WO2001045598A1

WO2001045598A1 - Custom knee brace impression sleeve, kit and method

Info

Publication number: WO2001045598A1
Application number: PCT/US2000/033496
Authority: WO
Inventors: Richard M. Stess; Peter M. Graf; Clarence Dawiedczyk
Original assignee: Synthetic Tubular Socks, Inc.
Priority date: 1999-12-21
Filing date: 2000-12-11
Publication date: 2001-06-28

Abstract

A custom knee brace impression kit including a tubular impression sleeve (21, 21a, 21b) formed of an elastic fabric material providing elasticity sufficient to conform the sleeve to the leg of a patient. The impression sleeve includes an upper sleeve portion (25, 25a, 25b) having a large diameter dimensioned to resiliently conform to the patient's thigh above the knee, and a lower sleeve portion (27, 27a, 27b) having a smaller diameter dimensioned to be less than the large diameter and dimensioned to resiliently conform to the patient's calf below the knee. The impression sleeve (21, 21a, 21b) is hardened, preferably with a quantity of a water-curable resin, into an impression cast suitable for forming a custom knee brace. A method of creating a custom knee brace impression also is disclosed.

Description

CUSTOM KNEE BRACE IMPRESSION SLEEVE. KIT AND METHOD

TECHNICAL FIELD

This invention relates, in general, to the construction of custom leg braces or orthoses, and particularly knee braces, and more particularly, relates to methods and* apparatus for the formation of a cast impression of a patient's knee in order to enable the subsequent formation of a knee orthosis.

BACKGROUND ART

Adjustable mechanical knee braces have been subject of extensive development. In such systems, the leg bracing structures preferably are adjustable to the patient's thigh and calf to customize the manner in which the knee brace fits the patient's leg and therefore supports the patient's weight. Typical of such adjustable orthoses are the devices of U.S. Patent Nos . 5,372,572, 5,554,104, 5,693,007 and 5,891,071.

Considerable effort also has been directed toward the development of orthopedic casting systems in which a fabric sock impregnated with a hardenable resin, is used to create an impression or casting that is subsequently used to form pads and/or mechanical components of knee braces. Typical of such prior _^rt casting systems are the kits disclosed in U.S. Patent Nos . 4,700,698, 4,793,330, 5,555,584, 5,637,077, 5,752,926 and 5,807,295. Similar materials and casting techniques are also shown in our U.S. Patent No. 5,228,164 for the formation of a shoe last, which invention also can be used to construct ankle-foot orthoses.

One problem which has been encountered with impression casting sleeves is that when impregnated with a curable resin, they tend to lose elasticity. Thus, many impression casting systems employ viscous, water-curable resins which impregnate or soak the fabric sleeve. The resin viscosity lessens the overall elasticity of the sleeve and resists the sleeve's dry-state tendency to conform to the patient's limb. The medical professional, therefore, must take care to ease the resin soaked elastic sleeve into conformance on the limb and be careful that the sleeve or sock is evenly stretched over the patient's limb in an unwrinkled condition.

A related problem can be that the sleeve is locally over- stretched. As the fabric or yarn fibers are stretched apart, the resin content locally diminishes or thins out in the stretched area, resulting in insufficient resin to provide the necessary strength for the hardened impression.

The problems of elasticity loss and local resin depletion are not as significant in ankle-foot or arm casting applications because parts of the limbs being cast usually do not have great dimensional variation. Thus, a patient's wrist, elbow and ankle tend to have roughly similar diameters across the area being cast. Thus, a casting sleeve for a patient's arm can be cylindrical or formed with a constant diameter, and it will have sufficient elasticity to have good conformance, even when resin soaked. Moreover, local areas of the sleeve tend not to be over-stretched so tnat resin is evenly distributed over the sleeve, and the hardened impression will be strong throughout.

Knee castings, however, can present extreme problems. A typical impression will extend 10-12 inches above and below the center of the knee so that padding and supporting components can be customized to the patient's from upper thigh and lower calf. The patient's nominal upper thigh diameter may be as much as twice the patient's nominal calf diameter. As a result, impression sleeve sized to have good resilient conformance to the patient's calf when resin soaked can be over-stretched on the patient's thigh, resulting in localized resin loss. Conversely, sleeves which are sized to accommodate a patient's thigh, tend to be oversized on the calf_/_ making smooth conformance tedious .

Accordingly, it is an object of the present invention to provide a custom knee brace impression sleeve, kit and method which is capable of producing a custom knee impression of the patient's leg from the upper thigh to below the calf which has high conformance and is of uniform high strength.

Another object of the present invention is to provide an impression sleeve for use in making a custom knee cast which is easier to apply to the patient, conforms better to the patient's leg and is more uniformly stretched when in place so as to evenly retain casting resin for hardening.

A further object of the present invention is to provide a knee impression casting kit and method which produces a high strength uniform knee impression suitable for use in forming a permanent knee orthosis. The custom knee brace impression sleeve, casting kit and method of the present invention have other objects and features of advantages which will become apparent from, or are set out in more detail in, the accompanying drawing and following description of the Best Mode of Carrying Out the Invention.

DISCLOSURE OF INVENTION

The custom knee brace impression sleeve and kit of the present invention are comprised, briefly, of a tubular impression sleeve formed in part of an elastic fabric material providing elasticity sufficient to conform the sleeve to the leg and thigh of a patient. The sleeve is formed with an upper sleeve portion having a large diameter dimensioned to resiliently conform to the patient's thigh above the knee, and a lower sleeve portion having a small diameter dimensioned to be less than the large diameter and dimensioned to resiliently conform to the patient's calf below the knee. In the kit, a quantity of curable resin is provided which is sufficient to rigidify the sleeve into an impression cast . The resin may be in a separate container or coated on, or impregnated into, the fabric material of the sleeve .

The method of the present invention is comprised, briefly, of the steps of mounting an elastic impression sleeve impregnated with a water-curable resin having a large diameter upper sleeve portion and a small diameter lower sleeve portion on a patient's leg across the patient's knee, manipulating the leg to orient the knee, hardening the resin in the sleeve, and removing the hardened sleeve. The hardened sleeve may then be used to prepare a custom knee brace. BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a side elevation view of an impression sleeve suitable for use in a custom knee brace impression kit constructed in accordance with the present invention.

FIG. 2 is a side elevation view of the sleeve of FIG. 1, shown in a rolled-up condition.

FIG. 3 is a top plan view of the rolled-up sleeve of FIG. 2 placed in a plastic bag, together with an optional separate resin container.

FIG. 4 is a side elevation view corresponding to FIG. 1 of an alternative embodiment of the impression sleeve of the present invention.

FIG. 5 is a side elevation view corresponding to FIG. 1 of a further alternative embodiment of the impression sleeve of the present invention.

FIG. 6 is a side elevation view of a patient's leg showing the impression sleeve of the present invention mounted thereon.

BEST MODE OF CARRYING OUT THE INVENTION

A human leg varies substantially in diameter between the upper thigh and the mid to lower calf. Custom knee braces often include portions which engage both the thigh and calf to provide the necessary support across the patient's knee, for example, as shown in the knee braces of U.S. Patent Nos . 5,554,104 and 5,891,017. In order to customize the fit of such knee braces, the patient's leg above and below the knee, as well as in the area of the knee itself, must be cast. The wide range of leg diameters over the desired impression length, however, causes problems. In the present invention, an improved impression sleeve and custom knee brace impression kit are provided which better accommodates the anatomy of a typical patient.

Referring now to FIG. 1, a custom knee brace impression sleeve, generally designated 21, is shown. The impression sleeve is preferably formed of a knit fabric material, as will be set forth below, and includes elastic fibers which will cause the fabric to resiliently conform to diameter variations and irregularities over the length of the patient's leg being cast. Thus, there must be sufficient elasticity in sleeve 21 to conform or adjust to the size variations of the patient's leg above, below and across the knee.

In order to ensure that the impression sleeve is neither over-stretched nor so loose as to have poor conformance, sleeve 21 is formed with an upper sleeve portion 23 having a large diameter, for example, the diameter at upper end 25, which is dimensioned to resiliently conform to the patient's thigh above the knee, most preferably the upper thigh. Upper end 25 has a diameter which will resiliently conform to the patient's upper thigh without over-stretching. Sleeve 21 further includes a lower sleeve portion 27 having a small diameter, for example, at lower end 29 which will resiliently conform to the patient's calf below the knee, most preferably the mid- calf or below. As we see from FIG. 1, smaller diameter end 29 is less than large diameter end 25.

In the preferred form of impression sleeve 21, upper sleeve portion 23 is frusto-conical and tapers from upper end 25 to a plane 31 at which it is joined to lower sleeve portion 27. The lower sleeve portion can be seen to preferably be substantially cylindrical so that the small diameter of the sleeve is substantially constant over the length of lower sleeve portion 27 from lower end 29 to plane 31. Upper sleeve portion 23, therefore, tapers from a large diameter at end 25 to the same diameter as the lower sleeve portion end 29, that is the diameter at plane 31. The position or plane 31 at which the upper and lower sleeve portions are joined preferably is at about the middle of the length of sleeve 21, although that is not required in the broadest aspect of the present invention. Similarly, the sleeve portions do not have to be joined along a common plane, although that is a particularly easy configuration to fabricate.

In the preferred form of the impression sleeve, upper sleeve portion 23 is tapered by an amount which will produce relatively even, radially outward, elastic displacement or stretching of the impression sleeve oves the length of upper portion 23. At end 25, the greater diameter will accommodate the larger thigh diameter which will be encountered at the upper thigh of the patient. The lower end of upper sleeve portion 23, namely plane 31, will be dimensioned to resiliently stretch outwardly at about the mid-point of the patient's knee by an amount which is similar to the amount of stretching required at upper end 25. Some uneven stretching can occur, but in the areas of greatest stretching, end 25, the fabric should not separate by an amount causing localized resin depletion so as to reduce casting strength.

Since the typical patient's leg is more uniform in diameter between the knee and the mid-calf, lower sleeve portion 27 can advantageously be formed as a cylinder, that is, of substantially constant diameter. There will be some variation in the amount of stretch between ends 29 and plane 31, but the variation will not be so great as to cause localized over-stretching of the impression sleeve . In order to accommodate a range of anatomies, sleeve 21 also can be formed in various sizes. Thus, for larger individuals, the largest diameter 25 at the upper sleeve portion will be larger than would be the case for "average" sized individuals or "petite" sized individuals. It is contemplated, therefore, that two or three sleeves sizes may be required to accommodate the full range of anatomies, with the doctor or medical technician making a selection as between sizes so as to obtain elastic conformance without over-stretching.

As can be seen from FIG. 2, it is preferable that sleeve 21 be rolled up outwardly upon itself in a double-donut structure. Lower sleeve portion 27 can be rolled outwardly and upwardly from end 29 toward mid-plane 31 to form a lower donut , while end 25 of upper sleeve portion can be rolled outwardly and downwardly toward mid-plane 31 to form the upper donut structure. As so rolled up, the impression sleeve can be easily stored, preferably while coated or impregnated with a quantity of a curable resin sufficient to rigidify the sleeve into an impression cast. As shown in FIG. 3, therefore, sleeve 21 can be stored in an air-tight plastic bag or air-tight metal foil pouch or envelope 33 having a sealed end 35. The resin can either already be coated on or carried by the impression sleeve inside container

33 or provided in a separate container 37. When separate, resin 39 can be added to impression sleeve 21 before positioning on the patient's leg. Since water- curable resins are storable and stable while impregnated or coated on the sleeve 21, the custom knee brace impression kit of the present invention preferably has the resin already coated on the impression sleeve. A separate container 37 with resin 39, therefore, is usually not required for the kit of the present invention. Referring now to FIGS. 4 and 5, two alternative embodiments of the custom knee brace impression sleeve of the present invention are shown. In FIG. 4, an impression sleeve, generally designated 21a, is provided which has an upper sleeve portion 23a and a lower sleeve portion 27a. The sleeve has a general frusto-conical shape which tapers radially inwardly from an upper end 25a to a lower end 29a. Upper end 25a diameter preferably again is selected to resiliently conform to the patient's thigh above the knee without overstretching, while lower diameter end 29a is sufficiently small to resiliently conform to the diameter of the patient's calf without requiring substantial technician manipulation .

While somewhat simpler to manufacture than the impression sleeve of FIG. 1, the sleeve of FIG. 4 can lack the desired conformance around the patient's knee. Thus, while over-stretching is avoided at the upper thigh, the doctor or medical technician must be careful to ease the impression sleeve in the area of the patient's knee so as to ensure smooth, wrinkle-free conformance to the knee. Such adjustment may require a little more time than would be the case for the sleeve of FIG. 1, but the large diameter end 25a of sleeve 21a would ensure that over-stretching would not reduce concentration of resin to the point of diminishing the strength of the resulting impression.

In FIG. 5, an impression sleeve 21b is shown in which upper sleeve portion 23b is cylindrical, as is lower sleeve portion 27b. The upper and lower sleeve portions are joined by a frusto-conical intermediate sleeve portion 24, which will be generally positioned over the patient's knee. Usually, the intermediate sleeve portion 24 will be relatively short in length compared to the upper and lower sleeve portions. Impression sleeve 21b is somewhat more complexed to manufacturer than that of FIG. 1, and it can have less than the desired amount of elasticity in the area immediately above the patient's knee. Nevertheless, it is suitable for use in the present invention in that it avoids over-stretching in the large diameter areas of the impression sleeve and produces good elastic conformance, and minimal manipulation during casting, over most of the length of the sleeve.

The impression sleeves of the present invention can advantageously be formed of synthetic fabric materials such as lofted glass yarn or polyester yarn, and they are preferably are knit with elastomeric fibers that provide the necessary elasticity for the sleeve. A sleeve such as shown in FIG. 4 can be continuously woven knit member, while the sleeves of FIGS. 1 and 5 can be joined at the various planes at which the sleeve geometry changes. It is preferable that the sleeve fabric exhibit extensibility of about 100% in a direction transverse to a longitudinal axis of the sleeve.

Most preferably, the present impression sleeve is used with a water-curable resin. This enables the doctor or technician to remove impression sleeve 21 from its container 23, dip it in a bucket or container of water and apply it to the patient's limb. Alternatively, the sleeve can be positioned on the patient's leg and the resin activated or hardened by spraying the sleeve with water while on the limb. Dipping the sleeve in water prior to application is preferred.

Sleeve materials and resins which are suitable for use in practicing the present invention are set forth in our U.S. Patent No. 5,228,164, which disclosure is incorporated herein by reference in its entirety. The shell-forming fabric and water curable resin of our U.S. Patent No. 5,228,164 were originally created for the formation of lasts for custom footwear, but they also are suitable for use in the knee brace impression kit of the present invention.

Referring now to FIG. 6, the method of using the custom knee brace impression kit of the present invention can be described in more detail . Prior to mounting impression sleeve 21 on the user's leg, it is preferable to place a barrier layer of material 51 over the length of the leg which will be cast. Thus, a sheet of polyethylene or other plastic material of a few thousands of an inch in thickness can be employed as the barrier layer which will prevent resin from bonding to the patient's leg. Since layer 51 can be very thin, a slightly oversized polyethylene tube can be used.* Alternatively, a sheet of barrier material can be positioned over the leg and secured by tape or the like with a slight overlap along the sheet edges.

Moreover, it is preferable that a protective plastic cutting strip 53 extend down the length of the area to be cast, preferably on a posterior aspect of the patient's leg. A material such as a layer of felt or other cushioning material can be employed, and it is the purpose of this strip to protect the leg when the hardened impression is removed during use of a cast cutting saw or scissors to cut through the hardened sleeve .

The rolled-up impression sleeve 21 can then be removed from its container 33, dipped in a pail of cool water and mounted on the patient's leg 41 in a rolled-up condition. The double donut is preferably positioned at about the patient's knee 43, as shown in broken lines in FIG. 6. The small diameter or lower sleeve portion 27 is positioned just below the mid-point of knee 43, while rolled-up upper sleeve portion 23 is positioned just above the mid-point of the knee. Next, the upper and lower sleeve portions can be unrolled in opposite directions, with upper portion 23 being unrolled to the solid line position shown in FIG. 6. Upper end 25 typically will be positioned over an upper section of thigh 45, and lower end 29 of the sleeve will be unrolled to a position on the user's calf 47.

Once the sleeve is rolled out on the patient's leg, the doctor or medical technician can manipulate the leg to achieve a desired orientation of knee 43. This may depend upon the nature of the problem requiring the knee brace and/or the doctor's preferences and experiences with knee braces. Typically, the leg will be in a position ranging from fully extended, as shown in FIG. 6, to 10°, or even 30°, flexed from the fully extended position.

The impression sleeve will then be hardened, usually by spraying the sleeve with water so that a water-curable resin on the sleeve will be activated and form, with the fabric of the sleeve, a hardened shell. If the kit is one in which the resin is separate from the sleeve, it most preferably will be added to the sleeve before placing the sleeve on the patient's leg. It would be possible, however, to apply resin to the sleeve as rolled out on the patient's leg, although this is more tedious and not generally recommended. Spraying the patient's leg with a hardening material, such as water, can be easily accomplished with the sleeve in the rolled-out condition and the patient's leg oriented as desired.

Once the impression sleeve hardens, which takes about 4-6 minutes, the hardened impression sleeve can be removed from the patient's leg. This usually is accomplished using a cast saw or scissors by cutting along the protective strip 53 from end 29 to end 25. Usually, only one cut is necessary since the hardened sleeve will be flexible enough to allow it to be flexed and removed from the patient's leg. If desired, however, two longitudinal cuts could be made and the hardened impression sleeve removed in halves.

In a typical embodiment constructed in accordance with FIG. 1, an impression sleeve for larger patients might have a small diameter end 29, 31 which is in the range of about 2 to 2 1/2 inches in diameter, while the large diameter end 25 will be in the range of about 2 1/2 to about 3 inches in diameter. A version of the same sleeve for smaller patients would have a diameter in the range of about 1 1/4 to 1 1/2 inches at the small diameter end 29 and a diameter in the range of about 1 3/4 to about* 2 inches at large diameter end 25. Obviously, both ends, and in fact the entire length of the sleeve, must stretch radially to be mounted on the patient's leg, but in a resin-soaked condition, the elastic yarn will lose some of its resilient capability as a result of the viscous resin material. Thus, sleeves 21, 21a, 21b of the present invention always will be considerably smaller in their relaxed diameters than the diameter of the patient's leg. Accordingly, the impression sleeve must be sufficiently undersized so as to retain enough elasticity to produce good conformance to the patient's leg without the need for undue, tedious manipulation to create conformance. Using the double-donut approach and rolling the sleeve out in both an upward and a downward direction further ensures conformance with less sleeve manipulation. The provision of an upper portion 23 on the sleeve which has a larger diameter than lower portion 25, moreover, ensures that sleeves 21, 21a, 21b will not be over-stretched and resin locally depleted at the thigh of the patient.

Claims

WHAT IS CLAIMED IS:

1. A custom knee brace impression kit comprising:

(a) a tubular impression sleeve formed in part of an elastic fabric material providing elasticity sufficient to conform said sleeve to a leg of a patient above, below and across the patient's knee, said impression sleeve being formed with:

(i) an upper sleeve portion having a large diameter dimensioned to resiliently conform to the patient's thigh above the knee, and

(ii) a lower sleeve portion having a small diameter dimensioned to be less than said large diameter and dimensioned to resiliently conform to the patient's calf below the knee , and b. a quantity of curable resin sufficient to rigidify said sleeve into an impression cast, said resin being provided in one of a container separate from said sleeve and coated on the fabric forming said sleeve.

2. The custom knee brace impression kit as defined in claim 1 wherein, said upper sleeve portion is substantially conical tapering from said large diameter proximate an upper end thereof to a diameter substantially equal to said small diameter of said lower sleeve portion proximate a lower end of said upper sleeve portion; and said lower sleeve portion is substantially cylindrical .

3. The custom knee brace impression kit as defined in claim 1 wherein, -lb- said upper sleeve portion and said lower sleeve portion are continuously tapering from a large diameter end of said sleeve portion to a small diameter end of said lower sleeve portion.

4. The custom knee brace impression kit as defined in claim 1 wherein, said upper sleeve portion and said lower sleeve portion are both substantially cylindrical, and an intermediate sleeve portion formed with a frusto-conical shape and joining said upper sleeve portion to said lower sleeve portion.

5. The custom knee brace impression kit as defined in claim 1 wherein, said resin is provided as a water-curable resia impregnated in said fabric of said sleeve, and said sleeve and said resin are housed in a common container.

6. The custom knee brace impression kit as defined in claim 1 wherein, said fabric material is provided by an elastic fabric exhibiting extensibility of about 100 percent in a direction transverse to a longitudinal axis of said sleeve .

7. The custom knee brace impression kit as defined in claim 1 wherein, said fabric material is a synthetic yarn with elastomeric fibers.

8. The custom knee brace impression kit as defined in claim 1 wherein, said upper sleeve portion and said lower sleeve portion are provided by a woven knit tubular member.

9. A custom knee brace impression sleeve comprising: - - a tubular impression sleeve formed in part of an elastic fabric material and having an upper sleeve portion having a large diameter dimensioned to resiliently conform to the patient's thigh above the knee, and a lower sleeve portion having a small diameter dimensioned to be less than said large diameter and dimensioned to resiliently conform to the patient's calf below the knee.

10. The custom knee brace impression kit as defined in claim 9 wherein, said upper sleeve portion is substantially conical tapering from said large diameter proximate an upper end thereof to a diameter substantially equal to said small diameter of said lower sleeve portion proximate a lower end of said upper sleeve portion; and a said lower sleeve portion is substantially cylindrical .

11. The custom knee brace impression kit as defined in claim 9 wherein, said upper sleeve portion and said lower sleeve portion are continuously tapering from a large diameter end of said upper sleeve portion to a small diameter end of said lower sleeve portion; and said lower sleeve portion is substantially cylindrical.

12. The custom knee brace impression kit as defined in claim 9 wherein, said upper sleeve portion and said lower sleeve portion are both substantially cylindrical, and an intermediate sleeve portion formed with a frusto-conical shape and joining said upper sleeve portion to said lower sleeve portion.

13. The custom knee brace impression sleeve as defined in claim 9, and a water-curable resin coated on said fabric of said sleeve .

14. The custom knee brace impression sleeve as defined in claim 9 wherein, said upper sleeve portion and said lower sleeve portion are provided by a continuously woven knit tubular member .

15. A method of creating a custom knee brace impression comprising the steps of: mounting a tubular elastic hardenable impression sleeve having a large diameter upper sleeve portion and a small diameter lower sleeve portion on a patient's leg with an upper end of said upper sleeve portion positioned above the patient's knee, a lower end of said lower sleeve portion positioned below the patient's knee, and a remainder of said impression sleeve extending over the patient's knee; manipulating the patient's leg to achieve a desired orientation of the patient's knee; hardening a resin in the said impression sleeve while the patient's knee is in the desired orientation; and removing the hardened impression sleeve from the patient' s leg .

16. The method as defined in claim 15 wherein, said mounting step is accomplished by mounting said impression sleeve on said patient's leg in a rolled-up condition proximate the patient's knee, said upper sleeve portion being rolled outwardly upon itself from said upper end to produce an upper donut -like roll and said lower sleeve portion being rolled outwardly upon itself from said lower end to produce a lower donut-like roll, and unrolling said upper donut -like roll upwardly onto the patient's lower thigh and unrolling the lower donut- like roll downwardly onto the patient's upper calf.

17. The method as defined in claim 15 wherein, said hardening step is accomplished by applying water to a water-curable resin contained in said impression sleeve, and said removing step is accomplished by cutting said impression sleeve longitudinally to enable removal from the patient's leg.

18. The method as defined in claim 17, and the steps of: prior to said mounting step, placing a protective plastic cutting strip on an anterior aspect of the patient's leg and placing a layer of barrier film over the patient's leg over a length thereof at least equal to the length of said sleeve.