• 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 degrees +/- 1.9 degrees 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 degrees +/- 1.3 degrees C) was significantly larger than that of the thinner (six and twelve-ply) casts (1.5 degrees +/- 1 degrees C) (p < 0.05). Use of dip water with a temperature of <24 degrees C avoided cast temperatures that can cause thermal injury regardless of the thickness of the plaster cast. A dip-water temperature of 50 degrees 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 injury.
  • CONCLUSIONS
    • Excessively thick plaster and a dip-water temperature of >24 degrees 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.