Principles of use of plaster of paris

PRINCIPLES OF USE OF POPBASSEY, A E MBBSUATH, ABUJA

Outline• INTRODUCTION

• DEFINITION• STATEMENT OF IMPORTANCE• HISTORICAL BACKGROUND

• PHYSICOCHEMICAL CHARACTERISTICS OF POP• CLASSIFICATION

• SLAB/CAST/SPICA/BRACE• UNPADDED/PADDED

• INDICATIONS• ADVANTAGES/DISADVANTAGES• PATIENT ASSESSMENT• RULES GUIDING POP USE• TECHNIQUE

• MATERIALS• APPLICATION• REMOVAL

• AFTERCARE• COMPLICATIONS• ALTERNATIVE CASTING MATERIALS• CONCLUSION

Introduction• POP – Plaster of Paris

• Ever since it was first applied in the treatment of fractures over 150 years ago, POP has proven indispensable in the non-operative management of not only musculoskeletal injuries but other ailments requiring immobilization as well. Its use however isn’t without risk, therefore sound knowledge and properly-honed skills in its application and care are necessary to maximize outcome

Introduction• Casting properties of POP first observed when

a house in Paris built on gypsum burnt down. It was found after rain fell, that the footprints in the mud were caked upon drying

• First used in fracture care by Antonius Mathijsen, dutch army surgeon in 1852

Physicochemical properties of POP• POP is CaSO4.½H2O in its anhydrous form

impregnated in gauze which has been pre-strengthened with starch or dextrose

• Obtained from heating gypsum to 120oC• 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

Physicochemical properties of POP• 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• Reduced by high temp, salt solution, borax solution, addition

of resin• Increased by low temp, sugar solution

• Setting time is three times longer at 5oC than at 50oC

• Movement of the plaster while it is setting will cause gross weakening

Physicochemical properties of POP• 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

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

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

Advantages/Disadvantages• Advantages– Slower setting– Infinitely mouldable when wet– cheap

• Disadvantages– Heavy– Messy– Significantly weakened if cast is wet– Partially radio-opaque

PATIENT ASSESSMENT• The surgeon should examine the limb and

fracture site, documenting any skin lesions and neurovascular status

• Radiographs should also be reviewed thoroughly to determine fracture pattern

• The motions required to adequately reduce the fracture should be rehearsed ahead of commencement of procedure

Rules guiding POP use• POP should be applied by the surgeon• Procedure requires an assistant• As a guide to appropriate size

• Arm & forearm – 6”• Wrist – 4”• Thumb & fingers – 3”• Thigh & leg – 8”• Ankle & foot – 6”

• Apply POP one joint above and below• Joint should be immobilized in functional

position

Rules guiding POP use• 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

Technique• Indication met• Materials

• POP bandage• Crepe bandage (for slabs)• Casting gloves• Basin of water• Bandage scissors• Padding (Soffban®)• Sheets• Stockinette• Adhesive tape

Technique• Prepare injured site

• Fracture is reduced and assistant holds limb in position of function, in a manner that is unobtrusive to the application of cast• Stockinette is measured, extending 10cm beyond

determined limits of cast, and threaded over limb. Upper limbs: 2-3” wide; lower limbs: 4” wide• 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 is anticipated• Padding sizes, hand: 2”, rest of upper limb: 3-4”; foot: 3”,

rest of lower limb: 4-6”

Technique• POP application

• POP to be used is dipped completely with both hands into tepid or slightly warm water and held there till bubbling stops• Prior to this, for slabs, the required length is measured

and layered. On average 6-10 layers for upper limb and 12-16 layers for lower limb would suffice• It is then brought out and lightly squeezed to get rid of

excess water• 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 when dry

Technique• For slabs

– POP slab is applied and moulded onto the limb contours – Moulding is only with palms– Stockinette & padding are rolled over the edge of slab and

crepe bandage is applied from distal to proximal– Slabs may be used alone or to reinforce casts

• For cast– POP is applied in distal to proximal with 50% overlap– POP is applied snugly, compressing padding thickness by 50%– The padding is rolled over and the final turns of POP are rolled

over it

Technique• Above Elbow

• An above elbow plaster cast or slab is applied from knuckles of hand (distal palmar crease anteriorly] and covers lower two thirds of arm

• Below Elbow• While distal extent is same as above, proximally the

plaster ends below elbow crease.

• Above Knee• Distal extent is up to metatarsophalangeal joints and

proximally it covers lower two thirds of thigh.

• Below Knee• Distal extent is same, proximal extent ends below knee.

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)

• POP removal• Slabs are removed by cutting the bandage, carefully avoiding nicking

the skin• For casts

– Using shears» Heel of the shears must lie between plaster and skin, avoiding bony

prominences» Avoid cutting over concavities» The route of the shears should lie over compressible soft tissue» The lower handle should be parallel to the plaster

– Using electric saw» Do not use unless there’s wool padding» Do not use over bony prominences» The cutting mov’t should be up and down not lateral» Do not use blade if bent, broken or blunt

Aftercare• Following POP application check neurovascular

status and check reduction by xrays• Counsel the patient on signs of neurovascular

compromise – excessive pain, excessive swelling, bluish or whitish discolouration of digits

• Reinforce all cracks and weak areas with more POP locally

• Limb elevation reduces swelling, pain and risk of too tight cast

• Check if the POP is restricting mov’t• Ensure that all joints not immobilized by cast

have full range of motion

Aftercare • Keep POP dry• 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

Complications • Due to tight cast

• Pain• Pressure sores• Compartment syndrome• Peripheral nerve injury

• Due to improper application• Plaster blisters• Breakage • Loose cast

• Due to allergy• Allergic dermatitis

• Others• Muscle wasting• Skin abrasion/laceration

Alternatives to POP• POP with melamine resin

• Fibreglass– Advantages• Lighter• Three times stronger than POP• Impervious to water• Radiolucent

– Disadvantages• Costly• Less pliable• Requires gloves

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 attendant risks

THANK YOU

References• Apley’s system of orthopaedics and fractures, 9th

Ed, pp 698 – 700• Pocketbook of orthopaedics and fractures, 2nd Ed,

pp 55 – 67• 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-

ofparis• http://www.aafp.org/afp/2009/0101/p16.html