Seal and suspension liner for a prosthesis

A seal (24) for a suspension liner (30) comprises a tubular substrate having an axis and a plurality of fins (26) projecting radially from the substrate. The tubular substrate has an axis and the fins (26) nm reciprocate axially as they nm peripherally around the substrate. The seal (26) may be mounted on the suspension (30) liner or fins may be integrally formed on the outer surface of the liner.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Section 371 of International Application No. PCT/GB2017/052108, filed Jul. 18, 2017, which was published in the English language on Jan. 25, 2018 under International Publication No. WO 2018/015736 A1, which claims priority under 35 U.S.C. § 119(b) to British Patent Application No. 1612436.4, filed Jul. 18, 2016, the disclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a suspension liner for a lower limb prosthesis. In particular, the present invention relates to a seal and a suspension liner bearing such a seal for use in maintaining a reduced pressure in a socket when used with a prosthesis.

BACKGROUND TO THE INVENTION AND PRIOR ART

A prosthesis can be attached to a residual limb in the following manner. A hollow hard socket is custom made to accommodate the shape of the residual limb. The socket includes means for attaching the prosthesis to the socket. Before inserting the residual limb into the socket a soft flexible liner is typically donned on the residual limb to serve as an interface between the residual limb and the socket. The liner is typically made from an air impermeable material such as silicone.

An intimate fit is required between the residual limb, the liner and the socket. This close fit is required to prevent relative motion between the socket and liner and the residual limb, to prevent irritation of the skin and other soft tissue of the residual limb. The intimate fit better distributes forces on the residual limb when weight is applied to the prosthesis via the socket. For a lower limb prosthesis, this will occur when the prosthesis is in contact with ground, for example when standing and during the stance phase of the gait cycle. Additionally, air expulsion, typically via a one-way valve, achieved as a result of the intimate fit is used to contribute to the formation of a reduced pressure/(partial) vacuum between the liner and the socket so that the prosthesis remains suspended from the residual limb. For a lower limb prosthesis, this will occur during the swing phase of the gait cycle, when the limb is not in contact with the ground. Hence, the presence of a low pressure/vacuum between the socket and the residual limb/liner combination is a desirable feature of such prostheses.

A number of methods have been used to maintain a reduced pressure between the socket and the liner during the swing phase. For example, our patent application published as GB-A-2486817 describes a vacuum assisted suspension device for a prosthesis comprising an air impermeable socket shaped to receive a limb portion. The socket has a peripheral edge and includes an evacuation port and a non-return valve associated with the evacuation port. The evacuation port and return valve are arranged to maintain a vacuum between the socket and the limb portion when the latter is received by the socket. The device includes a sleeve which spans the peripheral edge of the socket and the limb portion. When air is evacuated/expelled from the socket via the evacuation port the sleeve acts as a seal.

As a further example, our patent application published as EP-A-2254526 describes a vacuum-assisted liner system for the socket of a limb prosthesis which secures the prosthesis to a residual body portion. The system includes a flexible liner made of an impermeable material, at least a distal part of the liner being porous to allow the transport of air and fluid directly away from the residual body portion to the outer surface of the liner. A fabric distribution layer is located over the liner and between the liner and the socket to allow transmission of such extracted air and fluid laterally over the liner to an evacuation port in the socket.

There are other known methods of sealing the cavity between the exterior of the suspension liner and the interior of the socket. For example the liner may include peripheral seals which bear on the interior wall of the socket to form an airtight seals. US-A1-2011/0264239 describes a suspension liner sleeve having an elongate, generally conical body. The liner sleeve includes a plurality of resilient seal elements protruding radially from the liner sleeve outer surface. A pair of adjacent annular recesses may be located above and below each of the seal elements. When the limb and liner are inserted into the socket the seal deforms against the force exerted by the socket into its associated annular recess and seals against the interior of the socket. A number of alternate seal designs are described in that document. Other prior art publications include U.S. Pat. Nos. 6,726,726, 6,645,253, WO-A-01/070147 and WO-A-02/067825.

US-A1-2015/0105867 describes a gel liner with a patterned texture on its outer surface and a socket with a complementary and interlocking patterned texture on its inner surface.

US-A1-2012/0116538 describes a liner a medial zone of which comprises ridges aligned with a posterior portion of an associated articulating zone.

WO-A1-2016/015024 describes a system and method for sealing a prosthetic socket.

WO-A1-2015/073793 describes a seal component selectively placed over an outer surface of a suspension liner having a plurality of seal bands.

A disadvantage of existing seal products and liners bearing such seals is that the seal makes the liner difficult to don. This is because of the thickness of the seal and its rigidity which makes stretching of the corresponding portion of the liner difficult. Additionally, once the liner is donned it can cause increased pressure on the residuum in the area of the seal, which can lead to irritation of the skin and adjacent tissue. This is particularly the case where the seal is positioned against bony areas and neuromas. This problem has been mitigated somewhat by providing seals which can be disposed at different heights along the length of the liner, thereby avoiding sensitive areas of the skin. However, these seals are typically relatively inelastic and exert a high hoop-stress around the limb portion where they are positioned. In addition, it is not always possible to locate the seal at a position along the liner without impinging on a sensitive area of the residual limb.

The present invention provides an improved seal and a liner bearing that seal.

SUMMARY OF INVENTION

According to a first aspect of the invention, there is provided a seal for a suspension liner, the seal comprising: a tubular substrate having an axis; and one or more fins projecting radially from the substrate and running peripherally around the substrate, wherein the or at least one of the fins reciprocates axially as it runs peripherally around the substrate.

The wave form of the fins of the seal may provide one or more of the following advantages:Natural flow of movements of material in donning, thereby creating a more robust seal with the socket.Natural flow of movements of material in doffing the residual limb from the socket interface made with less resistance from direction of frictional forces.Easier circumferential stretch (producing lower hoop-stresses) than would be the case with a simple circumferential fin/seal.Easier donning/doffing due to the easier circumferential stretch of the “wavy seal”.The wave shape of the seal allows the positioning of sensitive areas away from rigid or thickened fin regions, in other words outside the seals, between the waves.

The fin or fins may be endless. All of the fins may reciprocate axially as they run peripherally around the substrate. The fin or fins may reciprocate sinusoidally around the substrate.

A plurality of or all of the fins may be parallel to each other and edges of the substrate may be parallel to the fins.

The fin or fins may have a triangular, rounded, saw-tooth or other shaped profile or a mixture of such profiles.

According to a second aspect of the invention there is provided a seal for a suspension liner, the seal comprising: a tubular substrate extending along an axis; and a plurality of fins projecting from the substrate and running circumferentially around the substrate, wherein at least one of the fins runs around the substrate and reciprocates between the intersection of a pair of planes which pass through first and second points along the axis and which are perpendicular to the axis, the first and second points being separated by a distance greater than the width of the fin.

According to a third aspect of the invention there is provided a seal for a suspension liner, the seal comprising: a tubular substrate; and a plurality of fins projecting from the substrate and running circumferentially around the substrate, wherein the length of at least one of the fins is greater than the shortest circumference around the substrate passing through any point of that fin.

The seals as described above may be is made from a resiliently elastic material.

According to a further aspect of the invention there is provided a suspension liner comprising an elongate, generally frusto-conical or cylindrical body which is closed at a first end and open at a second end, the body bearing a seal as described above at a position between the open and closed ends of the body.

According to a further aspect of the invention there is provided a suspension liner comprising an elongate, generally frusto-conical or cylindrical body having an axis and one or more fins projecting radially from the body and running peripherally around the body, wherein the fin or one or more of the fins reciprocate axially as it/they run peripherally around the body.

The fins may be grouped together over a minority of an axial length of the liner or may be spaced apart over a majority of an axial length of the liner.

The liner may be perforated distal and/or proximal to the fin or fins.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring toFIGS. 1A and 1B, a seal10for a suspension liner in accordance with the invention has a substrate12and a plurality of fins14projecting radially from the substrate10. The seal10is made from a flexible silicone material, for example by moulding. The substrate12is generally tubular, i.e., it is open at both ends and is made such that when viewed from above it has a round cross section around a longitudinal axis16. However, since the seal10is made from flexible silicone material it is easily deformed and does not necessarily maintain a tubular shape. The substrate12should be as thin as possible to be able to support the fins14and may have a thickness of around 0.5 mm. The inner diameter of the tubular substrate12can be varied in order to accommodate limbs of different girth. For example, this diameter may vary between 20 cm and 55 cm for lower extremity prostheses and the range would be smaller when used in conjunction with upper extremity liners. The seals can also be attached peripherally around edges of an inner wall of a hip dis-articulation socket, a shoulder dis-articulation socket or to an orthotic device.

There are four endless fins14running peripherally around the substrate12. The fins14are ‘wavy’ in that the fins14reciprocate axially as they run peripherally around the substrate12. The wavy shape of the fins14mimics a sinusoidal curve as the fins14pass around the substrate12. Each fin14extends longitudinal (parallel to axis16) along the substrate12between positions which intersect with a pair of planes (P1, P2) which pass through first and second points along the axis16and which are perpendicular to the axis16, the first and second points being separated by a distance greater than the width (W) of the fin14. In other words, the fins14do not run directly around the substrate12but deviate from a plane running perpendicular to the axis16.

The fins14inFIGS. 1A and 1Bhave a round profile. The fins14project radially from an outer surface18of the substrate12by around 5 mm and have a width of around 3 mm. As can be seen fromFIGS. 1A and 1B, the fins14run parallel to each other as they circle the substrate12. Upper20and lower22edges of the substrate12run parallel to the fins14such that they also follow a wavy sinusoidal path.

In use, the seal10is placed over a liner (as described below) before the liner and seal12are inserted into a prosthetic socket. Since the fins14have a raised profile, the fins14in use press against an inner wall of the prosthetic socket to create an airtight seal with that wall. The liner and seal combination is typically used with a socket incorporating an expulsion valve placed distal to the position of the seal, to provide for expulsion of air from the socket cavity. The expulsion valve may optionally be connected to an external vacuum source. The fins14can be constructed using silicone or another material having a single durometer or a variety of durometers throughout their profile and which may be the same or different to the durometer of the substrate12.

FIG. 2Ais a side view of a seal24according to a second embodiment of the invention andFIG. 2Bis a cross-section thereof. The seal24has a similar overall shape to the seal10ofFIGS. 1A and 1B, however the fins26of the seal24have a triangular profile, rather than the rounded profile of the fins14of the seal10.

FIG. 3Ais a side view of a seal28according to a second embodiment of the invention andFIG. 3Bis a cross-section thereof. The seal28has a similar overall shape to the seal10ofFIGS. 1A and 1B, however the fins29of the seal28have a saw-tooth profile, rather than the rounded profile of the fins14of the seal10ofFIGS. 1A and 1Band the triangular profile of the fins26of the seal24ofFIGS. 2A and 2B.

FIG. 4is a perspective view of a suspension liner30on which is mounted the seal24shown inFIGS. 2A and 2B. The suspension liner30may be a ‘standard’ liner, typically made from a non-porous/air impermeable material, or may be a perforated liner, for example, as described in our granted patent EP-B-2653138, to assist with sweat/moisture management. Alternatively the liner in part or whole may be made of a porous material. When the seal24is mounted on a perforated liner (to be used with a vacuum suspension system) the perforations will typically be in the distal portion of the liner beyond the seal. Additionally it is conceivable to perforate the liner both proximal and distal to the seals, as long as the area of the liner30where the seal is mounted is sufficient to be airtight against the amputee's skin and the seal24is airtight against the socket wall in the region of the fins26.

The liner30is flexible and is to be fitted over the body portion (whether upper or lower limb) and made of a material impermeable to air. The liner may optionally be covered with a fabric layer, to ease insertion and removal from the socket. When the seal24is placed over the liner30it is positioned such that it engages with an inner wall of a socket to provide a sound seal with the socket and it also to be positioned such that the fins26do not align with a sensitive part of the amputee's limb, thereby avoiding applying pressure to such a sensitive area. Hence an advantage of having a separate seal24and liner30provides for easy customisation and repositioning of the seal24on the liner30. Also, since the fins26are subject to greater lateral forces on insertion into and removal from the socket than the liner30, not adhering the seal24to the liner30allows for easily replacement of the seal24whilst the liner30itself maintains its structural integrity.

The seal24can be fixed in place on the liner30by applying an adhesive (e.g., liquid adhesive or double-sided tape) or the seal24can be held in place merely by means of the compressive force which it applies to the liner30when worn on the limb. Attaching the seal24to the liner30using adhesive may be performed by spreading a liquid adhesive on the seal24and/or the liner30or the adhesive may be applied to these parts within micro-spheres which burst when the seal24is pushed against a chosen part of the liner30. Alternatively other permanent or semi-permanent attachment means may be used.

FIG. 5is a perspective view of a suspension liner40comprising a liner body42and incorporating fins26A as shown inFIGS. 2A and 2B. The liner40has a similar appearance to the liner30ofFIG. 3other than the integral formation of the fins26A together with the liner body42of the suspension liner40.

WhilstFIGS. 4 and 5have been described as including fins26,26A having a profile as shown inFIGS. 2A and 2B, the skilled person will understand that the fins may have the profile as shown inFIGS. 1A and 1B,FIGS. 3A and 3Bor another profile.

FIG. 6is a cross-section view of a lower part of a suspension liner50on which is mounted the seal28as shown inFIGS. 3A and 3Bwhen inserted into a socket52. As can be seen in this Figure, when the liner50and seal28combination is inserted into the socket52the fins29push against an interior wall54of the socket52to seal the distal portion56of the liner50in the socket52. Where the socket includes an expulsion valve (not shown) a reduced pressure can be maintained in the cavity58formed between the distal portion56of the liner50, the fins29and the socket52. Note that for diagrammatic convenience the volume, and in particular the width, of the cavity58is exaggerated inFIG. 6, whereas in practice the volume of this cavity58will be minimal in the presence of a reduced pressure when an expulsion valve is used. In other words, the outer surface of the liner50will generally abut the inner wall54of the socket52.

It can be seen fromFIG. 6that a feature of the fins29having a saw-tooth profile is that the liner50and seal28combination can be easily inserted into the socket52whereas removal of the liner50and seal28combination from the socket52will be impeded by the fins28which will be drawn into closer contact by the associated increase in vacuum generated in cavity58, unless the expulsion valve is opened.

Various modifications will be apparent to those in the art and it is desired to include all such modifications as fall within the scope of the accompanying claims.

In the embodiments described above the fins have either a triangular, a rounded profile or a saw-tooth profile. In other embodiments the fins have other profiles including either solid or inflatable profiles.

In the embodiments described above all of the fins are wavy. In other embodiments one or more, but not all, of the fins may be wavy, i.e., the non-wavy seals may circle straight around the substrate, following a plane passing perpendicular through an axis of the seal/liner.

In the embodiments described above the fins follow a wavy trajectory around the seal substrate or liner. In other embodiments the fins may have straight sections whilst overall reciprocating axially along the substrate or liner.

In the embodiments described above the fins are grouped together and equally spaced over a minority of the length of the liner. In other embodiments there may be a single fin or the plurality of fins may be spaced unequally or the plurality of fins may be spaced along the majority of the length of the liner.

In the embodiments described above both upper and lower edges of the substrate are wavy and run parallel to the fins. In other embodiments one or both of the edges may not run parallel to the fin or fins, e.g., they may be cut straight along a plane running perpendicular to a point along the axis of the substrate.

Rather than incorporating a seal into a seal as described with reference toFIG. 5, the seal may be incorporated into a fabric tube which would allow easier positioning of the tube and seal on a liner.

Similarly, the seal may be incorporated into a sock which is to be placed over a liner whether or not the liner already includes a fabric cover. Such a sock would require a means for sealing the interior of the sock in the region of the seal against the liner, for example by disposing rubber or silicone on the interior of the sock.

When the seal is placed over a liner the inner wall of the seal may seal against the outer wall of the liner to produce an airtight seal. In other embodiments the seal between the inner wall of the seal and the liner outer wall may not be completely airtight. For example, where an external vacuum source is attached to the socket there may be sufficient vacuum produced to allow ingress of some air between the inner wall of the seal and the liner outer wall, where a fabric layer may be deployed. This gentle flow of air over the liner outer surface could be used to cool the limb, for example.

In the present invention the fin or fins which project radially from the substrate of the tubular sleeve or from the body of the liner are used to provide a seal against an interior surface of a socket. In other embodiments, a fin or fins may be provided on an interior surface of the tubular substrate or on an interior surface of the liner body, to improve the seal between the tubular sleeve and the liner and/or between the liner and the skin.

In the embodiments described above the fins have a height of around 5 mm. In alternative embodiments the fins may have a height of between 3 mm and 8 mm, and preferably between 4 mm and 6 mm. In other embodiments the height of the fins may vary as the fins pass around the seal or liner.

In the embodiments described above the fins have a width of around 3 mm. In alternative embodiments the fins may have a width of between 1.5 mm and 5 mm, and preferably between 3 mm and 4 mm. In other embodiments the width of the fins may vary as the fins pass around the seal or liner.