Patent Application
20240060220
The invention relates to a method for producing a compression knitted fabric for producing prosthetic stockings supplying a compressive effect on an amputated limb of a patient, and to a compression knit for producing prosthetic stockings.
Prosthetic stockings for application to amputated limbs (limb stockings) are known in the prior art, wherein the prosthetic stockings are formed from a compression knit which exerts a compressive effect on an amputated limb of a patient in order to therapeutically compress the limb stump. Such a compression therapy can suppress swelling of the limb stump caused by edema. To avoid obstructing blood circulation in the limb stump, the compression pressure exerted by the prosthetic stocking must be precisely adjusted. To promote the lymphatic system in the limb stump, a pressure profile with a gradually decreasing compression pressure from the distal end of the limb stump is preferred. At the open proximal end of the prosthetic stocking, the compression knitted fabric thus generates a lower compression pressure than at the closed distal end.
Known compression knitted fabrics used for the production of compression stockings are knitted, for example, as circular knits on circular knitting machines. Thereby, the production of the dome-shaped end at the distal end of the stocking is problematic. For this purpose, a round opening is left at the distal end of the circular knitted compression stocking, which is closed, for example, by a circular pad or a knitted end cap by sewing on the circular pad or the knitted end cap. Due to the seam required for this, a thickening occurs at the distal end of the stocking, which distorts the gradual progression of the compression pressure and leads to friction between the stocking and the limb stump and thus to skin irritations on the limb.
Also known from the state of the art are compression knits for prosthetic stockings consisting of two flat knitted parts, each knitted on a flat knitting machine, which are sewn together along a longitudinal seam at their side edges. Here, the longitudinal seams impair the desired pressure distribution and causes skin irritation on the limb as well, and the longitudinal seams are perceived by the patient as annoying.
To avoid these disadvantages in circular knitted prosthetic stockings or stockings composed of two flat knitted parts, compression knits have been proposed in the prior art which can be produced seamlessly on a flat knitting machine with two opposing needle beds. Such a compression knit is known from U.S. Pat. No. 7,363,778 B2, which discloses a stretchable fabric sleeve that can be received on an amputated limb and has a distal end that conforms to the amputated limb. The stretchable fabric sleeve substantially comprises a unitary receptacle for the amputated limb, the receptacle substantially comprising a tubular section and a rounded end section. In particular, the rounded end section includes opposing panels knitted in series with a plurality of knitted short rows that create a progressive taper from an open edge of the tubular section to the proximal toe end of the end portion. The progressive taper of the knitted panels allows the outermost edge of the rounded end section to assume a rounded shape that comfortably conforms to an amputated limb and has no seams that would otherwise irritate the sensitive end of the amputated limb.
Known compression knits for amputated limbs (or for manufacturing prosthetic stockings) are knitted from an elastic knitting thread, e.g. a wound thread with an elastic elastane core thread, in order to produce a stretchable knit which can expand when applied to an amputated limb and thus exert a compression pressure depending on the stretch. However, it is difficult to precisely set a desired compression pressure and particularly to generate a gradual pressure profile with a decreasing compression pressure from the distal end of the stocking to the proximal end. The compression pressure generated by the compression knit on the limb of a patient depends on the stretch of the knitted fabric in the circumferential direction of the limb. The stretch in turn depends on the exact shape of the limb, in particular the course of the limb circumference along the longitudinal direction of the limb, and on the knitted weave of the knitted fabric. Therefore, the knitting of the distal end of the prosthetic stocking with a dome-shaped closed end of the knitted fabric without a seam and supplying a high compression pressure by the stocking onto the amputated limb of a patient is difficult to achieve.
Based on this background, one aspect of the invention relates to a method for the production of a compression knit for knitted prosthetic stockings for exerting a compressive effect on an amputated limb of a patient. The compression knit thereby shall enable to produce prosthetic stockings which can be worn comfortably in an efficient manner without causing skin irritations on the patient's limb and which generate an individually adjustable compression pressure with a gradual pressure profile, which can be individually adapted to the shape of the amputated limbs on which the limb prosthetic stocking is to be worn.
Preferred embodiments of the method and of the compression knitted fabric are disclosed herein.
With the method according to the invention, an at least substantially tubular compression knit extending from an open proximal end to a closed distal end can be manufactured, wherein a first tubular section of a stitch-forming basic knitted fabric is knitted from at least one knit yarn along a knitting direction extending from the proximal end to the distal end of the compression knit with a plurality of rows of stitches following in succession in the knitting direction, wherein an elastic weft yarn is bound into the stitches of the basic knitted fabric in each row of stitches or in every nth row of stitches with n ∈ and n≥2 by tuck stitches, and subsequently a second section is knit seamlessly onto the first section of the basic knitted fabric from the at least one knit yarn along the knitting direction, wherein in the second section the number of stitches is successively reduced at least in some or all of the successive rows of stitches by transferring stitches, thereby a dome-shaped closed end is formed in the second section of the basic knitted fabric towards the distal end by reducing the number of stitches.
The reduction of stitches in the second section gives the second section a shape progressively tapering towards the distal end. The number of stitches in the circumferential direction of the tubular knitted fabric in the second section is successively reduced by overhanging of stitches in every row of stitches or only in selected rows of stitches, e.g. in every second, third or fourth row of stitches, so that the circumference of the tubular knitted fabric in the knitting direction, i.e. from the open proximal end to the closed distal end, becomes successively smaller, .i.e. from the open proximal end to the closed distal end, until only a single stitch remains in the last knitted row of stitches at the distal end of the compression knitted fabric, which is knitted off on a needle of a flat knitting machine to fix the knitted fabric.
By successively reducing the circumference of the tubular knitted fabric in the second section, a dome-shaped closed end is formed at the distal end of the compression knitted fabric. This dome-shaped end forms a closed distal end in a prosthetic stocking made from the compression knit, designated for receiving the end of an amputated limb of a patient, as for example a leg stump.
By reducing the number of stitches in the second section of the compression knit, the shape of this second section can be adapted precisely to the body shape of the amputated limb. For this purpose, the amputated limb can be scanned, for example by an imagine device, and the number of stitches in the individual rows of stitches of the second section of the compression knit can be adapted to the detected circumferential course of the limb in its longitudinal direction. In a corresponding manner, the number of stitches of the basic knit in the first section of the compression knit can also be adapted to the circumferential course of the body extremity. In this way, a compression article individually adapted to the shape of the limb of a patient, for example an individually adapted stocking, can be produced.
Since an elastic weft yarn is bound into the basic knitted fabric during the manufacturing process, the compression pressure generated by the compression knitted fabric on a limb can be precisely adjusted. The compression pressure depends on the tension of the elastic weft yarn with which it is bound into the basic knitted fabric. The elastic weft yarn can be bound in the knitted fabric by forming tuck stitches. The stretchability of the knitted fabric (and thus the compression pressure that can be generated on a limb) can be adjusted by the tension of the weft yarn and/or via the length of the tuck stitches. By incorporating the elastic weft yarn into the basic knitted fabric with a variable yarn tension, it is thus possible, in particular, to generate a predefined pressure profile of the compression pressure exerted by the compression knitted fabric when applied to a limb with a gradual pressure profile. Preferably, the pressure profile at the distal end of the first section of the compression knit (or at the proximal end of the second section immediately adjacent thereto) has a higher compression pressure than at the proximal end of the compression knit.
Preferably, the weft yarn is bound in both the first section and the second section of the basic knitted fabric, whereby the weft yarn can be bound in, for example, in every row of stitches or in every nth row of stitches with n ∈ and n≥1 via tuck stitches. Preferably, a density of the weft yarn in the rows of the second section is smaller than a density of the weft yarn in the rows of the first section. The density of the weft yarn in the stitch rows of the basic knitted fabric can be varied, for example, by incorporating the weft yarn in every stitch row, to achieve a high density and only in every second, third or fourth stitch row, etc., to achieve a lower density. It is also possible to incorporate the weft yarn irregularly in the successive rows of stitches of the basic knitted fabric or to form irregular individual rows of stitches without incorporating the weft yarn. In this way, the generated pressure profile of the compression pressure can be varied along the knitting direction or along the longitudinal direction of a limb to which the compression knitted fabric is applied, because the generated compression pressure depends on the density of the weft yarn in the basic knitted fabric. Preferably, the density of the weft yarn in the dome-shaped end decreases compared to the (average) density in the other parts of the second section, in order to generate a lower compression pressure at the distal end of the compression knit, which, for example, comes into contact with the end of an amputated limb when used as a prosthetic stocking. This can prevent irritation at the very sensitive end of the limb stump.
Preferably, the knitting process is carried out in an uninterrupted manner on a flat knitting machine having a front needle bed and a rear needle bed, wherein the compression knitted fabric is knitted seamlessly by knitting a front ply of the compression knitted fabric on the front needle bed and a rear ply, which is opposite to the front ply, on the rear needle bed. Therein, the front ply and the rear ply are knitted seamlessly together by interchanging the at least one knitting yarn from the front needle bed to the rear needle bed, and vice versa, at the end sections of the front and rear needle beds. Thus, the side edges of the front ply and the rear ply are knitted together to form the tubular basic knitted fabric, into which the elastic weft yarn is bound by means of a weft yarn device of the flat knitting machine by forming tuck stitches. Due to the seamless knitting of the compression knitted fabric in an uninterrupted seamless knitting process, the produced compression knitted fabric obtains on the one hand a good wearing comfort, which avoids skin irritations at the body extremity of the wearer, and on the other hand the knitting process can be carried out very efficiently and quickly.
In particular, the stitch reductions in the second section of the compression knitted fabric can be effected in a very efficient manner by transfer operations with offsetting the needle beds of the flat knitting machine, whereby the needle beds can be offset with respect to each other by one, two or more needles. The number of stitches in the relevant row of stitches in the second section of the basic knitted fabric is reduced in accordance with the number of needles by which the two needle beds of the flat knitting machine are offset relative to one another during the respective transfer operation. The stitch reduction takes place in particular in selected stitch reduction zones between the edges of the front ply and the rear ply of the compression knitted fabric, which are each seamlessly knitted together with the edge of the respective opposite layer by transferring the knitting yarn from the front needle bed to the rear needle bed, and vice versa, at the end sections of the needle beds. In selected stitch courses having a higher number of stitch reductions, several such stitch reduction zones, at which the stitch reductions take place in a stitch course, are preferably arranged at a predefined distance from one another within a stitch row. In this way, the total number of stitch reductions within a row of stitches can be evenly distributed over the extend of the row of stitches in the circumferential direction of the tubular knitted fabric, resulting in a more uniform knitted pattern and avoiding bulges at the edges of the front and rear plies of the compression knitted fabric.
To fix the basic knit and to close the dome-shaped end, the knitting yarn can be knitted off once or several times at the distal end of the compression knit in the area of the last occupied needle of one of the two needle beds of the flat knitting machine.
To form a dome-shaped end of the basic knitted fabric, the number of stitch reductions in the rows of stitches of the second section preferably increases towards the distal end of the compression knitted fabric, as viewed in the knitting direction, until only one last needle remains on one of the needle beds of the flat knitting machine as an occupied needle and the knitting yarn is knitted off, one or more times, on this last needle to fix the distal end of the compression knitted fabric. In particular, in the rows of stitches of the dome-shaped end, in which a high number of stitch reductions take place, preferably a plurality of stitch reduction zones are provided, which are arranged at a distance from one another in a row of stitches.
To fix the weft yarn in the basic knitted fabric, the weft yarn is drawn from a weft yarn package and is conveniently locked in the basic knitted fabric at the distal end of the compression knitted fabric in the area of the last knitted stitches of the basic knitted fabric by several catching hooks and then the weft yarn is cut off from the weft yarn package. This ensures that the weft thread does not come loose from the basic knitted fabric.
The method according to the invention can be used to produce compression knitted fabrics, in particular for the production of knitted prosthetic stockings with a compressive effect, wherein the compression knitted fabric is comprising a stitch-forming basic knitted fabric with a plurality of successive rows of stitches and containing a tubular first section which is open at the proximal end and a second section which adjoins the first section in the knitting direction and is knitted seamlessly onto the first section. Therein, the second section is forming a dome-shaped closed end at the distal end of the compression knitted fabric, which end is formed in the second section by successively reducing the number of stitches at least in some or all of the successive stitch rows of the basic knitted fabric towards the distal end. An elastic weft yarn is bound in the basic knitted fabric, in particular in the first and in the second section, via tuck stitches.
Preferably, the compression knitted fabric is seamless overall. This prevents skin irritation and local pressure points that can occur in knitted fabrics with seams in the seam areas.
In a preferred embodiment, the basic knitted fabric is a right-left knit. However, other knitted structures can also be used to form the basic knitted fabric, e.g. a right-right knit.
The weft yarn can be included in the basic knitted fabric in every row of stitches or in every second, third or fourth, etc., row of stitches.
The knitting yarn can be, for example, a single wound spandex yarn or an elastic single yarn, a plied yarn or a twisted yarn. The weft yarn is preferably a double wound spandex yarn.
When applied to an amputated limb of a patient, the compression knitted fabric generates a compression pressure on the limb, preferably with a gradual pressure profile, whereby the compression pressure particularly increases gradually in the first section from the proximal end to the distal end of the compression knit. Towards the closed end, i.e. at the distal end of the compression knitted fabric, the generated compression pressure preferably decreases again. The compression pressure generated is at a maximum, for example, at the transition from the first section to the second section and decreases gradually in the second section towards the distal end of the compression knit. In this way, irritation of the sensitive end of the limb stump of an amputated limb caused by excessive compression in the second section, and in particular in the region of the closed end, can be avoided. This can be achieved, for example, by progressively decreasing the density of the weft yarn in the final rows of stitches of the basic knitted fabric towards the distal end. At the proximal end of the compression knit, a compression pressure of 10 mmHg to 30 mmHg is expediently and the maximum compression pressure is preferably less than 35 mmHg.
The compression knitted fabric according to the invention can be used to produce seamless compression articles for various medical indications, such as a prosthetic stocking for application to an amputated limb of a patient or a compressive head mask for application to the head of a patient. Depending on the use, the shape of the knitted fabric is adapted to the patient's body part, in particular by individual customization, for which purpose the shape of the body part is recorded, for example by means of a scanner or a camera. The recorded shape of the body part is taken into account in the manufacture process of the compression knitted fabric, for example by adjusting the circumferential profile of the tubular basic knitted fabric and the length of the knitted fabric in the knitting direction during the knitting process, or by omitting any openings (e.g. a facial opening in the case of a face mask) during the knitting process.
These and other advantages as well as preferred features of the invention result from the embodiments described below with reference to the accompanying drawings, which serve to explain the invention and do not limit the scope of protection of the invention defined by the following claims. The drawings show:
The compression knitted fabric shown in
An elastic weft yarn S is bound into the basic knitted fabric M formed from the knitting yarn T by means of a weft yarn device of the flat knitting machine. In the example shown in
The integration of the elastic weft yarn S into the basic knitted fabric M, which is indicated in the “Function” column of the drawings in
The knitting direction v shown in
The first section A1, which is shown in
The first, tubular section A1 of the basic knitted fabric M is followed in the knitting direction v towards the distal end d of the compression knitted fabric, by a second section A2 with a contour tapering towards the distal end d. In the embodiment shown in
The extension of the compression knitted fabric in the circumferential direction, i.e. in the direction of the rows of stitches of the knitted fabric, is successively reduced in the second section A2 of the compression knitted fabric by stitch reduction by means of transferring the knitting yarn T using a transfer device. The transfer of the knitting yarn T is indicated by the symbol “u” in the “Function” column of
The stitch reductions in the selected rows of stitches of the knitted fabric are carried out by overhanging u the knitting yarn T from the active needle bed of the flat knitting machine to the opposite needle bed, which is currently inactive, and a subsequent shifting of the inactive needle bed relative to the active needle bed by a predetermined number of needles. After the mutual displacement of the two opposing needle beds, the stitches of the knitting yarn T are hooked from the inactive needle bed back onto the active needle bed, whereby, due to the displacement of the opposing needle beds, a stitch reduction, i.e. a reduction in the number of stitches in the relevant row of stitches, takes place depending on the number of needles by which the two needle beds have been displaced relative to one another. The stitch reductions take place in selected stitch reduction zones MM within selected rows of stitches, the stitch reduction zones MM being arranged between the edges of the front ply L0 or the rear ply L1. Preferably the reduction zones MM are at a distance from the edges of the front ply or the rear layer. Several such stitch reduction zones MM can also be arranged at a distance from one another within a row of stitches.
The number of stitches reduced in this way in the stitch reduction zones MM can be controlled by the offset of the two opposing needle beds relative to one another. In the example shown in
The stitch reductions in the selected rows of the knitted fabric to stitches of the basic knitted fabric lying further inside can also be carried out by overhanging u the knitting yarn T from the active needle bed of the flat knitting machine to an auxiliary needle bed.
The overhanging u of the knitting yarn T takes place in each case at the edge of the relevant row of stitches R, i.e. either at the left edge 1 or at the right edge r, as can be seen from rows 4, 7, 13 to 15, 19, 21 and 23 of the knitting diagram in
By reducing the number of stitches in selected stitch rows R of the knitted fabric, the extent of the knitted fabric in the direction of the stitch rows can be varied along the knitting direction v, and the contour of the knitted fabric can thereby be optimally adapted to the body shape of a body extremity to which the compression knitted fabric is to be applied in order to exert a defined compressive effect. The number of stitches in the individual stitch rows R of the knitted fabric required for optimum adaptation of the shape of the knitted fabric to the body shape of the body extremity can be determined by scanning the body shape of the limb and subsequently calculating the necessary number of stitches in the individual stitch rows R depending on the shape of the limb.
In the second section A2 of the compression knitted fabric, which in the embodiment of
In this way, a tubular compression knitted fabric with an elastic weft yarn S, which is bound into the basic knitted fabric M, can be produced with a precisely defined pressure profile of the compression pressure exerted by the compression knitted fabric on a body extremity (limb) of a patient, wherein the tubular knitted fabric has an open proximal end p and a closed distal end d. The compression pressure exerted by the knitted fabric, when applied to a body extremity (limb) can thereby be controlled by the yarn tension of the weft yarn S, with which the latter is bound into the basic knitted fabric, and by the length of the tuck stitches F, by which the weft yarn S is bound into the basic knitted fabric. Preferably, at least in the first section A1, the compression knitted fabric generates a compression profile with decreasing pressure towards the proximal end p. Such a compression knitted fabric is particularly suitable for use as a compression stocking or as a compression head mask.
When used as a head mask, a face opening is knitted into the tubular knitted fabric of the first section A1. This can be done by reducing stitches in selected rows of stitches of the first section A1. When used as a stocking, in particular a prosthetic stocking, to be used on an amputated limb, the pressure gradient in the second section A2 may decrease towards the distal end d to prevent excessive pressure at the distal end of the amputated limb. In this example of use, the knitted fabric exhibits a maximum of compression pressure at the transition from the first section A1 to the second section A2.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2022 121 165.7 | Aug 2022 | DE | national |
