ORTHOPAEDIC ARTICLES

Abstract: A multi-layer orthopaedic article having an integrally knitted portion having a mechanical property different from that of the adjacent portion, or portions, of the article, this mechanical property may be, for instance, cushioning or support.

Description: ORTHOPAEDIC ARTICLES The present invention relates to orthopaedic articles comprising at least two interconnected layers of knitted fabric, at least one integral portion of said article having a desired mechanical property. Fabrics of the type employed herein are sometimes referred to as spacer fabrics and comprise at least two layers with a plurality of strands extending therebetween to maintain them in a spaced apart relationship. These types of fabrics are well known in the art and examples of which are disclosed in document US 5395684. Spacer fabrics find application in a number of fields such as the manufacture of car interiors and furniture. The present invention is concerned with orthopaedic articles such as (but not limited to) braces, splints, casts, bandages, collars and supports. There is a requirement in this field for articles which have differing mechanical properties within the same device. It is sometimes necessary, for example, to include a rigid non- deformable portion which can act as a splint. Equally, cushioned regions may also be required to protect parts of the body which must be shielded from knocks, such as the patella after a knee operation. In the past, these requirements have been met by adding materials to the finished article to create regions of higher strength or increased padding. Examples of such devices are disclosed in US 4,425,912 where vertical spiral stays are attached to the outside of the brace. Again, using the example of a brace, it is known to include pockets in braces into which rigid stays of plastic or metal are placed to limit movement of the joint. It is also known to create windows in orthopaedic articles over which a silicone cushion may be strapped, thus providing extra dampening against knocks. The above devices are complicated to make and are also overly complex in their own right, requiring the assembly of several different component parts. The additional seams required to provide pockets and around holes in the material (for cushion- insertion) can cause irritation to patients and represent weak points in the material. There is thus a need to develop orthopaedic articles which are less complex, i.e. involve fewer parts, which can be manufactured more easily and which remove the need for additional seams. The present invention provides a solution to the above- mentioned problems associated with the prior art. In its broadest aspect, the invention relates to an orthopaedic article comprising at least two interconnected layers of knitted fabric and at least one integrally knitted portion of a desired mechanical property, different from that of the adjacent portions of the article. According to the present invention there is provided an orthopaedic article comprising at least two interconnected layers of knitted fabric and at least one integrally knitted portion having a mechanical property different from that of the adjacent portion, or portions, of the article. Suitably the mechanical property referred to is that of strength, rigidity, flexibility, elasticity and/or cushioning. According to one aspect of the invention, there is disclosed an orthopaedic article comprising at least two interconnected layers of knitted fabric, wherein, over at least one first portion of said article, said at least two layers of knitted fabric are connected to one another by an integrally knitted cushioning portion. More specifically, there is disclosed an orthopaedic article comprising at least two interconnected layers of knitted fabric, wherein, over at least one first portion of said article, said at least two layers of knitted fabric are connected to one another by the respective ends of a plurality of lengths of fabric comprising courses of stitches knitted on empty needles, such that said plurality of lengths of fabric forms a cushioning portion. A process is also disclosed for manufacturing an orthopaedic article comprising at least two interconnected layers of knitted fabric, wherein over at least one first portion of said article said at least two layers of knitted fabric comprise an integrally knitted cushioning portion, said process comprising the following steps for manufacturing said at least one first portion: (a) knitting a first course of stitches on every n th needle of a first bed of needles, (b) knitting a second course of stitches on every n th needle of a second bed of needles, where n>1 (c) knitting a further course of stitches on the empty needles on the first bed, (d) repeating step (c) a plurality of times to obtain the length of material desired, (e) transferring the last row of stitches made in step (d) from the first bed to the second bed, (f) repeating steps (a) to (e) until the desired length of fabric is produced. The products directly obtainable from the above process also form part of the present invention. Preferably, the step of knitting on empty needles is carried out on every second needle: there is therefore disclosed a process for manufacturing an orthopaedic article comprising at least two interconnected layers of knitted fabric, wherein over at least one first portion of said article said at least two layers of knitted fabric comprise an integrally knitted cushioning portion, said process comprising the following steps for manufacturing said at least one first portion: A process for manufacturing an orthopaedic article comprising a spacer fabric and at least one integrally knitted cushioning portion of greater thickness than the spacer fabric, comprising the following steps for manufacture of the cushioning portion: (a) knitting a first course of stitches on every second needle of a first bed of needles, (b) knitting a second course of stitches on every second needle of a second bed of needles, (c) knitting a further course of stitches on empty needles on the first bed, (d) repeating step (c) a plurality of times to obtain the length of material desired, (e) transferring the last row of stitches made in step (d) from the first bed to the second bed, (f) repeating steps (a) to (e) until the desired length of fabric is produced. The products directly obtainable from the above process also form part of the present invention. In another aspect of the invention, there is disclosed an orthopaedic article comprising at least two interconnected layers of knitted fabric, wherein at least one first portion of said article comprises thermosetting fibres. Preferably said at least one portion is itself knitted with the thermosetting fibres. More preferably still, the area or areas comprising said at least one portion of thermosetting fibres have rounded edges. Advantageously, the areas of the finished orthopaedic article comprising thermosetting fibres are thermoset. In a further aspect of the invention, a process is provided for manufacturing an orthopaedic article comprising at least two interconnected layers of knitted fabric, said process comprising integrally knitting thermosetting fibres into at least one first portion of said article. Preferably, said at least one first portion is in one of the external layers of the article. Preferably, the process involves the further step of thermosetting the thermosetting fibres contained in said at least one first portion of said article. The present invention concerns ways of manufacturing a spacer fabric incorporating integrally knitted portions which have different mechanical properties from the adjacent portions. Reference is made to the figures of the application: Fig. 1 illustrates schematically the stitch pattern for knitting a spacer fabric. Fig. 2 is a schematic illustration of a spacer fabric. Fig. 3 illustrates schematically the stitch pattern for knitting a cushioned portion into a fabric. Fig. 4 illustrates a process whereby a thermosetting thread is inlaid part way across a course of stitches. Spacer fabrics and their manufacture is a known science, so need not be discussed in much detail here. The spacer fabrics used in the present invention are weft knitted fabrics. An example of the process on a machine with a front and back bed comprises yarn feed and loop formation at every needle in succession. Reference is made to Fig. 1 : in a simple structure, the first course of yarn knits on all the back bed (II) needles (step (a)). The second course of yarn then knits on all the front bed (I) needles (step (b)). During the subsequent courses (steps (c) - (h)), the front and back needle beds are connected by tuck loop stitches. In this example, the yarn tucks over four needles from back bed (II) to front (I), moving one needle across each time. The density of the connecting threads can be chosen according to the requirements of the application. The density of the fabric can be altered by tucking over more or less needles, thereby altering the cross-over arrangement and thus the internal structure. The space between the two structures depends on the space between the two needle beds. The fabric is built up on both needle beds so as to achieve a two faced structure. This allows the thickness of said structure to be varied, preferably from 2 mm to 10 mm, more preferably from 3 mm to 5 mm. A schematic representation of a spacer fabric is shown in Fig. 2. This figure shows the two outer layers of fabric (1 ,2) and the connecting yarns (3). According to one aspect of the invention, a cushion is integrally knitted into the product. With reference to Fig. 3, step (a) involves knitting a first course of stitches on every second needle of a first bed of needles. In step (b), a second course of stitches is knitted on every second needle of a second bed of needles. The process step that follows is known in the art as knitting on empty needles. Steps (c) to (e) of this example illustrate the procedure. In this example, it takes place on the first bed. According to step (c), a course of stitches is knitted on the unused (empty) needles of the first bed, i.e. the needles not knitted on in step (a). According to step (d), a further course of stitches is knitted on the unused (empty) needles from step (c). According to step (e), a course of stitches is knitted on the unused (empty) needles of step (d). The procedure according to steps (c) - (e) is repeated a number of times, as indicated by the arrow shown, until a desired length of material has been created. The word "length" is strictly speaking the correct term, although, in the finished product this length translates to some extent to become a thickness, as will be explained. It can be useful to an understanding of the structure of the final product to know this. With reference to step (f) of the process schematic of Fig. 3, when the phase of knitting on empty needles is completed, the final course of stitches made on the first bed during this phase is transferred over to the second bed. The process then begins again with step (a). The result of this transfer step is that the length of material made during the phase of knitting on empty needles which is already attached to one of the external layers of fabric (that made on the first bed) is now also attached to the second layer of fabric (that made on the second bed). As a result of this, the piece of material made during the phase of knitting on empty needles now extends between the two external layers of knitted fabric, thus helping to build the width of said fabric. It is the essentially parallel strata of these lengths of fabric stretching between the two external layers of fabric that builds up into a cushioned portion. These strata may extend essentially perpendicular to the external layers of fabric, but more usually extend at an angle. The thickness of the cushioned portion is directly related to the number of courses of stitching on empty needles, i.e. the lengths of the fabric thereby created. Whereas, in this example, the course of stitches was completed on every second needle, the invention is not limited to this embodiment. It is also within the scope of the invention to stitch on, every n th needle. As with the example given, knitting on empty needles in such a case means that every needle not knitted on in the previous step is knitted on the following step. With reference to the discussion of spacer-fabric manufacture, above, it can readily be appreciated that it is a trivial matter on an automated, computer-controlled machine, to generate a program to cause the needles of the back and front beds to pass from a phase of generating a stitch pattern, as illustrated in Fig. 1 , to a stitch pattern as illustrated in Fig. 3 and then back again, so that a cushioned region of any desired shape can be generated at any location over the spacer fabric. As already stated, said cushioned region can be of any desired thickness. The mechanical properties of the cushion, e.g. strength and density, can be controlled by means of the phase of knitting on empty needles - which controls, among other things, the thickness and degree of openness of the structure. According to a second aspect of the invention the orthopaedic articles comprise thermosetting fibres, which are then thermoset to provide a rigid region. With reference to Fig. 4, this can be achieved by inlaying a thermosetting thread (5) part way across a course of stitches, at point A, so that the thermosetting thread is on the surface, until it reaches point B. The thermosetting fibres will generally be knitted into a layer of fabric which faces away from the skin, because, once thermoset, they are less pleasant to the touch than normal spacer fabric. The thermosetting fibres are knitted into a region of the orthopaedic article which can have any shape, e.g. circular, oval etc. Preferably the areas comprising said thermosetting fibres have rounded edges. This avoids the risk that said area, once thermoset, will have sharp edges which may penetrate and damage the surrounding material. The thermosetting fibres can be any thermosetting fibres, but should have a melting point below that of the surrounding knitted article. Polypropylene fibres are suitable for this purpose. One example combines TWINTEX™ fibres, which comprise a polypropylene matrix (and 60% glass), with an orthopaedic product made of nylon. Consolidation of the polypropylene matrix takes place by heating above the melting temperature of 180°C, while the nylon, from which the rest of the product is made, melts at 260°C, so remains unaffected. Other examples of thermosetting fibres are those comprising polyethylene, setting at between 40°C and 60°C and those comprising caprolactone, setting at around 40°C. In these latter cases, however, the rigidity of the regions comprising thermosetting fibres tends to be lower than in the case of polypropylene. The orthopaedic product can be tailored to give the required mechanical properties, like rigidity and modulus in specified regions. The degree of rigidity, for example, can range in these regions from a point at which mobility is severely restricted, if not totally prevented, to a point at which significant movement can occur. This is achieved by altering the type of thermosetting fibres used, the fibre thickness, the type (density) of knit (i.e. strands per unit volume) and the size of the area into which said fibres are incorporated. Thermosetting can be achieved using a heating press. In some cases, a simple heating device like a domestic iron can be used. Advantageously, the regions containing thermosetting fibres are of a different colour from the adjacent regions of the article. In a preferred embodiment of the invention, the orthopaedic articles comprise both cushioning portions and rigid portions comprising thermosetting fibres which have been heated and thermoset. An example of such an article is a knee brace. Traditional knee braces comprise longitudinal or spiral stays which provide rigidity as well as a central hole over which a cushion may be placed as protection for the patella. A knee brace according to the invention will have both an integrally knitted cushion, as protection for the patella, and integrally knitted longitudinal portions of thermosetting fibres. In the event that rigidity is required, these will be thermoset using a heating device. The fabrics referred to herein may be made from yarns of a number of materials. Non-limiting examples are bulked filament nylon, polyester, cotton and viscose. An example of a suitable yarn is 2/78/24 nylon. The yarns themselves may be prepared from filaments which have been gathered and twisted, crimped, flat or air intermingled. Furthermore, elastomers may also be incorporated to provide desired stretch properties. An example of a suitable elastomer is 135 dtex bare LYCRA™ or other elastane. Different yarns can be used to manufacture each of the two external fabric layers, with, for example, softer yarn being used on what will be the skin-facing layer, for enhanced comfort.

Claims: CLAIMS 1. An orthopaedic article comprising at least two interconnected layers of knitted fabric and at least one integrally knitted portion having a mechanical property different from that of the adjacent portion, or portions, of the article. 2. An orthopaedic article as claimed in claim 1 in which a portion of the two interconnected layers are connected to one another by an integrally knitted cushioning portion. 3. An orthopaedic article as claimed in claim 1 or 2 in which a portion of the two interconnecting layers are connected to one another by the respective ends of a plurality of lengths of fabric comprising courses of stitches knitted on empty needles such that said plurality of lengths of fabric forms a cushioning portion. 4. An orthopaedic article as claimed in any preceding claim in which a portion of said article comprises integrally knitted thermosetting fibres. 5. An orthopaedic article as claimed in claim 4 in which the thermosetting fibres have rounded edges. 6. An orthopaedic article as claimed in claim 4 or 5 in which the thermosetting fibres are in one of the external layers of the article. 7. A method of manufacture of an orthopaedic article having at least two interconnected layers of knitted fabric, wherein over at least one first portion of said article said at least two layers of knitted fabric comprise an integrally knitted cushioning portion, said process comprising the following steps for manufacturing said at least one first portion: a. knitting a first course of stitches on every n th needle of a first bed of needles, b. knitting a second course of stitches on every n th needle of a second bed of needles, where n>1 c. knitting a further course of stitches on the empty needles of the first bed, d. repeating step (c) a plurality of times to obtain the length of material desired, e. transferring the last row of stitches made in step (d) from the first bed to the second bed, f. repeating steps (a) to (e) until the desired length of fabric is produced. 8. A method of manufacture of an orthopaedic article as claimed in claim 7 in which n = 2.

Inventors: ROBERTS JOANNE CAROL, ROBERTS, JOANNE, CAROL
Applicants: ROBERTS JOANNE CAROL, SMITH & NEPHEW, ROBERTS, JOANNE, CAROL, SMITH & NEPHEW PLC
Application year: 1999
Main classification: A61F5
IPC codes: A61F5, A61F13, D04B1