In vitro assessment was used to learn the effect of various loading conditions on the material behavior of compliant cast material used for joint immobilization. Nylon joint models of varying shapes were loaded in pure bending, and data wascollected to calculate the cast material modulus of elasticity (E). No significant effect (P≤0.05) caused by model geometry was detected. A fourth model, a turkey cadaver joint, was used to evaluate the effects of soft tissues within the cast. Thepresence of soft tissue within the cast affected E. Tensile tests were done to determine if tensile modulus of elasticity was a sufficient descriptor of material behavior at the clinical level. The tensile E was not detected to be significantly differentfrom the E determined using the three nylon joint models; however, the tensile modulus and the modulus determined from the cadaver joint model were significantly different. Conclusions were drawn that material comparisons in the linear region can be madewith any of the loading methods. However, accurate material properties for prediction purposes must be determined in the presence of soft tissues.
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