Principles of use of plaster of paris

Guidelines on the use of plaster of paris in fracture management. Quite useful for orthopedic residents, GPs, plaster techs, orthopedic care nurses, rehabilitation physicians, physiotherapists

1. PRINCIPLES OF USE OF POP
BASSEY, A E MBBS
UATH, ABUJA

2. 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

3. 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

4. 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

5. Physicochemical properties of POP
•POP is CaSO
4
.½H
2
O in its anhydrous form
impregnated in gauze which has been pre-
strengthened with starch or dextrose
•Obtained from heating gypsum to 120
o
C
•The hydration of CaSO
4
.½H
2
O 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

CaSO
4
.½H
2
O +
3
/
2
H2O → CaSO
4
.2H
2
O

6. 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 5
o
C than at
50
o
C
•Movement of the plaster while it is setting will
cause gross weakening

7. 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

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. 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

10. Advantages/Disadvantages
•Advantages
–Slower setting
–Infinitely mouldable when wet
–cheap
•Disadvantages
–Heavy
–Messy
–Significantly weakened if cast is wet
–Partially radio-opaque

11. 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

12. 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

13. 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

14. Technique
•Indication met
•Materials
•POP bandage
•Crepe bandage (for slabs)
•Casting gloves
•Basin of water
•Bandage scissors
•Padding (Soffban®)
•Sheets
•Stockinette
•Adhesive tape

15. 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”

16. 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

17. 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

18. 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.

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. THANK YOU

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

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