basics of plaster and slabs

basics of slab and cast application

1. Basic Trauma management in emergency setting DR. NANDAN MARATHE DR. S.K.SRIVASTAVA Dept. of Orthopaedics Seth gsmc and KEM Hospital

2. Principles of casting Lucas cham - immobilization and a lot of functional therapy and massage lead to f racture healing. lorenzo bohler - immobilizing the bone fragment and adjacent joint in a functional position. SIR JOHN CHARNLEY

3. Fracture healing Two types of healing Direct healing The fracture gap is very small(less than 0.5) this healing occurs under condition of absolute stability(plate) WHERE remodelling occurs without callous formation Indirect healing This is the usual way of healing in non- operative fracture care, involves callous formation

4. 3 r’s of casting Reduction Fragments must reduced properly before casting and placed in a functionally acceptable limb alignment Retention Fragments must be kept in a reduced position until healing of bone occurs Rehabilitation First the free joints has to be mobilized during cast immobilization and followed by mobilization of entire limb post cast removal

5. 5,000 years ago Egyptians began to produce a powder by heating gypsum, when mixed with water it formed a paste that hardened as it dried, they used this to join stone blocks for building the Great Pyramid of Cheops Plaster of Paris was abundant and widely used by persians for building purpose and paris became the capital of gypsum, hence the name plaster of paris

6. first used by a Dutch military surgeon antonius matthysen in 1952, he developed plaster bandages during the crimean war, by filling cotton bandages filled with powered pop. The modern pop bandage consist of a roll of muslin stiffened by dextrose/ starch with impregnated hemihydrate of calcium sulfate

7. Antonius Matthysen - inventor of the plaster cast Monument at his birthplace , U del , in The Netherlands

8. Chemical and physical features Gypsum is a sedimentary crystalline rock, it is calcium sulfate dihydrate (CaSo4. 2H2O) When it is heated it converts into calcium sulfate hemihydrate (CaSo4.1/2H20) CaSo4.2H2O + heat -  CaSo4.1/2H2O + 11/2H2O This process is called calcination When water is added to this hemi hydrate 2(CaSo4.1/2H2O)+3H2O -- --> 2(CaSo4.2H2O )+heat This exothermic reaction is responsible for the feeling of warmth following application of a pop slab/ cast

9. Setting time : 3- 9 min(start of reaction to formation of crystalline form) Drying time : 24 – 72 min ( crystalline form to amorphous form) Load bearing : 48 hrs The setting time can be Increased decreased Cold water hot water Sugar salt Potssium sulfate sodium borate

10. Various forms Slab/ splint : only a part of circumference of limb is incorporated Cast : encircle whole circumference Spica : Cross bandage applied to the root of a limb Brace : a device fitted to injured part of the body, to give support

11. Splint/ slab If complete immobilization is not required( in order to decrease swelling or to protect against soft tissue damage) non circumferential splint made out of pop or synthetic material can be used used in post operative stabilization, shifting of patients, support to reduce the swelling

12. Cast It is circumferential application of pop, done when high degree of immobilization is required

13. Split cast When a circumferential cast is applied to a fresh fracture or post operatively it has to be split opened longitudinally to allow swelling to occur without increase in pressure, the split cast is then wrapped with an elastic bandage

14. spica

15. Biomechanics of cast In # there may be imbalance between the forces on the extremities and resulting in displacement of the fracture, the cause of this displacement could be due to DIRECT force , or due to the leverage of the muscle inserted A support to counter these forces is required for stabilization, this depends on the amount of force acting on the # site( more tension the forearm # than clavicle # hence the former requires high degree of immobilization)

16. Three point stabilization of the # is required as two point stabilization (proximal and distal) will not be sufficient for control of angulations In forearm # AE cast/ splint has to be given to counteract the force acting on the # site, but in a ankle # which is far from the proximal tibia only an BK cast will suffice to counteract the force acting on the # site

17. The three point principle, using the example of a traction and reduction cast for the distal radius using POP Point one dorsal moulded rim Point two palmar aspect, where the surgeons palm is situated Point three proximal shaft of the cast where the four fingers are shown

18. Ideal material for casting Driect application Easy to mould Non – toxic Unaffected by fluid Transparent to xray Easy to modify Easy to remove cheap

19. Conformability and plasticity Plaster should be sufficiently pliable and plastically deformable, to cut the circumferential plaster along a single line, this is done if there is swelling and immediate release of pop is required, this process is called univalving as opposed to bivalving which is cutting along two lines Porosity and absorption It must be pours to allow the transmission of perspiration, which allow skin moisture to dry, pop also absorbs water and discharge from the wound and looses its rigidity

20. Strength and stability depends on the crystal structure and if the cast is manipulated while it becomes harden or prevented from drying out it will be weak because of impaired crystallization depends on the layer of plaster and the shape of the cast contoured around the injured extremity The water depth should be at least 20 – 30cm, the immersion time is approximately 3 seconds or until air bubbles stop appearing, the plaster must be uniformly wet, dry spots forms puffy pastry plaster. It is important to rub the moist paste into the fabric in oder to maintain a smooth, uniform composite Low strength to weight, 20% increase in the weight of pop will double the strength

21. Materials for casting 1) Plaste R of paris : Modern pop are made by grinding gypsum and heating it under pressure it is mixed with various addities to improve its handling character, the resultant slurry is added to leno. 2)POP with Melamine Resin: water resistant cast 3)Materials which undergo polymerisation - water activated - non water activated 4) Low temperature thermoplastics

22. Synthetic cast material Synthetic cast materials typically consist of one layer of polyester knit or polypropylene knit with fiberglass fabric or fiberglass free polymer (the latter also called thermoplastic). The important part of the material is the knitted fabric impregnated with a polyurethane resin, the prepolymer . The resin polymerizes and hardens after being exposed to humidity or water. gloves should be used during application because the resin adheres to skin and causes irritation

23. properties Moldability is les than plaster Retains the strength even when wet Modifiying the resin polymer can form rigid or semirigid cast

24. types Polyster : Polyster fabric is coated with polyurethane resin, strength depends upon the number of layers, interferes less with xray , this produces less dust during removal, it can be applied as a primary or subsequent application Fiberglass Fiberglass with polyurethane resin provides rigid durable immobilization, the rigidity depends upon the composition of resin based on this they can be of Rigid: is applied for perfect immobilization, Semi rigid: they are pliable and they are meant for maintaining alignment during functional use, The setting time is 5 minutes and weight bearing after 30 minutes

25. Thermoplastic This consist of knitted polyester with thermoplastic polyester, there is no resin here, they are reversibly moldable depending on the temperature, the material harden on cooling and can be molded on heating

26. Plaster of Paris versus synthetic cast material these include: • Greater material costs of synthetic • Shorter working time or the application of synthetic • Less frequent need or recasting with synthetic • Less abrasive and smoother edges in semi rigid synthetic casting • Heavier weight of POP • Time required or complete setting with POP • The amount of heat that can be produced in POP, particularly with warm dipping water or a thick plaster cast.

27. RULES FOR CAST Cast should be moulded with palm One joint above and below Cast should not be too tight or too loose Uniform thickness is preferred, applying rolls over extremities prevents easy breakage

28. Application of POP Padding: padding is done from distal to proximal with a 50% overlap, minimum 2 layers, and extra padding at bony prominence(fibular head, patella) Layers: 20 for adult lower limb 15 for adult upper limb 12 – 15 for child upper limb 10 – 12 layer for child upper limb Size: 8 inch for thigh 6 inch for leg 4 inch for arm and forearm

29. Application of synthetic cast There are two different ways to apply synthetic cast material. Normally the material is dipped into tepid water (around 18–20° C) and then applied to the limb. The working time using this technique is about 2–4 minutes and the initial setting time takes about 6–8 minutes Another way o applying synthetic cast material is the dry application method where the material is first applied to the limb and then moistened by spraying water on it or by wrapping it with a wet bandage. This technique gives more working time

30. Unpadded plaster Applying without any padding or applied over stockinette Introduced by bohler Bandage should roll itself round the limb, no tighteninig

31. Padded plaster Cotton wool Is applied between the skin and the plaster The cotton wool enhances the fixation due to its elastic property (tissue shrinkage) One inch thickness of cotton roll is applied which gets reduced to 1/8 th on application plaster

32. Triple sequence in application Phase 1 : examination and rehearsal Phase 2: plastering Phase 3: reduction and holding

33. WEDGING OF CAST

34. MAKING A WINDOW

35. InstructionS to patient on plaster To report immediately Increased pain or pins and needle Finger or toes become blue or numb Unable to move your finger Your unable to hold pencil or coin Not to rest the cast on firm surface Not to hang the limb To do movements of the immobilised joint To keep the plaster dry

36. complications Due to tight cast Pain Pressure sore Compartment syndrome: if pt is having pain on flexing/ extending the fingers the plaster has to be cut fully to evaluate for compartment syndrome Peripheral nerve injuries: when adequate padding is not given, common peroneal never palsy when padding is not given over fibula head

37. Due to improper application Joint stiffness Plaster blister and sores Breakage Slippage of reduction Due to allergy Allergic dermatitis

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