EP0777979A2

EP0777979A2 - Component of a shoe or boot for preventing ankle sprains

Info

Publication number: EP0777979A2
Application number: EP96118998A
Authority: EP
Inventors: Thomas A. Mcmahon
Original assignee: Nordica SpA
Current assignee: Nordica SpA
Priority date: 1995-12-06
Filing date: 1996-11-27
Publication date: 1997-06-11
Also published as: ITMI952578A1; EP0777979A3; ITMI952578A0; IT1277054B1

Abstract

The anti-inversion device has an upper rigid compression element (30) connectable to an item of footwear at a portion thereof encircling a wearers ankle, and a lower rigid compression element (20) connectable to an item of footwear below the upper compression element. A flexible and inextensible traction element (40) interconnects the compression elements, which have abutting bearing surfaces defining an angle therebetween. The angle is such to allow rocking and twisting motion of the upper compression element (30) with respect to the lower compression element (20) for permitting ankle dorsiflexion and plantarflexion, but delimits the degree of inversion of the ankle.

Description

The present invention relates to an anti-inversion device for preventing ankle sprains, which can be incorporated into an item of sports footwear having an ankle portion, such as a boot for hiking or climbing, or a shoe provided with a strap or collar encircling the leg above the ankle. An item of sports footwear incorporating the device according to the invention is also disclosed.
A common injury of the foot is an inversion sprain. When a moment is applied to the subtalar joint of the ankle in a sense to cause inward rotation or inversion, the plantar (bottom) surface of the foot rotates medially (toward the midline of the body). When this rotation is sufficient, a downward force on the ankle contributes an applied moment about the ankle joint which tends to continue the rotation. This condition is unstable because continued inversion of the ankle leads to an increasing moment, promoting further inversion. When such a situation develops, it may lead to angles of inversion that exceed the physiological range, followed by trauma to muscles or ligaments. This trauma is an inversion sprain. Situations which place the foot at risk of an inversion sprain occur in sports activities, as in the games of basketball, football, baseball, soccer, tennis, handball, and other games. Also, inversion sprains may occur in hiking and climbing, in work activities, in aerobic dancing exercise, and in ordinary walking.
A principal aim of the present invention is to provide an anti-inversion device for preventing ankle sprains, which may constitute a component of a shoe or boot that protects the ankle from inversion sprains by contributing a large stiffness acting to resist inversion, when the inversion angle of the ankle is greater than some specified angle AO, but contributes very little stiffness at angles below AO.
An additional aim is to ensure that when the anti-inversion device is incorporated in an item of footwear, as a component thereof, it contributes little or no moment for the normal range of plantarflexion and dorsiflexion of the ankle and inward and outward rotation of the ankle joint. Thus, for normal playing, working, or walking, the component of the item of footwear constituted by the device according to the invention may as well not be present because it does not interfere with normal activities. When, however, some accident threatens to force the ankle beyond its normal inversion range, the component contributes a large stiffness, preventing dangerous and injurious angles of inversion.
Within the scope of the above aims, an object of the invention is to provide an anti-inversion device for preventing ankle sprains which can be incorporated into an item of footwear, in an aesthetically pleasing manner.
Another object of the invention is to provide an anti-inversion device for preventing ankle sprains which does not adversely affect the comfort of the footwear for the user thereof.
A further object of the invention is to provide an anti-inversion device for preventing ankle sprains which is structurally simple and has low manufacturing costs.
With the foregoing aims and objects in view, the invention provides an anti-inversion device for preventing ankle sprains, for sports footwear, characterized in that it comprises at least one upper rigid compression element connectable to an item of footwear at a portion thereof encircling a wearers ankle, a lower rigid compression element connectable to an item of footwear below said upper rigid compression element, and a flexible and inextensible traction element connected to said upper rigid compression element and to said lower rigid compression element.
An item of sports footwear having a sole and an upper, which incorporates the device for preventing sprains according to the invention, is also disclosed herein.
The anti-inversion device according to the invention is advantageously a component of a high-topped shoe or boot. It may also be used, as mentioned heretofore, with a low-topped shoe, provided that a strap or collar encircling the leg above the ankle is also worn.
Further characteristics and advantages of the device for preventing ankle sprains according to the invention, will become apparent from the following detailed description of some preferred embodiments, illustrated only by way of non-limitative example in the accompanying drawings, wherein:

FIG. 1 is a lateral perspective view of a shoe or boot incorporating one embodiment of the anti-inversion device for preventing sprains, which has two rigid elements;
FIG. 2 is rear view of the shoe or boot of FIG. 1;
FIG. 3a is an exploded rear view of the anti-inversion device of figures 1 and 2;
FIG. 3b is an exploded lateral view of the anti-inversion device of figures 1, 2 and 3a;
FIG. 4 is a perspective view of a boot incorporating the anti-inversion device illustrated in the preceding figures 1-3b, showing the insertion of the anti-inversion device through a slit in the boot during the assembly process;
FIG. 5 is a perspective view of a boot having an anti-inversion device inserted therein as illustrated in figure 4, and additionally showing how a flap may be brought down over the lower portion of the anti-inversion device;
FIG. 6 is a schematic front elevational view of the shoe or boot shown in figure 1, defining an angle of inversion (A);
FIG. 7 is a graph showing the relationship between the moment (M) developed by the anti-inversion device shown in figure 3 and the inversion angle (A);
FIG. 8 is a rear perspective view of an alternative embodiment of the anti-inversion device for preventing sprains according to the invention, having a cable and several rigid elements;
FIG. 9 is a lateral elevational view of the anti-inversion device shown in figure 8, and;
FIG. 10 is a rear elevational view of the anti-inversion component of FIG. 8;
FIG. 11 is a rear elevational view of the anti-inversion device of figure 8, showing, in broken lines, a normal condition wherein the cable is buckled and, in solid lines, a stressed condition wherein the cable is taut.

The invention concerns a device for contributing a large anti-inversion moment to the ankle when an attempt is made to exceed a certain threshold angle AO, but the device contributes little or no anti-inversion moment for angles less than AO. Furthermore, the device contributes little or no moment when it is deformed throughout the normal range of dorsiflexion, plantarflexion, inward rotation and outward rotation. In some embodiments of the invention, the angle AO is adjustable by the wearer. Critical elements of the invention include a flexible but inextensible cable, two or more rigid elements that bear a compressive force when the cable is in tension, and a series of narrow gaps or compliant elements interposed between the rigid elements.
A lateral perspective view of one embodiment of the invention is shown in FIG. 1, and a rear view thereof is illustrated in FIG. 2. The shoe or boot 10 includes an anti-inversion device made up of a first rigid compression element hereinafter referred to as a lower element 20 connected to a second rigid compression element, hereinafter referred to as an upper element 30 by a flexible but inextensible traction element, advantageously constituted by a cable 40. The ends of cable 40 are preferably retained in elements 20 and 30 by pressed-on cable ends 43. The upper element is joined to a collar 50 encircling the leg above the ankle. An exploded view of the anti-inversion component excluding the boot is shown in FIG. 3. The lower element 20 is fixed to the wall of the boot, preferably via a backing plate 60 that is continuous with the sole plate of the boot. Rivets 61 or other suitable fixing devices penetrate the backing plate 60. They also penetrate the wall of the boot, and terminate in the lower element 20. The member formed by the upper element 30 and collar 50 is not joined to the boot by any connection other than the cable 40. The length of the cable 40 bridging the gap between the lower and upper compression elements 20 and 30 may be decreased, and the gap closed, by turning set screw 25, thereby pushing the cable into the cavity 27 and causing it to assume a bent shape within the cavity. The upper element is cut away, forming angles C and D with respect to a horizontal plane (FIG. 3), to permit the upper element 30 to rock on the lower element 20 at the mutually abutting bearing surfaces. Either one or both of the compression elements may be shaped to provide the desired freedom for mutual rocking movement between the upper and lower compression elements. This rocking freedom is necessary to prevent movement-restraining contact of the upper and lower elements during normal plantarflexion and dorsiflexion of the ankle.
An appreciation of the geometry can be obtained from FIG. 4 and FIG. 5, showing the assembly process in two stages. In FIG. 4, the anti-inversion device is not yet attached to the boot; the lower element 20 is being pushed from the inside through slit 70 in the wall of the boot. In FIG. 5, the lower element 20 is in place, and has been fastened to the backing plate and boot wall via rivets 61. Alternatively, backing plate 60 and rivets 61 may be omitted, and the lower element 20 may be cemented or in some other way adhered to the outer wall of the boot. The final step in the assembly is to bring the flap 75 down over the lower element and to sew or cement it to the boot wall, thereby containing the anti-inversion component in a pouch over the ankle.
The use of the device for preventing sprains is as follows: In putting on the boot, the wearer spreads the margins 51 of the collar 50 and pushes the foot into the boot. Next, the margins 51 of the collar 50 are closed using laces or a strap fastened with a collar, or with a flexible fastening strip known by the Registered Trademark "Velcro". This step fixes the collar to the lower leg above the ankle. Finally, the laces of the boot are tied in the usual way.
The angle of inversion A is defined in FIG. 6 as the angle between a normal to the plantar surface of the shoe or boot and the centerline of the wearer's shank. Thus, when the wearer stands upright on a flat surface, A is close to zero. As shown in FIG. 7, the device according to the invention provides an anti-inversion moment M to the wearer's shank which increases only modestly with increasing inversion angle up to some threshold angle AO, but increases rapidly with A thereafter, as the medial edge of the upper element 30 bears on the lower element 20, causing the cable 40 to become taut. In the preferred embodiment, the gap between the upper element 30 and the lower element 20 is adjustable by turning the set screw 25 shown in FIGS. 2 and 3. Advancing the set screw 25 pushes the cable 40 into the cylindrical space 27, thereby causing the cable to assume a bent shape, decreasing the overall length of the cable and closing the gap. Alternative adjusting devices may be provided to change the length of the cable or to otherwise close the gap, thereby making the angle AO adjustable.
Another alternative embodiment of the device for preventing sprains according to the invention is shown in FIG. 8, where the shoe or boot 100 includes an elongated pouch 120 which is firmly attached to an encircling collar 140 which grips the leg well above the ankle. The elongated pouch 120 is generally vertical with a semi-circular cross-section and is attached to the lateral aspect of the shoe or boot behind, over, or ahead of the ankle. Additional pouches containing anti-inversion elements may be included on the lateral aspect of the shoe or boot ahead of or behind the ankle joint. Within the pouch 120, the anti-inversion device 160 is tethered or anchored at the lower end where it inserts into the rigid sole plate 180, but is otherwise free to slide within the pouch. In FIG. 9 (side elevation) and FIG. 10 (rear elevation), the anti-inversion element 160 is shown separately. It consists of a number of rigid compression elements 200 separated by compliant disks 220. A flexible but inextensible cable 240 extends along the lateral margin of the device and is held by spine elements 280 projecting from compression elements 200. A flexible but inextensible fabric band 300 preserves the alignment of compression elements 200. The broken view in FIG. 11 shows the cable 240 in a buckled state contributing no tension (as in normal use), and the solid configuration in FIG. 11 shows the device pushed medially, with the cable bearing tension (as when the ankle is inverted).
An important difference between the embodiments shown in FIG. 1 and FIG. 8 is whether or not the anti-inversion device passes over the ankle. In FIG. 1, the gap between the lower compression element and the upper compression element is close to the center of the ankle joint, so that no mutual sliding movement is required between the upper and lower compression elements during normal motions of the ankle. In FIG. 8, if the anti-inversion device does not pass over the ankle, some sliding of the anti-inversion device 160 with respect to the pocket 120 would be required, in order to prevent any restraint of ordinary motions of the ankle.
In the presently preferred embodiments of the invention (FIG. 1 and FIG. 8), the central non-extensible cable 40 or 280 is preferably constituted by twisted or braided steel wire rope 0.079 cm to 0.318 cm (1/32-inch to 1/8 inch) in diameter, or braided, or woven cable made of Nylon or material known by the Registered Trademark Kevlar 0.318 cm to 0.635 cm (1/8 to 1/4 inch) in diameter. Rigid compression elements 20 and 30 or 200 are preferably made of Nylon or polyurethane, Delrin, polyvinylchloride, Kevlar, aluminum, steel, or other hard material with a thickness in the medial-lateral direction of 0.318 cm to 3.18 cm (1/8 inch to 1.5 inches). The sole plate 60 or 180 is preferably made of a hard material such as polyurethane, Delrin, polyvinylchloride, Kevlar, aluminum, steel, or the like. Compliant separating elements 220 are preferably made of polyurethane foam, latex foam, or other easily-deformable material. The angle AO in FIG. 7 is between 15 and 45 degrees, with a preferred value near 25 degrees.
The angle B in FIG. 2 is between 0 and 30 degrees, with a preferred value near 10 degrees. The angles C and D in FIG. 3 are between 0 and 40 degrees, with preferred value near 30 degrees.
From the foregoing, it can be seen that the device according to the invention protects the ankle from inversion sprains by contributing a large stiffness acting to resist inversion, when the inversion angle of the ankle is greater than some specified angle AO, but contributes very little stiffness at angles below AO. The device does not impede the normal range of plantarflexion and dorsiflexion of the ankle and inward and outward rotation of the ankle joint, but when a force is exerted on the ankle which pushes it beyond the normal inversion range, the device contributes a large stiffness, preventing dangerous and injurious angles of inversion. Furthermore, the device according to the invention is structurally simple, has low manufacturing costs, and can be incorporated into an item of footwear, in an aesthetically pleasing manner.
Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

An anti-inversion device for preventing ankle sprains, for sports footwear, comprising at least one upper rigid compression element connectable to an item of footwear at a portion thereof encircling a wearers ankle, a lower rigid compression element connectable to an item of footwear below said upper rigid compression element, and a flexible and inextensible traction element connected to said upper rigid compression element and to said lower rigid compression element.
The anti-inversion device according to claim 1, wherein said upper rigid compression element and said lower rigid compression element define mutually abutting bearing surfaces, said bearing surfaces defining an angle therebetween, whereby to allow rocking motion of said upper rigid compression element with respect to said lower rigid compression element at said bearing surface, for permitting ankle dorsiflexion and plantarflexion.
The anti-inversion device according to claim 2, wherein an anti-inversion angle (B) from 0 to 30 degrees, and dorsiflexion and plantarflexion angles (C, D) from 0 to 40 degrees are defined between said bearing surfaces.
The anti-inversion device according to claim 1, further comprising a plurality of rigid compression elements connected to said flexible and inextensible traction element and located between said upper rigid compression element and said lower rigid compression element.
The anti-inversion device according to claim 1, wherein upper rigid compression element and said lower rigid compression element are separated by a gap, said device further comprising means for adjusting the length of said traction element and the width of said gap.
The anti-inversion device according to claim 1, wherein said at least one upper rigid compression element is fixable to a collar of a footwear item encircling a wearer's leg above the ankle, and wherein said lower rigid compression element is fixable to a wall portion of said footwear item.
The anti-inversion device according to claim 1, wherein said at least one upper rigid compression element is fixable to a collar of a footwear item encircling a wearer's leg above the ankle, and wherein said lower rigid compression element is attached to a rigid plate fixable below the sole portion of an item of footwear.
The anti-inversion device according to claim 1, wherein said rigid compression elements are separated by compliant pads.
An item of footwear incorporating an anti-inversion device as defined in claim 1.
An item of footwear incorporating an anti-inversion device as defined in claim 8.
An item of footwear according to claim 9, comprising at least one rigid compression element included in an envelope within a lateral wall of said item of footwear.
An item of footwear according to claim 10, comprising at least one rigid compression element included in an envelope within a lateral wall of said item of footwear.