Patent Application
20230190440
This invention relates to liners for use in a prosthetic assembly. Specifically, the described invention relates to liners having a thermoplastic elastomer lining that is smooth to the touch via the use of surface modification of the molds used to create the liners and which are designed to relieve perspiration between the liner and the residual limb of the wearer.
Silicone liners have been used since the 1980s in the prosthetic industry such as those described in U.S. Pat. No. 4,923,474 granted to Klasson and Kristinsson. Other examples of such liners include U.S. Pat. No. 5,728,168 to Laghi et al., U.S. Pat. No. 5,830,237 granted to Kania, U.S. Pat. No. 5,507,834 to Laghi et al., U.S. Pat. No. 5,443,525 to Laghi et al., and U.S. Pat. No. 5,728,168 to Laghi et al.
However, silicone liners have historically been difficult to don and doff due to the high coefficient of static friction of silicone. As such, they tend to stick to the skin of a residual limb. This prevents relative movement at the interface skin/liner and therefore induces high shear forces on the skin in localized portions of the residual limb as the ground reaction to ambulation is transmitted to the skeleton through the silicone interface and the skin. These resulting shear forces increase the likelihood of blistering of the skin, especially for patients with sensitive skin. It is therefore desired to develop a silicone liner having a reduced frictional effect such that the user can easily don and doff their prosthetic liner.
Further, most amputees have had amputations for vascular, as opposed to traumatic, reasons. This means that the amputation was because of poor circulation. Most amputees are also elderly. As such, most amputees have thinner, more delicate, skin which is prone to damage and have reduced blood flow to the extremities giving them less ability to heal sores and wounds. Some elderly amputees end up having recurring amputations as the skin of their residual limbs becomes damaged and infected.
One method that has been developed to thwart these issues is to include additives that exude from the silicone matrix and act as a lubricant between the liner and skin. The issue with this solution is that the exudate can collect dirt on the inside surface of the liner, exacerbating skin damage. Exudates also require more thorough cleaning and make the liner slippery.
Likewise, it is known in the art to use a thermoplastic elastomer gel instead of silicone for prosthetic liners such as those described in 11,179,252 to Laghi et al. These thermoplastic elastomer gels generally comprise a styrene triblock copolymer mixed with a plasticizer which forms a composite with an outer fabric layer. One of the issues with gel liners is that they can be considered sticky by certain users which can prevent relative movement at the interface between the skin and liner.
The present invention utilizes a novel surface modification technique so as to create “microcraters” in the silicone or elastomer gel used for the prosthetic liner, as it is molded, which allow for the liner to be donned and doffed with ease and which is skin-friendly. The method described herein is particularly effective for silicone liners because silicones, when in the liquid state, have low surface tension which allows them to penetrate tiny holes and cracks and, therefore, to create the microcraters. Silicones' viscosity is also inversely proportional to temperature which makes silicone flow easier as they get closer to the surface of the hot mold. As a result, silicones produce a faithful mirror image of the cratered mold surface. Despite having different molding processes, the elastomeric gels normally used for prosthetic liners share similar properties when using the methods described herein.
One issue with elastomeric liners is their ability to thermally insulate which tends to increase the rate at which the residual limb perspires. The supple elasticity which makes elastomeric liners suitable for long term skin contact can have negative consequences when the contact with the skin is broken by a liquid, such as perspiration. While mild perspiration may enhance the seal between the residual limb and the liner, the amount produced quickly increases such that a layer of perspiration is formed between the liner surface and the residual limb surface.
Because of the pressures exerted on the liner during ambulation, particularly by the prosthetic socket, the liner can pull away from the residual limb, causing air to be sucked into the liner. As the air pockets join upon further ambulation, a volume is produced between the liner and the limb. The air in the volume contracts and expands with each step, creating a suction and causing the residual limb to expand inside the liner. Such an expansion affects the fit of the limb and liner inside the socket. Many methods for fitting the limb inside the prosthetic socket can require that the limb be repositioned in order to give a comfortable fit. However, upon cessation of ambulation, such as while sitting down or sleeping, it is not uncommon for the residual limb to shrink inside the liner to its original size, necessitating yet another refitting. Thus, it is of paramount importance that air be excluded from the liner. Toward that end, it is thus important that the build-up of perspiration be prevented, and that perspiration be removed as it is being formed, or soon thereafter, from between the liner and the residual limb. It would be an advance in the art to provide a liner having the beneficial advances of a microcratered surface in addition to the ability to eliminate perspiration.
Therefore, it is an object of this invention to provide an improvement which overcomes the aforementioned inadequacies of the prior art devices and provides an improvement which is a significant contribution to the advancement of the liner art.
Another object of the invention is to provide a silicone liner with a more comfortable interior silicone lining.
Another object of the invention is to provide a method of manufacturing silicone liners having reduced frictional characteristics.
Another object of the invention is to provide a liner having microcraters.
Another object of the invention is to describe a method of making silicone liners by molding the liners using mold mandrels that have been sandblasted.
Another object of the invention is to provide a method of manufacturing a thermoplastic elastomeric gel liner having reduced frictional characteristics.
Another object of the invention is to provide a prosthetic liner having a perspiration voiding system which functions upon ambulation with or without a vacuum pump.
The foregoing has outlined some of the pertinent objects of the invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.
The present invention relates generally to a liner for use in a prosthetic assembly having a thermoplastic elastomer gel interior comprising microcraters by sandblasting the mandrel using #36 grit at 100 psi. Using a sandblasted mold mandrel, a prosthetic liner can be manufactured having improved friction characteristics. The liner of the present invention may optionally include a fabric cover bonded to the exterior surface. The liner further includes a sweat port incorporated into the distal end with a one-way valve for the elimination of perspiration.
The foregoing has outlined rather broadly the more pertinent and important features of the present invention in order that the detailed description of the invention that follows may be better understood so that the present contribution to the art can be more fully appreciated. Additional features of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.
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:
Similar reference numerals refer to similar parts throughout the several views of the drawings.
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.
The present invention relates to a liner 100 for use with prosthetic devices. As shown in
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
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.
Three tests were performed to exhibit the beneficial properties of the present invention, the results of which are shown in
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.
In addition, as shown in
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.
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
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.
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.
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.
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
The sweat port 26, as shown in
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.
The sweat port 26 can be removably attached in series with the pin 40 as illustrated in
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.
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.
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.
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.
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.
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.
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.
Now that the invention has been described,
This application is a continuation-in-part of application Ser. No. 18/083,658 entitled “Novel Elastomeric Gel Liner”, filed Dec. 19, 2022, which is a continuation-in-part of application Ser. No. 17/742,721 entitled “Novel Silicone Liner”, filed May 12, 2022, which is a continuation-in-part of application Ser. No. 16/868,776 entitled “Novel Silicone Liner”, filed May 7, 2020, which claimed the benefit of provisional application No. 62/844,253, filed May 7, 2019, and provisional application No. 62/844,296, filed May 7, 2019, the disclosures of which are incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 18083658 | Dec 2022 | US |
| Child | 18113662 | US | |
| Parent | 17742721 | May 2022 | US |
| Child | 18083658 | US | |
| Parent | 16868776 | May 2020 | US |
| Child | 17742721 | US |
