Plaster of Paris(POP)

Muhammad Abdelghani

Historical Perspective

• 9th century AD: – Arab physicians used

strips of linen soaked in a mixture of lime and egg white which would set “hard as stone” for treatment of fractures.

Historical Perspective

• 1852: Classical plaster bandage.– Antonius Mathysen, a Dutch army surgeon,

treated battle wounds in the Crimean War with cotton bandages filled with dry plaster of Paris (POP).

– POP was so called because it was first prepared from the gypsum mined in Paris, France.

Historical Perspective

• 1927: Binder ingredients (starches, gums, and resins) were added to improve the adherence of the plaster to the gauze.

• Later, other additives were incorporated to change the physical properties pf POP, such as setting time, which allowed standardized production.

• 1970s: Synthetic materials.

Current Indications

• Immobilisation of fractures

• Correction of deformities

• Splinting limbs

• Immobilisation of the spine.

Complications

• Deformity

• Skin injuries

• Rashes

• Compartment syndrome

• Burns

What Causes Complications?Technical Error Resulting Complication

Improper and irregular application of padding

Pressure sores beneath the cast

Inadequate padding material at the ends of the cast

Sharp edges and skin irritation

Aggressive cast molding Pressure sores beneath the cast

Inadequate casting materialCast breakdown and loss of control of the unstable fracture

Tight application of casting material or failure to allow for underlying injury swelling

Compartment syndrome

Hot dip water Elevated setting temperatures / Skin burns

Exothermic Reaction

• Occurs as the cast hardens.

• Causes the temperature within and beneath the cast material to rise.

• Temperature may rise to dangerous levels: Risk of thermal injury.

Exothermic Reaction

• Recommendations for safe casting:– Use luke-warm water with plaster casts– Use cool water with fiberglass casts– Pad appropriately to avoid sharp edges or

cast pressure points

Exothermic Reaction

• Lavallette et al:– Risk of burns is directly related to:

• dip water temperature • length of time the plaster is kept in the dip water

– Dip water temperature can play a key role in the ultimate temperature beneath the cast.

Exothermic Reaction

• Kaplan: – Temperature elevations can be related to the

plaster being dipped too briefly and the water being squeezed too aggressively out of the plaster.

– The water itself helps to release the heat, and if there is not enough, the plaster gets hotter.

Exothermic Reaction

• Selesnick & Griffiths– With fiberglass cast materials, use only cool

dip water to reduce the chance of burns.

Exothermic Reaction

• Hutchinson and Hutchinson (2008):– There is a direct relationship with increasing

dip water temperature from 32 to 39º C and the ultimate peak temperature beneath both plaster and fiberglass casts.

Exothermic Reaction

• Dirty dip water and ambient humidity have also been implicated as contributing to temperatures beneath maturing casts.

• Lavalette and Ganaway: – Plaster residue in the dip water might play a

role in elevating cast temperature and broadening the time-temperature curve; i.e., maintaining the peak temperature for a longer period.

Exothermic Reaction

• Ganaway: – Cast padding plays little role in effecting the

temperature beneath a cast. • Hutchinson & Hutchinson:

– Increased cast padding: • little effect on the fiberglass casts.• significant effect of elevated temperatures with additional

layers of Webril applied beneath 20 layers of extra-fast setting plaster.

– Explanation: increased insulation traps the heat beneath.

• Cast padding likely plays a greater role to protect the skin against pressure points than its effect on temperature.

Exothermic ReactionConclusion:• Extra fast setting plaster achieves peak temperatures quicker and

higher than slower setting plasters.• Increased thickness of casting materials (both plaster and

fiberglass) are related to increased temperatures beneath the cast.• Dip water temperature is directly related to the peak temperature

beneath the cast.• Prefabricated splints do not achieve the same temperature levels

when compared to circumferential casts and, therefore, from a thermal perspective, may be safer.

• Thickness and type of cast padding did not play a significant role regarding ultimate temperatures beneath the cast in this study.

• At the thicker levels of padding, it may actually serve as an insulator entrapping additional heat.

• The greatest risk of thermal injury occurs when a thick cast using warm dip water is allowed to mature while resting on a pillow.

Cast Wedging

• When fracture reduction is incompletely obtained in a cast, wedging may be a viable technique to correct deformity and avoid surgical intervention.

Cast Wedging

• Types of wedging:– Open wedging

– Closed wedging

– Combination of opening and closed wedging.

Cast Wedging

• Open wedging:– More commonly used– Avoids the risks that accompany closing

wedges

Cast Wedging

• Closed wedging:– Possible complications:

• Pinching of the skin (may cause skin breakdown)• Accumulation of cast padding at the wedge site

(may also cause skin breakdown) • Fracture shortening• Reduction of the volume of the cast (may result in

compartment syndrome).

Cast Wedging

• Predicting the wedge size:– Bebbington, Lewis, and Savage:

• Trace the angle of displacement onto the cast itself using a marking pen.

• The line is meant to represent the fracture fragments. • Wedges are then inserted until the bent line becomes

straight.

– Guastavino and Husted: • Both introduced formulae that could be used to predict the

amount of wedging.• Husted’s method even accounted for radiographic

magnification.

Synthetic Cast Materials

• Introduced on the market place in the seventies, but have not superseded traditional POP.

Synthetic Cast Materials

• Advantages:– Better physical and mechanical properties

than traditional POP– Lighter– More resistant to humidity– More radiotransparent– Generate less dust when removed

Synthetic Cast Materials

• Disadvantages:– Less malleable– Cause higher pressure in case of limb edema

Synthetic Cast Materials

• POP therefore remains indicated in the acute posttraumatic or postoperative period.

• This material is also cheaper, but the pecuniary benefit is limited for several reasons, particularly because POP is associated with a higher rate of cast replacement.

Synthetic Cast Materials

• Thermoplastic Materials:– More recent– Used to make splints and orthoses,

particularly at the wrist and hand.

References

• Colditz JC: Plaster of Paris: The Forgotten Hand Splinting Material. J Hand Ther 2002; 15:144-157

• Hutchinson MJ, Hutchinson MR: Factors contributing to the temperature beneath plaster or fiberglass cast material. Journal of Orthopaedic Surgery and Research 2008, 3:10

• Schuind F, Moulart F, Liegeois JM, Dejaie Strens LC, Burny F: La contention orthopédique. Acta Orthopædica Belgica 2002; 68(5):439-461

• Wells L, Avery AL, Hosalkar HH, Friedman JE, Davidson RS: Cast Wedging: A “Forgotten” Yet Predictable Method for Correcting Fracture Deformity. UPOJ 2010; 20:113-116