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Introduction to Plaster of Paris (POP)

Overview about POP use in orthopaedic.

drzhafir
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Introduction to Plaster of Paris (POP)

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  1. PLASTER OF Paris (pop) Dr. Ahmad zhafir bin zulkfli @ zulkifli 2018

  2. Content 1. Introduction 2. Physicochemical properties of POP 3. Classification 4. Indication 5. Rules guiding POP 6. Technique 7. POP aftercare 8. Complication 9. Alternatives to POP 10. Conclusion

  3.  introduction • Introduced for clinical practice by Antonius Mathijsen, a Dutch military surgeon in 1852 (over 160 years ago!) • Parent compound: gypsum hemihydrate (calcium sulphate),which forms gypsum when in contact with water • Its use however isn’t without risk, therefore sound knowledge and properly-honed skills in its application and care are necessary

  4.  Physicochemical • POP is CaSO4.½H2O in its anhydrous form impregnated in gauze which has been pre- strengthened with starch or dextrose • Obtained from heating gypsum to120oC • The hydration of CaSO4.½H2O converts it from powder form to crystalline form which gives rise to cast. This is the process of setting and is an EXOTHERMIC REACTION,explained: • CaSO4.½H2O + 3/2H2O →CaSO4.2H2O

  5.  Physicochemical • POP incorporates 20% of the water its soaks up, the remaining 80% lost during drying • Setting time – time taken to convert from powder form to crystalline form • Average time is 3 – 10mins • Setting time is three times longer at 5°C than at 50°C • Movement of the plaster while it is setting will cause gross weakening

  6.  Physicochemical • Drying time – time taken for POP to convert from crystalline form to anhydrous form • Influenced by ambient temperature and humidity • Arm cast: 24 – 36hrs • Leg cast: 48 – 60hrs • Hip spica: up to 7 days • The optimum strength is achieved when it is completely dry

  7.  INDICATIONS • Fractures • Ligament injuries • Reduced dislocations • Musculoskeletal infections • Deformity correction • Severe soft tissue injuries esp across joints • Post tendon repair • Post-operatively to augment internal fixation • Inflammatory conditions – arthritis, tenosynovitis

  8.  Classification • Based on pattern of application • Slab: POP encloses partial circumference • Cast: POP encloses full circumference • Spica: includes trunk and one or more limbs • Brace: splintage which can allow motion at adj joints • Based on interposition of material • Unpadded • No material interposed btwn POP & skin • Practiced by Bohler • Sir Charnley recommended its use in Rx of Colles, scaphoid and Bennet fractures • A practice in antiquity • Padded • Interposed material may be stockinette & wool or wool alone • This is current practice

  9.  Rules guiding POPuse • The surgeon should examine the limb and fracture site, documenting any skin lesions and neurovascularstatus • Radiographs should also be reviewed thoroughly to determine fracturepattern • The motions required to adequately reduce the fracture should be rehearsed ahead of commencement ofprocedure • Procedure requires an assistant • Apply POP one joint above and below • Joint should be immobilized in functional position

  10.  Rules guiding POPuse • Padding should be adequate esp over bony prominences e.g. olecranon, ulnar styloid, patella, fibular head, malleoli, heel • POP shouldn’t bee too tight or too loose • The plaster should be of uniform thickness throughout • Check neurovascular status after cast application • Do check xray for acceptability of reduction

  11.  Technique • Indication met • Materials • POP bandage • Crepe bandage (for slabs) • Casting gloves • Basin of water • Bandage Padding (Orthoban) • Sheets • Adhesive tape

  12.  Technique • Prepare injuredsite • Fracture is reduced and assistant holds limb in position of function, in a manner that is unobtrusive to the application ofcast • Wool padding is applied gently but snugly, starting from distal to proximal with 50% overlap between successive turns, extending 2-3cm beyond edges of splint • Padding is applied generally in 2 layers, but may be increased where there are bony prominences or if significant swelling isanticipated

  13.  Technique • POPapplication • The required length is measured and layered • POP to be used is dipped completely with both hands into tepid or slightly warm water and held there till bubblingstops • Prior to this, for slabs, It is then brought out and lightly squeezed to get rid of excesswater • If a slab is to be created, the wet plaster is kept on a flat surface and the hand is run from one end to another to get rid of air bubbles which may cause slab to be brittle and the layers to separate whendry

  14.  Technique • Forslabs • POP slab is applied and moulded onto the limbcontours • Moulding is only with palms • Padding are rolled over the edge of slab and crepe bandage is applied from distal toproximal • Slabs may be used alone or to reinforcecasts • Forcast • POP is applied in distal to proximal with 50%overlap • POP is applied snugly, compressing padding thickness by50% • The padding is rolled over and the final turns of POP are rolled overit

  15.  Technique • Made by making layers of the plaster from the rolls • Adult upper limb : 15 layers, lower limb : 20 layers • Child upper limb: 10-12 layers, lower limb: 12-15 layers • In obese patients more number of layers may be required

  16.  Technique • AboveElbow • An above elbow plaster cast or slab is applied from knuckles of hand (distal palmar crease anteriorly] and covers lower two thirds ofarm • BelowElbow • While distal extent is same as above, proximally the plaster ends below elbowcrease. • AboveKnee • Distal extent is up to metatarsophalangeal joints and proximally it covers lower two thirds ofthigh. • BelowKnee • Distal extent is same, proximal extent ends belowknee.

  17.  Technique • POP removal: • Slabsare removed by cutting the bandage, carefully avoiding nicking theskin • Forcasts • – Usingshears • – Using electricsaw • Do not use unless there’s woolpadding • Do not use over bonyprominences • The cutting movement should be up and down, notlateral • Do not use blade if bent, broken orblunt • The cast saw is made to vibrate and cut through the cast but not to cut the skin underneath

  18.  Technique • POP precautions: • Where swelling is anticipated use a slab instead of cast, if a cast must be used then it should be well-padded • POP applied postoperatively may have to be split as swelling may be significant (eg post-tourniquet release, inflammatory oedema)

  19.  POP AFTERCARE • Following POP application check neurovascular status and check reduction byxrays • Counsel the patient on signs of neurovascular compromise – excessive pain, excessive swelling, bluish or whitish discolouration ofdigits • Reinforce all cracks and weak areas with more POPlocally • Limb elevation reduces swelling, pain and risk of too tightcast • Check if the POP is restrictingmovement • Ensure that all joints not immobilized by cast have full range ofmotion

  20.  POP AFTERCARE • Keep POPdry • Any area of localised pain should be windowed as it may be a developing pressure sore • The patient should be reviewed in 1 – 2 weeks and xrays done to reaffirm maintenance of reduction

  21.  Complications • Pain • Pressuresores • Compartmentsyndrome • Peripheral nerveinjury • Plasterblisters • Breakage • Loosecast • Allergicdermatitis • Pruritis • Muscleatrophy • Skinabrasion/laceration • Joint stiffness • Volkmann’s ischaemia

  22.  POP ALTERNATIVES • POP with melamine resin • Fiberglass • Advantages • Lighter • Three times stronger than POP • Impervious to water • Radiolucent • Disadvantages • Costly • Less pliable • Requires gloves

  23.  CONCLUSION • Despite revolutionary advances in management of injury, especially those of the musculosketelal system, POP still remains very useful in carefully selected cases, obviating the need for unnecessary surgery with its attendantrisks

  24. References • Apley’sSystem of Orthopaedicsand Fractures, 9th Edition • UpToDate- General principles of definitive fracture management • http://boneandspine.com/plaster-of-paris/ • http://boneandspine.com/how-to-apply-plaster-of-paris-cast/ • http://boneandspine.com/plaster-cast-application-and-aftercare-of-the-plaster/ • http://www.slideshare.net/medicojack/plaster-of-paris • https://www.slideshare.net/Ahmed-shedeed/cast-slab • https://www.huffingtonpost.com/entry/volkmanns-ischemic-contracture_us_5a21657fe4b04dacbc9bd645

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