of the hollow part 4 of the reinforcing member 2 gradually increases from the distal end of the reinforcing member 2 to the proximal end of the reinforcing member 2, and simultaneously the thickness of the wall of the hollow part 4 of the reinforcing member 2 gradually increases from the proximal end of the reinforcing member 2 to the distal end of the reinforcing member 2. In another alternative exemplary embodiment, the inner wall of the hollow part 4 of the reinforcing member 2 is not smooth but comprises a thread, circumferential grooves (recesses), a grid, through openings, or any combination of these elements.

[0051] In another alternative exemplary embodiment, the connecting interlayer 3 is a laminating resin layer.

[0052] In another alternative exemplary embodiment, the reinforcing member is made of metal.

[0053] In another alternative exemplary embodiment, the reinforcing member is made of a composite material. Industrial Applicability

[0054] The 3D printed prosthetic socket described above can be used as part of a transtibial or transfemoral prosthesis for a patient with a lower extremity amputation.

[0055] List of Reference Signs

[0056] 1 - shell

[0057] 2 - reinforcing member

[0058] 3 - connecting interlayer

[0059] 4 - hollow part of the reinforcing member

[0060] 5 - chamfering

[0061] 6 - bottom

[0062] 7 - connecting part of the reinforcing member

[0063] 8 - modular coupling adapter

[0064] 9 - modular tubular adapter

[0065] 10 - prosthetic foot

[0066] 11 - neutral axis of the prosthetic socket

Claims

CLAIMS1. A 3D printed prosthetic socket with a reinforced distal end comprising a shell (1 ) formed by 3D printing using a method of material extrusion, wherein the shell (1 ) comprises a proximal end of the shell (1 ) with an opening for inserting a residual limb of a lower extremity and a distal end of the shell (1 ), characterized in that the prosthetic socket further comprises a reinforcing member (2) fixed to the distal end of the shell (1 ) by means of a connecting interlayer (3), wherein the reinforcing member (2) comprises a hollow part (4) of the reinforcing member (2) surrounding the lateral wall of the distal end of the shell (1 ) on all sides.

2. The 3D printed prosthetic socket according to claim 1 , characterized in that the hollow part (4) of the reinforcing member (2) has the shape of a hollow cylinder.

3. The 3D printed prosthetic socket according to claim 1 , characterized in that the thickness of the hollow part (4) of the reinforcing member (2) gradually increases from the proximal end of the reinforcing member (2) to the distal end of the reinforcing member (2).

4. The 3D printed prosthetic socket according to any one of claims 1 or 3, characterized in that the inner diameter of the hollow part (4) of the reinforcing member (2) gradually increases from the distal end of the reinforcing member (2) to the proximal end of the reinforcing member (2) and follows the outer shape of the shell (1 ).

5. The 3D printed prosthetic socket according to any one of the preceding claims, characterized in that the proximal edge of the hollow part (4) of the reinforcing member (2) is chamfered from the inner side.

6. The 3D printed prosthetic socket according to any one of the preceding claims, characterized in that the distal end of the hollow part (4) of the reinforcing member (2) comprises a bottom (6).

7. The 3D printed prosthetic socket according to any one of the preceding claims, characterized in that the reinforcing member (2) further comprises a connectingpart (7) of the reinforcing member (2) adapted for connection of a modular coupling adapter (8).

8. The 3D printed prosthetic socket according to claim 7, characterized in that the connecting part (7) of the reinforcing member (2) lies outside the neutral axis (11 ) of the prosthetic socket.

9. The 3D printed prosthetic socket according to any one of the preceding claims, characterized in that the connecting interlayer (3) is an adhesive layer, or a laminating resin layer.

10. The 3D printed prosthetic socket according to any one of the preceding claims, characterized in that the reinforcing member (2) is 3D printed.

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