WO2020127353A1

WO2020127353A1 - A prosthesis

Info

Publication number: WO2020127353A1
Application number: PCT/EP2019/085761
Authority: WO
Inventors: Thangaramanujam MUTHUKUMARAN
Original assignee: University College Dublin, National University Of Ireland, Dublin
Priority date: 2018-12-18
Filing date: 2019-12-17
Publication date: 2020-06-25
Also published as: GB201820599D0

Abstract

A foot prosthesis comprising an artificial foot (1) having a mid-foot portion (8). The mid-foot portion has a mid-foot flexion region (9) having bendability greater than bendability of portions of the artificial foot (1) adjacent the mid-foot flexion region (9). The mid-foot flexion region (9) comprises a cavity (17) formed in the mid-foot portion (8) to provide for the flexing ability of the mid-foot flexion region (9).

Description

A PROSTHESIS

Field of the Invention

The present invention relates to a prosthesis, more specifically a foot prosthesis.

Background to the Invention

A foot prosthesis is an artificial foot which replaces a missing or damaged foot. A foot prosthesis can be provided and used on its own, but more often it is utilised as a unit with a below-knee leg prosthesis. The latter typically includes a pylon, the part replacing the shin bones and a socket, the part that is coupled with the leg stump. Numerous designs of artificial feet have been developed so far that provide increased mobility and functionality. Some are made of moulded plastics and resemble a real foot in an attempt to aestheticise the appearance of the prosthesis. Some include intricately arranged energy store and release springs intended to reduce energy expenditure of the patient during walking and reduce the risk of consequential secondary disabilities or diseases. However, disadvantages are still associated with nearly all existing designs, such as, for example high manufacturing cost, high weight, lack of comfort, patient fatigue, and lack of patient- specific manufacturing of prosthetic foot.

In view of the above, it is an object of the present invention to alleviate and mitigate the above disadvantages.

Summary of the Invention

According to a first aspect, the present invention provides a foot prosthesis comprising: an artificial foot having a mid-foot portion, wherein

the mid-foot portion has a mid-foot flexion region said mid-foot flexion region having bendability greater than bendability of portions of the artificial foot adjacent the mid-foot flexion region.

The combination of the material of the artificial foot and the provision of the said mid-foot flexion region render the mid-foot portion of the artificial foot resiliently deformable in the mid-foot flexion region so that the artificial foot can sequentially flex and return into a non- flexed state during walking, akin the user’s existing foot or a comparable human foot. This is known as energy store and return (ESAR) functionality. ESAR functionality has been shown to provide for a reduced step-to-step transition effort, higher mechanical push-off power, extended forward progression of the centre of pressure under the artificial foot and greater overall user comfort.

The material of the artificial foot is preferably one that deforms under stress and returns to its original shape.

In a preferred arrangement, the mid-foot flexion region is located inside the artificial foot. Preferably, the mid-foot flexion region is completely contained inside the artificial foot. Preferably, a layer of artificial foot material is present between the outer surface of the artificial foot and the mid-foot flexion region.

The shape of the mid-foot flexion region may be similar to a segment of the outer contour of the mid-foot portion. Preferably, the shape of the mid-foot flexion region is defined by copying and inwardly offsetting a segment of the outer contour of the mid-foot portion. Accordingly, the shape of the mid-foot flexion region is preferably a scaled down copy of a segment of the outer contour of the of the mid-foot portion. The scale factor for the mid foot flexion region could be 75% of the original size or another clinically relevant size. In other words, the mid-foot flexion region has a shape that repeats the outer surface of a segment of the mid-foot portion but is scaled down to be located inside the mid-foot portion. Such a shape is believed to facilitate optimal flexing of the flexion region in that areas of under- or over-flexing are minimised or avoided. It will be appreciated that the invention is not limited to such particular shape and other shapes of the mid-foot flexion region are indeed envisaged as will be understood by those skilled in the art.

In one arrangement, the mid-foot flexion region is provided by forming a cavity in the mid foot portion of the artificial foot to provide for the flexing ability. The mid-foot flexion region may include material having reduced density or rigidity compared to that of material adjacent the mid-foot flexion region to provide for the flexing ability. The provision of cavity and material having reduced density or rigidity can be used separately or in combination.

In a preferred arrangement, the mid-foot portion corresponds anatomically to the Lisfranc joint zone of a human foot.

Preferably, the artificial foot has the appearance similar to that of an intact real foot, such as, for example, a generic human foot, i.e. it has an outer surface substantially emulating the outer surface of an intact foot. In a preferred arrangement, the artificial foot has an outer surface that is a mirror image of the user’s intact foot. Preferably, the outer surface of the artificial foot is formed by 3D scanning the intact foot, creating a virtual mirror image of the intact foot and making the artificial foot based on the virtual mirror image. In a preferred arrangement, the artificial foot is made by using a rapid prototyping technique, such as, for example, printing on a 3D printer from a 3D image file. Rapid prototyping enables quick and inexpensive fabrication and facilitates speedy re-making of the artificial foot to replace an existing artificial foot which requires replacement or to adjust to the patient’s requirements.

Preferred materials for the artificial foot include plastics, more preferably thermoplastic elastomers (TPEs), a highly versatile elastomer with a wide range of properties that offer superior performance, flexibility and durability. The advantage of using TPE is that it’s hardness or softness can be selected as needed, e.g. as soft as rubber or as hard as rigid plastics. Another advantage is that TPEs are suitable for rapid prototyping, e.g. 3D printing. Furthermore, TPEs allow the overall weight of the foot prosthesis to be reduced compared with existing metal or hard plastics models. In the present invention, the following TPEs have been found to provide the required performance:

FilaFlex™ - for artificial foot which requires greater flexibility

NinjaFlex™ - for artificial foot which requires medium flexibility

CheetahFlex™ - for artificial foot which requires reduced flexibility, i.e. greater rigidity

With CheetahFlex™ all types of artificial feet can be additively manufactured by varying 3D printing parameters, such as infill percentage, and foot design optimisation as needed.

The choice of the degree of flexibility of above materials is for the most part dictated by the individual user’s requirements, usually after testing a pilot artificial foot. Upon the user determining their requirements, a new artificial foot in accordance with the invention can be readily fabricated with the necessary adjustments.

With a similar foot design, a generic foot can be also manufactured with various sizes, flexibility, and configurations, such as commercially available generic prosthetic feet.

It further should be noted that flexibility/rigidity of the artificial foot in the mid-foot flexion region is determined, in addition to the material of the artificial foot, by the size and shape of the mid-foot flexion region. For example, a larger mid-foot flexion region affords greater flexibility and, conversely, a smaller mid-foot flexion region affords greater rigidity. Thus, upon the user testing a pilot artificial foot, the size and shape of the mid-foot flexion region can be altered to adjust flexibility, and a new artificial foot in accordance with the invention can be readily fabricated with the necessary adjustments.

Preferably, the artificial foot comprises a coupling arrangement for fastening the artificial foot to a pylon of an artificial leg. The coupling arrangement may comprise a receiver interface for coupling with a pyramid joiner interface. The coupling arrangement is designed and/or can be made compatible with the relevant prosthetic joiner mechanism such as the pyramid joiner, which would allow the foot prosthesis to be attached with a pylon or prosthetic socket.

The coupling arrangement is preferably fabricated together with the artificial foot, preferably, using a rapid prototyping technique, such as 3D printing. The coupling arrangement is preferably integrally formed with the artificial foot.

Optionally, the artificial foot may be provided with a calcaneal flexion region in a calcaneal portion of the artificial foot, said calcaneal flexion region having deformability greater than deformability of portions of the artificial foot adjacent the calcaneal flexion region.

In a preferred arrangement, the calcaneal flexion region is located inside the artificial foot. Preferably, the calcaneal flexion region is completely contained inside the artificial foot. Preferably, a layer of artificial foot material is present between the outer surface of the artificial foot and the calcaneal flexion region.

The shape of the calcaneal flexion region may be similar to a segment of the outer contour of the calcaneal portion. Preferably, the shape of the calcaneal flexion region is defined by copying and inwardly offsetting a segment of the outer contour of the calcaneal portion. Accordingly, the shape of the calcaneal flexion region is preferably a scaled down copy of a segment of the outer contour of the of the calcaneal portion. The scale factor for the calcaneal flexion region could be 75% of the original size or another clinically relevant size. In other words, the calcaneal flexion region has a shape that repeats the outer surface of a segment of the calcaneal portion but is scaled down to be located inside the calcaneal portion. Such a shape is believed to facilitate optimal flexing of the calcaneal flexion region in that areas of under- or over-flexing are minimised or avoided. It will be appreciated that the invention is not limited to such particular shape and other shapes of the calcaneal flexion region are indeed envisaged as will be understood by those skilled in the art. In one arrangement, the calcaneal flexion region is provided by forming a cavity in the calcaneal portion of the artificial foot to provide for the deforming ability. The calcaneal flexion region may include material having reduced density or rigidity compared to that of material adjacent the calcaneal flexion region to provide for the deforming ability. The provision of cavity and material having reduced density or rigidity can be used separately or in combination.

According to a second aspect, the invention provides a method of making a foot prosthesis, the method comprising the steps of:

forming an artificial foot having a mid-foot portion, wherein

providing the mid-foot portion with a mid-foot flexion region said mid-foot flexion region having bendability greater than bendability of portions of the artificial foot adjacent the mid-foot flexion region.

Preferably, the method comprises the step of providing the mid-foot flexion region with a shape similar to a segment of the outer contour of the mid-foot portion. Preferably, the method comprises the step of defining the shape of the mid-foot flexion region by copying and inwardly offsetting a segment of the outer contour of the mid-foot portion.

Preferably, the method comprises the step of forming a cavity in the mid-foot portion of the artificial foot to provide the mid-foot flexion region. The mid-foot flexion region may be provided using material having reduced density or rigidity compared to that of material adjacent the mid-foot flexion region.

Preferably, the method comprises the step of providing an outer surface of the artificial foot as a mirror image of the user’s intact foot. The method may include, forming the outer surface of the artificial foot by 3D scanning the intact foot, creating a virtual mirror image of the intact foot and making the artificial foot based on the virtual mirror image. The method preferably includes fabricating the artificial foot using a rapid prototyping technique, such as, for example, printing on a 3D printer from a 3D image file.

Optionally, the method comprises the step of providing the artificial foot with a calcaneal flexion region in a calcaneal portion of the artificial foot, said calcaneal flexion region having deformability greater than deformability of portions of the artificial foot adjacent the calcaneal flexion region. Preferably, the method comprises the step of providing the shape of the calcaneal flexion region similar to a segment of the outer contour of the calcaneal portion. Preferably, the method comprises the step of defining the shape of the calcaneal flexion region by copying and inwardly offsetting a segment of the outer contour of the calcaneal portion.

Preferably, the method comprises the step of forming a cavity in the calcaneal portion of the artificial foot. The calcaneal flexion region may be provided using material having reduced density or rigidity compared to that of material adjacent the calcaneal flexion region.

Features of the first aspect of the invention can be incorporated into the second aspect of the invention as appropriate and vice versa.

Detailed Description of the Invention

The invention will now be described with reference to the accompanying drawings, which show, by way of example only, an embodiment of the invention. In the drawings:

Figure 1 is a virtual 3D model M1 of the artificial foot of the invention;

Figure 2 is a virtual 3D model M2 of a segment of a mid-foot portion of the model M1 ;

Figure 3 is a further virtual model M3 formed by subtracting scaled down version of M2 from M1 ;

Figure 4 shows an intact foot being scanned by a 3D scanner;

Figure 5 shows a virtual 3D model M1 of the artificial foot of the invention being created by flipping the scanned image of the intact foot;

Figure 6 shows a prior art foot prosthesis attached to a pylon via a conventional pyramidal joiner interface;

Figure 7 is the model M3 of Figure 3 aligned with a model R1 of a pyramidal joiner interface;

Figure 8 is a virtual 3D model R2 of a receiver interface;

Figure 9 is the model M3 of Figure 7 aligned with the model R1 of a pyramidal joiner interface and the model R2 of a receiver interface;

Figure 10 is a virtual 3D model M4 of a complete artificial foot of the invention;

Figure 11 is the model M3 of Figure 3 aligned with a model R1 of a pyramidal joiner interface and a virtual 3D model of a scaled down segment of a calcaneal portion of the model M1 ; and

Figure 12 shows an artificial foot of the invention assembled with a pylon and socket to form a leg prosthesis. Referring to Figures 1 to 12, a foot prosthesis of the present invention and a method of making thereof will be jointly described. A finished artificial foot 1 of the invention assembled with a pylon 3 and socket 5 to form a leg prosthesis 7 are shown in Figure 12. Figures 1 to 11 show 3D models of the artificial foot of the invention at various stages of modelling.

In its broadest sense, as shown in Figures 3, 7, 9, 10 and 12, the present invention provides a foot prosthesis comprising an artificial foot 1 having a mid-foot portion 8, the mid-foot portion 8 having a mid-foot flexion region 9, the mid-foot flexion region 9 having bendability greater than that of portions of the artificial foot 1 adjacent the mid-foot flexion region 9.

The material of the artificial foot 1 is preferably one that deforms under stress and returns to its original shape.

In the present embodiment, the mid-foot flexion region 9 is provided by forming a cavity 17 in the mid-foot portion 8 of the artificial foot. In other embodiments, the mid-foot flexion region 9 may be provided using material having reduced density or rigidity compared to that of material adjacent the mid-foot flexion region 9. The cavity 17 and material having reduced density or rigidity can be used separately or in combination to provide for the required flexion.

In the present embodiment, the mid-foot portion 8 corresponds anatomically to the Lisfranc joint zone of a human foot.

The combination of the material of the artificial foot 1 and the provision of the said mid-foot flexion region 9 render the mid-foot portion 8 of the artificial foot 1 resiliently deformable in the mid-foot flexion region 9 so that the artificial foot 1 can sequentially flex and return into a non-flexed state during walking, akin the user’s good foot. This is known as energy store and return (ESAR) functionality. ESAR functionality has been shown to provide for a reduced step-to-step transition effort, higher mechanical push-off power, extended forward progression of the centre of pressure under the artificial foot and greater overall user comfort.

The mid-foot flexion region 9 is located inside the artificial foot 1 and completely contained therein so that a layer of artificial foot material is present between the outer surface 11 of the artificial foot 1 and the mid-foot flexion region 9.

The shape of the mid-foot flexion region 9 is similar to a segment 15 of the outer contour of the mid-foot portion 8. In the present embodiment, the shape of the mid-foot flexion region 9 is obtained by copying and inwardly offsetting the segment 15 of the outer contour of the mid-foot portion 8 (Figures 3, 7, 9). Thus, the shape of the mid-foot flexion region 8 is a scaled down copy of a segment 15 of the outer contour of the of the mid-foot portion 8. The scale factor for the mid-foot flexion region 9 could be 75% of the original size or another clinically relevant size. In other words, the mid-foot flexion region 9 has a shape that repeats the outer surface of a segment 15 of the mid-foot portion 8 but is scaled down to be located inside the mid-foot portion 8. Such a shape is believed to facilitate optimal flexing of the mid-foot flexion region 9 in that areas of under- or over-flexing are minimised or avoided. It will be appreciated that the invention is not limited to such particular shape and other shapes of the mid-foot flexion region 9 are indeed envisaged as will be understood by those skilled in the art.

In the present embodiment, the outer surface the artificial foot 1 is a mirror image of the user’s intact foot 45. The outer surface 11 of the artificial foot 1 is formed by 3D scanning the intact foot 45, creating a virtual mirror image MO of the intact foot (see Figures 4 and 5) and making the artificial foot based on the virtual mirror image MO. In the present embodiment, the artificial foot 1 is made by using a rapid prototyping technique, such as, for example, printing on a 3D printer from a 3D image file. Rapid prototyping enables quick and inexpensive fabrication and facilitates speedy re-making of the artificial foot 1 to replace an existing artificial foot which requires replacement or to adjust to the patient’s requirements.

The material of the artificial foot 1 is preferably one that deforms under stress and returns to its original shape. Preferred materials for the artificial foot 1 include plastics, more preferably thermoplastic elastomers (TPEs), highly versatile elastomers with a wide range of properties that offer superior performance, flexibility and durability. The advantage of using TPEs is that it’s hardness or softness can be selected as needed, e.g. as soft as rubber or as hard as rigid plastics. Another advantage is that TPEs are suitable for rapid prototyping, e.g. 3D printing. Furthermore, TPEs allow the overall weight of the foot prosthesis to be reduced compared with existing metal or hard plastics models. In the present invention, the following TPEs have been found to provide the required performance FilaFlex™ - for artificial foot which requires greater flexibility

NinjaFlex™ - for artificial foot which requires medium flexibility

The choice of the degree of flexibility of above materials is for the most part dictated by the individual user’s requirements, usually after testing a pilot artificial foot 1. Upon the user determining their requirements, a new artificial foot 1 in accordance with the invention can be readily fabricated with the necessary adjustments.

It further should be noted that flexibility/rigidity of the artificial foot 1 in the mid-foot flexion region 9 is determined, in addition to the material of the artificial foot 1 , by the size and shape of the mid-foot flexion region 9. For example, a larger mid-foot flexion region 9 affords greater flexibility and, conversely, a smaller mid-foot flexion region 9 affords greater rigidity. Thus, upon the user testing a pilot artificial foot 1 , the size and shape of the mid foot flexion region 9 can be altered to adjust flexibility, and a new artificial foot 1 in accordance with the invention can be readily fabricated with the necessary adjustments.

The artificial foot 1 comprises a coupling arrangement in the form of a receiver interface 19 (Figure 10) for coupling with a pyramid joiner and with the pylon 3 of the artificial leg 7. The receiver interface 19 can be fabricated together with the artificial foot 1 during the rapid prototyping.

Depending on the patient’s requirements, as shown in Figure 11 , the artificial foot 1 may be provided with a calcaneal flexion region 23 in a calcaneal portion 21 of the artificial foot 1 , calcaneal flexion region 23 having deformability greater than that of portions of the artificial foot 1 adjacent the calcaneal flexion region 23.

The calcaneal flexion region 23 is located inside the artificial foot and completely contained inside the artificial foot so that a layer of artificial foot material is present between the outer surface 11 of the artificial foot 1 and the calcaneal flexion region 23.

In the present embodiment, the calcaneal flexion region 23 is provided by forming a cavity in the calcaneal portion 21 of the artificial foot 1. In other embodiments, the calcaneal flexion region 23 may be provided using material having reduced density or rigidity compared to that of material adjacent the calcaneal flexion region 23.

The shape of the calcaneal flexion region 23 is similar to a segment 25 of the outer contour of the calcaneal portion 21. In the present embodiment, the shape of the calcaneal flexion region 23 is obtained by copying and inwardly offsetting the segment 25 of the outer contour of the calcaneal portion 21. Thus, the shape of the calcaneal flexion region 23 is a scaled down copy of the segment 25 of the outer contour of the of the calcaneal portion 21. The scale factor for the calcaneal flexion region could be 75% of the original size or another clinically relevant size. In other words, the calcaneal flexion region 23 has a shape that repeats the outer surface of the segment 25 of the calcaneal portion 21 but is scaled down to be located inside the calcaneal portion 21. Such a shape is believed to facilitate optimal flexing of the calcaneal flexion region in that areas of under- or over-flexing are minimised or avoided. It will be appreciated that the invention is not limited to such particular shape and other shapes of the calcaneal flexion region 23 are indeed envisaged as will be understood by those skilled in the art.

Similar procedure as described above in relation to the mid-foot flexion region 9 can be followed to adjust flexibility/rigidity of the calcaneal flexion region 23.

An example of the process steps of designing and fabricating the artificial foot 1 of the invention is provided below: 1) Surface anatomical data is acquired through 3D scanning of existing foot (Figure 4).

2) The foot is segregated (MO) and a digital 3D mirror image is created, e.g. in Meshmixer software (Figure 5).

3) This first digital foot mirror image is referred to as M1 (Figure 1).

4) A duplicate of this mirror foot is created as M2.

5) To create selective flexibility in the Lisfranc joint (mid-foot) area an anatomical hollow space is created using the duplicated mirror foot M2.

6) The mid-foot area is chosen (anatomically the Lisfranc joint zone) and separated on M2 (Figure 2).

7) This separated Lisfranc section M2 is minimized to 75% of its original size or another clinically relevant size.

8) The minimized Lisfranc section is then subtracted from the original mirror image (M1-M2) using the Boolean function, e.g. on Meshmixer software, to create M3 (Figure 3).

9) A conventional prosthetic foot is typically attached to a pylon via a pyramidal joiner 35 (Figure 6). To create a pyramidal joiner interface (R1), a cylinder is created, from the software, e.g. Meshmix, option and aligned with the M3 foot model (Figure 7).

10) The cylinder (R1) then is subtracted from the M3 foot model using Boolean function.

11) This creates hollow cylindrical space in the M3 model to position a model receiver interface (R2) for the pylon (Figure 8).

12) The receiver interface (19, R2) acts as a connector for the pyramid joiner, which enables the artificial foot 1 to be attached to a pylon 3.

13) The dimensions of the pyramid joiner to be used on the artificial foot 1 are then determined. 14) Based on the dimensions, a receiver interface is designed using a 3D modelling software, such as, for example, Autodesk Inventor/Solidworks.

15) This receiver interface (19, R2) acts as the hardware female connector for the pyramid joiner.

16) The receiver interface (R2) is then aligned as per patient’s anatomical form and biomechanical function requirements on the M3 foot model (Figure 9).

17) The receiver interface (R2) is then merged with M3 Foot model through the Boolean Union function to form the final foot model (M4) (Figure 10).

18) This final foot model (M4) is prepared for 3D printing by checking for any errors, and extruded as a Standard Tessellation Language (.stl) File.

19) This file is then imported into a slicing software such as, for example, Cura; the printing parameters optimised and finally extruded as a Geometric Code (.geode) File to be 3D-printed.

20) The 3D printer, for example, BQ Witbox, may be optimized to 3D-print soft materials for a longer duration.

21) To minimise the travelling distance of the filament to the nozzle, the following steps may be taken:

-the material spool mounted superior to the 3D-printer using a laboratory clamp stand.

-the top panel removed to access the extruder

-the filament is directly loaded through the top.

22) The artificial foot 1 is then 3D-printed and material spools replaced when necessary.

23) The printed artificial foot 1 is then handed over to the prosthetist for fitting.

24) The prosthetist initially attaches a pyramid joiner 35 and a pylon 3. 25) The prosthetist then customises the pylon 3 to be fitted as per the patient’s specifications. The patient’s socket 5 is then attached to the pylon 3. The patient is then fitted with the leg prosthesis 7.

26) When the patient is fitted with the leg prosthesis 7, subjective and objective data is obtained.

27) Based on visual gait assessment and patient feedback, adjustment of the artificial foot 1 design was done.

28) The artificial foot 1 was modelled to be more rigid and to facilitate selective plantar flexion (like a single-axis prosthetic foot) during the initial contact of the foot during the gait cycle.

29) To created flexibility in the calcaneal region 21 , a cavity 23 was created in the calcaneal region, in a manner similar to the cavity 9 in the Listfranc section described above.

30) The patient felt that the artificial foot was too flexible. To make it more rigid, the pyramid joiner mechanism was re-designed. The lower section of the receiver interface (R2) was left as opaque, to be drilled later. A final artificial foot 3D model was created with this configuration. X-Ray slicing of the final artificial foot was performed using a slicing software, such as Cura, to check the final configuration, and the anatomical foot was 3D-printed.

31) The 3D printed foot was then drilled to insert the bespoke joiner. It was then fitted with the bespoke joiner. The artificial leg was fitted on patient and gait was analysed.

It will be appreciated by those skilled in the art that variations and modifications can be made without departing from the scope of the invention as defined in the appended claims.

Claims

CLAIMS:

1. A foot prosthesis comprising:

an artificial foot having a mid-foot portion, wherein

2. A foot prosthesis according to claim 1 , wherein the mid-foot flexion region comprises a cavity defined in the mid-foot portion of the artificial foot to provide for the flexing ability of the mid-foot flexion region.

3. A foot prosthesis according to claim 1 or claim 2, wherein the mid-foot flexion region includes material having reduced density or rigidity compared to that of material adjacent the mid-foot flexion region to provide for the flexing ability of the mid-foot flexion region.

4. A foot prosthesis according to any preceding claim, wherein the combination of the material of the artificial foot and the provision of the said mid-foot flexion region render the mid-foot portion of the artificial foot resiliently deformable in the mid-foot flexion region so that the artificial foot can sequentially flex and return into a non-flexed state during walking, akin the user’s good foot.

5. A foot prosthesis according to any preceding claim, wherein the mid-foot flexion region is located inside the artificial foot.

6. A foot prosthesis according to claim 5, wherein the mid-foot flexion region is completely contained inside the artificial foot.

7. A foot prosthesis according to claim 6, wherein a layer of artificial foot material is present between the outer surface of the artificial foot and the mid-foot flexion region.

8. A foot prosthesis according to any preceding claim, wherein the shape of the mid-foot flexion region is similar to a segment of the outer contour of the mid-foot portion.

9. A foot prosthesis according to claim 8, wherein the shape of the mid-foot flexion region is a scaled down copy of a segment of the outer contour of the of the mid-foot portion.

10. A foot prosthesis according to any preceding claim, wherein the mid-foot portion corresponds anatomically to the Lisfranc joint zone of a human foot.

11. A foot prosthesis according to any preceding claim, wherein the artificial foot has the appearance similar to a generic human foot.

12. A foot prosthesis according to any preceding claim, wherein the artificial foot has an outer surface that is a mirror image of the user’s intact foot.

13. A foot prosthesis according to any preceding claim, wherein the material of the artificial foot is plastics.

14. A foot prosthesis according to any preceding claim, wherein the material of the artificial foot is a thermoplastic elastomer (TPE).

15. A foot prosthesis according to claim 14, wherein the material of the artificial foot is selected from FilaFlex™, NinjaFlex™ or CheetahFlex™.

16. A foot prosthesis according to any preceding claim, wherein the artificial foot comprises a coupling arrangement for fastening the artificial foot to a pylon of an artificial leg, wherein the coupling arrangement is integrally formed with the artificial foot.

17. A foot prosthesis according to any preceding claim, wherein the artificial foot is provided with a calcaneal flexion region in a calcaneal portion of the artificial foot, said calcaneal flexion region having deformability greater than deformability of portions of the artificial foot adjacent the calcaneal flexion region.

18. A foot prosthesis according to claim 17, wherein the calcaneal flexion region comprises a cavity in the calcaneal portion of the artificial foot to provide for the deforming ability of the calcaneal flexion region.

19. A foot prosthesis according to claim 17 or claim 18, wherein calcaneal flexion region includes material having reduced density or rigidity compared to that of material adjacent the calcaneal flexion region to provide for the deforming ability of the calcaneal flexion region.

20. A foot prosthesis according to any one of claims 17 to 19, wherein the shape of the calcaneal flexion region is a scaled down copy of a segment of the outer contour of the of the calcaneal portion.

21. A method of making a foot prosthesis, the method comprising the steps of:

forming an artificial foot having a mid-foot portion, wherein

22. The method of claim 21 comprising the step of defining the shape of the mid-foot flexion region by copying and inwardly offsetting a segment of the outer contour of the mid foot portion.

23. The method of claim 21 or claim 22 comprising the step of forming a cavity in the mid foot portion of the artificial foot to provide the mid-foot flexion region.

24. The method of any one of claim 21 to 23 comprising the step of forming the outer surface of the artificial foot by 3D scanning the intact foot, creating a virtual mirror image of the intact foot and making the artificial foot based on the virtual mirror image.

25. The method of any one of claim 21 to 24 comprising the step of fabricating the artificial foot using a rapid prototyping technique.