A simple technique to prolong molding time during application of a fiberglass cast: An in vitro study

Casting is routinely used for acute andpost-operative immobilization and remains a cornerstone in the non-operative management of fractures and deformities. Theapplication of a properly fitted and well-molded cast, especially for a trainee, can bechallenging. We present a simple method ofprolonging cure time of fiberglass cast — placing ice in the dip water. Eight-ply, five-inch fiberglass cast was circumferentially applied to an aluminum-wrapped cardboard cylinder. An electronic, 2-channel temperature sensor (TR-71wf Temp Logger, T&D Corporation, Matsumoto, Japan), accurateto 0.1oC and accurate to ±0.3oC, was placed between the fourth and fifth layers of fiberglass. Thirty total casts were tested using 9±1oC (cold), 22±1oC (ambient), and 36±1oC (warm) dip water. Room temperature was maintained at 24±1oC. Cast temperatures were measured during theexothermic reaction generated by the castcuring. Peak temperatures and cure timeswere recorded. Cure time was defined as the point of downward deflection on the time-temperature curve immediately after peak. Cure and peak temperatures were compared among groups using analysis of variance. Mean cure time was 3.5±0.1 minutes forwarm water, 5.0±0.4 minutes for ambient water and 7.0±0.5 minutes for cold water. Peak temperature, measured between layers 4 and 5 of the cast material, was 36.6±0.8oC for warm water, 31.1±1.4oC for ambient water and 25.2±0.5oC for cold water. Cold afforded, on average, an additional 2 minutes (40% increase) in cure time compared to ambient water and an additional 3.5 minutes (100% increase) compared to warm water. Cure time differences were significant (P<0.001) for all groups, as were peak temperature differences (P<0.001). Temperatures concerning for development of burns were never reached. Utilizing iceddip water when casting is a simple andeffective method to prolong the time available for cast application. Orthopedic residents and trainees may find this useful in learning to fabricate a high quality cast. For the experienced orthopedic surgeon, this method eliminates the need to bridge long-limb casts and facilitates the application of complex casts.