Novel Elastomer Gel Liner with Perspiration Elimination Mechanism

Abstract

A method of making a prosthetic liner for use with a prosthetic assembly that acts as the interface between the residual limb of an amputee and the socket assembly. The prosthetic liner comprises an open proximal end, a closed distal end, and sidewalls comprising an inner layer of molded thermoplastic gel. A thermoplastic material is molded over a mandrel that has been sandblasted using #36 grit and, optionally, #320 grit at 100 psi so as to form microcraters and reduce the coefficient of static friction. The liner further includes a sweat port incorporated into the distal end with a one-way valve for the elimination of perspiration.

Claims

1. A prosthetic liner comprising: an open upper end; a closed bottom end incorporating a sweat port having a one-way valve at a distal tip attached to a cylindrically symmetrical buttress; fabric sidewalls having a thickness wherein said sidewalls further comprise an inner layer of thermoplastic material having a Young's Modulus stress force value of less than 2.4 N per square millimeter containing no additives, said inner layer of thermoplastic material formed by sandblasting a mandrel prior to molding said thermoplastic material into said inner layer and further having a thermoplastic material thickness wherein said thermoplastic material has microcraters having a depth between 0.0100 and 0.0195 millimeters; and at least one channel in the distal end of the liner which penetrates the inner layer of thermoplastic material and the cylindrically symmetrical buttress such that the one-way valve of the sweat port can conduct air, gases, and perspiration from the inner layer of thermoplastic material to the exterior of the prosthetic liner.

2. The prosthetic liner of claim 1 wherein the thickness of the sidewalls is between 1.5 and 3 millimeters.

3. The prosthetic liner of claim 1 wherein the silicone thickness at the bottom end is between 3 and 12 millimeters.

4. The prosthetic liner of claim 1 wherein the thermoplastic material is silicone.

5. The prosthetic liner of claim 1 wherein the thermoplastic material is an elastomer gel.

6. The prosthetic liner of claim 6 wherein the elastomer gel is a styrene block copolymer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following descriptions, taken in conjunction with the accompanying drawings, in which:

[0022] FIG. 1 is a front view of the improved prosthetic liner;

[0023] FIG. 2 is a sectional view of a silicone or thermoplastic gel sheet formed using a mandrel that has not been sandblasted;

[0024] FIG. 3 is a sectional view of a silicone or thermoplastic gel sheet formed using a mandrel sandblasted with #36 grit at 100 psi;

[0025] FIG. 4 is a sectional view of a silicone or thermoplastic gel sheet formed using a mandrel sandblasted with #320 grit at 100 psi;

[0026] FIG. 5 is a graph showing the effect of sandblasting on the pulling force necessary to remove a silicone sheet from a steel substrate showing the effect on the static coefficient of friction;

[0027] FIG. 6 is a cross-sectional view of a non-pin locking liner incorporating a perspiration elimination mechanism of the present invention;

[0028] FIG. 7 is a cross-sectional view of the pin-locking liner incorporating a perspiration elimination mechanism of the present invention;

[0029] FIG. 8 is a cross-sectional view of an embodiment of the present invention wherein a buttress is present having cylindrically symmetric sections;

[0030] FIG. 9 is an elevational view of an integral sweat port and pin combination;

[0031] FIG. 10A is a top view of a separate sweat port having a vent; and

[0032] FIG. 10B is a side view of the sweat port illustrated in FIG. 10A.

[0033] Similar reference numerals refer to similar parts throughout the several views of the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0034] The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing one or more preferred embodiments of the invention. The scope of the invention should be determined with reference to the claims.

[0035] The present invention relates to a liner 100 for use with prosthetic devices. As shown in FIG. 1, the liner 100 for use with a prosthetic assembly comprises an open upper end 12 for receiving a residual limb, not shown, a closed bottom end 14, and sidewalls 16 of predetermined thickness. The liner is airtight when donned over a residual limb. The preferred thickness of the sidewalls 16 is about 1.5 mm to 3.0 mm. Note that the thickness is greater at the bottom end than in the sidewalls; the preferred thickness of the silicone at said bottom end 14 is about 3.0 mm to 12.0 mm. The sidewalls 16 have an inner layer 18 of the improved silicone or elastomer described herein. The sidewalls 16 can be fabric or another layer of more durable and higher friction silicone.

[0036] Prior to molding the silicone, a mandrel is sandblasted using #36 grit at 100 psi. The particular grit and pressure used provide the beneficial characteristics of the present invention. Other grits and pressures did not produce the benefits of reduced frictional hold and less chance of skin irritation. After sandblasting the mandrel, the silicone is molded over it, allowing the silicone to seep into the microcraters formed by the sandblasting. As can be seen in FIGS. 2-4, the size of grit used during sandblasting has a sizeable effect.

[0037] FIG. 2 depicts a sheet of silicone 20 that has not been sandblasted. As can be seen by the cross-section 2-2, not sandblasting the mandrel results in a smooth exterior surface 22 which maintains the high frictional characteristics of silicone. FIGS. 3 and 4, on the other hand, show a microscopic view of exterior surface 22 after having the mandrel sandblasted. FIG. 3 shows the microcratering the exterior surface 22 is subjected to using #36 grit at 100 psi thereby creating microcraters 24. Along line 3-3, the microcraters created generally have a depth of about 0.0195 mm. FIG. 4 shows the microcratering the exterior surface 22 is subjected to using #320 grit at 100 psi. Sandblasting with #320 grit may be done alone or after the mandrel has been sandblasted with #36 grit. Along line 4-4, the microcraters created generally have a depth of about 0.0100 mm. The deeper microcraters create a lower static coefficient of friction for silicone because there is less surface area for the exterior surface 22 to be in contact with, as can be seen when comparing the sheet in FIG. 3 with the sheet in FIG. 4. Sandblasting between #36 and #320 grit may also be performed.

[0038] Alternative methods of creating the microcraters 24 of differing depths include, but are not limited to, modification of the mandrel surface via rolling, compression of the mold against a textured surface, chemical etching, laser engraving, computer numerical control (CNC) engraving, electro-erosion (i.e. electrical discharge machining), electrodeposition, laser micro melting, shot blasting, shot peening, and pinwheeling. Similar methods now known or to be discovered which are equivalent to the methods included (i.e. methods that create microcraters in the exterior surface of a silicone layer in a prosthetic liner) are intended to be included in the above listing.

[0039] Three tests were performed to exhibit the beneficial properties of the present invention, the results of which are shown in FIG. 5. In the first, the mold was sandblasted using #36 grit at 100 psi and it took 1.6 N of force in terms of pull resistance, i.e. prior to tearing. In the second test, the mold was sandblasted using #320 grit. The result was 2.33 N of force in terms of pull resistance. In the final test the mold was not sandblasted at all and required 9.33 N of force. The tests were performed on smooth stainless steel using silicone strips that were 1-inch-wide and 7 inches long while applying 100 grams of weight.

[0040] The present invention can also be modified to improve the functionality of thermoplastic elastomer gel liners. Using thermoplastic molding techniques such as pressure molding or compression molding in combination with the methods described herein, the inner layer 18 of the liner 100 can be made of microcratered thermoplastic elastomer gel comprising a styrene triblock copolymer (such as those as described in U.S. Pat. No. 6,552,109 to Chen), polyurethane, polybutylene, or polypropylene. Unlike silicone, the sidewalls 16 of gel liners are usually thicker and can range from 3 to 12 millimeters in thickness with a preferred thickness at the bottom end 14 between 3 to 15 millimeters.

[0041] In addition, as shown in FIGS. 6-10B, the liner 100 may also include a sweat port 26. The liner 100 comprises a proximal edge 28 and a distal end 30 which includes a distal tip 32. A sweat port 26 is positioned at the distal tip 32. The distal tip 32 comprises, within it or attached to it, a buttress 34. The buttress 34 generally comprises a polymeric material having a degree of elasticity which is less than that of the liner, or in other embodiments, the buttress 34 comprises a support material, such as aluminum or other metals; or rigid plastics or other materials, which are over laid with a polymeric material. In embodiments in which the buttress 34 contacts the prosthetic socket, the polymeric component of the buttress softens the contact and prevents grinding which can wear the socket and irritate the wearer. The buttress can be embedded within the liner during liner manufacture, or in other embodiments, it is adhered to the end of the liner. It is preferably underlain by a section of the liner, regardless of whether it is embedded within the liner during liner manufacture or it is adhered to the liner distal tip during or after manufacture. The buttress 34 generally has cylindrical symmetry about the long axis of the liner. In one embodiment it is a disc of a thickness less than liner thickness and is entirely embedded within the liner. In another embodiment, it is partially within the liner and partially outside the liner (“anchored” in the liner). This embodiment is particularly useful in situations where a large buttress which is thicker than the liner is required.

[0042] In one embodiment, the buttress 34 is of a form such that a distal tip portion of the liner elastomer or silicone is between sections of buttress having cylindrical symmetry. In one embodiment, an internal buttress section 36 is embedded in the distal tip of the liner, and an external buttress section 38 is externally attached to the elastomeric liner distal tip. Such an arrangement can be created by mechanically sealing a portion of the distal tip section between the two buttress components, or it can be achieved by casting the liner around the buttress components using flow through holes 56, or otherwise including the buttress components in the fabrication and cooling of the liner, such that the buttress sections are essentially melt-sealed on both the inside and the outside of the distal tip of the liner.

[0043] When the liner is in use, the buttress 34 is structurally sandwiched between the residual limb stump and the socket, providing critical support for the pin 40, as shown in FIG. 7. In some embodiments, the support is further improved in that the buttress is shaped to facilitate insertion into the socket, or the socket has a shape which complements the shape of the buttress. In preferred embodiments, the buttress extends at least 0.5 cm from the vertical axis of the liner, and is at least half the thickness of the liner body at its distal tip, and preferably, at least as thick as the liner body at its distal tip.

[0044] The inner layer 18 which can be used in the system of the present invention comprises an elastomeric material preferably of a type compatible with long periods of dynamic wearer contact. Such materials are known in art and may include the following polymer types and materials which include them: polyurethanes; block copolymers such as styrene block copolymers, generally non-limiting examples of which may include SEBS, SEPS, SEEBS and SEEPS and other types of styrene block copolymers. Further examples of styrene block copolymers which may be useful in the liner of the present invention include the so-called “controlled distribution” polymers, such as those disclosed in U.S. Pat. No. 7,226,484; U.S. Patent Application Publication Nos. 20070238835; 20050008669. Other potentially useful polymers may include so-called “crystalline” polymers, such as, for example, polymers disclosed in U.S. Pat. Nos. 5,953,396; 6,420,475; and 6,148,830. The above list is non-limiting, and in general, the list of acceptable polymers and gels includes those known in the art to be useful in the fabrication of prosthetic liners. By the term “gel,” it is meant a polymer having associated with it, through means known in the art, such as absorption, mixing or other, a plasticizer. A suitable liner which can be modified to include a buttress is the “EZ Gel” liner, available from Alps South L.L.C.

[0045] The inner layer 18 comprises a channel 42 passing through the liner from its inner surface to its outer surface. The channel 42 may be formed by piercing or punching, with or without the removal of elastomeric material from the liner. In one embodiment, the liner 100 is pierced such that little or no material is displaced, and the channel 42 is essentially closed by the elastomeric response of the liner material. In such cases, the pressures associated with the ambulatory motion of the patient can cause perspiration produced during wear to be squeezed through the channel 42. The channel 42 essentially acts as a relief valve which allows the elimination of perspiration emitted by the wearer. The perspiration occupies a volume between the liner and the wearer, potentially giving rise to undesirable interruption of vacuum. In the foregoing embodiment, a closed channel can assist in maintaining and reestablishing the vacuum.

[0046] The channel 42 can also be open. Such a situation is experienced with removal or displacement of liner material, such as with a punch or heated awl-type tool. As the buttress 34 sections extend over the distal tip 32, the channel 42 traverses them such that it opens out onto the distal tip 32 i.e., the portions of the channel 42 traversing the elastomer and those traversing the buttress sections are continuous. It should be noted that the channels through the elastomer and those through the buttress sections need not be of the same diameter. For example, it is permissible for the channel through the elastomer to be of the type described above in which perspiration can be passed under pressure.

[0047] The distal tip 32 of the liner, including the buttress 34, comprises a sweat port 26. The sweat port 26 is continuous with the channel 42, and it is preferably located approximately at the distal apex 44. By “distal apex” it is meant the lowest point on the long axis of the liner, including the buttress, when its long axis is oriented vertically with its distal tip pointing downward. As explained in greater detail infra, the sweat port 26 is attached to a pin which is received by the socket of the prosthetic. In some embodiments, the pin may not be precisely at the distal tip. For example, it may be desirable in some embodiments to attach the prosthetic in such a way that the pin is located at a point near, but not precisely at the distal apex. However, it should be noted that regardless of where the sweat port 26 is located, it is continuous with the channel 42. The sweat port 26 is a nipple or port extending from or partially/fully embedded or recessed in the distal tip 32 of the liner. In a preferred embodiment, at least a portion of the channel 42 through the buttress 34 contains threads 48, and the sweat port comprises matching threads 46 by which it can be screwably attached to the channel. In a preferred embodiment depicted in FIG. 6, the channel 42 extends from the surface of the distal tip 32 in a threaded extension which is attached to the liner buttress 34. In the embodiment depicted in FIG. 7, the threaded channel 42 is recessed in the distal tip surface of the liner buttress.

[0048] The sweat port 26, as shown in FIGS. 10A and 10B, contains a one-way valve which allows an exit for perspiration, air, and other liquids or gases which cause a volume increase between the liner and the wearer. The valve 50 is small enough to fit within the sweat port and can be one of many different kinds of check valves. In different embodiments, the valve is a duckbill, ball, diaphragm, swing, clapper, lift or other type of check valve. In a preferred embodiment, the one-way valve is a duck bill valve.

[0049] The sweat port 26 is attached to a pin 40 which, in use, is inserted into a prosthetic limb. The pin 40 is a spike of a durable material such as stainless steel or other metal or could be plastic, which is generally in the range of from about 1 inch to about 3 inches, which is inserted into a prosthetic limb. It can bear protrusions or other irregularities in profile which aid in securely fitting the prosthetic to the liner. Optionally, the prosthetic limb can include a locking mechanism which maintains the prosthetic securely in place.

[0050] The sweat port 26 can be removably attached in series with the pin 40 as illustrated in FIG. 7 to form a port/pin assembly. Such a connection can be a threaded connection or other method of sealably engaging the sweat port 26 and the pin 40 and generally includes a vent 52 for the efflux of perspiration or another means of dissipating and draining the perspiration passing from the interior of the liner. In a preferred embodiment of the present invention, the sweat port 26 is integral with the pin 40, depicted in FIG. 9, for example, where a vent 52 is clearly visible on the side of the assembly.

[0051] In another embodiment of the present invention, the inner layer 18 has an inner fabric liner 52 on its inner surface which over lays the distal tip 32, and in some embodiments extends along the inner surface a distance in the range of from about 1 to about 19 inches from the proximal edge of the liner. In some embodiments, the fabric liner 52 extends to within no less than 0.5 inches from the proximal edge 28 of the liner 100, and in other embodiments, to within no less than 1.0 inches from the proximal edge 28. A fabric which absorbs perspiration helps to wick it toward the distal end of the liner. Preferred fabrics are those that absorb emitted perspiration, such as natural fibers, such as, for example, felt, wool and cotton fabrics and materials, as well as synthetic fabrics and materials, such as, for example rayon, orlon and nylon. In other embodiments, a sock which has a high perspiration absorbency can function as the fabric liner, preferably extending to no less than 0.5 inches from the proximal edge. It is preferred that the fabric have a thickness in the range of from about 0.5 to about 3.0 millimeters. It should be noted that regardless of fabric type and thickness, the present invention includes within its ambit embodiments comprising fabrics or materials having the ability to wick and/or store perspiration such that when weight is placed on the limb, the residual limb compresses the perspiration bearing fabric or material, and some or all of the perspiration is forced through the channel and the sweat port.

[0052] Furthermore, the fabric liner can be an elastic fabric to facilitate its ability to stretch somewhat with the motion of the liner. In some embodiments, the fabric liner comprises fabrics which are manufactured in such a way to optimize their elastic properties, especially when used as a liner material for an elastomeric liner body.

[0053] A benefit of the present invention is that the constant elimination of perspiration through the sweat port 26 one-way valve aids in restoring a vacuum to the liner/residual limb complex. A further benefit is that as small amounts of sweat are constantly eliminated through the sweat port, they evaporate readily from the area surrounding the sweat port, and thus no need exists to dispose of larger amounts of perspiration. However, if desired, perspiration can be routed to a receptacle, such as a void in the prosthetic or another method of containment.

[0054] In general, even in the absence of fabric, the compression motion which occurs during ambulation acts to force accumulated perspiration through the channel into the sweat port 26, and ultimately through the one-way valve 50. In this way, emitted perspiration is voided before it can have a significant effect on the vacuum, which is renewed with each step.

[0055] In general, liners of the present invention may comprise an elastic or elastomeric fabric 54 which overlays all or a portion of the sidewalls 16 of the liner body. Such fabrics can have an elasticity which is greater than or less than the elasticity of the liner body. In some embodiments of the present invention, the liner comprises elastic or elastomeric fabrics to improve the fit of the liner and affect the overall elasticity of the liner.

[0056] It should be noted that the pin 40 of the present invention can be used with both trans-femoral and trans-tibial amputees. It could be expected that in order to tailor the effectiveness of the inventive liner product and method to a particular circumstance, it may be expedient for one of skill in the art to locate the sweat port/pin at a location other than the distal apex in order to facilitate an efficient evacuation of perspiration. In general, because of the physical parameters involved in ambulation, it is expected that the location of the sweat port would not be more than an inch from the distal apex, and in all likelihood, a smaller distance. A liner having a sweat port which is relocated to meet the perspiration drainage needs of a particular wearer does not represent a departure from the teachings herein and is encompassed within the scope of the present invention.

[0057] The present disclosure includes that contained in the appended claims, as well as that of the foregoing description. Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention.

[0058] Now that the invention has been described,