Abstract:
A sole to be placed under a patient&#39;s foot inside a shoe or being part of a prosthesis or an orthosis, with the purpose of correcting a person&#39;s gait, characterised in that the sole have two or more areas of different flexural resistance. The boundary line between the different areas have a certain shape resembling an “S”. The sole is made up of carbon fibre composites, aramid fibre composites and/or other materials, and the differences in flexural resistance are achieved for example by applying composite materials with the reinforcing fibres arranged as parallel fibres, or weave, or fabric with the fibres crossing each other at different angels and in different number of layers in different parts of the sole or applying different types of fabric and weave in different areas.

Description:
THE FIELD OF THE INVENTION  
         [0001]    This invention relates generally to orthopaedic appliances such as, e.g. prostheses and orthoses for improving a handicapped or disabled person&#39;s gait, and in particular to soles having areas of different flexural resistance.  
         BACKGROUND  
         [0002]    Various inlays and appliances for compensating mere anatomical insufficiencies have been known for a long time. Those appliances take into account the statical aspects of weight and force distribution of the foot and lower limb. Attempts to take into account both statical and dynamical forces, i.e., forces generated during a stride, includes the patent publication SE 89967 to Ehrlich 1934. That document discloses an orthopaedic footwear together with method and device for its production.  
           [0003]    In EP 0,931,470 A2 to Pavesi is disclosed a sandwich type footwear stiffening element of rigid or at least semi-rigid behaviour, usable as part of a sole unit or insole.  
           [0004]    In GB 1,433,481 to Revill is disclosed a shoe insole comprising a non-woven bonded fibre mass having a greater density at a rear portion of the insole than at a forepart portion thereof and the rear portion being more rigid than the forepart portion.  
           [0005]    In U.S. Pat. No. 4,085,758 to Castiglia is disclosed a weight-redistribution orthopaedic appliance adapted to be attached to the sole of a shoe. That orthopaedic appliance is a non-resilient pad that is attached to the sole of a shoe forward of a break line of the sole, the pad being sufficiently flexible to be readily contoured to the sole&#39;s surface.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention solves the above-mentioned problem of compensating not only for mere anatomical insufficiencies but also for both statical and dynamical forces, i.e., forces generated during a handicapped or disabled person&#39;s stride, by providing an orthopaedic appliance in the shape of a sole having areas of different flexural resistance. Boundary zones, or boundary lines defining the boundaries of said areas has been given a certain favourable shape. The sole on its own or as an integral part of a prosthesis or an orthosis, is conceived, constructed and reinforced so as to adapt the position and/or the shape of the so called release line to relieve a patient&#39;s problems. The invention is based on the inventors realisation of the importance to control the extension of the so called progression line, particularly when dealing with an amputated foot or an impaired muscle. The invention is an important component in the struggle for preventing injuries affecting the knee, hip and back, among patients with impaired gait, as has been possible to describe with the aid of three dimensional gait analysis.  
           [0007]    The sole according to the invention solves the problem of correcting the position and shape of the progression line and the release line by being reinforced laterally and at the same time more frontally than a sole of a normal shoe. The sole supports the foot in a certain manner and the ground reaction-force progression-line is brought back to normal. This guiding and supportive effect makes it easier for the person to hold the foot in a straight position throughout a stride and also to avoid gait deviations at the ankle, knee and hip joints. The patient is spared an unphysiological gait of having to turn the foot at each step. Instead the leg can be swung in a straight line. A more natural gait is achieved. The above mentioned results including the transfer or shift of the ground reaction-force progression-line has been investigated using three-dimensional gait analysis.  
           [0008]    The sole can be manufactured in carbon fibre reinforced composite materials or the like and having different number of layers in different parts of the sole, including different types of and number of layers of weave and fabric with crossing fibre directions, of said fibres. The invention is not dependent upon the type of material used. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a plan view illustrating the progression line of the ground reaction force under the foot.  
         [0010]    [0010]FIG. 2 shows a number of alternative release lines.  
         [0011]    [0011]FIG. 3 shows areas with different flexural resistance.  
         [0012]    [0012]FIG. 4 shows a top view and side view showing different layers of the sole. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0013]    The development of pressure sensitive plates have made it possible for the inventors to measure the reactive force from the floor towards the sole of the foot or towards the sole of footwear. In FIG. 1 is shown a sole with both a defective  102  and a normal  101  progression line of the reactive force drawn into the figure for comparison.  
         [0014]    When a person with normal gait walks, the result is a neutral progression line  101 . The progression line  101  begins at the posterior part of the heel and advances forward towards the big toe. At the end stage the foot is bent at the metatarsophalangeal joints and the sole is bent along a so-called release line  105 . A normal release line  105  is shown in the figure and it runs along the ball of the foot. Good footwear is built to bend along this normal release line  105 . During normal gait there is no need to turn the foot at each step and the leg can be swung in a straight line. A number of alternative release lines  202 - 205 , corresponding to different person&#39;s pathology in gait, can be seen on the sole in FIG. 2. The normal release line  201  is shown as a dashed line.  
         [0015]    As an example people suffering from paresis and being partly paralysed or having a partly amputated foot cannot walk properly with normal footwear. For such a person the disability will give rise to a progression line  102  as can be seen in FIG. 1. The line  102  deflects towards the little toe because the foot (or what is left of it) cannot withstand the load. Because of the deflected progression line  102 , i.e. the ground reactive forces working in a faulty point of action, the foot must be turned in the swing phase and the leg cannot be swung in a straight line. Furthermore the knee will have an increased varus moment and the person will get a limping pattern, which in turn will give rise to problems with the persons&#39; ankle, knee, and hip joints.  
         [0016]    It is known how to build for example runner&#39;s shoes with soles for preventing supination and pronation. Those shoes are built up mainly around the heel and the metatarsus so as to straighten the foot up and tilt it medially or laterally. This tilt has by no means any influence on the release line, which is arranged, at the same position as in normal shoes.  
         [0017]    In FIG. 3 is shown areas of different flexural resistance of a sole according to the invention. The sole is conceived, constructed and reinforced so as to adapt the position and/or the shape of the release line to a patient&#39;s problems. The sole is reinforced laterally and frontally compared to a sole of a normal shoe, i.e. the portions of the foot (or what is left of it) that corresponds to the little toe portion of the foot, and the lateral part of the foot are given a stiffer support than is the areas corresponding to the big toe and the medial front part of the foot. The sole supports in this way the foot and thereby the ground counter-force progression-line is brought back to normal. This guiding and supportive effect makes it easier for the person to hold the foot in a straight position throughout the stride, and gait deviations at the ankle, knee, and hip joints are avoided. The patient is spared the inconvenience of having to turn the foot at each step and the leg can be swung in a straight line. A more natural gait is achieved.  
         [0018]    Again turning to FIG. 3, the sole has flexible areas of different flexural resistance. As an example in FIG. 3, the area labelled I is the most flexible. The area labelled II is a bit less flexible than area I. The area labelled M is a bit less flexible than area II. The area labelled IV is the stiffest area. Another positive side of this construction is a spring effect produced at toe-off, which preserves energy.  
         [0019]    A such flexible area of the sole is bounded by either an outer limit or edges of the sole and one or more boundary zones or boundary lines  301 ,  302 ,  303  or only by boundary lines. In the figures, boundary lines are drawn as thin lines, but in a real product these lines can have a width of up to a few millimetres incorporating an area of intermediate flexural resistance.  
         [0020]    Two boundary lines  301 ,  302  of a preferred embodiment of the invention as shown in FIG. 3 begin at a lateral side edge  310  of the sole  300 , extend towards a midline of the sole (not shown), extends at the same time in a posterior direction in such a way that when reaching a medial side edge  320  of the sole  300 , an end point  331 ,  332  of said boundary lines  301 ,  302  is arranged decidedly more posterior, i.e. closer to the heel end  340  of the sole  300 , than is a start point of said line. In this way the progression line will be moved in a direction towards the big toe. The release line will at the same time be moved or tilted towards a more normal or pronated position. A third boundary line  303  is arranged to extend in a straight line.  
         [0021]    As can be seen in FIG. 3 the boundary lines can assume curved shapes reminding of an “S” or they can be curved otherwise or be straight. Tests have shown that shapes of the boundary lines resembling an elongated “S” in general, also resembling the hyperbolic tangent function graph, the sigmoid function graph, the integral sign or the like is well suited for achieving proper function. A bend  351 ,  352  in a boundary line  301 ,  302  can be directed towards the toe end  360  of the sole or towards the heel end  340 . A bend can also be directed towards, or partly towards, the lateral  310  or medial  320  side edge of the sole  300 . In a preferred embodiment three boundary lines  301 - 303  are arranged. The first boundary line  301  is arranged with a first bend  351  being convex in a direction towards the toe end  360  of the sole  300 . Said boundary line  301  is also arranged with a second bend  352  being concave in a direction towards the toe end  360  of the sole  300 . The second boundary line  302  is arranged having a first bend  353  being convex in a direction towards the toe end  360  of the sole  300 . Said second boundary line  302  is also arranged having a second bend  354  being concave in a direction towards the toe end  360  of the sole  300 .  
         [0022]    The sole can be manufactured of carbon fibre reinforced composite materials or the like. The invention is however not dependent upon the type of material used. Every material with a suitable flexibility can be used, such as glass fibre reinforced plastics, other plastics, wood, steel or other metals. Preferred materials include KEVLAR® (aramid) fibre, carbon fibre, glass fibre, steel and thermoplastic resin.  
         [0023]    One preferred way of establishing the areas of different flexural resistance is to manufacture the sole of a number of layers of a material. Referring to FIG. 3, the sole could be constructed with one layer material in area I, two layer material in area II, three layer material in layer III, and four layer material in layer IV.  
         [0024]    In a preferred embodiment, however, the area I is composed of two layers of crossed direction carbon fibre fabric together with two layers of single direction carbon fibre material. Area II is composed of two layers of single direction fibre material together with two layers of crossed fibres together with two layers of single direction fibre material again. Area III is composed of the same as layer II but with an additional layer of single direction fibre material. Area IV is composed of three layers of single direction fibre material together with three layers of crossed fibres together with two layers of single direction fibre material again.  
         [0025]    In FIG. 4 another embodiment is shown. The sole is shown from above and from the side. The corresponding positions and lines C 1 , C 2 , and C 3  are marked in both views. Different layers of different extensions and materials are shown. The top layer  401  extends to the full width of the sole and consists of 45 degrees KEVLAR® fabric (45 degrees between warp and weft). The second layer  402  extends to the C 1  line and consists of 45 degrees carbon fibre fabric. The third layer  403  extends to the line C 2  and consists of straight carbon fibres. The fourth layer extends to line C 1  and consists of 45 degrees carbon fibre fabric. The fifth layer  405  extends the full sole and consists of 45 degrees carbon fibre fabric also. The sixth layer extends to the line C 3  and consists of straight carbon fibres. The seventh layer extends to C 1  and consists of 45 degrees carbon fibre fabric. The eighth layer extends to C 2  and consists of straight carbon fibres. The ninth layer extends to C 1  and consists of 45 degrees carbon fibre fabric. The tenth and bottom layer extends the full width of the sole and consists of 45 degrees KEVLAR® fabric.