31 – BIO-ENGINEERING STUDIES OF THE FORCES TRANSMITTED BY JOINTS: (II) Engineering Analysis

Publisher Summary This chapter discusses the bioengineering studies of the forces transmitted by joints. In the engineering design of a component, its strength and its deflection under load are among the factors to be considered. In the design of prostheses, it is of course necessary that fracture should not occur in service, but it is not always recognized that excessive deflection under load may impair performance. The loads imposed on the components of the human body are not generally known. The forces as a result of gravity on the foot, including shoe, shank, and thigh are calculated on an approximate basis, using Fischer's coefficients, which quote the weights as fractions of the weight of the whole subject. In the analysis presented in the chapter, force actions corresponding to angular accelerations of the parts about their long axes were not considered and certain simplifications were made in other respects. The accelerations were determined by differentiation of the measured values of the displacements of the significant points. In the analysis, the coordinates of the centers of gravity at each stage were first calculated from the joint coordinates, and this in itself constituted a preliminary smoothing process.