Biomechanical Properties of Splint Materials Immediately Following Dipping

CATEGORY: Basic Sciences/Biologics; Trauma INTRODUCTION/PURPOSE: Many studies have evaluated splint strength at maturity with multiple splint materials, methods, and configurations. No study to date has tested them while they were curing. This is an important for both emergency room management and post-operative splints. METHODS: Model splints of plaster, ten layers thick, and a standard prefabricated fiberglass splint were made of the same size, 125 total splints were made. They were dipped in two temperatures of water, room temperature (70oF) and warm temperature (100oF), an additional group of fiberglass with no water was tested as well. Then they were weighed to assure no outliers. A three-point bend was chosen at a constant displacement of 0.5 mm/s on an Instron 5848 machine. The splints underwent this test at three minutes, six minutes, nine minutes, twelve minutes and three days. RESULTS: Two generalized linear models (GLM) were performed with the data. One model included all time periods, and one included just the short time periods of three, six, nine, and twelve minutes. The GLM including all time frames allow for T-tests to be perform that showed significant differences in yield load and ultimate loads after three minutes between fiberglass and plaster. Plaster had a lower displacement at its yield load after 3 minutes and a higher stiffness at 1o of angulation at all time points after six minutes. The GLM that excluded the three-day time point showed that temperature increased initial stiffness in the splints as three and six minutes. A Chi squared analysis was performed between mature versus not mature stress strain curves that showed plaster to achieve it's 'mature' curve faster. CONCLUSION: Fiberglass is stronger and faster than plaster regarding ultimate load and yield load, however those loads happened at significant angular deformity. In situations where the surgeon desires the strongest splint, fiberglass may be preferable. However, the initial stiffness of plaster is better than fiberglass. This combined with the less displacement at yield point would make plaster the choice when the surgeon would like to limit micromotion or hold an exact mold with a splint.