CN100361639C - ankle foot orthosis - Google Patents

Abstract

An embodiment of the invention provides an ankle-foot orthosis comprising: a compression sock (50) formed from a continuous first tubular member (52) and a second tubular member (54) disposed at an angle relative to the first tubular member so as to define, at least in use, a generally L-shaped cavity (56) configured to receive and fit closely around a patient's foot and ankle; and a rib (58) permanently secured to an area of the compression sock overlying the dorsum of the patient's foot in use, said rib being formed of a silicone elastomer having an elasticity suitable to resist a particular degree of plantarflexion experienced by the patient to have an elasticity.

Description

ankle foot orthosis

technical field

The present invention relates to ankle foot orthoses.

Background technique

An orthosis is a mechanical device that exerts force on a patient's limb and can be used for many different purposes. For example, an orthosis may be used for supportive, functional, corrective or protective purposes, or indeed a combination of these purposes.

Ankle-foot orthoses are generally used to provide protection to a patient's ankle and foot while providing support against hyper-plantar flexion (or more colloquially referred to as "foot drop"). Plantarflexion is a medical condition caused by disease, trauma, or a congenital abnormality. Patients affected by this condition generally have difficulty walking because the patient's foot tends to droop when lifted off the ground, and the patient typically has to lift the foot higher than it should to avoid tripping. Since typical patients also tend to exhibit poor or impaired dorsiflexion, patients often also have problems during swinging through phases of their gait cycle.

The primary function of the ankle foot orthosis is to provide plantar flexion resistance, which helps keep the patient's foot in the correct position as the foot is lifted off the ground. In addition to this resistive function, a good ankle foot orthosis should also provide some degree of assistance in dorsiflexion during swing through the patient's gait phase.

Currently, a variety of different ankle-foot orthoses have been proposed for preventing plantarflexion and, in some cases, assisting dorsiflexion.

1 and 2 are schematic illustrations of what is commonly referred to in the art as a "plantar" orthosis 10 . As the colloquial name suggests, the orthosis fits on the sole of the foot, and in this case on the outside of the shoe 12 . This particular device cannot be worn without the shoe, which is therefore an integral part of the orthosis. The orthosis includes a pair of supporting metal rods 14 , each attached to either side of the shoe 12 at a heel region 16 . Each bar is connected to the shoe by a plantarflexion stop 18 that resists foot drop, and a spring (not shown) may be provided to assist dorsiflexion. The upper end of the rod is connected to a support strap adapted to be secured about the lower leg of the patient. As can be seen in FIG. 2, the support strap acts to secure the orthosis about the lower leg of the patient, while the plantarflexion stop 18 and shoe 12 provide support on the sole of the patient's foot, thereby resisting plantarflexion.

Figures 3 and 4 show another presently proposed "plantar" orthosis which must also be used with a shoe to provide intimate contact between the shoe and the foot in the instep region. In this example, the orthosis 22 includes a unitary plastic molding 24 that includes a calf rest area 26 and a plantar rest area 28 . The top of the calf rest area 26 is provided with a closure mechanism 27 which allows the device to be secured to the patient's calf. Plantar support area 28 and shoe 30 work together to support the patient's foot. The stiffness of the plastic molding and its shape in the ankle region define the plantar flexion resistance value. If more resistance is required, the spacing before passing the ankle can be reduced, or the stiffness of the plastic material can be increased.

Figure 5 is an orthosis that is functionally equivalent to the orthosis of Figures 3 and 4 and is therefore similar in many respects to the orthosis shown in Figures 3 and 4 . The main difference is that the device shown in Figure 5 is an "on-foot" orthosis, that is, the orthosis fits on the front (dorsal) surface of the foot, rather than on the sole of the foot as in the devices of Figures 1-4 . As shown, the device comprises a plastic shell 32 which is worn against the tibia and secured about the lower leg by suitable fixation straps 34 . The orthosis comprises a stirrup 36 which fits on the foot in the dorsum region and it is this stirrup which provides the patient with resistance to plantar flexion.

All of the above mentioned orthoses are sufficient to provide the patient with means for resisting plantarflexion. However, it is also true that each of them comes with some drawbacks.

A first disadvantage is that all of the aforementioned devices are very large and bulky devices, clearly visible when worn. This means that a patient wearing one of these devices can quickly be seen as "abnormal", which can have an extremely detrimental effect on the patient's mental state.

Yet another disadvantage is that all of these devices must be worn with shoes that may have to have been specially made or include suitable plantarflexion stops (and optionally springs), or be large enough to Holds medical devices placed inside the shoe. Since it is difficult, if not impossible, for the patient to use these devices with usual off-the-shelf footwear, the overall cost (including ongoing costs) of the orthosis can be greatly increased. It also means that patients who wish to perform certain activities without shoes, such as swimming, have to do so without any device for resisting plantarflexion.

Another economic disadvantage of these devices is related to the fact that each of them needs to be customized for a specific patient and assembled by qualified professionals. For example, the devices shown in FIGS. 3-5 must be molded by a technician to closely conform to the shape of the patient's foot and leg, and the assembly process will likely be repeated each time the patient needs a new pair of shoes.

Another disadvantage particularly associated with the orthosis shown in FIGS. 3-5 is that it can be uncomfortable to wear since the patient's weight is always supported on the rigid plastic shell. It is not uncommon for the shell to dig into the sole of the patient's foot causing great discomfort.

Yet another attendant disadvantage particularly associated with the orthoses shown in FIGS. 3-5 is that they provide little power assistance for dorsiflexion of the patient's foot. The plastic materials used are generally relatively difficult to flex and bend, and this means that these materials are not good at storing the energy that is released during swinging through the phases of the patient's gait cycle to assist dorsiflexion.

Another orthosis that has been proposed so far, which avoids some of the above-mentioned problems, is described in US Patent No. 4,559,934. The orthosis is made up of four separate parts, namely: an elastic support stocking; a dorsolateral plate, which fits anatomically to the dorsum of the foot; an elastic link, which attaches to the bottom end of the plate; and a retaining fitting , in use said elastic link is connected to the retaining fitting. The elastic stocking comprises a standard elastic support stocking such as can be purchased at any drugstore or pharmacy, and the plate is attached to the stocking by a pair of pockets sewn into the stocking. Once the panel has been fitted into the bag, the elastic connector is pulled through the slit in the panel and attached (eg, by mechanical hook and loop fasteners) to the retaining fitting. By selecting the appropriate elastic tension, the patient's foot can be raised to the desired degree.

This device is less obtrusive and more comfortable than the device shown in Figures 1-5. However, it is still quite noticeable, especially when looking at the foot from the side.

There are also instances where the device is generally difficult for the patient to put on and take off (caused by the number of separate parts), and it is easy for the patient to inadvertently slip the device simply by pulling through the gap with too little or too much elastic force. Select insufficient or excessive plantarflexion resistance. This last disadvantage is exacerbated because the patient has difficulty adjusting the plantar flexion resistance when the foot is off the ground, so it is not uncommon for patients wearing such a device to struggle several times to get the device adjusted correctly.

In order to alleviate the problems described above, the applicant has previously proposed (see granted UK Patent No. 2330309) a sock-like structure formed from a resilient, flexible material such as silicone. The sock-like structure provides resistance to plantarflexion by virtue of its elasticity, and the inherent elasticity of the material allows it to store energy that can be released to assist dorsiflexion. The orthosis can be painted to mimic the color of the patient's skin (and thus be cosmetically pleasing), fits comfortably within ordinary off-the-shelf shoes, and does not require wearing shoes in order to provide benefit.

This device provides a huge leap forward in the field and alleviates most of the disadvantages mentioned above. However, it still has the disadvantage of having to be carefully assembled by a clinical technician. This means that it may take considerable time to manufacture and fit the orthosis, so the most immediate drawback is that the applicant's previously proposed device is still quite expensive.

It is an object of the present invention to provide an orthosis which avoids (or at least alleviates) the above-mentioned problems. In particular, the object of the present invention is to provide an orthosis that works as well as previously proposed by the applicant, while being significantly less expensive to produce.

Contents of the invention

To achieve the above objects, a preferred embodiment of the present invention provides an ankle foot orthosis comprising: a compression stocking structure formed from a continuous first tubular member and a second tubular member disposed relative to the first A tube is angled so as to define, at least in use, a generally L-shaped cavity configured to receive and fit snugly around the patient's foot and ankle; Over an area overlying the dorsum of the patient's foot in use, the ribs are formed to be elastic from a silicone elastomer adapted to resist the particular degree of plantarflexion experienced by the patient.

The main advantage of this orthosis (over orthoses previously proposed by the Applicant) is that it is significantly less expensive to manufacture. Accordingly, Applicant's new orthosis is well suited for commercial retailing, such as in pharmacies or drugstores, where the patient can purchase a suitable device with minimal professional assistance. Further advantages of this orthosis (compared to other previously proposed devices) are that: (a) it can be put on and taken off quickly; (b) it is very unobtrusive; (c) it requires no adjustments; (d) it does not require shoes to wear; and (e) more comfortable than some previously proposed devices.

In a highly preferred embodiment, the compression stocking is operable to exert a compressive force of at least about 5 mm Hg (approximately 670 Pascals) on the patient's foot and ankle.

In another very preferred embodiment, the elasticity of the rib can be varied, for example by varying the thickness of the rib. Alternatively (or in addition), the elasticity of the rib can be varied by changing the composition of the elastomer. The ribs may be, for example, a silicone elastomer of 35 to 80 shore, preferably 65 shore.

Other purposes, features and advantages of the embodiments of the present invention will be clearer in the following description.

Description of drawings

Different preferred embodiments of the invention will now be described, by way of example only for illustration, with reference to the accompanying drawings, in which:

Figures 1 and 2 are schematic diagrams of previously proposed plantar orthoses;

Figures 3 and 4 are schematic views of another previously proposed plantar orthosis;

Figure 5 is a schematic diagram of a previously proposed upper foot orthosis;

Figures 6a and 6b are schematic illustrations of an orthosis according to an embodiment of the invention; and

7a to 7e are schematic diagrams of an orthosis according to another embodiment of the present invention.

Detailed ways

Figure 6a is a perspective view of an embodiment of the present invention. The orthosis in Figure 6a shows what it would look like when worn by a patient (the patient's foot and ankle have been omitted for clarity). When not worn by the patient, the orthosis assumes an approximately two-dimensional shape for ease of storage.

As shown, the orthosis includes a generally sock-shaped elastic structure 50 . The sock comprises a first tubular portion 52, and a continuous second tubular portion 54, which in most cases is integrally formed with the first tubular portion.

The first and second tubular portions are arranged at an angle to each other so as to form, at least in use, a generally L-shaped inner cavity 56 sized to accommodate a patient's foot and ankle (not shown). and fit tightly around it.

Elastic flexible ribs 58 are provided on the structure and extend along the dorsum of the patient's foot from the proximal end 60 of the orthosis (which is located at or slightly beyond the patient's ankle when worn) to the distal end 62 of the orthosis ( When worn by the patient, it is located in the area of the metatarsal head). The rib is formed to have a curved cross-sectional shape (ie, concave when viewed from the cavity 56), and the radius of curvature of the rib is selected to be smaller than that of a typical foot.

When the orthosis is worn by the patient, the patient's foot and lower leg bias the rib (against its inherent elasticity) to increase the radius of curvature of the rib so that it matches the patient's foot and lower leg. The increase in the radius of curvature of the rib allows the rib, through its inherent elasticity, to exert a compressive force on the patient's instep, and this force enables the rib to securely grip the patient's foot.

As mentioned above, the ribs of this embodiment are permanently attached to the structure during manufacture of the orthosis. The elasticity of the ribs can be tailored to provide elasticity tailored to resist the particular degree of plantarflexion experienced by the patient.

In an option particularly suitable for mass production, orthoses manufactured may be provided with elasticity falling within one of several discrete ranges (eg low elasticity, medium elasticity and high elasticity). Any particular patient then only needs to choose an orthosis with the flexibility appropriate for the particular degree of plantarflexion they are experiencing.

In a highly preferred embodiment, the ribs 58 are formed directly on the structure 50 from a silicone elastomer. It is conceivable that other materials could also be used (eg rubber, polypropylene or plastic), however the highly elastic properties of silicone combined with its ease of use mean that it must be the most preferred material. In a preferred aspect, ribs 58 are formed on the structure such that silicone penetrates into the material of the structure to form a permanent bond between the silicone rib and the structure along the entire length of the rib.

The main difference from the prior art is the use of elastic materials, which tend to recommend the use of non-elastic (ie rigid) materials. A major advantage of using elastic materials over rigid materials is that the material is flexible to store energy during certain phases of the patient's gait and release energy during other phases of the patient's gait, thereby actively assisting the walking process.

It will be apparent to those skilled in the art that the ribs can be formed on the structure in any of several different ways. A so-called lapping process, which is more suitable for the manual production of silicone ribs, will now be described by way of an illustrative example. More suitable methods for large-scale production have now been developed. As an alternative to forming ribs on the structure, the ribs could of course be formed separately and then permanently affixed to the structure by bonding or other suitable means.

In this illustrative example, the silicone can be one of two suitable elastomers, HCR9960 and MED4035, both sold by Nusil Technology of 1050 Cindy Lane, Carpinteria, CA, USA. HCR9960 has a working time of about 12 hours, while MED4035 has a shorter working time of about 3 to 4 hours after which the elastomer hardens. The elastomer is thermoset and preferably filtered through a 200 mesh screen to remove particulate impurities prior to rib formation.

Both elastomers are supplied as A and B components, which are then combined on a rolling mill or other suitable device prior to use. In this example, equal amounts of A and B components were used, and the B component was softened first on the rolling mill, followed by the A component being softened on the rolling mill. Next add the same weight of Component B to Component A and then allow the two components to mix thoroughly. At this stage, it is preferable to keep the temperature of the material as low as possible in order to maximize the table life of the elastomer.

Once fully mixed, the elastomer can be constructed in layers on the sock-like structure 50 which has been stretched over a generally foot-shaped anvil. Next, allow the elastomer 3 to 4 hours to harden, although heat can be used to accelerate hardening. Once the elastomer has hardened, the structure 50 can be removed from the anvil, whereupon the inherent resiliency of the elastomer causes the ribs to curl inwardly, thereby increasing their radius of curvature, yielding the advantages previously described herein.

The elasticity of the ribs can be varied as desired to provide the appropriate elasticity to relieve the most severe conditions experienced by the patient. This change in elasticity can be achieved, for example, by varying the thickness of the ribs. Alternatively (or in addition), the elasticity of the ribs can be varied by changing the composition of the elastomer. As an example, the ribs may be a 35 to 80 Shore silicone elastomer, preferably a 65 Shore silicone elastomer.

As noted above, the sock-like structure 50 of this embodiment is an elastic material, and in a highly preferred embodiment, the structure is sufficiently elastic to exert a compressive force on the patient's foot and ankle. The force may be on the order of at least 5 mm Hg (approximately 670 Pascals).

The sock-like structure may be a woven elastic unidirectional stretch construction. By this, the applicant means that the elastic structure can be woven from individual elastic fibers so that the structure can only be stretched in an outward direction that increases the cross-sectional area of the L-shaped cavity, but not in an increased Directional stretching along the length of the orthosis. Optionally, the elastic structure may be designed to be more likely to stretch in a direction that increases the cross-sectional area of the L-shaped cavity than in a direction that increases the length of the orthosis.

Broadly speaking, the sock-like structure may be a so-called compression stocking, and a distinction is made between this elastic stocking type and the support stockings of the commonly available type that can be bought from any pharmacy or pharmacy. An example of a commonly available support stocking is the support stocking under the trade name Tubigrip ^{(R) ,} which exerts much less compressive force on the wearer's foot and ankle than compression stockings of the type mentioned here.

While it is certainly possible to form silicone ribs on one of these common Tubigrip ^(R) support stockings, the stocking does not provide sufficient stretch to keep the ribs in close contact with the patient's calf as the patient walks. Specifically, it is likely that the weight of the foot (and shoe) lifted off the ground will simply stretch the proximal end of the sock so elastically that the ribs will no longer rest against the calf and the foot will sag.

In contrast, compression stockings of the type referred to herein have an elastic force sufficient to keep the ribs tightly against the patient's lower leg when the patient's foot is off the ground. This is important because only the tight rib-to-leg fit provided by the elastic stocking will keep the patient's foot in the correct position while the patient is walking.

Broadly speaking, in an effort to avoid or relieve ankle sprains, support stockings, of which the ^Tubigrip® hosiery is an example, are provided to control the lateral movement of the patient's ankle, wherein such ankle sprains typically cause strain on the subextensor retinaculum ( Muscles that support lateral movement of the ankle).

Clearly, the device of the invention provides a measure for resisting plantarflexion and assisting dorsiflexion of the patient's foot during, for example, the swing phase of the gait cycle. Dorsiflexion and plantarflexion of the foot are primarily controlled by the tibialis anterior muscle and tendon, and the structure of the present invention acts to assist the operation of this muscle, especially for those suffering from sustained nerve damage due to, for example, trauma, disease, and heredity. patients with foot drop. This biomechanical function of the device of the present invention is fundamentally different from support stockings of the type described above, which do not provide any means of assisting the operation of the anterior muscles and tendons of the tibia (to resist plantarflexion and assist dorsiflexion of the patient's foot). ), but entirely involves resistance to abnormal lateral movement of the foot.

Due to the elasticity of the ribs, the compressive force provided by the sock-like structure can be altered, eg to help treat other conditions, such as the effects and symptoms of venous insufficiency (eg varicose veins). It is also conceivable that different regions of the sock-like structure provide different compressive forces. For example, the sock-like structure may exert a greater compressive force on the patient's foot than the ankle, thereby creating a pumping effect to assist blood flow to and from the foot.

To make it easier for the patient to put on and take off the orthosis, the sock-like structure of any of the embodiments disclosed herein may be formed with an insertion slot (not shown) extending along the back of the patient's lower leg toward the ankle. Once the device has been donned by the patient, the insertion slit can be closed by any of a number of different mechanisms. For example, a tab may be formed on one side of the slot, and on the lower portion of the tab is disposed one part of a two-part mechanical hook-and-loop fastener (eg, such as Velco ^(R )), the fastener's The other part is fixed to the sock-like structure. Alternatively, both sides of the slit are provided with a series of apertures which can be closed by a strap passing therethrough.

FIG. 6b is a front view of the orthosis shown in FIG. 6a showing the manner in which the ribs 58 extend from the proximal end 60 of the sock-like structure 50 of the orthosis along the dorsum of the foot to the distal end 62 of the structure 50 .

Figure 7a is a perspective view of another embodiment of the present invention. The orthosis of this embodiment is similar in some respects to the previous embodiments in that it includes a generally sock-like structure 70 with ribs 71 formed or disposed thereon. For the sake of brevity, common features between the two embodiments will not be further described.

The main difference between the orthoses of the two embodiments is that in this embodiment the rib 71 is provided with a pair of proximal wings 72 and a pair of distal wings 74 extending from the rib towards the back of the ankle and the plantar surface of the foot respectively.

The wings 72 and 74 serve to increase the lateral stability of the orthosis, so that the orthosis of this embodiment is especially suitable for patients with weak ankles and problems resisting plantar flexion. Proximal wings 72 help reduce the likelihood of a patient falling from their ankle by providing a lateral and even stabilizing force to the patient's ankle. Distal wings 74 assist in this function while helping to keep the ribs in proper alignment with the patient's dorsum.

The elasticity of the wings and ribs can be the same or similar, or it can vary from patient to patient, eg, the patient is more likely to fall from their ankles than from plantarflexion. It should also be noted that the wings need not be the same material as the ribs.

Figures 7b and 7c are front and side views respectively of the sock showing how the ribs extend around the ankle and foot to form the aforementioned wings. Figures 7d and 7e are rear and bottom plan views of the orthosis, respectively.

Figure 7d shows how the proximal wings 72 extend around either side of the ankle. As shown, spacing 76 is left so that the sock-like structure remains sufficiently elastic in the proximal region of the orthosis to allow the patient to don the orthosis.

Figure 7e shows how the distal wings 74 extend around the foot and partly under the foot, also leaving a gap 78 so that the orthosis is sufficiently elastic in the distal region to allow the patient to don the orthosis.

As can be appreciated from the above, the orthosis of the preferred embodiment of the present invention provides an effective solution to the problem of plantarflexion. In addition to this function, advantageously, the orthosis of the present invention can significantly increase dorsiflexion during the swing phase of the patient's gait cycle. The main reason for this is believed to be that the elastic structure and elastic ribs store energy when compressed and release energy during the swing phase of the patient's gait cycle. Therefore, it is foreseeable that patients will find that the orthosis of the described embodiments not only addresses plantar flexion but also actively assists the walking process.

The applicant's previously proposed device (as described in granted UK Patent No. 2330309) was found to provide considerable improvement not only in the degree of plantarflexion in a group of patients, but also in the speed and effort involved in walking (referred to as Known as the Physiological Energy Consumption Index, or PCI), it also provided considerable improvement. Early in the study the orthosis was found to increase walking speed by about 10% and reduce PCI by about 2%. At the end of the study (approximately six months later) it was found that the same group of patients had an approximately 20% increase in walking speed and an approximately 32% reduction in PCI compared to the initial period without the orthosis. It is foreseeable that the orthosis of the present invention will provide similar results, and hopefully better results.

Although various preferred embodiments have been described in detail above, it should be clear and noted that modifications and changes can be made without departing from the spirit and scope of the invention as defined in the appended claims.

For example, the embodiment depicted in Figures 7a to 7e could be modified to include only a single pair of wings (distal or proximal) or indeed more pairs of wings extending from the ribs and located at the aforementioned proximal Between the end wing pair and the distal wing pair.

Claims (17)

CLAIMS 1. An ankle-foot orthosis for resisting plantarflexion of a patient's foot, the orthosis comprising: a compression stocking formed from a continuous first tubular member and a second tubular member disposed relative to a first tubular member A tube is angled so as to define, at least in use, a generally L-shaped cavity configured to receive and fit snugly around the patient's foot and ankle; Over an area overlying the dorsum of the patient's foot in use, the ribs are formed to be elastic from a silicone elastomer, the elasticity of which is adapted to resist the particular degree of plantarflexion experienced by the patient. 2. The orthosis of claim 1, wherein said compression stocking is operable to apply a compressive force on said foot and ankle of said patient. 3. The orthosis of claim 2, wherein said compression stocking is woven to provide elastic stretch in only one direction, which is to increase the cross-section of said generally L-shaped cavity. direction of the area. 4. The orthosis of claim 2, wherein the compressive force is at least 5 mmHg (approximately 670 Pascals). 5. The orthosis of claim 2, wherein different regions of the compression stocking exert different compressive forces on the patient's foot and ankle. 6. The orthosis of claim 5, wherein said second tube, or at least part of said second tube, exerts a greater compressive force on the foot than that exerted by said first tube on the ankle compression force. 7. The orthosis of claim 1, wherein the elasticity of the ribs can be varied by varying the thickness of the ribs. 8. The orthosis of claim 1, wherein the elasticity of the ribs can be changed by changing the composition of the ribs. 9. The orthosis of claim 1, wherein the ribs are a 35 to 80 Shore silicone elastomer. 10. The orthosis of claim 9, wherein the ribs are a 65 Shore silicone elastomer. 11. The orthosis of claim 1, wherein the rib includes a pair of proximal wings extending from the rib toward the back of the patient's ankle. 12. The orthosis of claim 11, wherein the proximal wings extend parallel to the proximal end of the compression stocking. 13. The orthosis of claim 11, wherein the proximal wings have the same or a different elasticity as the rib. 14. The orthosis of claim 1, wherein the rib includes a pair of distal wings extending from the rib toward the plantar surface in the region of the metatarsal head. 15. The orthosis of claim 14, wherein the distal wings extend generally parallel to the distal end of the compression stocking. 16. The orthosis of claim 14, wherein the distal wings have the same or a different elasticity as the rib. 17. A method of manufacturing an orthosis for resisting plantarflexion of a patient's foot, the method comprising the steps of: providing a compression stocking formed from continuous first and second tubular members, said first tubular member and the second tube are arranged at an angle to each other so as to define, at least in use, a substantially L-shaped cavity configured to receive and fit snugly around the patient's foot and ankle; on an anvil; prepare a silicone elastomer whose elasticity is adapted to resist the specific degree of plantar flexion experienced by the patient; apply the silicone elastomer to a compression stocking to form ribs that are permanently affixed to the compression stocking in use mediating the area overlying the dorsum of the patient's foot; hardening the silicone elastomer; and removing the compression stocking from the anvil.

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