Although regarded as conservative treatment, casting is not without risk. Injuries may be sustained during application, during cast valving, through the immobilization process, or during cast removal. We developed an experimental model to investigate safe parameters for the appropriate length of time between fiberglass cast application and bivalving for cast saw use.
A hospital sheet was rolled into a mock “arm” on which short-arm fiberglass casts were formed. An appropriate cast saw technique was used with complete withdrawal of the saw blade from the cast material between cuts. A total of 10 casts were made for control/no vacuum (N = 5) and study/vacuum (N = 5) groups. The temperature of the saw blade was measured at 1-minute increments beginning at 3 minutes after fiberglass submersion in water. A mixed factor analysis of variance assessed differences in temperature change over time between groups with a statistical threshold of P < 0.05.
Casts that set for 7 minutes were associated with lower blade temperatures compared with casts that set for 3, 4, 5, and 6 minutes. The average temperature increases for the 3- to 7-minute set times without the use of vacuum were 10.08 (± 1.42), 9.38 (±1.31), 9.32 (±1.85), 8.54 (±2.10), and 5.62°F (±2.42), respectively, and with the use of vacuum, they were 9.40 (±1.14), 8.36 (±1.64), 7.84 (±2.05), 7.30 (±3.14), and 4.82°F (±2.59), respectively. Independent of vacuum use, the change in temperature was significantly different from the maximum temperature (3 minutes) beginning at 7 minutes (all P < 0.043).
A minimum of 7 minutes of set time for a fiberglass cast before attempting to bivalve using segmented cuts is associated with the smallest increase in temperature of the saw blade. Blade temperature was not affected with the vacuum enabled. Clinicians can demonstrate best practices to minimize the risk of cast saw injuries.