Effect of Pressure Applied During Casting on Temperatures Beneath Casts

Background: 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? Methods: 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. Results: 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. Conclusions: 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. Clinical Relevance: Combined with other known risk factors, the pressure from molding a cast could increase the likelihood of causing cutaneous burns.