A prosthetic limb

Abstract

A porsthetic limb device comprising a first member 21a and a second member 21b each configured to be secured to a residual limb in use, wherein the first and second members are spaced apart from one a

Description

FIELD OF THE INVENTION This invention relates to a prosthetic limb. In particular, but not exclusively, the present invention relates to a limb prosthesis comprising a support structure to stabilise the prosthesis in use. BACKGROUND Every year there are more than 1,000,000 amputations leading to a total of 30 million people in need of prosthetics across the world. When a limb reduction or amputation has occurred, a prosthesis can be fitted to provide additional length and functionality to the user. There are three types of prosthetic, cosmetic, body powered and myoelectric. Typically, children are offered a cosmetic prosthesis which has no function and is purely used for body symmetry and to allow the child to get used to wearing something on their residual limb. Body powered prostheses are operated using the movement of the body and typically enable a pincer movement in a split hook. Myoelectric prostheses are the most advanced form of prostheses as these use sensors attached to the residual limb to create complex movements and motions in the prosthesis. These are typically only given to adults due to their high price and the high level of control which is required to operate them. Current development in prosthetics is heavily focused around myoelectric devices with little development seen in body powered devices in the past 50 years. As a consequence of this, many children and young adults do not have adequate access to suitable prosthetics due to the high price of newly developed prostheses and the lack of development in body powered devices. In addition to this, children and adolescents face further restrictions and limitations in the usefulness of prospective devices due to their rapid growth rate which causes their prosthetics to have a shortened useful lifetime and increases the number of prosthetics required during any given time period compared to an adult with a similar limb reduction. The present invention has been devised with the foregoing in mind. SUMMARY According to a first aspect there is provided a prosthetic limb device. The prosthetic limb device may comprise a first member and a second member each configured to be secured to a residual limb in use. The first and second members may be spaced apart from one another to contact the residual limb at different positions on the residual limb. The prosthetic limb device may also comprise a support structure. The support structure may be configured to be connected between the first and second members in use. The support structure may be releasably connectable to the first and second members. The support structure may provide additional mechanical stability and stiffness to a prosthetic limb device once secured to a residual limb of a user, whilst enabling a lightweight structure and design of the prosthetic limb device to be retained. That may enable a user to move or operate the prosthetic limb device more easily and accurately. The support structure may also limit or restrict movement of the residual limb within or relative to the prosthetic limb device between the first and second members, by providing a cover or bounding surface. That may reduce a likelihood of a part of the residual limb becoming disconnected from or inadvertently extending outward beyond the prosthetic limb device (which can occur, for example, for users having relatively shorter residual forearms when bending an elbow joint). The support structure may be quickly and conveniently retrofitted to an existing prosthetic limb device, which may enable improved performance of a prosthetic limb device without requiring a complete replacement of the prosthetic limb. The support structure may be particularly beneficial for users having relatively shorter residual limbs or lower strength in their residual limbs. The support structure may be configured to at least partially surround or cover the residual limb in use (that is, when connected between the first and second members). The first and second members may be configured to contact substantially opposing sides of a residual limb in use. The first and second members may extend generally parallel to one another. The first and second members may be spaced apart from one another in a direction substantially perpendicular to a length of each of the first and second members. The first and second members may each comprise an elongate structure. The support structure may be configured to be connected between the first and second members at a plurality of different connection positions on the first and second members. That may enable the support structure to be secured between the first and second members at a more optimal location on the first and second members, to improve or maximise an impact of the support structure on the mechanical stability and stiffness of the prosthetic limb device (for example as required by an intended use of the prosthetic limb device, or depending on a length or strength of the residual limb). The support structure may be configured to be connected between the first and second members so as to be located adjacent two or more of a top, front, side, back or lower surface of a residual limb. The support structure may be configured to be connected between the first and second members at a plurality of different connection positions along a length of the first and second members. The support structure may be configured to be secured between the first and second members using a strap. That may provide a convenient mechanism for securing the support structure to the first and second members which makes use of an existing mechanism used to secure many conventional prosthetics to a residual limb. Each of the first and second members and the support structure may comprise at least one aperture for receiving the strap. Each of the first and second members may comprise a plurality of apertures spaced apart from one another on the respective member. The support structure may comprise a plurality of apertures spaced apart from one another. A number of apertures in the plurality of apertures on each of the first and second members may be greater than a number of apertures in the plurality of apertures on the support structure. The respective apertures of the first and second members and the support structure may be configured to substantially align when the support structure is connected to the first and second members. The support structure may comprise a surface configured to substantially follow an external shape or profile of the residual limb. The support structure may comprise or form a surface configured to substantially follow an external shape or profile of the residual limb in use. That may enable the support structure to be incorporated into the prosthetic limb device without impacting comfort or convenience of the user. The support structure may comprise a substantially curved or arc-shaped cross-section. The support structure may comprise or form a substantially curved or arc-shaped cross-section in use. The curved cross-section may be or comprise a substantially semi-circular cross-section. The curved or arc-shaped cross-section of the support structure may provide the support structure with improved resistance to buckling under applied force, which may further improve a mechanical stability and stiffness of the prosthetic limb device in use. The support structure may comprise a main body. The main body may be configured to engage the first and second members The support structure may also comprise a protrusion extending from the main body. The protrusion may comprise at least one aperture for receiving a strap. The main body may comprise a substantially curved or arc-shaped cross-section, for example a substantially semi-circular cross-section. The support structure may comprise a substantially rigid structure. That may increase or maximise a mechanical stability and stiffness of the prosthetic limb device extending beyond the residual limb in use, by inhibiting or preventing relative movement between the first and second members in use. The support structure may comprise a flexible but substantially inelastic or non-extendible structure. A flexible but substantially non-extendible structure may allow the structure to bend or twist (for example, to conform to or substantially follow an external shape or profile of the residual limb in use, and / or to accommodate movement of the user when wearing the prosthetic limb device) without experiencing strain (for example, any significant strain under the magnitude of forces likely to be applied during use of the prosthetic limb device by a user). That may improve comfort for the user whilst also improving mechanical stability and stiffness of the prosthetic limb device in use. That may also enable the support structure to conveniently span over a portion of the prosthetic limb device including a movable joint (for example, a pivotable joint or hinged joint such as a wrist, elbow or knee), to limit movement of the residual limb relative to or within the prosthetic limb device without compromising or reducing an available range of motion of the movable joint The support structure may be configured to resist or inhibit a twisting or scissoring motion of the first and second members relative to one another, when connected between the first and second members in use. The prosthetic limb device may comprise an appendage or end effector connected to a distal end of the first and second members, wherein the appendage or end effector is movably connected to one of the first and second members. The appendage or end effector may be rigidly connected to the other of the first and second members. A moveable connection of one of the first and second members to an appendage or end effector of the residual limb may allow different widths or changes of width of residual limbs to be accommodated. However, such a movable connection can cause unwanted movement of the prosthetic limb device or appendage or end effector during use. The support structure may allow the prosthetic limb device to accommodate a range of residual limb widths whilst maintaining mechanical stability and stiffness of the prosthetic limb device once fitted to a user, which may improve ease of use of the prosthetic limb device. The appendage or end effector may be pivotably or hingedly connected to one of the first and second members. The first and second members may each be extendable to adjust a length of the first and second members. In an extended position (for example, at greater lengths), the prosthetic limb device is more likely to experience relative movement between the first and second members. The support structure may be particularly beneficial for such extendable prosthetic limb devices, by reducing relative movement between the first and second members and increasing mechanical stability and stiffness of the prosthetic limb device. That may improve ease of use and adaptability of the prosthetic limb device for use with different users. The first and second members may each comprise a telescopic extendable member. The telescopic member comprises a proximal portion and a distal portion which are telescopically connected and secured in position by one or more fastening means. The prosthetic limb may comprise a forearm including a prosthetic hand connected at a distal end of the first and second members) It may be that the hand includes fingers and thumbs hingedly connected to a palm and that the movement of the fingers and thumbs is controlled by control wires secured at distal ends of the fingers, such that the prosthetic limb is body powered. The support structure may improve mechanical stability and stiffness of the prosthetic limb device, allowing the prosthetic limb device to be used more easily and accurately. That may be particularly beneficial for a prosthetic limb device which can be operated to perform relatively fine motor tasks such as moving the fingers and thumb of a hand, and may increase a performance capability of the prosthetic limb device by enabling more precise movements to be carried out by a user. It may be that the fingers and thumb each have a hinged knuckle configured to allow them to bend in response to tension in the control wires. The fingers and thumb may be biased to return to a neutral position by resiliently biased members. The prosthetic limb may include an upper member connected to a proximal end of the first and second members by a pivot joint. The pivot joint may allow the first and second members to pivot relative to the upper member, about an axis perpendicular to their length. It may be that the control wires are anchored on a proximal side of the pivot joint and pass through or along the first and second members member such that bending the pivot joint (for example, used as an elbow joint) increases the path length of the wires which pulls on the ends of the fingers and thumb and hence pulls the fingers and thumb in towards the palm to form a fist. The distal portion may comprise a channel through which the wires pass. It may be that the wires are anchored by a whippietree assembly mounted on the upper member, the whippietree assembly being configured to allow the load to be unevenly distributed between the wires such that irregularly shaped objects can be gripped. The prosthetic hand may have a modular construction and the palm, fingers, and thumbs may be interchangeable. According to a second aspect, there is provided a support structure for a prosthetic limb device. The prosthetic limb device may comprise a first member and a second member each configured to be secured to a residual limb in use. The first and second members may be spaced apart from one another to contact the residual limb at different positions on the residual limb. The support structure may be configured to be connected between the first and second members in use. The support structure may be releasably connectable to the first and second members. The support structure of the second aspect may comprise one or more features of the prosthetic limb device of the first aspect. It will be understood that any feature discussed in relation to a particular aspect may also be applied to any other aspect, mutatis mutandis. BRIEF DESCRIPTION OF THE DRAWINGS The invention is shown, by way of example, in a series of drawings with an accompanying description which details the intricacies of an embodiment of the invention. The drawings include: Figure 1 is a perspective view of a prosthetic limb according to an embodiment of the invention, with the limb in tension, and the forearm in an extended position; Figure 2 is a perspective view of the prosthetic limb of Figure 1, with the limb in tension, and the forearm in a retracted position; Figure 3 is a cross sectional view of the palm and wrist of the prosthetic arm of Figure 1, showing the internal hinge; Figure 4 is a perspective view showing further detail of the wrist hinge shown in Figure 3; Figure 5 is a top down view of a palm showing an alternative connector to that shown in Figures 3 and 4; Figure 6 is a cross sectional view of the elbow joint of the prosthetic arm of Figure 1; Figure 7 is a perspective view of the proximal forearm portion of the prosthetic limb of Figure 1, including the outer section of the elbow joint; Figure 8 is a cross sectional view of the elbow joint of the prosthetic limb of Figure 1, showing the wires when the limb is in a neutral position; Figure 9 is a cross sectional view of the elbow joint of the prosthetic limb of Figure 1, showing the wires when the limb is in tension in low gearing; Figure 10 is a cross sectional view of the elbow joint of the prosthetic limb of Figure 1 showing the wires when the limb is in tension in high gearing; Figure 11 is a perspective view of the whippietree assembly of the prosthetic limb of Figure 1, in its neutral position, attached to the upper arm member; Figure 12 is a perspective view of the whippietree assembly of the prosthetic limb of Figure 1, in its taut position, attached to the upper arm member; Figure 13 is a perspective view of the whippietree of the prosthetic limb of Figure 1, assembly in its taut position; Figure 14 is a perspective view of the whippietree assembly of the prosthetic limb of Figure 1, in its neutral position; Figure 15 is a perspective view of the interior of the hand assembly of the prosthetic limb of Figure 1, when the limb is in tension with a varied force grip; Figure 16 is a perspective view of the exterior of the hand assembly of the prosthetic limb of Figure 1, when the limb is in its neutral position; Figure 17 is a cross sectional view of a finger of the prosthetic limb of Figure 1 showing the internal wire pathway and joints; Figure 18 is a perspective view of a thumb of the prosthetic limb of Figure 1 showing the three thumb portions; Figure 19 is a perspective view of the prosthetic limb in a neutral position, and the forearm is in an extended position; Figure 20 is a perspective view of part of the arm assembly of the prosthetic limb of Figure 1; Figure 21 is a top down view of the palm of the prosthetic limb of Figure 1, in three sizes; Figure 22 is a view of a support structure for a prosthetic limb according to embodiment of the invention; Figure 23 shows the support structure shown in Figure 22 connected to a prosthetic limb; and Figure 24 shows an alternative support structure comprising a flexible structure according to another embodiment of the invention. The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. DETAILED DESCRIPTION In the following description, reference will be made to proximal and distal ends / regions / portions. It will be appreciated that proximal refers to the end / region / portion closer to the body of the user and distal refers to the end / region / portion farther from the body of the user. Referring to Figure 1, a perspective view of the prosthetic limb is illustrated and referred to with numeral 14. The prosthetic limb 14 is formed of multiple sub-assemblies, including a hand assembly 16, a whippietree assembly 18 and a pair of arm assemblies 20a,20b. In the illustrated embodiment, the prosthetic limb 14 comprises an upper body limb, namely an arm, with the hand assembly 16 being disposed at the distal end of the arm assemblies 20a,20b. The hand assembly 16 comprises a palm 26, fingers 24, and a thumb 28. Each of the arm assemblies 20 comprises a forearm member 21, a pivot joint (elbow) 38, and an upper arm member 34. A distal end 35 of the upper arm member 34 is connected to a proximal end 41 of the forearm member 21 by the pivot joint 38 which is discussed in more detail below. The angle of rotation of the pivot joint 38 can be described by the angle between the upper arm member 34 and the proximal forearm portion 42. For example, an angle of 180 degrees represents a straight arm (as shown in Figure 1 9). Figures 1 and 2 show a prosthetic arm with a 90 degree rotation in the pivot joint 38. Each forearm member 21a,b is comprised of two portions: a distal forearm portion 36, and a proximal forearm portion 42. The distal and proximal forearm portions 36, 42 are arranged telescopically, as will be discussed in more detail below. As such, the forearm member 21 can be considered a telescopic member. The hand assembly 16 is connected to a distal end 37 of the telescopic forearm members 21a,b. A first arm assembly forms an outer arm assembly 20a, that connects to the back side of the hand assembly 16. A second arm assembly forms an inner arm assembly 20b, that connects to the palm side of the hand assembly 16. The arm assemblies 20a,b will now be described in more detail. As shown in Figures 6, 11 and 12, the upper arm members 34 of the outer arm assembly 20a and the inner arm assembly 20b have opposing planar surfaces 40a, 40b. A first surface is an outer surface 40a that, in use, faces away from the residual limb of the user, and the second surface 40b is an inner surface that faces towards the residual limb of the user. The opposing surfaces 40a,b are substantially rectangular in shape, and are separated by a thickness. The upper arm member 34 has a length perpendicular to the thickness, running from a proximal end 39 to a distal end 35, and a width perpendicular to the thickness and the length. The thickness is less than the length and width of the upper arm member 34, such that the upper arm member 34b is substantially flat. The length is also larger than the width and thickness, so the member 34 can be considered elongate. At or near its proximal end 39, the upper arm member 34b includes an attachment point 142. The attachment point 142 is in the form of an eyelet or hoop projecting from one a first of the planar surfaces 40a in a direction parallel to the thickness. As will be discussed in more detail below, a first portion of the elbow joint 38 is formed on the proximal end 39 of the upper arm member 34. The upper arm member 34a of the outer arm assembly 20a (shown in Figures 11 and 12) further comprises an integrally formed connector 72 to which the whippietree mount 32 is fastened. The whippietree assembly 18 will be discussed in more detail below. The whippietree connector 72 is omitted from the upper arm member 34b of the inner arm assembly 20b. Each proximal forearm portion 42 has a cross section defining a width and a thickness perpendicular to the width. The thickness extends between an outer surface 46a and an inner surface 46b, in a similar manner to the upper arm member 34. Each proximal forearm portion 42 also has a length running from a proximal end 41 to a distal end 45, the length perpendicular to the thickness and width. As best shown in Figure 7, the cross section of the proximal forearm portion 42 is discorectangular in shape, with a hollow core defining a passage extending along the length of the proximal forearm portion 42. The proximal forearm portion 42 is closed at its proximal end 41 and open at its distal end 45. The major dimension of the discorectangular cross section (i.e. the longest straight line between opposing sides) is along the width of the proximal forearm portion 42. With the pivot joint 38 in the neutral position (rotation of 180 degrees), the length of the proximal forearm portion 42 extends parallel to the length of the upper arm member 34, the width of the proximal forearm portion 42 extends parallel to the width of the upper arm member 34, and the thickness of the proximal forearm portion 42 extends parallel to the thickness of the upper arm member 34. The axis of rotation of the elbow joint 38 is parallel to the thickness of both the upper arm member 34 and the proximal forearm portion 42. In the illustrated embodiment, the proximal forearm portion 42 includes a second portion of the elbow joint 38 at its proximal end 41. Each proximal forearm portion 42 includes four attachment points 142. The attachment points 142 on the proximal forearm portions 42 are arranged in pairs, where the attachment points 142 of a single pair are located on opposite sides of the width of the proximal forearm portion 42, at the same position along the length. A first pair of eyelet attachment points 142 is located at or near the proximal end 41 of the proximal forearm portions 42, and the second pair is located substantially halfway between the proximal end 41 and distal end 45 of the proximal forearm portion 42. In use, the attachment points 142 on the upper arm members 34a,b face outward from the residual limb, and the attachment points 142 on the proximal forearm portions 42a,b extends perpendicular to the attachment points 142 on the upper arm members 34a,b. In use, the inner surface 40b of the upper arm member 34 and the inner surface 46b of the proximal forearm portion 42 rest against the residual limb of the user. The prosthetic limb 14 is attached to the user’s residual limb using an elasticated loop strap (omitted for clarity) which is passed through the attachment points 142 on each of the upper arms 34 and around the residual limb, above the elbow on the residual limb. Below the elbow on the residual limb, the prosthetic arm 14 is secured to the residual limb by a loop strap which passes through one eyelet 142 in the first pair of the proximal forearm portion 42a, b, in a direction away from the residual limb, around the proximal forearm portion 42a,b, and then back through the other eyelet of the pair in a direction towards the residual limb. This sequence is then repeated on the first pair of attachment points 142 on the other proximal forearm portion 42b,a, which is directly opposite the first mentioned pair, along the length of the residual limb. Thus, the strap loops around both proximal forearm portions 42a,42b and the forearm of the residual limb. A further strap is fitted in the same way using the second pairs of eyelets 142 on the proximal forearm members 42. Therefore, in the illustrated embodiment, three straps are used to attach the prosthetic limb 14 to the user’s residual limb, two on the proximal forearm 42, and one on the upper arm member 43. Straps are threaded through attachment points 142 that are directly above / below and opposite each other to ensure a secure loop is made around the user’s residual limb. Although the description discussed above uses elastic loop straps. Other straps may be used such as hook and loop straps, and other forms of belt or strap. Figures 22A, 22B show a support structure 200 for use with the prosthetic arm 14, and Figure 23 shows the support structure 200 connected to the prosthetic arm 14. The support structure 200 is configured to be connected between the forearm members 21a, 21b as shown in Figure 23. so as to provide the prosthetic arm 14 with increased stability and stiffness once secured to the residual limb. In the embodiment shown, the support structure 200 comprises attachment points 242 in the form of eyelets or apertures formed through the support structure 200. The support structure 200 is configured to be located between the forearm members 21a, 21b such that lateral edges 202a, 202b of the support structure 200 are effectively sandwiched or compressed between the respective inner surfaces 46b of the forearm members 21a, 21b as straps are used to secure the forearm members 21a, 21b to the residual limb as described above. The straps may also be passed through the apertures in the attachment points 242 of the support structure 200 to further secure the support structure 200 to the forearm members 21a, 21b. The support structure 200 is configured to be positioned between the forearm members 21a, 21b such that the apertures of the attachments points 142, 242 are substantially align with one another in use. In the embodiment shown, the support structure 200 comprises two attachment points 242, allowing a plurality of straps to be used to secure the support structure 200 between the forearm members 21a, 21b at different locations on the forearm members 21a, 21b (for example, at the positions at which the attachment points 142 of the forearm members 21a, 21b are provided), or a single strap to be passed through each of the attachment points 242 to provide the same function. In the embodiment shown, the support structure 200 comprises two attachment points 242 along its length whilst the forearm members 21a, 21b each comprise three attachment points 242 along their respective lengths. That may enable the support structure 200 to be connected between the forearm members 21a, 21b at different positions along the length of the forearm members 21a, 21b, although that is not essential. It will also be appreciated the support structure 200 may comprise a single attachment point 242 (for example, a single aperture for receiving a strap). Alternatively, the support structure 200 may be configured to be connected to the forearm members 21a, 21b in any suitable manner. The support structure 200 may be configured to be brought into sliding engagement with the forearm members 21a, 21b to secure the support structure 200 to the forearm members 21a, 21b, such as by having at least a part of the lateral edges 202a, 202b of the support structure 200 slidably receivable within a groove or channel provided on the forearm members 21a, 21b (for example on an inner surface 46b of each forearm members 21a, 21b). In another alternative arrangement, the support structure 200 and the forearm members 21a, 21b may each comprise complementary engagement features configured to secure the support structure 200 to the forearm members 21a, 21b, such as complementary snap-fit features on the support structure 200 and the forearm members 21a, 21b. The support structure 200 can be connected to the forearm members 21a, 21b at either of the opposing upper or lower sides of the forearm members 21a, 21b. For example, in the embodiment shown the support structure 200 can be connected to an upper side of the forearm members 21a, 21b facing towards a direction in which a thumb of the prosthetic hand 16 extends, or to the opposing lower side of the forearm members 21a, 21b facing away from the direction in which the thumb of the prosthetic hand 16 extends. In the embodiment shown, the support structure 200 comprises a main body 202 and a protrusion 204 extending from the main body 202. The main body 202 is configured to engage or contact the forearm members 21a, 21b. The lateral edges 202a, 202b of the main body 200 are configured to engage or contact the inner surfaces 26b of the forearm members 21a, 21b although that is not essential. The main body 202 comprises a substantially curved or arc-shaped cross-sectional shape, such as a substantially semi-circular cross-sectional shape, although that is not essential and the main body 202 may have or comprise any suitable shape or configuration. The protrusion 204 extends substantially radially away from the curved or arc shape of the main body 202, although that is not essential. In the embodiment shown, the attachment points 242 are provided in the protrusion 204. However, it will be appreciated the support structure 202 may be provided without such a protrusion 204, and attachment points or apertures 242 may be provided directly in or on the main body 202 itself. The support structure 200 may act to increase a mechanical stiffness and stability of the prosthetic arm 14, by providing additional connection between the forearm members 21a, 21b to reduce or restrict relative movement (for example, twisting or separation) between the forearm members 21a, 21b in use. The support structure 200 is also configured to limit movement of the residual limb within or relative to the prosthetic arm 14, by acting as a cover or shield preventing the residual limb from extending outwardly beyond the prosthetic arm 14 and retaining the residual limb between the forearm members 21a, 21b. That may be particularly beneficial for users having shorter residual forearms which are more likely to slip out of the straps looped around the proximal forearm portions 42a, 42b when the elbow joint 38 is bent. In the embodiment shown, the support structure 200 is a substantially rigid structure formed from PLA (polylactic acid) although it will be appreciated any suitable substantially rigid material may alternatively be used, for example a polymer material such as polypropylene, nylon, or a metal or metal alloy material, or wood. The support structure 200 is formed using an additive manufacturing (“3D printing”) process, although any suitable manufacturing process may alternatively be used, for example a moulding process such as injection moulding. In the embodiment shown, the support structure 200 provides a substantially continuous surface acting as a cover or shield at least partially surrounding the residual limb, although that is not essential and one or more apertures or cutaway sections may be provided in the support structure 200 (for example, forming a web-like or net-like structure, or a perforated structure). That may reduce or minimise weight of the support structure 200 without compromising mechanical performance, and may also improve breathability and comfort of the support structure 200 for a user. It will be appreciated the support structure 200 may equally be used in combination with any suitable prosthetic limb, for example a prosthetic arm 14 having forearm members 21a, 21b of a substantially fixed length rather than telescopically extendable forearm members 21a, 21b. It will also be appreciated a support structure 200 may additionally or alternatively be provided between the upper arm members 34a, 34b of the prosthetic arm 14. Figures 24A to 24D shows a support structure 200’ according to another embodiment of the present invention. Rather than being a substantially rigid structure, the support structure 200’ comprises a flexible but substantially inelastic or non-extendible structure. In the embodiment shown, the support structure 200’ is formed from leather, although that is not essential and any suitable flexible but substantially non-extendible material may alternatively be used, such as a textile or fabric material. Similar to the support structure 200 described above with respect to Figures 22A, 22B and 23, the support structure 200’ comprises attachment points 242’ in the form of apertures to receive straps S to secure the support structure 200’ to the forearm members 21a, 21b (straps S which also secure the forearm members 21a, 21b to the residual limb, shown in Figures 24C and 24D but not shown in Figures 24A and 24B for clarity). The support structure 200’ may bend to substantially conform to or follow a surface of the residual limb once it is secured to the prosthetic arm 14 and to the residual limb, but may not hold that shape when disconnected from the prosthetic arm 14 due to its flexible structure. That may enable the support structure 200’ to be more easily and compactly transported and stored when not in use. In the embodiment shown, the support structure 200’ is secured to the forearm members 21a, 21b, but also continuously extends across or around the area of the elbow joint 38 on a lower or rear side of the prosthetic arm 14, and is secured to the upper arm members 34a, 34b in a similar manner using straps. That may provide a support structure 200’ which increases a mechanical stability of the prosthetic arm 14 by providing additional resistance to relative movement (such as twisting or separation) between the forearm members 21a, 21b and also between the upper arm members 34a, 34b in use. The support structure 200’ also provides additional covering for the residual forearm to retain the residual forearm within the prosthetic limb device (for example, between the forearm members 21a, 21b) when the elbow joint 38 is bent, without compromising movement of the elbow joint 38 itself. However, it will be appreciated the support structure 200’ may alternatively be configured to connect to either the forearm members 21a, 21b alone or the upper arm members 34a, 34b alone. The support structure 200’ comprises cutaway sections 206 located to enable the support structure 200’ to more easily accommodate bending movement of the support structure 200’ and the residual limb in the desired bending direction. That may also improve breathability of the support structure 200’ in use. In the embodiment shown, the cutaway sections 206 are provided substantially adjacent the elbow joint 38a, 38b of the prosthetic arm 14 on lateral sides of the support structure 200’, and also adjacent a point or back of the elbow of the residual limb to provide additional space for the point of the elbow to move into during bending. However, that is not essential, and the support structure 200’ may comprise a substantially continuous surface or structure surrounding the residual limb. Each distal forearm portion 36 has a discorectangular cross section arranged to form a tight fit inside the channel of the proximal forearm portion 42. The distal forearm portion 36 has a length extending parallel to the length of the proximal forearm portion 42, a width extending parallel to the width of the proximal forearm portion 42 and a thickness extending parallel to the thickness of the proximal forearm portion 42. The distal forearm portion 36 extends into the open end 45 of the proximal forearm portion 42, and can slide along the direction parallel to the length of the forearm portions 36, 42. The forearm portions 36, 42 are held at a chosen length. This can be considered a telescopic connection, as it allows the total length of the forearm member 21 (from the distal end 37 of the distal arm portion 36 to the proximal end 41 of the proximal arm portion 42 to be varied. In order to secure the forearm portions together, both the distal 36 and proximal 42 forearm feature holes 10a, 10b which extend through their thicknesses. The holes 10a, 10b can be aligned to enable bolts (omitted for clarity) to be passed through the proximal 42 and distal 36 forearms and engage with nuts (omitted for clarity), to secure the telescopic forearm member 21 at a suitable extension length. The holes 10a and / or 10b may be threaded, and a screw may used in place of a bolt to engage with the screw thread of the holes. In this way, a nut may not be necessary to ensure the screw is secure. In the illustrated embodiment, both the proximal forearm portion 42 and the distal forearm portion 36 comprise pairs of holes 10a, 10b, the separation between the holes 10a, 10b within the pair being smaller than the separation between adjacent pairs. The proximal forearm portion 42 includes elliptical projections 47 on the outer surface 46a, in which the pairs of holes 10a are formed. Both holes 10a, 10b in a pair are intended to be used to receive fasteners at the same time. By using a pair of fastening points, the proximal 42 and distal 36 forearm may be more securely and rigidly fastened. The holes 10b on the distal forearm 36 may not be in pairs, and may instead be evenly spaced, the spacing between each hole 10b being equal to the spacing within each pair of holes 10a on the proximal forearm 42. In this way, there would be more possible lengths and so such an arrangement would increase the adjustability of the forearm 21. Ensuring that the separation between the holes 10b on the distal forearm 36 matches the spacing within each pair of holes 10a on the proximal forearm 42 means that a pair of holes 10a can still be used to fasten each proximal forearm 42 and distal forearm 36 together, as discussed above. In some, but not all, embodiments the spacing between pairs of holes 10a on the proximal forearm 42 is a multiple of the spacing between holes 10a within pairs such that, when the distal forearm portion 36 is sufficiently received within the proximal forearm portion 42, more than one pair of holes 10a may be used to fasten the proximal 42 and distal 36 forearm portions together. Other fastening means, such as pins or screws for example, may be used in place of nuts and bolts, and will be apparent to the person skilled in the art. In the illustrated embodiment, each of the proximal 42 and associated distal 36 forearm portions has a discorectangular cross-section. The proximal 42 and distal 36 forearm portions may be of substantially the same or of different cross-sectional shapes. One or each may, for example be of a tubular cross-section, such as a circular or rectangular cross section or of a ‘C’ section channel shape or elliptical, provided the distal forearm portion 42 can slide within the channel of the proximal forearm portion 36. Referring to Figures 1 and 2, the prosthetic limb 14 is illustrated in two positional configurations. Figure 1 shows the prosthetic limb 14 in a first extended configuration. Figure 2 shows the prosthetic limb 14 in a second, shorter, configuration. Extension of each telescopic forearm member 21 facilitates lengthening of the prosthetic limb 14, as needed, such as to accommodate the rapid growth of a child, for example. As discussed above, the hand assembly 16 is connected to the distal end of the telescopic forearm members 21a,b, which is formed by the distal end 37 of the distal forearm portion 36. As best shown in Figure 15 and 16, the hand assembly 16 includes a pair of connectors 22a,b for connecting the palm 26 to corresponding arm assemblies 20a,b. The connectors 22 include sleeves 23 having an open end shaped to receive the distal end 37 of the distal forearm portions 36. Holes 50 in the distal forearm portions 36 align with holes 52 in the connectors 22, which allows a bolt or other fastening means to be passed through the lower forearms 36 and the connectors 22, the bolts being secured with respective nuts to ensure the two parts remain attached. In an outer connector 22a, the sleeve 23, which receives the distal forearm portion 36a of the outer arm assembly 20a, is rigidly connected to the back of the hand assembly and does not feature any rotation. In an inner connector 22b, the sleeve 23, which receives the distal forearm portion 36b of the inner arm assembly 20b, is connected to the palm 26 by a pinet hinge 33. The pinet hinge 33 is configured to rotate about a single axis perpendicular to the length of the forearm member 21 and to the thickness of the forearm member 21. It may alternatively be that the pinet hinge 33 is located on the outer connector 22a, and the connector 22b on the inner side of the prosthesis 14 does not feature any rotation and is fixed. Figure 3 features a cross sectional view of the inner connector 22b. The sleeve 23 includes a projection 32 extending from its distal end (opposite the open end that receives the distal forearm portion 36b) in a direction parallel to the length of the forearm 21. The projection 31 includes a pair of cylindrical or conical protrusions 136 extending perpendicular to the length 21 of the forearm, defining the angle of rotation of the hinge 33. Internal recesses 134 on the palm 26 can be seen, which are configured to engage with protrusions 136 formed on the projection 31 of the sleeve portion 23. The engagement allows rotation of the protrusions 136 within the recesses 134. Figure 4 shows the sleeve and projection 31, in detail. Adjustment of the width of the prosthetic limb 14 is facilitated by adjusting the separation of the two arm assemblies 20. The arm assemblies 20a,b are only connected at the hand assembly 16 at their distal end 37, and by elastic or adjustable loop straps at or near their proximal end. Therefore, adjustment of the separation between the arm assemblies 20 occurs at the inner connector 22b on the hand assembly 16. The pinet hinge allows the inner arm assembly 20b to pivot about an axis substantially perpendicular to both the length and thickness of the distal forearm member 36b. The angle of the two arm assemblies 20 with respect to each other is therefore adjustable and hence the distance between the two assemblies at the upper arm members 34, where the prosthetic arm 14 is attached to the residual limb, is adjustable. This adjustment allows the prosthetic arm 14 to adjust in width when fitted to a user, to accommodate differences in the width of the residual limb. Figure 5 features a top down view of palm 26 having an alternative connector 22. The connector 22 of Figure 5 includes a pair of holes 52. The sleeve 23 has on its outer face an elliptical projection 47 through which the holes 52 are formed. This arrangement is similar to that of the holes 10b in the proximal forearm portion 42. In embodiments including a connector 22 as shown in Figure 5, two holes 50 in the distal forearm member 36 may be provided. In this way, a pair of fastening means can be used to fasten the hand assembly 16 to the distal forearm 36. Such an arrangement will provide a more rigid connection. The holes 50 may be the two most distal holes 10b in the distal forearm portion 36. Figure 16 shows the hand assembly 16 in detail, whilst Figure 17 shows a finger 24 and Figure 18 the thumb 28. The hand assembly 16 includes the palm 26, palm top 78, thumb 28 and fingers 24. The thumb 28 is comprised of three moving parts, the thumb top 80, thumb middle 82 and thumb base 84. The thumb 28 is connected to the palm 26 via a threaded bar that is inserted from the wrist through a channel in the palm and allows rotation about one axis. The threaded bar pivotally joins the thumb base 84 to the palm 26. The thumb base 84 is able to pivot about the axis of the threaded bar, mimicking the movement of the Carpometacarpal joint. The screw thread on the threaded bar engages with internal thread in the channel through the palm 26. In other embodiments, the channel may not be threaded, and the bar may be held in place with an external nut. The thumb can be best seen in Figure 18. In the illustrated embodiment, the three parts 80, 82, 84 are connected with integrally formed pinet hinges 86 which cannot be separated. The fingers 24 are comprised of two moving parts which are connected with integrally formed pinet hinges 128 and hence cannot be separated. The pinet hinges 128 have the same internal construction (with protrusions and recesses) as explained in relation to hinge 33 on the connector 22b. The four fingers 24 are joined to the palm 26 at joint 130. This joint is formed using the same threaded bar arrangement that joins the thumb 28 to the palm 26. A single threaded bar passes through the base of all four fingers, and engages with internal threads in the channel through the palm 26. In other embodiments, the channel may not be threaded, and the bar may be held in place with an external nut. The movement of the digits (fingers 24 and thumb 28) is controlled by control wires 54. The wires 54 are connected at or near the distal ends of the digits 24, 28 (shown in Figure 17), and are also anchored at the whippietree 30 on the proximal side of the pivot joint 38 a. Rotation of the pivot joint 38, such that the forearm 21 and upper arm member 34 are not parallel (i.e. the angle of rotation is less than 180 degrees), increases the path distance of the wires 54. This increased path distance increases tension in the wires 54, and causes the wires 54 to pull on the ends of the digits 24, 28 which bends the pinet hinges 86, 128 in the digits, such that the hand 16 begins to form a fist, which eventually closes with sufficient tension in the wires 54. Both the thumb 28 and the fingers 24 feature inbuilt channels 88 shown in Figure 1 7 that allow a wire 54 to be passed therethrough. This wire 54 creates movement in the digit by translating the rotational movement of the pivot joint 38 about its axis into movement of the digit 24, 28 due to tensioning the wire 54. Figure 1 shows the prosthesis 14 in its tensed position whilst Figure 17 shows the prosthesis 14 in its neutral position. In the neutral position, a certain amount of tension exists in the wires 54, but this is increased in the tensed position. As shown in Figure 17, the wire 54 is attached to the prosthesis 14 as follows: A first end of a wire 54 is secured at the tip 92 of a first finger 24 through an inbuilt attachment point 94 (for example by knotting). This wire 54 is then passed through a channel 88 in the finger 24 and through a channel in the palm 26. From the palm 26, the wire 54 is passed through a channel 98 in the wrist connector 22a, into a channel 100 in the distal forearm 36a, as seen in Figure 20. The channel 100 in the distal forearm 36a is offset from a centreline defined bisecting the width of the distal forearm 36a since the central region of the distal forearm 36a is occupied with the holes for fastening it to the proximal forearm 42a and connector 22a. The wire 54 is then passed through the channel 100 in the distal forearm portion 36a where it continues along its path through the proximal forearm portion 42a, passing within the same channel in which the distal forearm portion 36 slides. At the proximal end of the proximal forearm portion 42, the control wire 54 passes through a hole 102, into the elbow joint 38a. As with the channel in the distal forearm portion 36a, the hole 102 is offset from the centreline of the forearm 21. The wire 54 is then passed across the elbow joint 38, passing perpendicular to the axis of rotation, and through a hole 70 in the opposite (proximal) side of the elbow joint 38. From the hole 70 on the proximal side of the elbow joint 38 the wire 54 is passed along the upper arm member 34a to the whippietree 30. From the whippietree 30, the wire 54 completes the same journey in reverse, passing through a second finger 24, adjacent the first finger 24. The second end of the wire 54, opposite the first end, is secured to the attachment point 94 of a second finger 24, adjacent the first finger. The index finger 24a (first finger from thumb) and middle finger 24b (second finger from thumb) are connected by a single piece of wire 54 that passes through the whippietree 30 and the ring finger 24c (third finger from thumb) and little finger 24d (fourth finger from thumb) are also connected by a single piece of wire 54 that passes through the whippietree 30. The wire 54 connecting the thumb 28 to the whippietree 30 follows the same path as that of the wire 54 connected to the fingers 24. However, the second end of the wire is secured to the whippietree 30 and is not passed through the prosthesis 14 on a return journey. The palm top 78 is removable to allow the wires 54 to be threaded along their respective paths. Figure 16 shows the palm 26 with the top 78 removed. In the embodiment discussed above, the control wires 54 are passed through the outer arm assembly 20a. In alternative embodiments, the control wires 54 may extend through the inner arm assembly 20b, in which case the proximal forearm portion 42b and associated distal forearm portion 36b of the inner arm assembly 20b may define a protective passageway through which the control wires 54 extend. Furthermore, in alternative embodiments, single wires 54, secured to the finger 24a-d at one end and the whippietree 30 at the other end, may be used. Figures 11-14 illustrate the whippietree assembly 18 in further detail. The whippietree assembly 18 comprises a connector 72 which is integrally formed on the upper arm member 34a of the outer arm assembly 20a, the whippietree body 30, and the whippietree mount 32. The whippietree body 30 is a solid triangular shaped element. The whippietree body 30 is pivotally connected to the whippietree mount 32 at one apex of the body 30, and the whippietree mount 32 is rigidly connected to the connector. Therefore, the whippietree body 30 is able to rotate with respect to the whippietree mount 32 and the upper arm member 34, about an axis perpendicular to the axis of rotation of the pivot joint 38, and the surfaces of the upper arm member 34. The whippietree body 30 comprises three internal passages which act as loop points about which the control wires 54 for the fingers 24 and thumb 28 can be looped. The loop points retain the wires with respect to the whippietree 30, thus anchoring the wires 54. In the example shown, each loop point comprises a pair of adjacent holes 140 formed in the body of the whippietree 30. The holes 140 of the loop points are internally connected by an arcuate passage such that a wire 54 can be threaded into the whippietree body through the first hole of a pair and then back out of the body 30 through the second hole of the pair. As discussed above, the wires 54 attached to the fingers 24 loop around a loop point at the whippietree 30 and then pass back down the arm assembly 20 to the adjacent finger. The wire 54 which is attached to the thumb loops around a loop point, but is then tied off at the exit of the second hole of the pair, anchoring the wire 54 at the whippietree 30. It will be appreciated that for embodiments where each finger 24 has a separate control wire 54, additional anchor points may be provided for each wire. Furthermore, any suitable type of anchor point may be used. For example, the passages which form the loop points may pass straight through the entire whippietree, such that a wire passes into the first passage at the distal end of the whippietree 30, out of the first passage at the proximal end of the whippleteree, then back into a second passage at the proximal end and out of the second passage at the distal end, forming a loop. Other anchor points such as pegs or the like may also be used. Rotation of the whippietree 30 varies the path length of each wire 54 (or portion of wire) between the whippietree 30 and digit 24. This enables a varied grip whereby there is a difference in the amount of travel undertaken by the index finger 24a compared to the little finger 24d. This can be necessary when grasping irregular shaped items which have a significant variation in diameter, such as conical objects. When holding a regular shaped object, (for example a cylinder) the whippietree body 30 is symmetrically oriented with respect to the with respect to the whippietree mount 32 and upper arm member 34, as shown in Figures 11 and 14. However, when an uneven object is held, the whippietree body 30 rotates about its pivot point. For example, when holding a conical item with the larger end near the thumb, the index finger 24a requires much less travel that the little finger 24d the whippietree body 30 rotates in a first direction to ensure a secure grip. Similarly, if the conical item is held the opposite way around, the whippietree body 30 rotates in the opposite direction. The whippietree 30 facilitates an uneven grip as the rotation of the whippietree 30 creates additional slack in the wires 54 connected to one side of the hand 16 whilst tensioning the wires 54 on the opposite side of the hand 16. This creates an uneven distribution of force across the wires 54 and therefore allows for a variation in the travel of the fingers 24 and thumb 28. This is shown in Figure 1 5 where the little finger 24d has increased travel compared to the index finger 24a. In addition to adjusting the length and width of the prosthesis 14, the palm 26, thumb 28 and fingers 24 are modular and hence removable and replaceable. The use of a single threaded bar to join all four fingers 24 to the palm 26 means that the fingers 24 are quick and easy to remove and replace. This enables a suitably sized hand 16 to be attached that is in proportion with the user’s body. Figure 21 shows three differently sized interchangeable palms 26 next to each other. Though the palm 26, thumb 28 and fingers 24 are available in a variety of sizes, the connection points 90 remain the same size to enable them to be easily interchanged to allow for customisation of the prosthesis 14. Fingers 24 of various sizes can be fitted to any palm 26 to allow a completely customisable prosthesis 14 that is suitably sized for the user. When this is used in combination to the adjustable width and length of the arm assembly 20, the user has the ability to resize and refit their prosthesis 14 whenever required using their current prosthesis 14 and the components contained within it, as well as new components that have been purchased. The wires 54 are taut when the prosthesis 14 is in its neutral position as shown in figure 1 9. When the elbow joint 38 is bent, meaning that the upper arm member 34 and proximal forearm 42 are no longer collinear, the tension on the wire 54 is increased causing the fingers 24 and thumb 28 to be pulled inwards towards the palm 26 creating a fist, as seen in Figure 1. When the tension is decreased, the fingers 24 and thumb 28 return to their neutral position with the aid of elastic bands 108 on the knuckle side of the fingers 24 which act as biasing means. Figure 19 shows the prosthesis 14 in its neutral position. The prosthesis 14 uses elastic bands 108 (shown in Figure 16), in this case small circular elastic bands akin to dental elastics used for securing braces, to ensure the fingers 24 and thumb 28 remain in the neutral position unless tension is applied to the wires 54. In alternative embodiments elasticated wire could be used to provide the same functionality. In the neutral position, all elastic bands 108 are visible and the recesses 110 in which they sit can easily be viewed. These recesses 110 have a cross section of a right-angled trapezoid with an undercut, whereby the sloped edge undercuts the central section and allows the elastic 108 to contract. This shape reduces the likelihood of the elastic bands 108 coming loose and pulling out of their recess 110. It will be appreciated that any suitable resiliently biased member may be used to secure bias the digits back to the neutral position. Each finger 24 features recesses for two separate elastic bands 108, one elastic band 108 tensions the finger knuckle 128 (proximal interphalangeal joint), whilst the other elastic band 108 tensions the palm knuckle 130 (metacarpophalangeal joint). In the illustrated embodiment the distal interphalangeal joints 132 have been fused and therefore do not have any movement as they are in a permanent fixed position. In alternative embodiments, the distal interphalangeal joints 132 may be hinged in the same way as the other finger joints 128, 130. The thumb 28 features recesses 110 for three separate elastic bands 108, tensioning both thumb knuckles 128, 130 (metacarpophalangeal joints) and the carpometacarpal joint 86 between the palm 26 and the thumb 28. The elastic bands 108 act as biasing means and pull the fingers 24 and thumb 28 back to a neutral position after they have been in tension. As discussed above, the upper arm members 34 are connected to the proximal forearm portions 42 via pivot joints 38. In the illustrated embodiment (an arm) the pivot joint 38 is an elbow joint 38. The elbow joint 38 will now be described in more detail, with reference to Figures 1, 2, 6 to 11 and 19. The elbow joint 38a comprises an inbuilt revolute joint 56, 58 formed as a single part. This may be, for example by 3D printing or other additive manufacturing process. During the printing process, support material separates the moving components. The support material is then removed after the print is complete, providing parts that can move relative to each other, whilst being formed as a single integral component. The joint 38 comprises an inner cylindrical member 58 and an outer cylindrical member 56, arranged around the inner member 58. Figure 6 shows the upper arm member 34, with the joint 38 shown in cutaway (such that the forearm member 2 1 extends into the page). With reference to, for example, Figure 11, the upper arm member 38 includes the inner cylindrical member 58 of the elbow joint 38a. In the illustrated embodiment, the inner cylindrical member 58 is integrally formed with and rigidly connect to the upper arm member 34. The inner cylindrical member 58 is formed by a cylindrical sidewall 51 defining a central passage 66a. The sidewall 51 extends from the first surface 40a of the upper arm member 34, in the same direction as the connection points 42. A central axis of the cylinder defines the axis of rotation of the joint 38. At each end of the cylindrical wall 51 there is a flange 55 projecting radially outward from the sidewall 51. In the example shown, the flange 55 extends around the entire circumference of the cylindrical wall 51. A pair of slots 60 are formed through the sidewall 51, extending a portion of the length of the wall 51 between the flanges 55. The slots 60 are situated diametrically opposite each other around the cylindrical wall 51. Each slot 60 extends for approximately 90 degrees around the circumference of the sidewall 51, such that they are considered elongate. Wire deflection portions 59 are defined by the sidewall 51 between the slots 60. Figure 7 shows the proximal forearm portion 42 which features the outer member 56 of the elbow joint 38a. In the illustrated embodiment, the outer member 56 is integrally formed with and rigidly connected to the proximal forearm member 42. The outer member 56 is formed by a cylindrical sidewall 53, defining a central passage 66b. The sidewall 53 is formed as a hoop at the proximal end 41 of the proximal forearm portion 42, with the primary axis of the hoop extending perpendicular to the length and width of the forearm member 21. The length of the cylindrical sidewall 53 along its primary axis is substantially equal to the spacing between the flanges 55 of the inner cylindrical member 58. The inner diameter of the outer cylindrical member 56 is greater than the outer diameter of the inner cylindrical member 58. In this way, the inner cylindrical member 58 may be received within the central passage 66a of the outer section cylinder 56. In the illustrated embodiment, the inner diameter of the outer section cylinder 56 is smaller than the outer diameter of the flanges 55 on the inner cylindrical member 58. The flanges 55 therefore hold the inner section cylinder 58 in place along the axial direction, within the outer cylindrical member 56. To ensure stable rotation about a single axis only, the outer diameter of the inner cylindrical member 58 is a tight fit to the inner diameter of the outer cylindrical member 58. This prevents wobbling, whilst still allowing rotation. The outer diameter of the outer cylindrical member 56 is the same as the outer diameter defined by the flanges 55. Furthermore, in order to provide a stop on the rotation of the elbow joint 38, the proximal forearm portion 42 includes a projection 48 extending along its length. The projection 48 ends short of the proximal end 41 of the proximal forearm portion. The spacing of the projection 48 from the elbow joint 38 and the shaping of the end of the projection 48 is arranged such that the projection contacts the flange 55 of the inner cylindrical member 58 projecting from the inner surface 40b of the upper arm member 34 once the joint has rotated by a certain amount, preventing further rotation. In one example, the elbow joint 38 and proximal forearm portion 42 may be arranged to limit rotation to just over 90 degrees (for example 95 degrees). However, it will be appreciated that the arm may rotate anywhere between 0 degrees and 180 degrees in either a clockwise Z2 or anticlockwise Zi direction. The outer cylindrical member 56 comprises two holes 102, 70 extending through the cylindrical wall 53, at diametrically opposed positions on the sidewall 53. The first hole 102 passes from within the passage 66b of the cylindrical sidewall 53, into the channel 100 of the proximal forearm portion 42. The first hole 102 is elongate, extending around a portion of the circumference of the sidewall 53. The first hole 102 aligns asymmetrically with the centreline of the proximal forearm portion 42a, and allows the control wires 54 to pass from inside the proximal forearm 42a into the elbow joint 38a. The hole 102 is asymmetric around the centreline of the proximal forearm 42a since the channel 100 in the distal forearm 36a is offset from the centreline of the distal forearm 36a. The second hole 70 is circular and is located directly in line with the centreline of the proximal forearm 42 a. The second hole 70 extends through the sidewall 53, and allows the control wires 54 to exit the elbow joint 38a such that they can be anchored at the whippietree 30. The diameter of the second hole 70 is approximately equal to the height of the first hole 102 and the slots along the axial direction of the cylindrical sidewalls 51, 53. On the inner surface of the cylindrical wall 53, there is a groove 57 which extends around the entire circumference of outer cylindrical member 56. In the illustrated embodiment, hole 102 is larger than hole 70. This is to minimise the risk of wires 54 catching or snagging during movement of the elbow 38a. In the assembled joint, the inner cylindrical member 56 is received within the passage of the outer cylindrical member 58, such that their primary axes coincide. Therefore, the passages 66a, 66bformed in the cylindrical members 56, 58 also coincide, forming a central passage 66 of the elbow joint having a primary axis along the axis of rotation of the joint. In the neutral (unbent) position, as shown in Figures 8 and 19 (180 degree angle of rotation), the holes 70, 102 in the outer cylindrical member 56 align with an end of the slots 60 in the inner cylindrical member 58. Thus wire deflection portions 59 are located such that when the elbow 38a is in the neutral position, the wire deflection portions 59 are on either side of the wires 54, and are close to touching them such that the angular distance from each wire deflection portion 59 to the nearest hole 102, 70 is much greater in a first rotational direction, for example anticlockwise Zi in Figure 8, than in a second rotational direction, for example clockwise Z2 in Figure 8. Therefore, when the cylindrical members 56, 58 are rotated relative to each other, about their coincident primary axes, the holes 70, 102 remain aligned with the slots, whilst when rotated in the opposite direction, the holes 70, 102 move out of alignment with the slots 60. In the neutral position, the wires 54 enter the elbow joint 38a from the proximal forearm 42a, and then pass first through the first hole 102. The wires 54 then pass through the slots 60, between the wire deflection portions 59, and out of the second hole 70. The path of the control wires 54 is therefore substantially straight, along a diameter of the cylindrical portions 56, 58. Consider rotating the proximal forearm member 42 relative to the upper arm member 34 in directions Zi (anticlock wise) and Z2 (clockwise) shown in Figure 8. Figure 9 shows the elbow joint 38a with the proximal forearm member 42 rotated through 90 degrees in direction Zi, such that the holes 70, 102 remain aligned with the slots 60. When the prosthesis 14 is in tension (i.e. the elbow joint is bent), the wires 54 are still able to pass across the central passage 66 of the elbow joint linearly but additional tension is created due to the increased travel between the elbow exit hole 70 and the whippietree 30, as shown in figure 9. Figure 10 shows the elbow joint 38a rotated through 90 degrees in the opposite rotational direction (Z2). In this case, the control wires 54 pass along the extended path length from the whippietree 30 to the exit hole 70 as discussed above. In this configuration, the control wire 54 cannot pass straight across the central passage 66 of the joint 38. Instead, the wire 54 passes through the hole 70, around a portion of the groove 57, before passing out a first slot 60. The wire 54 then extends diametrically across the central passage 66, in through a second slot 60, around a further portion of the groove 57 and out the hole 102 into the proximal arm portion 42. Now, when the prosthesis 14 is in tension, the wires 54 pass through the elbow joint 38a in an “S” shape, therefore increasing the path length of the wires 54 when the elbow 38a is bent, compared to Figure 9. Therefore, in the second configuration, rotation in the second direction Z2 causes a greater change in the path length (and therefore applies a greater tension) than the same amount of rotation in the first direction Zi. Alternatively, this increased path length in the second configuration means that less rotation is required at the elbow 38a to move the digits (fingers 24 and thumb 28) by the same amount than is required when the elbow 38a is bent in the first configuration. This arrangement means that when the elbow joint 38a is rotated in one direction, the wire deflection portions 59 move away from the wires 54 and so do not affect the path length (low gearing), but when the elbow joint 38a is rotated in the opposite direction, the wire deflection portions 59 contact the wires 54 immediately and then carry the wires 54 through their rotation, forming the “S” shaped path discussed above (high gearing). As discussed above, elbow joints 38 tend to bend in a single direction. Therefore, dependent on the orientation of the installed elbow joint 38a the prosthesis can be set at either high or low gearing which determines the amount of movement required at the elbow joint 38 a to fully open and close a fist. With low gearing, shown in Figure 9, more movement at the elbow 38a is required to open and close the fist. High gearing, shown in Figure 10, however increases the distance the wires 54 must travel during elbow contraction and therefore less movement is required in the elbow 38a to open and close the fist. In the illustrated embodiment, the elbow joint 38a through which the wires 54 pass is provided on the outer arm assembly 20a (i.e. the arm assembly on the side of the residual limb away from the body of the user). The joint 38a in the Figures is configured to provide low gearing on a right arm when the inner surface 40b of the upper arm member 34 is provided against the residual limb. The same joint 38a would therefore provide high gearing if used as a left arm since the arm assembly 20a would have to be flipped such that inner surface 40b of the upper arm member 34a was in contact with the residual limb, and so the relative rotational direction would also flip (from Zi to Z2). To provide an elbow joint 38a which is configured to provide high gearing on a right arm and low gearing on a left arm, the arrangement of the slots 60 in the sidewall 51 is mirrored in the centreline of the forearm. In one example, the elbow joint 38b of the inner arm assembly 20b may have this mirrored arrangement, so that to switch between high gearing and low gearing, the inner and outer arm assemblies 20ab, may be swapped (and the control wires 54 re-wired in the new outer arm assembly 20a). To achieve this, both upper arm members 34a,b may include whippietree assemblies 18, or at least whippietree connectors 72 to allow the whippietree assembly 18 to also be switched. In an alternative example, the proximal elbow joint 38b of the illustrated embodiment does not include any slots 60 or holes 70, 102, since the control wires 54 do not pass through the proximal joint 38b. As such, to switch between high gearing and low gearing, a separate outer arm assembly 20a is required. In a further alternative example, the outer arm assembly 20a may simply be flipped over to switch between high gearing and low gearing, such that the outer surface 40a of the upper arm member 34 and the outer surface 46a of the proximal forearm member 42a are now in contact with the residual limb. In yet a further example, the elbow joint 38 may be able to be disconnected, to allow just the upper arm member 34a to be exchanged or flipped. The above description sets out one way of implementing a telescopic forearm member 21. It will be appreciated by the person skilled in the art that any suitable telescopic coupling between the two portions 36, 42 of the form arm may be used to allow the length of the forearm member 21 to be modified. Furthermore, in the example discussed above, pinet joints 33 are used at one of the connectors 22b from the forearm member 21 to the hand 16, and at the joints within the hand. However, it will be appreciated that this is by way of example only, and any suitable hinged, pivotable or movable joint may be used. Optionally the joint may have a single axis of rotation, two axes of rotation or three axes of rotation. In the above example, a whippietree joint mechanism is used to anchor the control wires 54 at the proximal end 39 of the arm. It will be appreciated that this is by way of example only. Any suitable anchor point for fixing the control wires 54 may be used. The anchor may be rigid or pivoted to allow variation in tensions in the control wires 54 as the prosthetic arm 14 is bent. In the illustrated embodiment two arm assemblies 20 are provided. It is envisioned that the prosthetic 14 may comprise a different number of arm assemblies 20, for example there may be only a single arm assembly 20, or three or more arm assemblies. In the above embodiment, the parts are formed using additive manufacturing techniques. It will be understood that any suitable manufacturing technique may be used such as casting, milling, carving for example. In the illustrated embodiment, the prosthesis 14 is a prosthetic arm. It is envisioned that the prosthesis 14 may be configured to replace another limb, such as a leg, with a foot at the distal end. The pivot joint 38 may be a knee joint. In the illustrated embodiment, a prosthetic hand assembly 16 is fitted to the distal end of the telescopic member. It is envisioned that other attachments may be used, such as a split hook. Embodiments with a split hook may not have a whippietree assembly 18 since the split hook is not capable of variable grip and so uneven tension in the wires 54 is not required. It is preferable that the connector 22 through which the control wires 54 pass forms a rigid connection to the hand assembly 16 whilst the other connector 22 comprises a pinet hinge, however it is envisioned that the control wires 54 may pass through a connector 22 comprising a pinet hinge. For example, the wires 54 may pass through passages formed in the projection forming the pinet joint 33. In the illustrated embodiment, the distal forearm 36 is at least partially received within the proximal forearm 42. It is envisioned that the proximal forearm 42 may instead be received within the distal forearm 36. In the above embodiment, a pair of holes is used to receive fastening means to lock the telescopic member in place. In other embodiments, more or fewer holes may be used. For example, triplets of holes may be used. In the illustrated embodiment, the inner 58 and outer 56 elbow sections are integrally formed with the upper arm member 34 and the proximal forearm 42 respectively. In alternative embodiments, this may be the other way around such that the inner section 58 is integrally formed with the proximal forearm 42 and the outer section 56 is integrally formed with the upper arm member 34. It is also envisioned that one or both of the pivot joint sections 56, 58, may not be integrally formed with an arm member, and may instead be provided as separate parts. In this case, the inner cylindrical member needs to be formed in separate parts to allow the joint to be assembled. The joint 38 may be assembled using welding, adhesive, clips, friction fits or the like. In the illustrated embodiment, two wire deflection portions 59 and two slots 60 are provided on the inner section 58 of the pivot joint 38. In other embodiments, different numbers of slots 60 and wire deflection portions 59 may be provided. For example, only a single slot 60 and wire deflection portion 59 may be provided. Furthermore, the elbow joint 38a may be arranged such that rotation in either direction is low gearing and rotation in the other direction is high gearing, by changing the relative rotational positions of the wire deflection portions 59 in the neutral position. The high gearing direction will always be in the same direction as the shorter distance between the holes 70 102 in the outer cylindrical member 58 and the wire deflection portions 59. In addition, the elbow 38 may be arranged to have a configuration that has low gearing over a first range of rotation in a first direction, and then high gearing over a second range of movement in the same direction (for example low gearing over the 0 to 15 degrees and high gearing over rotation over 15 degrees in the same direction). This may be accomplished by modifying the alignment of the holes 70, 102 in the outer cylindrical member 58 and the slots 60 in the inner cylindrical member in the neutral position. For example, if the holes 70, 102 are arranged such that, in the neutral position, the holes are 15 degrees from one end of the slots 60, there is a range of movement over which low gearing is maintained, before the high gearing commences. Thus, but varying the amount the joint 38 can rotate before the holes 70, 102 and slots are no longer aligned, direction in the same direction can have both low and high gearing is made. In the opposite direction, there is a range of the remainder of the slot (in the example discussed above 75 degrees) before high gearing is adopted. Alternatively, the rotational length of the slot may be increased to maintain low gearing across a longer or shorter extent. Embodiments may be provided without the groove 57 in the outer cylindrical member 58. In the illustrated embodiment, the control wires 54 are housed inside the palm 26, fingers 24, and thumb 28. In other embodiments, these components may be solid and the wires 54 may be provided on the outside surface of the digits. Although the invention has been described with different features in combination with one another it is to be understood that one or more features may be provided separately from others in a prosthetic limb or in another application and also that one or more features may be provided in combination with alternatives of other described features in a prosthetic limb. For example, the telescopic forearm member 21 may be used with any elbow joint 38, and the elbow joint 38 may be used with any forearm member 21. It will be appreciated by the person skilled in the art that various modifications may be made to the above described embodiment without departing from the scope of the present invention.

Claims

1. A prosthetic limb device comprising:a first member and a second member each configured to be secured to a residual limb in use, wherein the first and second members are spaced apart from one another to contact the residual limb at different positions on the residual limb; anda support structure configured to be connected between the first and second members in use, wherein the support structure is releasably connectable to the first and second members.

2. The prosthetic limb device of claim 1, wherein the first and second members each comprise an elongate structure.

3. The prosthetic limb device of claim 1 or of claim 2, wherein the support structure is configured to be connected between the first and second members at a plurality of different connection positions on the first and second members.

4. The prosthetic limb device of claim 3, wherein the support structure is configured to be connected between the first and second members at a plurality of different connection positions along a length of the first and second members.

5. The prosthetic limb device of any preceding claim, wherein the support structure is configured to be secured between the first and second members using a strap.

6. The prosthetic limb device of claim 5, wherein each of the first and second members and the support structure comprises at least one aperture for receiving the strap.

7. The prosthetic limb device of claim 6, wherein each of the first and second members comprises a plurality of apertures spaced apart from one another on the respective member.

8. The prosthetic limb device of claim 6 or of claim 7, wherein the support structure comprises a plurality of apertures spaced apart from one another.

9. The prosthetic limb device of claim 8 dependent from claim 7, wherein a number of apertures in the plurality of apertures on each of the first and second members is greater than a number of apertures in the plurality of apertures on the support structure.

10. The prosthetic limb device of any of claims 6 to 9, wherein the respective apertures of the first and second members and the support structure are configured to substantially align when the support structure is connected to the first and second members.

11. The prosthetic limb device of any preceding claim, wherein the support structure comprises a surface configured to substantially follow an external shape or profile of the residual limb.

12. The prosthetic limb device of any preceding claim, wherein the support structure comprises a substantially curved or arc-shaped cross-section.

13. The prosthetic limb device of claim 12 dependent from any of claims 6 to 10, wherein the support structure comprises:a main body configured to engage the first and second members; anda protrusion extending from the main body, wherein the protrusion comprises the at least one aperture for receiving a strap.

14. The prosthetic limb device of any preceding claim, wherein the support structure comprises a substantially rigid structure.

15. The prosthetic limb device of any preceding claim, wherein the support structure is configured to resist or inhibit a twisting or scissoring motion of the first and second members relative to one another, when connected between the first and second members in use.

16. The prosthetic limb device of any preceding claim, comprising an appendage or end effector connected to a distal end of the first and second members, wherein the appendage or end effector is movably connected to one of the first and second members.

17. The prosthetic limb device of claim 16, wherein the appendage or end effector is pivotably or hingedly connected to one of the first and second members.

18. The prosthetic limb device of any preceding claim, wherein the first and second members are each extendable to adjust a length of the first and second members.

19. The prosthetic limb device of claim 18, wherein the first and second members each comprise a telescopic extendable member.

20. A support structure for a prosthetic limb device, the prosthetic limb device comprising first and second members each configured to be secured to a residual limb in use and spaced apart from one another to contact the residual limb at different positions on the residual limb:wherein the support structure is configured to be connected between the first and second members in use, and wherein the support structure is releasably connectable to the first and second members.

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