Background: Thermal injuries caused by application of casts continue
to occur despite the development of newer cast materials. We studied the risk
of these injuries with contemporary methods of immobilization.
Methods: Using cylindrical and L-shaped limb models, we recorded the
internal and external temperature changes that occurred during cast
application. Variables that we assessed included the thickness of the cast or
splint, dip-water temperature, limb diameter and shape, cast type (plaster,
fiberglass, or composite), padding type, and placement of the curing cast on a
pillow. These data were then plotted on known time-versus-temperature graphs
to assess the potential for thermal injury.
Results: The external temperature of the plaster casts was an
average (and standard deviation) of 2.7° ± 1.9°C cooler than
the internal temperature. The external temperature of twenty-four-ply casts
peaked at an average of 84 ± 42 seconds prior to the peak in the
internal temperature. The average difference between the internal and external
temperatures of the thicker (twenty-four-ply) casts (4.9° ±
1.3°C) was significantly larger than that of the thinner (six and
twelve-ply) casts (1.5° ± 1°C) (p < 0.05). Use of dip water
with a temperature of <24°C avoided cast temperatures that can cause
thermal injury regardless of the thickness of the plaster cast. A dip-water
temperature of 50°C combined with a twenty-four-ply cast thickness
consistently yielded temperatures high enough to cause burns. Use of splinting
material that was folded back on itself was associated with a significant risk
of thermal injury. Likewise, placing a cast on a pillow during curing resulted
in temperatures in the area of pillow contact that were high enough to cause
thermal damage, as did overwrapping of a curing plaster cast with fiberglass.
Attempts to decrease internal temperatures with the application of isopropyl
alcohol to the exterior of the cast did not decrease the risk of thermal
Conclusions: Excessively thick plaster and a dip-water temperature
of >24°C should be avoided. Splints should be cut to a proper length
and not folded over. Placing the limb on a pillow during the curing process
puts the limb at risk. Overwrapping of plaster in fiberglass should be delayed
until the plaster is fully cured and cooled.