Techniques used to assess compliant synthetic cast material behavior

In vitro assessment was used to learn the effect of various loading conditi ons on the material behavior of compliant cast material used for joint immo bilization. Nylon joint models of varying shapes were loaded in pure bendin g, and data was collected to calculate the cast material modulus of elastic ity (E). No significant effect (P less than or equal to 0.05) caused by mod el geometry was detected. A fourth model, a turkey cadaver joint, was used to evaluate the effects of soft tissues within the cast. The presence of so ft tissue within the cast affected E. Tensile tests were done to determine if tensile modulus of elasticity was a sufficient descriptor of material be havior at the clinical level. The tensile E was not detected to be signific antly different from the E determined using the three nylon joint models; h owever; the tensile modulus and the modulus determined from the cadaver joi nt model were significantly different Conclusions were drawn that material comparisons in the linear region can be made with any of the loading method s. However accurate material properties for prediction purposes must be det ermined in the presence of soft tissues.