News Column

Patent Issued for below Knee Amputee Prosthesis Liner

August 20, 2014



By a News Reporter-Staff News Editor at Journal of Engineering -- From Alexandria, Virginia, VerticalNews journalists report that a patent by the inventors Pianykh, Oleg (Salt Lake City, UT); Polta, Charles C. (Salt Lake City, UT); Bussiek-Cillien, Kai (Gottingen, DE); Schneider, Scott John (Sartell, MN), filed on November 18, 2011, was published online on August 5, 2014.

The patent's assignee for patent number 8795386 is Otto Bock Healthcare GmbH (Duderstadt, DE).

News editors obtained the following quote from the background information supplied by the inventors: "The use of prosthetic liners for below knee amputees is well known from the prior art. A prosthetic liner is worn between the amputation limb and the prosthesis socket, carrying the lower leg portion of the prosthesis. The liner is worn directly on the amputation limb. At the closed distal end of the liner body the liner is provided with means for connecting the liner to the prosthesis socket. These means might, for example, be threaded inserts, which may be molded into the polymer-like liner material, in particular by injection molding.

"Since the liner usually is the only part of the prosthesis getting in direct contact with the skin of the amputee and the liner is usually worn the whole day, it is important to make the liner as comfortable to wear as possible. The liners might be, for example, constructed either of a fabric impregnated with silicone or another polymer-like material or from the polymer-like material only.

"From U.S. Pat. Nos. 6,440,345 B1 and 6,918,936 B2 a liner is known, which comprises a knee part having a pre-flexed angle. This is also known from U.S. Pat. No. 5,888,216. Compared with the straight tubular shape liner, this pre-flexed angle minimizes the wrinkling behind the knee, especially when the knee is bent. In addition it increases the range of motion of the knee joint and is more comfortable to wear when sitting.

"Since the diameter of the amputation limb of the person usually decreases towards the distal end of the amputation limb, the distal part of the liner according to U.S. Pat. No. 5,888,216 is tapered. This leads to a better fit and a more homogeneous distribution of pressure at the amputation limb of the person.

"From US 2010/0016993 a liner is known, which also shows a knee part, in which a strip or a tendon is attached to urge the elastomeric material in this region of the tubular liner body to contract. This strip or tendon is, for example, of silicone having a higher durometer hardness value than the material of the liner body and may be, for example, integrally molded with the knee portion of the tubular liner body.

"In order to provide a perfect fit of the liner at the residual limb of the person it is possible to use a fully individualized liner or to individualize a standard liner, as, for example, is known from WO 2009/109182. Since the construction of an individual liner is time-consuming and expensive it is much cheaper and faster to provide some standard liners which may be available in different sizes and to use these standard liners for each amputation limb.

"Unfortunately, amputation limbs are shaped very individually. When a standard liner is used it is possible that cavities occur between the amputation limb of the person and the liner. This may lead to swelling or chafing at the residual limb. In order to prevent at least most of these cavities from occurring between the liner and the residual limb it is known, for example, from US 2005/0240283 A1 to insert some cushions into the liner. This leads to a more homogeneous distribution of pressure at the surface of the amputation limb covered by the liner.

"At the distal end of the liner there is usually a means for connecting the liner to the remaining parts of the prosthesis. Silicone liners particularly utilize a hard unyielding material such as aluminum or thermoplastics such as polycarbonate or polyamids as a shuttle screw housing for fixing the lower leg portion of the prosthesis. The said means may also be a screw housing or a threaded insert which might be molded into the material of the liner body. In order to prevent these hard materials from being felt by the wearer of the prosthesis liner, the thickness of the molded polymer-like liner material is considerably enhanced at the closed distal end of the liner body.

"In order to increase the wearing comfort of the prosthesis even further, it is known to insert some cushions into the prosthetic socket, which is to be fixed to the liner. Since the prosthetic socket is made from a rigid material, this may lead to bruising and chafing and hence to discomfort and pain.

"These cushions are usually positioned at an inner surface of the prosthetic socket. This leads to dirt pockets making the cleaning of the prosthetic socket difficult and time-consuming. In addition it is difficult to position these cushions at the inner surface of the prosthesis socket exactly. This might lead to wrong positions of the cushions so that the desired cushioning effect is not realized or at least is not realized at the desired locations at the amputation limb. This again leads to chafing, pressure points, swelling and pain."

As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventors' summary information for this patent: "An object of the present disclosure is to provide a liner for a below knee amputee prosthesis, which increases the wearing comfort of the prosthetic device and makes the prosthetic socket to be attached to the liner easier to clean.

"Another object of the present disclosure is to provide a method for producing such a liner.

"In one example, a below knee amputee prosthetic liner comprises a molded polymer-like liner body for receiving a below knee amputation limb of a person, the liner body having a closed distal end and an open proximal end, wherein the liner comprises at least one thickening in at least one of a first region and a second region, the first region being adapted to cover a head of the fibula of the amputation limb and the second region being adapted to cover a shinbone of the amputation limb, once the amputation limb is received in the liner body.

"The at least one thickening provides a cushioning effect for the head of at least one of the fibula and the shinbone of the amputation limb. Because of this additional cushioning of the prominent bones of the amputation limb the liner is very comfortable to wear. In addition, there are no more cushions to be provided at an inner surface of a prosthetic socket, which is to be attached to the prosthesis liner. Hence, the inner surface of a prosthetic socket may be flat and smooth making it is easier to clean.

"In one embodiment the liner is symmetric with respect to a plane of symmetry in which the knee of the amputation limb is bendable, once the amputation limb is received in the liner body. The plane of symmetry is the so called sagittal plane. By this it is possible to use the same liner for a below knee amputation limb of a right leg and of a left leg. The liner hence has two thickenings for covering the head of the fibula, one of which is provided on the right hand side of the liner body and the other one is provided is one the left hand side, i.e. on the medial and lateral sides.

"The at least one thickening may be formed by at least one pad arranged at the liner body. These pads may be prefabricated making it easier to produce a liner according to the present disclosure. The pad and the liner body may either be made from the same material, such as polyurethane or silicone or any other suitable polymer-like material, or from different materials. In this case it is possible to use materials with different shore hardnesses.

"In one embodiment the liner body is molded to the at least one pad or the at least one pad is, for example, glued to the liner body.

"In one embodiment, the liner body comprises a knee portion having a pre-flexed angle. By this it is easily possible to determine which part of the liner body is intended to cover the head of the fibula and which part is intended to cover the shinbone. This is possible, because the position of the knee is predetermined to be in the knee portion. In addition, it is very easy to put on the liner in a reproducible manner such that it is ensured that the thickenings are arranged at their proper positions.

"An example method for producing a liner according to the present disclosure comprises the step of forming at least one thickening in at least one of the first region and the second region. This forming may comprise the steps of positioning at least one prefabricated pad at a mold core, applying a layer of liner body material, and hardening of the liner body material.

"The step of applying the layer of liner body material may include immersing the mold core and the positioned pads into the liner body material. Alternatively the applying of the layer of liner body material includes injection molding, casting or dipping of the liner body material.

"In another embodiment of the method, the forming the at least one thickening includes the step of applying at least one prefabricated pad onto an outer surface of the liner body. This may be done, for example, by gluing the pad on the surface of the liner body. Alternatively, the at least one thickening is integrally formed with the liner body, in particular by injection molding."

For additional information on this patent, see: Pianykh, Oleg; Polta, Charles C.; Bussiek-Cillien, Kai; Schneider, Scott John. below Knee Amputee Prosthesis Liner. U.S. Patent Number 8795386, filed November 18, 2011, and published online on August 5, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8795386.PN.&OS=PN/8795386RS=PN/8795386

Keywords for this news article include: Silicones, Siloxanes, Prosthetics, Medical Devices, Otto Bock Healthcare GmbH.

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Source: Journal of Engineering


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