WO2017221019A1

WO2017221019A1 - Prosthetic system and method

Info

Publication number: WO2017221019A1
Application number: PCT/GB2017/051833
Authority: WO
Inventors: Malav SANGHAVI
Original assignee: Creoto Limited
Priority date: 2016-06-22
Filing date: 2017-06-22
Publication date: 2017-12-28
Also published as: GB201610926D0

Abstract

A system for a prosthetic comprises a plurality of expandable gas bladders (140) and at least one valve (120) to allow gas to flow into and/or out of the bladders. The system has a plurality of pressure sensors (160). The system has one or more vents in fluid communication with the source of gas and/or the plurality of gas bladders. At least one of the one or more vents is arranged to direct gas to an area to be cooled. There is also at least one vent valve (150a) to control gas exit from the one or more vents. The system further has a control system (104) for controlling the pressure in the plurality of gas bladders in response to measurement data produced by the plurality of pressure sensors. A method of fitting a prosthetic is also provided.

Description

PROSTHETIC SYSTEM AND METHOD

This invention relates to a prosthetic system and a method of operating a prosthetic system. In particular, the invention relates to a system that cools the stump of person using a prosthetic.

Background

The number of amputees in the world is vast and is ever increasing. People who have lost a limb either use crutches or prosthetic limbs to facilitate their day to day life. A prosthetic limb typically comprises a socket for receiving and attaching to a residual limb and an artificial limb or rod that may have some of the functionality to replicate the lost limb. The socket is an important part of the prosthetic limb as it serves as the interface between the residual limb and the artificial limb and determines the comfort and fit of the prosthetic limb. Comfort level is considered the most important aspect of a prosthetic socket without which the functionality of the prosthetic limb is compromised. It is a primary factor which an amputee considers when deciding whether to wear a prosthetic limb or not. The socket must grip the residual limb by some means to prevent detachment of the prosthetic limb. Common types of socket include suction-type sockets, whereby the space between the residual limb and the socket is evacuated to prevent the prosthetic limb from detaching from the residual limb, or interference-type sockets whereby the residual limb is retained in the socket by virtue of the fit or pressure exerted on the residual limb by cushions around the interior surface of the socket. Such sockets are often moulded for a specific user and comprise a substantially rigid shell.

The volume of a residual limb fluctuates during the course of the day depending on the degree and type of activity of the user, and also undergoes considerable change during the first few years following the amputation. Such volume fluctuations can lead to poor socket fit and considerable discomfort to the user. As a result several replacement sockets may be required in the first few years following amputation. Existing solutions to compensate for volume fluctuations and improve comfort include sockets comprising inflatable cushions between the residual limb and the interior of the socket. US5387245 discloses a system combining air cushions with suction: a liner covers the residual limb including selectively (manually) inflatable bladders for customising the liner to fit individual patients. Upon inflation, the liner conforms to the residual limb and the interior surfaces of the socket. Meanwhile, an annual bladder at the proximal rim of the socket creates a seal to maintain suction within the socket. CN201445574 describes an air cushioned socket with an automatic inflation device capable of being regulated according to the residual limb shape. However, air cushioned sockets proposed to date apply constant unrelieved pressure which can adversely affect blood supply. Heat and sweat generated during activity and from the intimate contact between the residual limb and the socket are a major problem of even the best fitting prosthetic devices. Sweat generated within the socket is not easily evaporated or dried. This in itself may cause discomfort; however, prolonged exposure to sweat/dampness can lead to dermatological problems such as skin irritations, blisters and folliculitis that further compound the problem of discomfort and eventually restrict the use of the prosthetic device.

There is therefore a need for an improved socket that can compensate for volume fluctuations and reduce heat and sweat generation.

Summary

Aspects and embodiments of the invention are set out according to the appended claims.

An aspect of the invention comprises a system for a prosthetic comprising: a plurality of expandable gas bladders in fluid communication with and configured to receive gas from a gas source; at least one valve to allow gas to flow into and out of the bladders; a plurality of pressure sensors configured to produce measurement data corresponding to the pressure in the plurality gas bladders; one or more vents in fluid communication with the source of gas and/or the plurality of gas bladders; at least one vent valve to control gas exit from the one or more vents; and a control system for controlling the pressure in the plurality of gas bladders in response to measurement data produced by the plurality of pressure sensors, wherein the control system is arranged to control the pressure in at least one of the gas bladders independently to the pressure in at least one other of the plurality of gas bladders.

The control system may further be configured to control the venting of gas through the one or more vents.

At least one of the one or more vents may be arranged to direct gas to an area to be cooled. The area to be cooled may be an anatomy part, such as the stump of an amputated limb.

The use of gas, as opposed to a liquid, advantageously allows the gas to be vented from the system to control the pressure(s) in the plurality of bladders. It also allows the vented gas to be used to cool an area of the user' s anatomy, such as the user's stump. Gas may be vented through the one or more vents directly from the gas source or from one or more bladders.

In use, the gas bladders are normally fitted or positioned between a prosthetic socket and the stump of an amputated limb. The system allows the different bladders to be inflated to different pressures and/or exert different pressures. This enables the fit of the prosthetic to be customised to a particular stump. The plurality of expandable bladders are inflatable so as to adapt to different shapes and sizes of stumps. The plurality of bladders therefore serve as a dynamic interface between the socket and the stump of an amputated limb.

An advantage of the system is that prosthetic with generic socket can be used for different amputees. This reduces the cost of manufacture of the prosthetic and the time required for fitting the prosthetic by, say, a prosthetist. In some cases the prosthetic could be fitted without a prosthetist. Such advantages are particularly important in developing countries. Alternatively, the system may comprise the prosthetic socket and the plurality of bladders may be integrated or embedded within the prosthetic socket. In this way, the socket and the bladders are or comprise a single unitary part, as opposed to several separate parts that must be fitted together. In this case, the socket itself is a dynamic socket adaptable to different sized stumps. This may allow the system, i.e. the prosthetic socket with the plurality of bladders (dynamic interface) to be mass produced. For example, the socket and the bladders do not need to be customised to particular stump according to the individual user, it may be non-user specific. The bladders may be inflated to fit a variety of different users. The inflation/fit can be controlled by the user themselves. The degree of inflation of the bladders can be altered over time to account for volume loss of the stump or a change in the shape of the stump. This can be done dynamically with the bladders being controlled in response to signals from the pressure sensors. For example, it can be done automatically without user input. The user of the system, for example an amputee or a prosthetist, can customise the level of the grip and/or the position of the grip provided by the bladders to improve the comfort of wearing the prosthetic.

In an embodiment of the invention, each of the plurality of bladders has a pressure sensor associated with it and the control system is configured to control the pressure in each individual bladder in response to a signal produced by its associated pressure sensor. That is, each bladder is individually addressable. This means that there will be a plurality of positions on the stump at which the pressure exerted at that position can be individually controlled and/or measured. In an embodiment, each pressure sensor may be arranged to measure the pressure exerted by the bladder on an anatomy part, such as the stump of an amputated limb, and the control system may be configured to control the pressure exerted by each individual bladder in response to a signal produced by its associated pressure sensor. Each pressure sensor may be arranged on a respective bladder. The sensor may be force resistive sensor.

In use, the system may continually monitor the pressure in each of the bladders or the pressure exerted on a user' s stump at that position. The monitored pressure data may be stored, for example, in a memory in the control system. When a user fits the system, the plurality of bladders may be inflated to a predetermined or user-defined pressure/level to hold/grip the stump according to the required fit. While moving (e.g. walking), the pressure in each bladder and/or the pressure exerted by the stump on each of the bladders (and vice versa) may change, periodically or gradually. This advantageously allows the system to accurately monitor the pressure exerted on/by the stump at a plurality of different points over time. That information may be stored and fed back to the user for future use (for example to optimise the fit). The pressure information may be used to provide a dynamic pressure map of the stump. The pressure data may be used to understand or analyse the user' s stump activity and/or changes. If there are, say, 25 or 33 individual bladders then the pressures exerted by these bladders, at respective 25 and 33 positions, can be monitored/controlled independently. Therefore, there would be 25 and 33 degrees of freedom in the terms of the positions where pressure can be applied.

It is possible for the pressure exerted by each bladder to be set to take different values to each other. However, sub-groups of the plurality of bladders may be set to exert the same pressure. Each subgroup of bladders may correspond to a different region on the stump. In an embodiment of the invention each bladder has a valve to control the flow of gas into and out of the bladder and the control system is operable to control the valve to control the gas pressure inside each bladder. In one embodiment, one control valve may control the gas pressure in more than one bladder. In an embodiment of the invention, the one or more vents are arranged to direct gas to an area to be cooled for example the gas can be directed inside the prosthetic socket. The gas may be vented in the direction of the stump of the amputated limb. One or more vent conduits may be used to direct the gas.

Venting gas from the gas source, either directly or via one or more of the bladders, provides a cooling effect on the stump. This increases the comfort of the stump and reduces the build-up of sweat and potential skin irritations.

In an embodiment of the invention, there is a plurality of vents so that different areas of the stump may be cooled. Each vent may have its own vent valve and the controller is arranged to control each vent valve. In this way different degrees of cooling may be applied to different areas of the stump.

In an embodiment of the invention, the system comprises a porous liner for placement between the plurality of bladders and an anatomy part, such as the stump of an amputated limb, wherein the one or vents are arranged to direct gas to the porous liner.

The porous liner may be a sock suitable for placing over a stump of an amputated limb.

The porous liner may allow vented gas to pass through the liner and also help to distribute the gas over a stump.

In an embodiment of the invention, the porous liner comprises one or more vent outlets and/or vent valves.

The system may further comprise one or more temperature sensors to provide measurement data to the control system. The control system may control the venting of gas directed at areas of the user's stump in response to measurement data produced from the one or more temperature sensors. The one or more temperature sensors may be positioned at different points. Each point may correspond to the area to be cooled. Each individual bladder or group of bladders may have a temperature sensor associated with it. The system may further comprise one or more moisture sensors to provide measurement data to the control system. The control system may control the venting of gas directed at areas of the user's stump in response to measurement data produced from the one or more moisture sensors. The one or more moisture sensors may be positioned at different points. Each point may correspond to the area to be cooled. Each individual bladder or group of bladders may have a moisture sensor associated with it.

The system may monitor and store temperature and/or moisture measurement data. In an embodiment of the invention, the walls of the/each bladder are comprised of a material that has a Young's modulus equal to or greater than 1 GPa. Using a bladder material with a Young's modulus equal to greater than 1 GPa provides sufficient elasticity for the bladder to expand and to conform to the shape of the stump and the socket of a prosthetic. In an embodiment of the invention, the walls of the bladder are comprised of a material that has tensile strength sufficient for the bladder to withstand a pressure in the range 20-40 psi or greater. Generally, suitable bladder materials have a tensile strength of at least 20 MPa.

Suitable materials for making the bladders include plastics. In embodiments of the invention the walls of the bladder are comprised of a plastic material such as a polyvinyl chloride (PVC), thermoplastic polyurethane; elastomer polyurethane; polyester, nylon and combinations thereof. Certain types of latex could also be used.

In an embodiment, the system comprises the source of gas. The source of gas may be a compressed gas source. The gas source may be in fluid communication with the plurality of gas bladders.

In an embodiment of the invention, the gas is air and the source of gas comprises a motor/pump arranged to compress air from the atmosphere. The source of gas may also comprise a reservoir in fluid connection with the pump and arranged to store compressed air received from the pump. Whilst a pump works at a certain flow rate, the reservoir can contain pressurised air that can pressurise the bladders quickly. This is useful if the bladders are inflated and deflated rapidly so as to message a stump.

The gas source may comprise a vessel containing compressed gas. This vessel may be in addition to, or instead of the pump (or pump plus reservoir).

The pump may be motorised pump or a manual mechanical pump. For example, the pump may be a cylinder pump that is configured to pump and compress gas when the user walks.

In an embodiment of the invention, the plurality of gas bladders comprises a plurality of arrays of bladders that are connected together at one end of each of the arrays. For example each array may share a common (e.g. central) bladder. The controller may comprise one or more modules that are in wired or wireless communication with each other.

In an embodiment of the invention, the system comprises a remote control device, wherein the remote control device is configured to communicate to the controller or wherein the controller comprises the remote control. The remote control device may a mobile telephone, Personal Digital Assistant (PDA), Personal Computer (PC), laptop or tablet. The system may further comprise a wireless communication module configured to exchange data between the controller and the remote control device(s).

The sy stem may further comprise a rechargeable battery pack. The battery pack may be coupled to and supported by a/the socket. The control system and/or the pump may be powered by the rechargeable battery pack.

The system may further comprise a pump housing coupled to the socket. The pump housing may be positioned around a periphery of a prosthesis pylon that extends from the socket.

An aspect of the invention provides a system for a prosthetic comprising:

one or more gas bladders;

a source of gas in fluid communication with the one or more gas bladders;

at least one valve arranged to control the flow of gas into and out of the one or more gas bladders;

at least one pressure sensors configured to produce measurement data corresponding to the pressure in the one or more gas bladders;

one or more vents to allow gas to exit the system, wherein each vent comprises a conduit directed to a surface to be cooled;

one or more vent valves to control the exit of gas from the system;

a control system for controlling the pressure in the one or more gas bladders in response to measurement data produced by the one or more pressure sensors, the control system also being configured to control the operation of the one or more vent valves.

The system may comprise a prosthetic socket. The bladders may be integrated with the socket.

An aspect of the invention provides a socket insert for insertion into a socket of a prosthetic device for receiving a residual limb, the socket insert comprising:

a plurality of air bladders arranged to receive pressurised air from a compressed air module, wherein each of the plurality of air bladders is coupled to the compressed air module via a control valve;

a plurality of pressure sensors, wherein each of the plurality of pressure sensors is positioned to measure the pressure exerted by each of the plurality of air bladders;

one or more vents, wherein each of the one or more vents is coupled to the compressed air module and each of the plurality of air bladders via a vent valve; and a controller operable to control the compressed air module, the control valve of each of the plurality of air bladders and the vent valve, based on readings received from the plurality of pressure sensors. The socket insert may comprise the compressed air module.

An aspect of the invention provides a socket of a prosthetic device for receiving a residual limb, the socket comprising:

one or more vents, wherein each of the one or more vents is coupled to the compressed air module and each of the plurality of air bladders via a vent valve; and

a controller operable to control the compressed air module, the control valve of each of the plurality of air bladders and the vent valve, based on readings received from the plurality of pressure sensors. The socket may comprise the compressed air module.

An aspect of the invention provides a system for a prosthetic comprising: a gas source; one or more gas bladders; one or more sensors configured to produce measurement data corresponding to the gas pressure in the one more gas bladders; a vent valve having an input and an output; a supply conduit having an input arranged to receive gas from the gas source, a vent output coupled to an input of the vent valve, one or more bladder outputs in fluid communication with the gas bladders, wherein the bladder outputs are defined between the input and the vent output; a control system for controlling the pressure in the gas bladders in response to measurement data received from the sensors. Each of the one or more sensors is configured to produce measurement data corresponding to the gas pressure in at least one of the one or more gas bladders.

In an embodiment, the control system is arranged to control the pressure in at least one of the one or more gas bladders independently to the pressure in at least one other of the one or more gas bladders.

In an embodiment of the invention, the system further comprises one or more vent conduits, each of the one or more vent conduits having an input arranged to receive gas from the output of the vent valve.

In an embodiment of the invention, the system comprises a plurality of vent valves and a plurality of vent outputs, wherein the vent outputs are in parallel, and wherein each vent outputs is coupled to an input of a vent valve.

The one or more bladder outputs may be defined between any two vent outputs. In an embodiment of the invention, an electronic device is in wireless communication with the controller for controlling the socket insert remotely, generally the electronic device has a user interface and may be, for example, a mobile telephone, PC, PDA, laptop or tablet.

An aspect of the invention provides a method comprises fitting the system socket insert into a prosthetic socket and controlling the pressure exerted by the plurality of bladders so that the bladders grip the stump of an amputated limb placed in the socket. An embodiment of the invention provides a method of adjusting the fit of a prosthetic device to an anatomy part (such as a residual stump) by adjusting the gas pressure in the bladders of the system. An embodiment of the invention provides a method of adjusting the grip of the prosthetic on the stump.

An aspect of the invention provides a method of fitting of a prosthetic to an anatomy part of a user comprising: placing a plurality of gas bladders between the prosthetic and the anatomy part; inflating the plurality of gas bladders using a gas source so that the anatomy part is gripped by the gas bladders; monitoring the pressure applied to the anatomy part by at least one of the plurality of bladders; controlling the degree of inflation of the plurality of bladders so that the monitored pressure is at a predetermined pressure or is within a predetermined range of pressures; venting gas from at least one of the plurality of gas bladders and/or the gas source.

In an embodiment of the invention venting gas comprises venting gas to the anatomy part.

The anatomy part is normally the stump of an amputated limb and fitting the prosthetic comprises inserting the stump into a socket of the prosthetic that contains the bladders.

Alternatively, the bladders may be integrated with the prosthetic socket that is adapted to receive the stump. Controlling the degree of inflation may comprises venting gas from at least one of the plurality of gas bladders so as to reduce the pressure exerted by that bladder

Controlling the degree of inflation of the plurality of bladders may comprise controlling the degree of inflation of one or more of the plurality of bladders so as to exert a pressure that is different to the pressure exerted by least one other of the plurality of bladders.

Controlling the degree of inflation may comprise controlling the pressure exerted by each individual bladder of the plurality of bladders in isolation to the other bladders. The pressure exerted by the bladders may be controlled in response to a user input.

The user input may be received wireless from a remote device such as a personal computer, laptop, PDA, tablet or mobile phone. An aspect of the invention provides a kit comprising the system of any aspect or embodiment of the invention and instructions that define a method according to any aspect or embodiment of the invention. The skilled person will appreciate that various aspects and embodiments of the invention can be used in combination and/or conjunction with each other. For example, the aspects and embodiments of the invention relating to a kit or method can make use of the prosthetic system of other aspects and embodiments of the invention. Similarly, the system of aspects and embodiments of the invention can be operated according to methods set out in other aspects and embodiments of the invention.

Brief Description of Drawings

There now follows, by way of example only, a detailed description of embodiments of the present invention with reference to the accompanying drawings in which:

Figure 1 is an illustration of a person indicating the common types and locations of amputations;

Figure 2 is an illustration of a prosthetic device comprising a socket for receiving a residual limb of an amputee;

Figure 3 is a schematic illustration of an example bladder system for use with a prosthetic device;

Figure 4 is a schematic oblique view of a bladder with an inlet;

Figure 5 is a schematic side view of a bladder for use with the bladder system;

Figure 6 is a schematic bottom view of a bladder;

Figure 7 is a schematic top view of a bladder having a pressure sensor and means to output data from the sensor;

Figure 8 is a schematic oblique view of a bladder having a pressure sensor and means to output data from the sensor;

Figure 8a is a schematic oblique view of adjacent connected bladders each having bladder having a trapezoidal shape;

Figure 9 is an illustration of a compressed gas source comprising a compressed gas chamber;

Figure 10 is an illustration of a compressed gas source comprising a compressed gas reservoir and a pump; Figure 11 is a 2D schematic illustration of 33 bladders connected to form a unitary star-type structure suitable for conforming to the interior of a socket;

Figure 12 is a 3D schematic illustration of the plurality of bladders shown in Figure 11 folded to conform to the interior of a socket;

Figure 13 is a 2D schematic illustration of 25 bladders connected to form a unitary star-type structure suitable for conforming to the interior of a socket;

Figure 14 is a 3D schematic illustration of the plurality of bladders shown in Figure 13 folded to conform to the interior of a socket;

Figure 15 is a 2D schematic illustration of 16 bladders connected to form a unitary belt-like structure suitable for conforming to the interior of a socket;

Figure 16 is a 3D schematic illustration of the plurality of bladders shown in Figure 15 folded to conform to the interior of a socket;

Figure 17 illustrates a liner with a plurality of exhaust valves suitable for distributing vented gas;

Figure 18 illustrates a liner with a single exhaust valve suitable for distributing vented gas; Figure 19 shows a socket comprising a plurality of integrated bladders;

Figure 20 shows a cross-sectional view of the socket of Figure 19;

Figure 21 shows an integrated bladder of the socket of Figure 19;

Figure 22 illustrates a bladder system for use with a prosthetic device;

Figure 23 illustrates a bladder system with multiple vent valves for use with a prosthetic device

Figure 24 illustrates a bladder system with a single vent valve for use with a prosthetic device;

Figure 25 illustrates a bladder system wherein bladders are not individually addressable;

Figure 26 illustrates a bladder system wherein bladders are arranged into groups of bladders, each group being individually addressable and having a pressure sensor; Figure 27 illustrates a bladder system wherein bladders are individually addressable and one or more bladders that have their own vent valve;

Figure 28 illustrates a bladder system with multiple vent conduits each having a vent valve;

Figure 29 illustrates a bladder system with multiple vent conduits sharing a common vent valve;

Figure 30 illustrates a user operating the bladder system via a wireless electronic device; and

Figure 31 illustrates a user operating the bladder system via a wireless electronic device in different grip or activity modes.

Detailed Description

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the deta il s of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.

Prosthetics can be used on various places of the body, in particular where a limb or other body part has been removed by trauma, medical illness or surgery. By way of example, Figure 1 shows a sketch of a human body illustrating the following types of amputation: forequarter amputation 1 , shoulder disarticulation 2, transhumeral (above elbow) 3 , transradial (below elbow) 4, wrist disarticulation 5, hip disarticulation 6, transfemoral (above knee) 7, knee disarticulation 8, transtibial (below the knee) 9, and foot amputations 10.

Embodiments of the invention can be used for prosthetics for various body sites and are particularly useful for prosthetics that have a socket, for example prosthetics for transhumeral 3 , transradial 4, wrist disarticulation 5, transfemoral (above knee) 7, knee disarticulation 8, transtibial (below the knee) 9 and foot amputations 10.

Figure 2 illustrates a stump 20 of an amputated limb and a prosthetic limb 40. The stump 20 normally has a generally convex shape and the prosthetic limb 40 is provided with a socket 30 for receiving the stump 20.

Figure 3 illustrates an example system 100 that comprises a plurality of inflatable bladders 140 that are inserted into the socket 30 of the prosthetic before the prosthetic is fitted. The bladders 140 are then inflated so that the bladders 140 exert pressure outwards on the stump 20 and prosthetic socket 30. In this way the bladders 140 grip the stump 20 and retain the stump 20 within the socket 30. The amputated limb, or other anatomy part that the prosthetic is to be fitted to, may have a different shape to that illustrated in Figure 1. For example, in some rare cases, the muscle around the end of a stump becomes loose and swells down. The inflatable bladders 140 are flexible and can be arranged in various ways to conform to sockets and stumps of arbitrary shape.

The system 100 may have a gas handling system that controls the flow of gas into and out of the bladders 140. The system 100 comprises a gas source 110, a plurality of valves 120, 140, 150, a plurality of pressure sensors and a controller 170. The gas source 110 may be a compressed gas source. Figure 4 illustrates a generic bladder 140. The generic bladder 140 illustrated has a roughly rectangular footprint but it can be of any shape or form. For example, the bladder 140 can be considered to be an "air bag" (or more generally a "gas bag"). The bladder 140 may be generally circular, hexagonal, or triangular, a non-regular shape or be of any generally organic shape. A surface 144 of the bladder (illustrated in Figure 5) is arranged to exert pressure on the stump 20 of a limb. This is nominally referred to as the "top surface" of the bladder 140. When the bladder 140 inflates the top surface 144 of the bladder 140 tends to conform to the outer surface of the stump 20 in contact with the bladder 140. This is due to the nature of a gas being a compressible fluid. When inflated the top surface 144 tends to be free of creases thereby eliminating or reducing a source of irritation to the stump 20. The bladder 140 may uniformly expand on all corners of its surface according to its design and maintain its profile (e.g. trapezoidal), rather than preferentially expanding in the centre of the bladder e.g. creating a peaked cross-section. In use, this may allow a larger area of the top surface 144 of the bladder 140 to be in contact with, and apply pressure to, the stump 20 of a limb. Consequently, for a given gas pressure in the bladder 140, the pressure exerted on the stump 20 may be substantially lower than that which would be applied by a conventional bladder having a substantially peaked cross- section, whilst the larger surface area of the bladder 140 maintains the level of grip.

The material used to make the bladders 140 is preferably a sheet or thin film. The material should be flexible enough in the out-of-plane direction to allow inflation of the bladder whilst strong enough to make bladders that will withstand pressurised gas and deployment with a prosthetic. If the bladders 140 are made with a material that is too stiff then they will not conform well to the prosthetic socket 30 or the stump 20. Such non-conformity will result in a poorly fitting prosthetic and is likely to lead to discomfort for the user and possible tissue damage. A surface 148 of a bladder 140 that is to press against the prosthetic may be larger than the surface of the bladder 144 that is to press against the stump 20. As one example, one or more of the bladders 140 have a trapezoidal shape in side view as illustrated in Figures 5 and 8. As compressed gas enters the bladders 140 it expands a little, the trapezoidal shape provides extra space at the sides of the bladders 140, compared to a cuboid, to account for the gas expansion. In this way, trapezoidal shape allows the bladder 140 to more easily adapt to the shape of the stump 20.

Figure 8a shows two trapezoidal bladders 140 side by side and illustrates the extra space provided between the bladders 140 due to their shape. Materials suitable for manufacture of the bladders 140 include, but are not limited to : polyvinyl chloride (PVC); thermoplastic polyurethane; elastomer polyurethane; latex, polyester; and nylon. The material used can be chosen to suit the application or type of prosthetic. For example, prosthetics associated with the leg may be required to bear more load than prosthetics associated with the arms.

The suitability of the material can be determined using material properties such as tensile strength and Young's modulus (or a related modulus such as the elasticity modulus). These material properties can readily be determined using well known procedures.

The walls of the bladder are comprised of a material that has tensile strength sufficient for the bladder to withstand a pressure in the range 20-40 psi or greater.

The material can also be chosen to have a Young' s modulus greater than 1 GPa, greater than 2 GPa, in the range 1 -5 GPa, in the range 1.5-5 GPa, in the range 2-4.5 GPa.

PVC was found to be a material that has good flexibility and strength and suitable for most bladder applications. One method of making the bladders 140 is to heat seal sheets of material together. Test bladders have been made by heat sealing the edges of PVC sheets. The test bladders had a footprint area of 20 cm x 10 cm and were able to withstand the weight of two people (in excess of 160 kg) without rupture. The size of bladders used in a working system depends on the size of the stump and socket, but may typically be in the region of 5 cm x 5cm for a prosthetic associated with a knee amputation.

In the illustrated system 100, each of the bladders 140 is in fluid connection with the compressed gas source 110. Also in fluid connection with the gas source 110 is a vent having a vent valve 150. In the example system 100 of Figure 3 , each of the bladders 140 has its own control valve 130 so that each bladder 140 can be isolated (i.e. be in "fluid isolation") from the other bladders 140 in the system 100 and the compressed gas source 110. This allows the gas pressure in each bladder 140 to be set at different levels. In addition, one or more bladders 140 may be set (pressurized) at any one time.

The valves 120, 130, 150 are generally two-way valves so that the valves 120, 130, 150 are either open or closed. For example, the valves 120, 130, 150 may be, for example, solenoid valves or other electrically controlled valves. In another example, the valves may be analogue valves with a range of settings between open and closed. Vent valves 150 may also be associated with a downstream flow regulator to limit the flow of gas exiting the system.

As illustrated in Figures 7 and 8 each of the bladders 140 is associated with a pressure sensor 160. The sensor 160 may be, for example, a force resistive sensor that produces an electrical signal in correspondence with the force applied to it. Force resistant sensors are advantageous for this application because they are: relatively thin (typically less than a 0.5 mm thick), flexible, low cost and shock resistant. The sensor 160 may have wires to feed the sensor signal back to the controller 170. Alternatively, a sensor may be used in conjunction with a transmitter that wirelessly communicates the sensor signal to the controller 170.

The sensors 160 can be arranged at different positions on the socket 30 of the prosthetic. The bladders 140 are arranged over the sensors 160 so that there is one bladder 140 over each sensor. For example, as illustrated in Figures 7 and 8, a bladder 140 may be arranged so that there is a sensor 160 at, or near, the centre of the bladder 140. Or, to build in redundancy, there may be more than one sensor 160 per bladder 140. The bladders 140 may touch the sensors 160 directly or there may be an intermediate material between the bladders 140 and the sensors 160. Alternatively, the pressure sensors 160 may be positioned on or coupled to the individual bladders 140 to simplify the fitting.

As illustrated in Figures 5 and 6, a bladder 140 may have a sensor contact area 142 or pad that acts on a sensor 160 such as a force resistive sensor. The sensor contact area 142 is relatively hard compared to the bladder material to facilitate uniform transfer of pressure from the bladder 140 to the sensor 160. The sensor contact area 142 may comprise a hard plastic pad attached to the bladder 140. The sensor contact area 142 does not compress significantly when subjected to the pressure exerted by the bladder 140. The sensor contact area 142 may be of substantially the same size as the active area of the sensor 160. The pressure sensors 160 send sensor signals to the controller 170 corresponding to the pressure exerted by the bladders 140. In response to the sensor signals the controller 170 sends control signals to the control valves 130 so that each of the bladders 140 exerts a predetermined pressure as measured by the pressure sensors 160. In this way each of the bladders is individually addressable. The system 100 may comprise one or more temperature sensors (not shown) to monitor and provide measurement data of the temperature within the socket 30. For example, the temperature may change due to the presence of the user' s stump. Each of the one or more temperature sensors may be associated with an area or group of bladders 140. Alternatively, each bladder may be associated with a temperature sensor.

Alternatively or additionally, the system 100 may comprise one or more moisture sensors (not shown) to monitor and provide measurement data associated with the moisture in the socket 30. For example, moisture may be produced from the user' s stump perspiring. The temperature and/or moisture sensor are in wired or wireless data communication with the controller 170. The sensors 160 can be arranged at different positions on the socket 30 of the prosthetic. Alternatively, the pressure sensors 160 may be positioned on or coupled to one or more individual bladders 140 to simplify the fitting. Signals from the pressure sensors 160, temperature sensor(s) and moisture sensor(s) may be monitored continuously and stored, for example, in a memory in the controller 170. As illustrated in Figure 9, the compressed gas source 110 may take the form of a bottle or canister of compressed gas 112, or more generally a compressed gas reservoir. For example the canister of compressed gas 112 may be a compressed air canister or a canister of compressed nitrogen or other inert gas. Using nitrogen has the advantage that the pressure inside the bladder 20 will remain correct for longer because the rate at which nitrogen passes out the walls of a bladder is slower than for oxygen. Bottled nitrogen is, however, generally more expensive than bottled air.

As illustrated in Figure 10, the compressed gas source 110 may take the form of a pump 114 that compresses ambient air (i.e. air from the surrounding atmosphere) so that the compressed air may be supplied to the system by one or more conduits. The use of a pump 112 that compresses air from the atmosphere overcomes any issues that may occur with bottled gas running out. It also negates the need for a supply of a consumable, i.e. , bottled gas, therefore reducing the operating costs of the system.

The pump 114 may be in fluid connection with a container or chamber 112 so that the compressed air produced by the pump 114 may be stored in the chamber 112, that is, the chamber 112 acts a reservoir of compressed air. The flow of air from the pressurised chamber 112 into the one or more conduits is controlled by an inlet/source valve 120. By using a reservoir 112 in this way, the pressure of the air entering the system the can be more easily controlled. The pump 114 may "re-charge" the compressed gas reservoir 112 periodically at predetermined intervals, or automatically when the pressure in the reservoir drops below a predetermined threshold pressure. Alternatively, the pump may be operated manually by the user. Furthermore, the pump 114 only needs to be operated for short periods of time to "re-charge" the reservoir 112 with compressed air. The pump 114 may preferably be a low maintenance oil-free pump, such as a diaphragm pump. The pump 114 and the reservoir 112 mat be attached to, housed or otherwise carried by the prosthetic. There may be a connection between the pump 114 and the reservoir 112 to allow the pump 114 to be disconnected from the reservoir 112. Such a connection allows the pump 114 to be separated from the reservoir 112 so that it does not need to be carried by the prosthetic. That is, the pump 114 can be connected to the reservoir 112 only when the reservoir 114 needs re-charging.

Figure 11 illustrates a 2D arrangement of 33 bladders 140 for insertion into a prosthetic socket 30. That is, the figure shows the bladders 140 as if spread out on a flat surface. In the arrangement illustrated, there are eight linear arrays 149 of bladders 140 radiating out from a central bladder 141. The arrangement can be said to have a "spider" or "star" shaped pattern.

In each array 149, the bladders 140 are flexibly connected to each other. The arrangement of bladders 140 forms a unitary structure since each bladder 140 has a connection to another bladder 140. The unitary structure and the flexible connections allow the arrangement of bladders to be easily fitted into a prosthetic socket 30 so that each bladder 140 is in a set position within the socket 30 and the unitary structure readily conforms to the socket 30 and the stump 20. For example, if there are pressure sensors 160 at predetermined positions on the inside of the socket 30, each bladder 30 in the arrangement of bladders 140 can be easily placed so it is over a corresponding sensor 160. Figure 12 illustrates the 3D structure that the bladders 140 will take inside a socket 30, when conformed to the interior of the socket 30.

For alternate arrays 149 of the star shaped structure, the array 149 is connected to the central bladder 141 by a triangular shaped bladder 144 so that the bladders 140 can be arranged in the socket 30 without overlapping each other.

Figure 13 illustrates a similar 2D arrangement of bladders as that illustrated in Figure 1 1 except that there are 25 bladders. Figure 14 illustrates the 3D structure that the arrangement will take when placed inside a prosthetic socket 30.

Figure 15 illustrates a 2D arrangement of bladders in a belt type arrangement. Figure 16 illustrates the 3D structure that the arrangement will take when placed inside a prosthetic socket 30. The arrangement may be made up of two or more linear arrays 149 of bladders 140 that can be placed circumferentially in a socket 30. In the example illustrated there are two linear arrays but there may be a single array or more than two arrays. If there are two or more arrays they may be flexibly connected along their longitudinal edges.

The bladders 140 may be arranged inside a socket 30 in conjunction with a liner or sock worn by the amputee over the stump 20, as described in more detail below in reference to Figures 17 and 18.

Figure 19 shows an alternative embodiment whereby the plurality of bladders 140 is integrated with a socket 30. The bladders 140 may be embedded within the socket 30 itself. The bladders 140 may be embedded within an interior surface 32 of the socket 30. The bladders 140 may be bonded to the interior surface 32 or secured by any suitable means (e.g. mechanical).

Figures 20 and 21 show an example of a socket 30 comprising integrated bladders 140 where each bladder 140 is secured to the socket 30 by a clamp or retainer 140a. Each bladder 140 may fit into a recess 34 in the interior surface 32 and be held in place by the clamp/retainer 140a. The clamp/retainer 140a may also fit within the recess 34 such that, in use, the outer surface of the clamp/retainer 140a is substantially flush with the interior surface 32 of the socket 30. The clamp/retainer 140a may be secured to the socket 30 by one or more fittings 140b (e.g. screws). Tightening the fitting(s) may secure the bladder 140 to the socket 30. As shown, the clamp/retainer 140a may extend substantially around the periphery of the/each bladder 140 to hold the bladder 140 in place. Alternatively, where there are a plurality of bladders 140 arranged and connected in an array 148 (e.g. as shown in figures 1 1 to 16), the clamp/retainer 140a may extend substantially around the periphery of the array 148. Alternatively, the socket 30 may comprise a plurality of clamp/retainer elements (not shown) positioned around the periphery of the array 148 to hold the array of bladders 148 at a plurality of points.

It will be understood that the embodiments and features described above with reference to figures 1 to 18 apply equally to the embodiment shown in figures 19 to 21. Figure 22 is an example system 100 in which each bladder 140 has an inlet conduit 146 and an inlet valve 130 to control the flow of gas into and out of the bladders 140. For clarity, only a single array of five bladders 140 is illustrated. However, the system 100 can be used with various bladder configurations such as, for example, the arrangements illustrated in Figures 11 -16. Each bladder also has an associated sensor 160 which is connected to a controller 170 by, for example, electrical wires 172. The controller 170 is also connected to the inlet valves 130 so that the valves 130 can be controlled in response to signals from the sensors 160. In another example, the sensors 160 and valves 130 may be in wireless communication with the controller 170. In the example illustrated in Figure 22, the inlet conduits 146 are connected in parallel to a common supply conduit 152 that is connected to the compressed gas source 110. The common supply conduit 150 also has a vent valve 150 so that gas may be expelled from the system. The output of gas from the system 100 is controlled by the controller 170 via the vent valve 150. The controller 170 may take the form of one or more electronic control chips. The controller 170 may be operated by one or more manual controls and/or by a graphical user interface (GUI), for example, a touch sensitive screen of a hand held device. In one embodiment, the controller 170 is operated by a user interface 190 that is in wireless communication with the controller 170. The user interface 190 may also be in wired connection with the data output e.g. by electrical wires or optical fibres. The user interface 190 can be a bespoke user interface or it may be a suitably programmed mobile device such as a mobile telephone, PC, PDA, tablet, laptop or similar. The software may be available as an "App" which may be pre-installed on the device or downloaded/purchased and/or updated via the Internet. Figure 19 illustrates the user interface 190 in the form of a suitably programmed smart phone. Gas from the vent 150 can be advantageously expelled so that it can cool the stump 20 of a limb that is inserted into the prosthetic socket 30. For example, the gas can be expelled into the region between the socket 30 and the stump 20. The gas from the vent could be expelled outside of the socket 30 but this would not have the desired cooling effect. As illustrated in Figure 17, a liner 200 can be provided that fits over the stump 20 and inside the socket 30 of a prosthetic. The liner 200 is used between the bladders 140 and the stump 20. The liner 200 is preferably constructed from a fibrous material such that gas may pass or diffuse through the liner 200 to reach the surface of the stump 20. The liner 200 may be provided with a plurality of vent valves 150 so that gas can be directed to different areas of the stump 20. Each vent valve 150 can be individually controlled so that specific areas of the stump 20 can be cooled.

The vent valves 150 can also be used to control the degree of venting to the stump 20. This may be achieved by opening only a proportion of the vent valves 150. For example, only alternate vent valves or every third vent valve may be opened so that the amount of cooling gas being vented is reduced but there is still good distribution of gas around the stump 20. Figure 23 illustrates how the vent valves 150 illustrated in Figure 17 may be used as part of a bladder control system 102. The bladder control system 102 can be operated in the same way as described for system 100 illustrated in Figures 3 and 22. The number and/or configuration of vent valves 150 that are opened can be controlled by a user for example using the controller 170. For example, the valves 150 may be controlled by the user interface 190. The proportion of vent valves 150 operated can be chosen to be anything from 0 to 100% or there may be graduated levels of cooling that can be chosen by the user (e.g. low, medium or high). The vent valves 150 may also be operated automatically in response to signals produced by one or more temperature sensors and/or moisture sensors. The controlled venting of gas through the vent valves 150 may occur independently from the control of the bladders 140 and without affecting the pressure in the bladders 140.

Figure 18 illustrates a liner 200 that has a network of vent conduits 210 that are connected to a single vent valve 150. Each vent conduit 210 has one or more vent outlets 220 positioned to vent gas to different parts of the liner 200. Figure 24 illustrates how the vent valves 150 and vent outlets 220 illustrated in Figure 18 can form part of a bladder control system 104. The bladder control system 101 can be operated in the same way as described for system 100 illustrated in Figures 3 and 22. It is normal for the stump 20 of an amputated limb to be fitted with a sock or liner before it is placed in the socket 30 of a prosthetic so as to improve comfort to the wearer of the prosthetic. The liner 200 may be used in place of or as well as such a conventional sock. The vent conduits 210 could also be retrofitted to a conventional sock. The systems 100, 102 and 104 illustrated in Figures 3 and 22-24 are just some examples of how a bladder system can be configured. Figures 25-29 illustrate further example system configurations. Figures 25-29 are simplified diagrams but may comprise further components such as those illustrated in Figures 22- 24. For example, the valves 120, 130, 150 illustrated may be in wired connection with the controller 170 and the controller 170 may be operated by a user interface 190 such as a mobile telephone etc. Alternatively, valves 120, 130, 150 may be in wireless communication with the controller 170.

Figure 25 illustrates a system in which there is an inlet valve 120 controlling the flow of gas from the gas source 1 10 to a plurality of bladders 140 and a vent valve 150 that controls the flow of gas venting from the system. In this example, each individual bladder 140 does not have its own control valve and the pressure exerted by each bladder 140 is not individually addressable. Since there is nothing to isolate the bladders 140 from each other, when the vent valve 150 is closed the pressure in each of the bladders 140 will be substantially the same. Since the bladders 140 all reach the same pressure, the pressure in the bladders can be measured by a single senor 160 associated with the one of the bladders 140 or connected to a conduit that is in common fluid communication with the bladders 140. When there is a change in pressure by gas entering via supply valve 120 or exiting via vent valve 150 the pressure, the pressures in the bladders 140 may take a short time to equilibrate. The system of Figure 25 is simpler in that it has fewer components than in the previously described systems but it still provides cooling to a stump 20 via the vent valve 150.

Figure 26 illustrates a system in which the bladders 140 are arranged in groups 135 so that the pressure in each group of bladders 135 is controlled by its own control valve 130. In this way, the same pressure may be applied to a particular zone of a stump 20. Having a group of bladders 135 comprised of two or more small bladders 140 to apply pressure to a particular zone of a stump is advantageous over using a single larger bladder because the smaller bladders can be more easily conformed to the shape of the zone of the stump 20 in question, and the pressure applied to specific regions/zones of the stump 20 can be more accurately controlled.

Figure 27 illustrates a system in which one or more of the bladders 140 has its own vent valve 150a, so that gas can be vented directly from the bladders 140. In this way a bladders can be vented without opening its control valve 140. The system may also have one or more additional vent valves 150.

Figure 28 illustrates a system that has a several vent lines 210, with each vent line 210 having its own vent valve and being able to operate independently from each other.

Figure 29 illustrates a system that has several vent lines 210 that are controlled by a single vent valve 150.

In the systems described above, the controller 170 may be operated in different modes to provide different levels of grip. For example, in a one mode, where the user (i.e. an amputee) is seated or reclined, a low level of grip can be set thereby reducing pressure exerted by the bladders 140 on the stump 20. Such a mode may be termed a "passive mode" or a "rest mode" . Another mode may be used when the user is moderately active, for example, the user may be walking. Such a mode may be termed "active mode" or "walking mode". In this mode a higher level of grip may be required so the bladders 140 are inflated to a higher pressure than they are in the passive mode. A yet further mode may be used when the user is more active, for example, when the user is playing sport. This mode may be termed "sport mode" . In this mode a still higher level of grip may be required so the bladders 140 are inflated to a higher pressure than they are in the active/walking mode.

Using different modes, according to the activity of the user, can reduce pain and bruising and, in turn, have a positive impact on a user's health.

The different modes may have different levels of ventilation in which different gas flow rates are vented from the bladder system to the stump of the user. In this case, the sports mode can have more ventilation than the active mode which can have more ventilation than the passive mode. Different modes can also be used to improve the blood circulation in a stump 20. For example, if the grip provided by the bladders 140 is high in one or more places on the stump 20 the grip in such places can be relaxed whilst the grip can be an increased in one or more different places. In this way, the same level of grip can be maintained but the muscles and arteries in the previous grip positions can be relaxed.

A massage mode can be used in which a variety of pressures are applied by the system at different points on the stump 20 for short periods of time. This leads to massaging of the stump 20 thus providing better blood circulation and muscle health.

Figure 30 illustrates a prosthetic 40 a fitted to the stump 30 of a user. The prosthetic has socket 30 within which is a bladder system is contained (e.g. the bladder system as described hereinabove). The user can control the fit of the socket 30 by controlling the bladder system with a user interface 190. In the example illustrated, the user interface 190 is in wireless communication 190 with the bladder system and the user interface is 190, for example, a mobile telephone etc. This provides the user freedom to control the degree of grip of the prosthetic on the stump 20 and/or change the amount of pressure applied at different points on the stump. For example, the user may be able to change the pressure applied by each of, say, 25 different points, corresponding to 25 separate bladders 140.

Figure 31 illustrates a user using a mobile phone to set the bladder system in either a passive (sitting), active (walking) or sports mode.

Pressure data can be captured by the system for analysis by the user, a prosthetist or other medical professional. Such data can help in determining how the system can be better operated or how the volume of the stump 20 fluctuates over time. Furthermore, the data can be used in the research and development of prosthetics.

Claims

1. A system for a prosthetic comprising:

a plurality of expandable gas bladders in fluid communication with and configured to receive gas from a gas source;

at least one valve to allow gas to flow into and/or out of the bladders;

a plurality of pressure sensors configured to produce measurement data corresponding to the pressure in the plurality gas bladders;

one or more vents in fluid communication with the source of gas and/or the plurality of gas bladders, wherein at least one of the one or more vents are arranged to direct gas to an area to be cooled;

at least one vent valve to control gas exit from the one or more vents; and

a control system for controlling the pressure in the plurality of gas bladders in response to measurement data produced by the plurality of pressure sensors, wherein the control system is arranged to control the pressure in at least one of the gas bladders independently to the pressure in at least one other of the plurality of gas bladders.

2. The system of claim 1 , wherein each of the plurality of bladders has a pressure sensor associated with it and the control system is configured to control the pressure in each individual bladder in response to a signal produced by its associated pressure sensor.

3. The system of claim 1 or claim 2, wherein each bladder has a valve to control the flow of gas into and out of the bladder and the control system is operable to control the valves to control the gas pressure inside each bladder.

4. The system of any preceding claim, wherein the gas vented from the system is directed by one or more vent conduits.

5. The system of any preceding claim, wherein the one or more vents are arranged to direct gas to the inside of a prosthetic socket.

6. The system of any preceding claim, further comprising a prosthetic socket, wherein the plurality of bladders are integrated with the socket.

7. The system of any of claims 2 to 6, wherein each pressure sensor is arranged to measure the pressure exerted by the bladder on an anatomy part, such as the stump of an amputated limb, and the control system is configured to control the pressure exerted by each individual bladder in response to a signal produced by its associated pressure sensor.

8. The system of any preceding claim, wherein the system further comprises a porous liner for placement between the plurality of bladders and an anatomy part, such as the stump of an amputated limb, wherein the one or more vents arranged to direct gas to the porous liner.

9. The system of claim 8, wherein the porous liner is a sock suitable for placing over a stump of an amputated limb.

10. The system of claim 8 or 9 wherein the porous liner comprises one or more vent outlets and/or vent valves.

1 1. The system of any preceding, wherein each vent has a vent valve and the controller is arranged to controller each vent valve.

12. The system of any preceding claim, wherein the walls of the bladder are comprised of a material that has a Young' s modulus equal to or greater than 1 GPa.

13. The system of any previous claim, wherein the walls of the bladder are comprised of a plastic material.

14. The system of claim 13 , wherein the walls of the bladder are comprised of one of:

(i) polyvinyl chloride (PVC);

(ii) thermoplastic polyurethane;

(iii) elastomer polyurethane;

(iv) polyester;

(v) nylon; and

(vi) a composite comprising one or more of (i)-(v).

15. The system of any preceding claim, wherein the plurality of gas bladders comprises a plurality of arrays of bladders that are connected together at one end of each of the arrays.

16. The system of any previous claim comprising a remote control device, wherein the remote control device is configured to communicate to the controller or wherein the controller comprises the remote control.

17. The system of claim 16 wherein the remote control device is a mobile telephone, PDA, PC, tablet or laptop

18. The system of any preceding claim, comprising the gas source, and optionally or preferably, wherein the gas is air.

19. The system of claim 18, wherein the source of gas comprises a pump arranged to compress air from the atmosphere.

20. The system of claim 19, wherein the source of gas comprises a reservoir in fluid connection with the pump and arranged to store compressed air received from the pump.

21. The system of claim 18, wherein the source of gas comprises a vessel containing compressed gas.

22. The system of any preceding claim, wherein the control system is configured to control the operation of the one or more vent valves.

23. A method comprising:

fitting the system of any of claims 1 to 5 or 7 to 22 into a prosthetic socket; and

controlling the pressure exerted by the bladders so that the bladders grip the stump of an amputated limb placed in the prosthetic socket.

24. A method of fitting a prosthetic to an anatomy part of a user comprising:

placing a plurality of gas bladders between the prosthetic and the anatomy part, or placing a prosthetic having a plurality of integrated bladders against the anatomy part;

inflating the plurality of gas bladders using a gas source, so that the anatomy part is gripped by the gas bladders;

monitoring the pressure applied to the anatomy part by at least one of the plurality of bladders;

controlling the degree of inflation of the plurality of bladders so that the monitored pressure is at a predetermined pressure or is within a predetermined range of pressures;

venting gas from at least one of the plurality of gas bladders and/or the gas source to the anatomy part.

25. The method of claim 24, wherein the anatomy part is a stump of an amputated limb; and placing the bladders comprises inserting the bladders inside a prosthetic socket that is adapted to receive the stump.

26. The method of claim 24 or 25, wherein, controlling the degree of inflation comprises venting gas from at least one of the plurality of gas bladders so as to reduce the pressure exerted by that bladder.

27. The method of any one of claims 24 to 26, wherein controlling the degree of inflation of the plurality of bladders comprises controlling the degree of inflation of one or more of the plurality of bladders so as to exert a pressure that is different to the pressure exerted by least one other of the bladders.

28. The method of any one of claims 24 to 27, wherein said controlling comprises controlling the pressure exerted by each individual bladder of the plurality of bladders in isolation to controlling the pressure exerted by the other bladders.

29. The method of any one of claims 23 to 28, comprising adjusting the pressure exerted by the bladders in response to a user input.

30. The method of any one of claims 23 to 29, comprising adjusting the flow rate of vented gas in response to a user input.

3 1. The method of claim 29 or 30, wherein the user input is received wireless from a remote device such as a personal computer, laptop, PDA, tablet or mobile phone 32. A kit comprising the system according to any one of claims 1 to 22 and instructions to operate the system following the method of any one of claims 23 to 31.