WO2000045754A1

WO2000045754A1 - Post-operative air splint prosthesis

Info

Publication number: WO2000045754A1
Application number: PCT/US2000/002931
Authority: WO
Inventors: Henry John Mcvicker
Original assignee: Aircast, Inc.
Priority date: 1999-02-03
Filing date: 2000-02-03
Publication date: 2000-08-10
Also published as: AU2870000A

Abstract

A post-operative air splint prosthesis is provided for use in rehabilitation management of lower extremity amputations comprising an outer, and an inner layer (36)(40) of air impervious material defining a first inflatable air chamber (42) having a layer of semi-rigid (44) material inserted therein. A second sealed inflatable air chamber (46) is disposed within the first chamber, and is configured to occupy only a bottom portion of the first air chamber. The prosthesis has an overall frusta conical shape such that when it is wrapped around the residual limb of an amputee it provides superior support for ambulation. The first, and second chambers can be inflated separately to provide for improved treatment of edema over prior art methods.

Description

POST-OPERATIVE AIR SPLINT PROSTHESIS

BACKGROUND OF THE INVENTION

1. Field of the Invention The present invention relates generally to a post operative air splint prosthesis of a type suitable for use by lower limb amputees and, more particularly, to an improved air splint prosthesis which is specifically designed to control edema effectively in the residual limb and also provide for improved ambulation by the amputee .

2. Description of the Related Art

Particularly in the elderly population, peripheral vascular disease is the most common cause of lower limb amputation. Many elderly patients have other medical problems, such as cataracts, degenerative arthritis and general muscle weakness, which also threaten their ability to ambulate independently. The early resumption of ambulation for all amputees is both physically and psychologically beneficial, and for elderly patients it may be essential if they are to remain independent in walking. Unfortunately, residual limb healing in these patients is often slow and imperfect because of vascular insufficiency and diminution of skin sensation. A goal of surgical and rehabilitation management for these patients has been to provide the opportunity of satisfactory healing of the residual limb and also allow early resumption of ambulation with partial weight bearing in a suitable prosthesis . To achieve this goal, it has been known to fit the amputee with a temporary plaster of Paris prosthesis on the operating table. Such an approach can offer the advantages of decrease in post-operative pain, better wound healing, early ambulation, rapid residual limb maturation, and improved psychological adjustment to loss of a limb. However, in spite of these beneficial effects, this method has not been generally practiced because it requires the attendance of a prosthetist in the operating room to apply the plaster socket, special prosthetic components must be available, and some of these components must be sterilized beforehand. In the peripheral vascular amputee, sensation in the residual limb is often impaired and damage may progress under the plaster cast to a serious degree before it is recognized. Where there is concern regarding the residual limb, the plaster must be removed and rapidly re-applied if swelling is to be prevented. Also, changes in the size and contour of the residual limb may require frequent changes of the plaster socket.

Proper control of post-operative edema is an integral component of the pre-prosthetic rehabilitation program for a lower limb amputation. Delay in prosthetic fitting because of excessive edema can be costly in terms of length of hospital stay and related service. Several requirements exist for any material used for managing post-operative edema. First, the material must apply selective pressure over the residual limb without restricting blood flow to the distal area. The material should also allow easy access for inspection of the incision site and any dressing changes. The method must also produce a minimum of patient discomfort, be easily applied by staff members, and should be cosmetically acceptable by the patient.

A method which has gained wide acceptance in recent times for the post -operative rehabilitation of lower extremity amputations is the use of an air splint. The air splint is a pneumatic device which can be applied to the residual limb immediately after surgery, but is usually applied two to ten days after amputation. A gauze pad is placed over the area when the incision is not healed. A stockinette is usually placed from the distal end of the residual limb to the proximal thigh area. The stockinette absorbs perspiration while the air splint is in place. The air splint is generally placed over the residual limb and inflated to between 25 to 40 mm Hg . The air splint remains on continuously but can be conveniently removed to inspect the residual limb frequently for drainage or changes in color. A form of air splint currently on the market is the Jobst^® post-operative air-boot.

Among the potential recognized advantages of the air splint are the following: (1) it seeks to maintain equal pressure on the residual limb with no danger of distal edema because of improper bandaging; (2) it is self-suspending; (3) it is lighter than other devices available; (4) it is easy to apply for both patients and staff with minimal in-service training required for new staff member; (5) it allows early ambulation on the residual limb. The patient remains mobile and does not lose the weight-bearing sensation. Mobility is especially important for the geriatric patient because confinement to a wheelchair can be detrimental to functional level; (6) using an air splint enables one to evaluate these patients as more realistic prosthetic candidates; and (7) it decreases the risk of knee-flexion contracture in the below-knee amputated limb. Although the splint allows some movement at the knee, the limb is maintained in an extended position for the majority of the day.

While the existing air splint offers advantages over prior art methods for managing rehabilitation after lower extremity amputation, it is in significant need of improvement. Patients find aspects of it objectionable over extended periods of use. First, the prior splints do not provide adequate ventilation resulting in heat build up and perspiration leading to both discomfort and potential slippage. Second, the generally rectangular prior shaped shell (when open) results in excess bulk when applied to the limb. Third, the prior shape does not permit adequate support to shift the bulk load bearing from the traumatized and healing portion of the limb to less sensitive areas, but without constricting the surgically affected area. Accordingly, it is desirable to provide a device which has the capability of providing adequate support for ambulation and yet is capable of allowing for knee flexion, as desired, when the patient has assumed a non-ambulatory posture. It is further desirable to provide such a device which offers considerably greater support for the residual limb during ambulation than is presently available from known devices. Still further, it is desirable to provide such a device which has the capability of varying the pressure applied to separate regions of the residual limb to better manage edema. It is also highly desirable to provide for such a device which is easily applied without undue training of medical staff and is easily adjusted to fit the specific size and contour of the residual limb. It is of considerable advantage to provide such a device having adequate ventilation as to avoid heat build-up and perspiration. Yet another advantage is to provide such a device having the capability to removably position an adjustable pylon support to accommodate wear of the device and permit adjustment of lengths for support for the user.

SUMMARY OF THE INVENTION

The present invention improves over the prior art by providing a post -operative air splint prosthesis for use in rehabilitation management of lower extremity amputations comprising an outer and an inner layer of air impervious material defining a first inflatable air chamber and having a layer of semi-rigid material inserted therein. A second sealed inflatable air chamber is disposed within the first chamber and is configured to occupy only a bottom portion of the first air chamber. The prosthesis has an overall frustoconical shape such that when it is wrapped around the residual limb of an amputee it provides superior support for ambulation. The first and second chambers can be inflated separately to provide for improved treatment of edema over prior art methods. BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other novel features and advantages of the invention will be better understood upon a reading of the following detailed description taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a side elevational view of a postoperative air splint prosthesis constructed in accordance with the principles of the invention;

FIG. 2 is a plan view of the prosthesis as shown in an open condition;

FIG. 3 is a schematic cross-sectional view taken substantially long the line 3-3 of FIG. 2;

FIG. 4 is a schematic cross-sectional view taken substantially along the line 4-4 of FIG. 2 ;

FIG. 5 is a side view of the pylon support structure; and

FIG. 6 is a schematic cross-sectional view similar to FIG. 3 but showing an alternative embodiment of the prosthesis having an additional air chamber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, and initially to FIG. 1, a post-operative air splint prosthesis constructed in accordance with the principles of the invention is designated generally by the reference numeral 10. The prosthesis includes as a principal component a reasonably flexible wraparound shell assembly 12 which will be described in detail hereinafter. The shell assembly 12 is supported by a generally circular disk 14 to which a suitable pylon 16 is connected. A series of straps 18 are fixed to an edge 20 of the shell assembly 12 and wrap around the body of the assembly 12. Preferably, the straps 18 are provided with hook and loop type fastening means of the type sold under the trade name VELCRO^® . The straps may be affixed to the shell in a conventional manner such as by thermal welding. The straps 18 extend around the shell assembly in a manner where the shell can accommodate different "diameter" limbs, while permitting adequate desired amount of tension to mating hook and loop fastening material attached to the outside of the shell assembly 12 (not shown) in a manner well-known in the art. Protruding from the shell assembly 12, and as will be described hereinafter, are a pair of flexible air supply tubes 22 having suitable check valves 24. A series of apertures 26 are formed in an upper portion of the shell assembly 12 to provide for ventilation of the interior of the assembly 12.

Turning now to FIG. 2, a plan view of the prosthesis 10 is illustrated in an unfolded or unwrapped, open condition. In this view, the shell assembly 12 can be seen as having a distinctly frustoconical shape when wrapped as in FIG. 1. The pylon 16 and disk 14 are attached to a cylindrical member 28 having hook and loop type fastening material 30 secured to its side wall. Correspondingly, the inside of the shell assembly 12 is provided with strips of complementary mating hook and loop fastening material 32 to thereby secure the cylindrical member 28, and thus the pylon 16, to the shell assembly 12 when the shell assembly 12 is wrapped around the cylindrical member 28.

Referring now to FIG. 3, a schematic cross-section of one form of shell assembly 12 can be seen. For purposes of this case, the word "shell" is intended to include a body that has some degree of rigidity, sufficient to provide a support function, but which also is significantly flexible to permit the device to be wrapped over itself. The shell assembly 12 includes an outer layer 36 of preferably an air-impervious thermoplastic material preferably Nylon, thermally welded around its entire periphery 38 to an inner layer 40 of thermoplastic material preferably polyurethane . The layers 36 and 40 are thin enough to be highly flexible and define a first, sealed internal air chamber 42. Internal to the chamber 42 and defining a polyhedron having a frustoconical shape about the size of the layers 36 and 40, is a stiffening member 44. The member 44 is formed of a semi-rigid, bendable layer of LDPE, for example. Member 44 is captured between the outer layer 36 and an intermediate layer 45, preferably of polyurethane, for purposes which will be described hereinafter. Also interior to the chamber 42 is a second chamber 46 formed by folding over a piece of thermoplastic material 48 and thermally fusing its lateral edges along with the fusing of the layers 36 and 40. A thermal weld 50 is formed between the material 48 and the inner layer 40 at a point spaced a distance from the bottom periphery 38 of the layers 36 and 40, or left hand end as viewed in FIG. 3. This construction assures that possible fraying of the layers 36 and 40 along the bottom edge of the shell assembly 12 will not break the seal of the chamber 46. It is important to note that the chamber 46 is dimensioned and configured to occupy only a portion of the chamber 42 favoring the bottom end of the assembly 12. Although not shown in FIG. 3, the air supply tubes 22 shown in FIG. 1 are sealingly connected, in well known manners, respectively, to the chambers 42 and 46. The use of overlapping air cells (with separate inflatable areas) is known and covered by U.S. Patent No. 5,125,400, commonly assigned.

The schematic cross-section of FIG. 4 illustrates a significant aspect of the invention. As shown in FIG. 2, a series of vertical welds 52 are formed around the apertures 26 from the upper edge of the assembly 12 extending downwardly preferably to a point coincident with the centerline of the amputee's patella. The welds 52 are sequentially closed at their bottoms. As shown in FIG. 4, these welds 52 are formed between the inner layer 40 of the assembly 12 and the intermediate layer 45 such that when the air chamber 42 is inflated, the inner layer 40 is teathered to create a series of vertical breathing passages along the thigh of the amputee. The passages, in combination with the aperatures 26 serve to significantly reduce perspiration by the amputee above the residual limb and thereby aid in the comfort of the amputee during use of the prosthesis 10. JO- FIG. 5 illustrates the plyon 16 support construction. The cylindrical member 28 is fitted with an internal sleeve which is dimensioned to slidingly receive the pylon 16. The sleeve 54 is provided with aperture 56 extending through it. Correspondingly, the pylon 16 is provided with a series of similarly sized apertures 58 which may be selectively aligned with the apertures 56. A suitable releasable pin (not shown) may thereby be used to secure the pylon 16 to the sleeve 54 by insertion through the apertures 56 and 58. A rubber crutch tip 60 may be attached to the end of the pylon 16. In preferred form, the pylon 16 will have sufficient apertures 58 as to permit vertical adjustment of the pylon through a distance of no less than four inches.

FIG. 6 illustrates an alternative construction of the shell assembly 12 wherein a third chamber or air cell 62 is provided internal to the chamber 42 at a position above the chamber 46 but spaced from the upper edge of the shell assembly 12. The chamber 62 may be formed of a folded piece of thermoplastic material 64 welded to form a tube and thermally bonded at its ends to the periphery 38 of the layers 36 and 40. A suitable air supply tube (not shown) is sealingly connected to the chamber 62. This use of a third chamber permits greater flexibility in terms of the pressure to be applied to the limb at various locations, thus providing several benefits: control of edema; bending of the residual knee joint or the perceived joint; and greater pressure above the joint to secure the device 10 to the limb. -lilt can now be appreciated that a post -operative air splint prosthesis constructed according to the present invention offers considerable advantages over prior art devices in the early management of lower extremity amputations. Preferably the prosthesis 10 is sized to extend above the knee of the amputee and because of its use of multiple straps 18 is highly adjustable to fit residual limbs, of various sizes and contours. Also the use of multiple air chambers 42 and 46 such as in the embodiment of Figures 2, 3 and 4 allows for differing degrees of pressure to be applied to different regions of the residual limb to provide for better control of edema and also of the comfort of the amputee. The chambers 42 and 46 may also be adjusted in pressure to permit knee flexure when desired while maintaining pressure on the lower residual limb. The use of three chambers 42, 46 and 62 as illustrated in Figure 6 provides for even greater flexibility in the application of pressure to the residual limb. The air apertures 26 together with the welds 52 provide a significant degree of ventilation for the underlying skin reducing overheating and perspiration. The frustoconical shape avoids excess bulk when wrapped and because the limb is enclosed in a cone, rather than a cylinder, greater contact and fit with the limb is achieved along the limb periphery, rather than primarily on the newly healing traumatized area. Preferably the chambers are inflated to a pressure of 30 to 50 mm Hg which can be done orally or by use of a known pump. Also, in modified form, the assembly 12 may include a thin layer of foam, on the order of 1/4 inch thick, for example, in the lower region of chamber 42 and the chamber 46 to provide for added comfort and regulation of air volume as taught in U.S. Patent No. 4,628,945, which is commonly assigned herewith.

While the present invention has been described in connection with preferred embodiments thereof, it will be apparent to those stilled in the art that many changes and modifications may be made without departing from the true spirit and scope of the present invention. Accordingly, it is intended by the appended claims to cover all such changes and modifications as come within the spirit and scope of the invention.

Claims

WHAT IS CLAIMED IS:

1. A post-operative air splint prosthesis for use in rehabilitation management of lower extremity amputations, said splint comprising: a shell having an outer layer of air impervious material ; an inner layer of air impervious material bonded to the outer layer to thereby define a first inflatable air chamber; a frame layer comprising a semi-rigid material dimensioned and configured to approximately match said first air chamber and being positioned within the first air chamber, and said frame layer serving to support said first air chamber; a second inflatable air chamber disposed within said first air chamber and dimensioned and configured to occupy only a portion of the area occupied by said first air chamber; means for separately inflating said first and second air chambers; and means for adjustably and releasably applying said shell to an associated limb.

2. The prosthesis of claim 1 wherein the inner and outer layers are substantially frustoconical in shape when wrapped around a residual limb of an amputee.

3. The prosthesis of claim 1 including adjustable straps disposed along an edge of said outer layer for permitting adjustable attachment of the prosthesis to a residual limb of an amputee.

4. The prosthesis of claim 3 wherein the straps include hook and loop type fastening means.

5. The prosthesis of claim 1 including a weight bearing pylon secured to an end of the prosthesis,

6. The prosthesis of claim 5 wherein said pylon is adjustable in length.

7. The prosthesis of claim 6 wherein said pylon is adjustable at least four inches in length.

8. The prosthesis of claim 5 wherein said pylon is secured by a support member and said support member is removably attached to the inner layer of the prosthesis .

9. The prosthesis of claim 8 wherein the support member is attached to said inner layer by hook and loop fastening means.

10. The prosthesis of claim 8 wherein the support member is generally cylindrical in shape.

11. The prosthesis of claim 1 wherein the second air chamber occupies a portion of the first air chamber disposed adjacent a bottom portion of the prosthesis .

12. The prosthesis of claim 1 wherein said second air chamber is formed of a folded piece of flexible material.

13. The prosthesis of claim 12 wherein said material is polyurethane.

14. The prosthesis of claim 12 wherein free edges of said folded piece of material are bonded to said inner layer.

15. The prosthesis of claim 14 wherein said edges are bonded by thermal welding.

16. The prosthesis of claim 14 wherein said free edges are bonded to said inner layer at a position proximate a lower edge of the shell.

17. The prosthesis of claim 16 wherein said free edges are bonded to said inner layer at a position slightly spaced from said lower edge.

18. The prostheses of claim 11 including a third inflatable air chamber disposed within the first chamber at a position above the second air chamber.

19. The prosthesis of claim 18 including means for separately inflating said third chamber.

20. The prosthesis of claim 1 including a plurality of ventilation apertures formed through said inner and outer layers and said frame at a position adjacent an upper end of the prosthesis.

21. The prosthesis of claim 1 including an intermediate layer of flexible material disposed within said first inflatable air chamber.

22. The prosthesis of claim 21 including a plurality of spaced longitudinal bonds between said inner layer and said intermediate layer along an upper portion of said shell.

23. The prosthesis of claim 22 wherein said bonds are formed by thermal fusion.

24. A post-operative air splint prosthesis for use in rehabilitation management of lower extremity amputations, said splint comprising: a shell having an outer layer of air impervious thermoplastic material and being generally trapezoidal in shape ; an inner layer of air impervious thermoplastic material having a shape similar to said outer layer and being thermal fused at its peripheral edges to said outer layer to thereby define a first inflatable air chamber; a second inflatable air chamber disposed within said first air chamber and dimensioned and configured to occupy only a first portion of the area occupied by said first air chamber; an intermediate layer of thermoplastic material disposed between said inner and outer layers; a plurality of spaced welds formed between said inner and intermediate layers at a second portion of the area occupied by said first air chamber; a frame layer disposed between said intermediate and outer layers; means for separately inflating said first and second air chambers; and means for attaching said shell to a residual limb of an amputee.

25. The prosthesis of claim 24 including adjustable straps disposed along an edge of said outer layer for attaching said shell to said residual limb.

26. The prosthesis of claim 25 wherein said straps include hook and loop fastening means.

27. The prosthesis of claim 24 including a weight bearing pylon assembly secured to an end of said prosthesis .

28. The prosthesis of claim 27 wherein said pylon assembly is secured to said shell by hook and loop fastening means.

29. The prosthesis of claim 27 wherein said pylon assembly is adjustable in length.

30. The prosthesis of claim 24 including ventilation apertures formed through said layers between said spaced welds .

31. The prosthesis of claim 24 wherein said second air chamber is formed of a folded piece of material .

32. The prosthesis of claim 31 wherein said material is polyurethane.

33. The prosthesis of claim 31 wherein free edges of said material and thermally bonded to said inner layer.

34. The prosthesis of claim 33 wherein said free edges are bonded to said inner layer at a position slightly spaced from an edge of said inner layer.

AMENDED CLAIMS

[received by the International Bureau on 26 June 2000 (26.06.00) ; original claims land 24 amended ; remaining claims unchanged (4 pages)]

1. A post-operative air splint prosthesis for use in rehabilitation management of lower extremity amputations, said splint comprising: a shell having an outer layer of air impervious material; an inner layer of air impervious material bonded to the outer layer to thereby define a first inflatable air chamber; a frame layer comprising a semi-rigid material dimensioned and configured to approximately match said first air chamber and being positioned within the first air chamber, and said frame layer serving to support said first air chamber; a second inflatable air chamber disposed within said first air chamber and dimensioned and configured to occupy only a portion of the area occupied by said first air chamber; means for separately inflating said first and second air chambers; and means for adjustably and releasably applying said shell to an associated limb; wherein said frame member is configured to wrap around the entire circumference of said limb and overlap at an edge for adjustability of fit.

a plurality of spaced welds formed between said inner and intermediate layers at a second portion of the area occupied by said first air chamber; a frame layer disposed between said intermediate and outer layers; means for separately inflating said first and second air chambers; and means for attaching said shell to a residual limb of an amputee; wherein said frame member is configured to wrap around the entire circumference of said limb and overlap at an edge for adjustability of fit.

26. The prosthesis of claim 25 wherein said straps include hook and loop fastening means .

28. The prosthesis of claim 27 wherein said pylon assembly is secured to said shell by hook and loop fastening means .

30. The prosthesis of claim 24 including ventilation apertures formed through said layers between said spaced welds.

32. The prosthesis of claim 31 wherein said material is polyurethane.