WO1999011300A2

WO1999011300A2 - Orthopedic casting material

Info

Publication number: WO1999011300A2
Application number: PCT/GB1998/002606
Authority: WO
Inventors: Mike Burns; Claire Peel
Original assignee: Smith & Nephew Plc
Priority date: 1997-08-29
Filing date: 1998-08-28
Publication date: 1999-03-11
Also published as: AU8875898A; ZA987842B; GB9718224D0; WO1999011300A3

Abstract

An orthopaedic splint bandaging system having a flexible, liquid permeable substrate carrying a layer of Plaster of Paris in its hemi-hydrate form and, separately, an aqueous vehicle characterised in that the aqueous vehicle contains water in an amount to provide from 4.5 to 7 times required to convert the hemi-hydrate from of Plaster of Paris to the di-hydrate form.

Description

CASTING MATERIAL

Plaster of Paris bandages are well known in the art and are generally employed for orthopaedic applications such as casting and splinting.

Plaster of Paris casts also tend to have a high failure rate and have to be reapplied or repaired. For patient comfort it is important to have a strong cast whilst being light in weight. Plaster of Paris casts however are also sensitive to water and patients wearing Plaster of Paris casts should avoid rain and cannot shower.

Polyurethane resin based casts have to some extent alleviated this problem as they are waterproof, however their cost is prohibitively expensive for many people.

Thus it is desirable to develop a strengthened and preferably water resistant Plaster of Paris cast.

The addition of a strengthening agent to the water in which the bandage is dipped prior to setting off has been documented.

This however requires the preparation of the water, measuring out the materials and would be time consuming and messy.

The previous addition of a strengthening agent to the Plaster of Paris during the manufacturing process were found to have limited effect due to insolubility.

The prior art also suggests that a waterproof material may be painted onto the cast after application to a patient. This however involves a second step.

We have found that the use of a limited amount of water optionally containing additives to set off a Plaster of Paris bandage results in a cast with greater strength. Limited is defined as 4.5 to 7 times the stoichiometric amount of water, where stoichiometric is the amount of water needed to convert the calcium sulphate hemi-hydrate to the calcium sulphate di-hydrate form of Plaster of Paris.

CaSO₄.%H₂O + 1.5 H₂O → CaSO₄.2H₂O

For example a 1.6m length of 10 cm wide Plaster of Paris coated substrate coated at 450gsm, reacted with 5 times the stoichiometric amount of water would require 66ml of water.

Therefore the amount of Plaster of Paris that will be used in the bandage is required in order to measure out the required amount of water that would give the stoichiometric amount of water or the desired multiple of this volume.

According to the present invention there is provided a splint bandaging system comprising a flexible, liquid permeable substrate carrying a layer of Plaster of Paris in its hemi-hydrate form and, separately, an aqueous vehicle characterised in that the aqueous vehicle contains water in an amount to provide from 4.5 to 7 times that required to convert the hemi-hydrate form of Plaster of Paris to the di-hydrate form.

In accordance with a modification of the present invention there is further provided a splint bandaging system comprising a flexible, liquid permeable substrate carrying a layer of Plaster of Paris in its hemi-hydrate form and, separately, an aqueous vehicle characterised in that the aqueous vehicle contains water in an amount to provide from 3 to 15 times that required to convert the hemi-hydrate form of Plaster of Paris to the di-hydrate form.

Surprisingly it was found that having a limited amount of water together with a strengthening additive would result in a cast of greater strength.

This would give a hardened cast that may be stronger and wear better against abrasions, than the casts of the prior art. The cast of the present invention may therefore have a longer useful life as a orthopaedic cast or splint. Having a stronger cast as described by the present invention may also allow less Plaster of Paris to be used thus giving a lighter cast that may still have the required strength needed for an orthopaedic cast or splint.

Although various concentrations of the additive may be used to alleviate the problems of a weak splint structure in practice it is desired that the aqueous vehicle can mix and penetrate through the bandage quickly and once the bandage is applied can dry out and harden quickly.

The aqueous vehicle should have a viscosity such that wetting out of the bandage will be in a sufficiently quick time to make it practicable.

The wetting out of bandaging material by the additive containing aqueous vehicle of the present invention may be determined by a Penetration Test as defined in full below.

Preferably such an aqueous vehicle of the present invention would have a Penetration Value to wet out according to our Penetration Test defined below of less than 400 seconds.

Also according to an embodiment of the present invention the aqueous vehicle comprises a solution, emulsion or dispersion of a strengthening additive and has a Penetration Value (as herein defined) of less than 400 seconds.

The strengthening additives of the present invention are those materials which will form a complex with the calcium sulphate of the Plaster of Paris whereby the complex is the bonding formed by an interaction of electrons from the strengthening additive with the empty orbitals of calcium forming a co-ordination bond thereby resulting in reduction of porosity. It is this reduction of porosity that causes an increase in strength. Suitable additives include both functionalised and unfunctionalised polymer materials and carbohydrates. Where there is the contraction of extended polymer chains, such as in high molecular weight polymers which have formed a complex as described above, and as for example shown in Figure 7, with the calcium sulphate, further reduction of porosity may result on dehydration.

Suitable strengthening additives therefore include: High molecular weight hydroxyl polymers, High molecular weight amine polymers,

High molecular weight polymers, Medium molecular weight hydroxyl polymers, Low molecular weight cyclic hydroxyl compounds.

By high molecular weight hydroxyl polymers we mean polymers which have a gram molecular weight of greater than 140,000 grams.

By high molecular weight amines we mean polymers that have a gram molecular weight amine greater than 10,000 grams and preferably have a gram molecular weight between 10,000 grams and 1 ,300,000 grams.

By high molecular weight polymers we mean polymers that have a gram molecular weight greater than 8000 grams and preferably between 8000 grams and 1 ,000,000 grams.

By medium weight hydroxyl polymers we mean polymers that have a gram molecular weight between 17,000 and 140,000 grams.

By low molecular weight cyclic hydroxyl compounds we mean compounds that have a gram molecular weight below 17,000 grams and preferably between 100 and 400 grams.

Examples of strengthening agents include but are not limited to polyvinyl alcohol polymers, polyvinylacetate/acrylic acid copolymers, polyvinyl pyrrolidone, cellulose derivatives, for example hydroxy ethyl or hydroxyl propyl derivatives. Using these additives with a limited amount of water according to the present invention addresses the problem of weak cast structures. Using the additives of the present invention may give casts with significant increases in strength.

This would give a hardened cast that may be stronger and wear better against abrasions, than the casts of the prior art. The cast of the present invention may therefore have a longer useful life as a orthopaedic cast or splint. Having a stronger cast as described by the present invention also allows less Plaster of Paris to be used thus giving a lighter cast that may still have the required strength needed for an orthopaedic cast or splint.

The aqueous vehicle may further comprise water resistant agents, antimicrobial agents, coloured dyes or mixtures thereof in addition to the strengthening agent. The additives may be in the form of an emulsion, solution or suspension in water.

The addition of a water resistant agent would result in a water resistant cast.

Examples of water resistant agents include polyvinyl acetate / acrylic acid copolymers and polyvinyl alcohol.

The addition of dyes would allow the preparation of a coloured cast. The dyes may be water based or oil based dyes.

Examples of water based dyes include any that on drying out would not easily redissolve on wetting and therefore leach out.

Suitably when a coloured dye or dyes are used these would be contained in the same container as the aqueous vehicle or in embodiments where the aqueous vehicle is added separately the coloured dye can simply be added then to the aqueous vehicle and bandage prior to applying the wet bandage. However in a Plaster of Paris application system of the present invention the dye or dyes could be contained in separate pouches within the system giving the plaster technician applying the bandage the choice of colour, or not, and if so which colour if more than one pouch containing coloured dye is used.

Dyes could also be incorporated into the splinting or casting material, or the splinting or casting substrate, or combination thereof.

It is envisaged that the additives of the present invention could be used in various concentrations however preferably the additive would be used in a concentrations between 1 and 20%.

The preparation of the strengthening additive containing aqueous vehicle requires specialist knowledge and experience. The additives of the present invention can be extremely difficult to process. The dissolving process requires the liquid to be heated at desired temperature for periods of time and the strengthening additives are required to be stirred in before the additives will dissolve. If the temperature of the liquid during the dissolving process is not sufficiently high the additives may not dissolve fully or may agglomerate. Alternatively the process may take far too long to make the process commercially viable. If the temperature is too high, the excess heat may damage the chemical structures of the additives causing loss of function and wastage.

By having the additive already dissolved in a limited amount of water and packaged ready for use as in the preferred embodiments of the present invention enables a person unskilled in the field of formulation chemistry to benefit from the present invention.

It is therefore possible for the cast technicians to quickly and accurately benefit from using the present invention, having casts with strengthening additives present without the specialist knowledge and experience, that would normally be required. Embodiments of the present invention include an orthopaedic splint system comprising a durable tear resistant outer container containing an orthopaedic splint material impregnated with an unreacted hardening agent, and an inner container containing an aqueous vehicle for reacting with said hardening agent to produce a cured splint.

The inner container is capable of being ruptured by manual pressure upon the outer container and is suitably in juxtaposition with the splint material so that when the outer container is manually squeezed to rupture the inner container, the aqueous vehicle from the inner container will be released, mixed with said material and reacted with the hardening agent therein to form a hard cured splint which can be used to protect and immobilise the injured member to which it is applied.

In embodiments that have a flexible outer container the splint material can be manually kneaded to uniformly work in the aqueous vehicle which will thereafter react with the hardening agent to form a hard stiff splint.

We have found that a two container system to measure out the amount of water required can address problems traditionally associated with Plaster of Paris casts such as loss of plaster and mess on dipping the bandage into a bucket of water.

In particular embodiments to the present invention there is provided a Plaster of Paris application system comprising at least a first pack and a second pack where the first pack contains a dry Plaster of Paris bandage and the second pack comprises a limited amount of water.

Further embodiments of the present invention there is provided a Plaster of Paris application system comprising at least a first pack and a second pack where the first pack contains a dry Plaster of Paris bandage and the second pack comprises an aqueous vehicle having a limited amount of water and optionally an additive. There is also provided a method of application of a two pack Orthopaedic Splint System the Plaster of Paris pouch of the present invention where the plaster technician releases the contents of the second pack into the first pack. The technician can then squeeze the bandage in the first pack, thereby mixing the limited amount of water into the bandage.

The bandage is then applied as normal.

In a preferred embodiment of the present invention the invention is suitable for use as a portable orthopaedic casting or splint system. In this preferred embodiment a bandage impregnated with an unreacted hardening agent is contained in a durable tear resistant outer container. Also contained within the outer container of a preferred embodiment is one or more inner containers or pouches containing an aqueous vehicle for reacting with the hardening agent to produce a cured cast or splint.

Suitably the inner containers or pouches, are capable of being ruptured by manual pressure upon the outer container without necessarily damaging or rupturing the outer container. The contents of one or more of the inner containers or pouches can be mixed with the bandage and hardening agent. When the aqueous vehicle from an inner container is released and mixed with the bandage and hardening agent therein which on application of the wet bandage form a hard cured cast or splint which can be used to protect and immobilise an injured body part.

Where the outer container is a flexible container, to ensure thorough mixing, the bandage can be manually kneaded to uniformly work in the liquid which will thereafter react with the hardening agent to form the hard cured cast or splint.

It is also envisaged that in some embodiments of the present invention that one or more of the containers can be of an inflexible or substantially rigid construction provided that the bandage, aqueous vehicle and optionally an additive can be stored safely and, when required, mixed.

The advantages of using an applicator as described herein is that the user's hands do not have to contact the device and the water containing chamber in the applicator may be pre-filled and pre-packaged with the device so that it is immediately ready to use and requires no other liquid although optionally further liquid can be added.

This process has the advantage that the amount of mess on applying the bandage is reduced, buckets of water are not required and the impregnation of the bandage with a strengthening material results in a harder cast. The process may also alleviate or address the problem of plaster loss on dipping the bandage into a bucket of water.

To use the device, either the outer container is opened and the aqueous vehicle is added or the aqueous vehicle reservoir contained in a container is disrupted or emptied in the outer container to activate the casting layer. In the embodiments which do not incorporate an aqueous vehicle reservoir within the outer container, the aqueous vehicle is added to the container either through an open edge or through a portal or by other means.

The device is then formed to the body part or workpiece which is to be formed to the body part or workpiece which is to be splinted or casted and allowed to set or cure. Multiple devices may be layered together in one application, as needed or these can be combined with others.

The outer container used may be made from any tough durable tear resistant material that will not tear or rip during rough handling, but preferably which can be opened by hand. Preferably this material should be impervious to liquid and gas. Such materials may be metallic foil or laminates or plastic e.g. polyethylene or the like. The inner containers or pouches, or at least a portion of the inner containers or pouches used, should be strong enough to withstand rough handling but weak enough so it may be ruptured when manually squeezed or torn. Preferably in embodiments where the outer container is a flexible container, the inner container can be ruptured through the outer container, within which it is contained, without necessarily rupturing the outer container. Again it is preferred that the material of the inner container will be impervious to liquid and gas.

Although it is preferred that the containers will be ruptured solely by hand to enable mixing, it is also envisaged that one or more or the containers may have a rupturing means to aid this. For instance on a flexible container, whether an inner container or an outer container, the container may have a weakened portion and finger grips to aid opening of the container. Another rupturing means may be a ring pull whereby pulling the ring will rupture the container. Having a rupturing means may be particularly advantages for an inner container that requires rupturing through the outer container material.

Another example of a rupturing means may be a spike, optionally located on one or more of the containers, which when brought into contact with a container with sufficient force may aid rupturing of the container.

Material for the inner container may be any conventional plastic film paper product, metallic foil, laminates or other material which will meet these requirements.

The outer container may be of any size and shape which is able to contain the required contents and allow mixing of the aqueous vehicle and the bandage. Suitable packaging to act as the outer container are 3 dimensional bags well known in the art.

Likewise the inner container can be of any size and shape which is able to contain the required contents and be contained within the outer container, while still allowing mixing of the aqueous vehicle and bandage.

The inner container need not be necessarily unattached inside the outer container but could form a pouch attached to the inner wall of the outer container.

According to the present invention there is provided a Plaster of Paris application system comprising at least a first pack and a second pack where the first pack contains a dry Plaster of Paris bandage and the second pack comprises a limited amount of water.

Further, according to the present invention there is provided a Plaster of Paris application system comprising at least a first pack and a second pack where the first pack contains a dry Plaster of Paris bandage and the second pack comprises a limited amount of water containing an additive.

In embodiments which do not incorporate an aqueous vehicle reservoir within the outer container the aqueous vehicle is added to the container, ideally through a portal but may also be added through an opened edge or by other means.

It is envisaged that in embodiments which do not incorporate an aqueous vehicle reservoir within the outer container that a dispenser of the aqueous vehicle optionally containing an additive will be used to supply the correct amount of water and additive.

Thus when a bandage is required to be cured the bandage contained in the outer container is taken to the dispenser to enable the correct amount of aqueous vehicle to be added to the container as directed by a technically trained person, instructions on the outer counter, dispenser or otherwise. This therefore ensures that the correct amount of aqueous vehicle is added and mixed with the bandage.

Ideally the dispenser will have means to accurately dispense a desired volume of aqueous vehicle. It is also desired that the dispenser and outer container have connectable openings that snugly fit each other that enables the desired volume of aqueous vehicle to be dispensed to the inside of the container easily and efficiently. Preferably the connectable openings of the container and dispenser will only fit each other, in order to lessen the risk of mixing the wrong liquid to a bandage. In a preferred embodiment of the present invention the connectable opening of the container will be resealable, to enable thorough mixing of the aqueous vehicle with the bandage without risk of losing any of the aqueous vehicle.

The invention will now be described by way of example only with reference to the accompanying drawings and tables.

Figure 1 shows a pouch of the invention.

Figure 2 shows an alternative embodiment of the pouch of the invention.

Figure 3 shows yet another embodiment of the pouch of the invention.

Figure 4 shows a further embodiment of the pouch of the invention.

Figure 5 shows a dispenser according to a further embodiment of the present invention.

Figure 6 shows a further embodiment of a pouch of the present invention.

Figure 7 shows an additive forming co-ordination bonds with calcium.

Figure 8 shows a substantially rigid container according to a further embodiment of the present invention. In Figure 1 there is shown a pouch 10 comprising two packs 20, 30 joined together with a weak seal 50 between them. Alternatively a single pack which is separated into two by the seal 50 can be used.

A rolled up Plaster of Paris bandages 40 is stored on one half and a solution of a water resistant material where the amount of water is a limited amount of water is stored in the other half. On use the weak seal 50 is ruptured allowing the contents to be mixed freely. The wet bandage can then be applied as normal.

In Figure 2 there is shown a pouch 60 comprising a loose, internal pack 70 with a weak seal 80 containing a limited amount of water and an external pack 90, surrounding pack 70, containing a rolled up Plaster of Paris bandage 100.

On use the weak seal 80 is ruptured allowing the contents to be mixed freely. The wet bandage 100 can then be applied in the normal manner.

In Figure 3 there is shown a pouch 110 comprising an internal pack 120 with a weak seal 130 containing an emulsion of water resistant material where the amount of water is a limited amount of water. The internal pack 120 is sealed along on edge into an external pack 140, which surrounds it. The external pack 140 contains a rolled up Plaster of Paris bandage 150.

On use the weak seal 130 is ruptured allowing the contents to be mixed freely. The wet bandage 150 can then be applied in the normal practice.

In Figure 4 the bandage 160 is stored in an oversized pack 170, and a sachet 180 containing a dye and strengthening agent in a water based emulsion where the amount of water is a limited amount of water is provided separately. On use the pack 170 is opened at one end and sachet 180 is opened and poured into pack 170. The contents are then mixed by squeezing the pack 170 and the bandage 160 is applied as normal. Figure 5 shows a dispenser 200 with a dispensing means 201 for dispensing the aqueous vehicle containing the ready mixed water and additive. The dispenser also has means 202 to accurately dispense a desired volume of the aqueous vehicle.

Figure 6 shows a rolled up bandage 16 stored in an oversized pack 17. The pack 17 has a resealable valve 199 to allow the addition of an aqueous vehicle to the inside of the pack 17 to mix with the bandage 16. The resealable valve 199 is suitable for use with the dispenser 200 shown in Figure 5.

On use the desired volume of water and additive is dispensed from the dispenser 200 into the oversized pack 17, the contents is mixed and the bandage 16 is applied as normal.

Figure 7 shows a complex formation formed by an interaction of electrons from the strengthening additive with the empty orbitals of calcium from the Plaster of Paris, forming a co-ordination bond.

Figure 8 shows a stiff container 300 according to the present invention. In this particular embodiment the limited aqueous vehicle 301 is contained in a different section to the bandage 303 in order to prevent premature curing of the bandage 303. The material separating the aqueous vehicle and bandage can be disrupted by partially crushing the container 300 to ensure that the bandage is mixed with the aqueous vehicle 301. The bandage 303 can also be mixed with the aqueous vehicle 301 by opening the lid 302 of the container 300 and rupturing the material separating the bandage 303 and aqueous vehicle 301. This can be simply by forcing the bandage 303 through the material separating the bandage 303 and the aqueous solution 301. The bandage can then be applied in the normal manner.

The invention will be further illustrated by the following examples.

Examples 1 and 2 The relative Breaking Load of a standard GYPSONA™ BP bandage was measured using a limited amount of water, the amount being defined as 4.5 to 7 times the stoichiometric amount of water needed to convert the calcium sulphate hemi-hydrate to the calcium sulphate di-hydrate form of Plaster of Paris.

The relative breaking load of the tested bandages using a limited amount of water was compared to a control bandage which was cured in unlimited water. The control value or control comparison for this bandage cured in unlimited water was 0.0248 Ng^"2.

Plaster of Paris bandages sold under the Smith & Nephew

Trade Mark GYPSONA Trade Mark were used. The bandage formulation is:

Herculite 30 (calcium sulphate hemihydrate) 97.6% Mowilith 60 (polyvylacetate) 1% Klucel 6 (hydroxy propyl cellulose) 1%

Potassium sulphate 0.4%

The bandages used were 1.6m in length and 10cm wide.

The coating weight of plaster mass on the substrate was between 390 to 510 grams per square metre. The substrate is leno gauze as supplied by Smith & Nephew Medical Fabrics.

The volume of water required to give an amount of water which was 5 times the stoichiometric amount of water was calculated from the known amount of Plaster of Paris used in the standard bandage. Penetration Test - Definition.

The Penetration Test is the time in seconds for an aqueous vehicle to travel from the upper layer of a ten bandage system to the bottom layer. Thus a aqueous vehicle with a high viscosity is likely to have a higher Penetration Value than an aqueous vehicle with a lower viscosity.

The ten layers of bandages were penetrated to the sample plane by a 20ml cylindrical head of the aqueous vehicle contained in a cylinder that is 20mm in diameter and 60mm in height. The time was measured for the solution to travel between the uppermost layer of the bandages and the filter paper below the tenth layer of bandage. This experimental time was recorded and the test repeated. GYPSONA BP bandages as described above were used while the filter paper used was Whatman No. 54.

Each sample solution was tested under the above conditions.

Examples 3 to 28

Examples 29 to 49

Various additives were tested for their strength improvement property. A limited amount of water, equal to 5 times the stoichiometric amount of water needed to convert the calcium sulphate hemi-hydrate to the calcium sulphate di-hydrate form of Plaster of Paris, was used in an aqueous vehicle containing the additive being tested. The bandage, a commercially available GYPSONA bandage as defined above, was cured with the aqueous vehicle and allowed to dry. The cured bandage was then tested for its relative breaking load compared to a control bandage of similar material that was cured in unlimited water only. The test results of various strengthening additives are shown below.

The poly(vinyl alcohol) used was grade GH17 poly( vinyl alcohol) supplied by Nippon Gohsei.

The poly(vinyl pyrrolidone) used was grade K15 poly (vinyl pyrrolidone) supplied by International Speciality Product (ISP).

The Klucel G was supplied by Hercules.

The ethylenediaminetetraaceticacid, poly(ethylene glycol)

10000, polyacrylamide and glycine were supplied from Aldrich. The dextran, gum guar, celloboise, lactose monohydrate, gum xanthan, gum locust bean, gum arabic and soy protein acid hydrolysate were supplied from Sigma.

Courtaulds Chemicals supplied the hydrxypropylmethylcellulose while the sucrose was supplied by Merck Limited.

Surpisingly, it was also found that having a limited amount of water optionally with a strengthening or abrasion resistant additive would result in a cast of greater resistance to abrasion.

Commercially available GYPSONA bandages as described fully above were made into slabs 20 layers thick using the aqueous vehicle of the present invention. The aqueous vehicle contained water at an amount equal to 5 times the stoichiometric amount of water needed to covert the calcium sulphate hemi-hydrate to the calcium sulphate di-hydrate form of Plaster of Paris.

The acqueous vehicle of the example also contained 3.3%

Polyvinylalcohol.

After drying, the slabs were cut into squares 100mm in dimension.

The samples were then sent to Ceram Research for testing of abrasion resistance on a Taber Machine Abrader. The testing loads were 500g. The cycle of the abrader were 500 and 2500.

The control bandage was a similar bandage cured with unlimited amount of water.

Claims

1. An orthopaedic splint bandaging system comprising a flexible, liquid permeable substrate carrying a layer of Plaster of Paris in its hemi-hydrate form and, separately, an aqueous vehicle characterised in that the aqueous vehicle contains water in an amount to provide from 4.5 to 7 times that required to convert the hemi-hydrate form of Plaster of Paris to the di-hydrate form.

2. A modification of claim 1 where an orthopaedic splint bandaging system comprising a flexible, liquid permeable substrate carrying a layer of Plaster of Paris in its hemi-hydrate form and, separately, an aqueous vehicle characterised in that the aqueous vehicle contains water in an amount to provide from 3 to 15 times that required to convert the hemi-hydrate form of Plaster of Paris to the di-hydrate form.

3. An orthopaedic splint bandaging system as claimed in claim 1 or claim 2 whereby the aqueous vehicle comprising a solution, emulsion or dispersion of a strengthening additive and has Penetration Value (as herein defined) of the aqueous vehicle of less than 400 seconds.

4. An orthopaedic splint system as defined in claim 1 or 2 or 3 whereby the strengthening additive is selected from the following group; high molecular weight hydroxyl polymers (as herein defined), high molecular weight amine polymers (as herein defined), high molecular weight polymers (as herein defined), medium molecular weight hydroxyl polymers (as herein defined), low molecular weight cyclic hydroxyl compounds (as herein defined) or mixtures thereof.

5. An orthopaedic splint system as described in any preceding claim wherein the additive contains at least one of the following: ploy(vinyl alcohol) or poly (vinyl pyrrolidone) or mixtures thereof.

6. A orthopaedic splint system as defined in any preceding claim comprising: a durable outer container containing the bandaging material impregnated with unreacted Plaster of Paris in its hemi-hydrate form and where said outer container being adapted to receive said aqueous vehicle.

7. An orthopaedic splint system of claim 6 in which the container containing the aqueous vehicle is capable of being ruptured within the outer container.

8. An orthopaedic splint system of claim 6 whereby the aqueous vehicle is dispensed from a dispenser.

9. An orthopaedic splint system of claim 6, 7 or 8 whereby the outer container containing the bandage has a portal which enables the aqueous vehicle to be dispensed into the outer container.

10. An orthopaedic splint system of claim 9 whereby the portal of the outer container is resealable.

11. An orthopaedic splint system of claim 9 or 10 whereby the portal of the outer container correspondingly fits a dispensing means of the dispenser.

12. An orthopaedic splint system as claimed in any preceding claim wherein the aqueous vehicle also contains at least one water resistant agent, antimicrobial agent, dye or a mixture thereof.

13. An orthopaedic splint system as claimed in any preceding claim where the bandage contains at least one water resistant agent, antimicrobial agent, dye or a mixture thereof.

14. An orthopaedic splint system as claimed in any preceding claim wherein the bandage is a cast bandage.

15. A method of using an orthopaedic splint system comprising the step of mixing; a flexible, liquid permeable substrate carrying a layer of Plaster of Paris in its hemi-hydrate form with; the aqueous vehicle as defined in any of the preceding claims.

16. An orthopaedic system as claimed in any preceding claim substantially as herein described with reference to any example thereof and with or without reference to the accompanying drawings.