Effect of pressure applied during casting on temperatures beneath casts

Burns and pressure sores are common injuries during cast application. Various factors such as water temperature, padding, and cast material layers may play a role in these injuries; however, the effect of cast molding on temperatures and pressures has not been investigated. This raises the following questions, does the application of molding during cast application: (1) alter skin level temperatures in a variety of cast materials? and (2) risk inducing either thermal injury or pressure necrosis?

An upper extremity model was created to measure pressure and temperature underneath casting materials. Cast padding, water bath temperature, and cast thickness were standardized. A 3-point mold was simulated using 3 casting materials-Fiberglass only, Plaster Only splint, and Plaster splint overwrapped with Fiberglass-while pressure and temperature were recorded.

: Pressure application led to a statistically significant (P<0.0001) increase in temperature at the sites where the mold was applied although absolute temperature did not reach the theoretical burn threshold of 49 to 50°C for the casting materials studied. With pressure applied, the Plaster/Fiberglass combination reached an average peak temperature of 47.9°C, which was maintained for up to 6 minutes. Neither Fiberglass nor Plaster Only reached peak temperatures of this magnitude (average of 42.7 and 43.6°C, respectively). Peak (369 mm Hg) and highest residual (21 mm Hg) pressures were below harmful levels.

Pressure application during casting is a risk factor for burn injuries. Care should be taken when molding a plaster splint overwrapped in fiberglass by waiting until the plaster has fully cooled.

Combined with other known risk factors, the pressure from molding a cast could increase the likelihood of causing cutaneous burns.