INFLUENCE OF MUSCULATURE ON MECHANICAL IMPEDANCE OF HUMAN ULNA, AN INVIVO SIMULATED STUDY

The first-generation, viscoelastic beam model of in vivo mechanical impedance of the human ulna which Orne proposed earlier (see Engineering Index 1974 Abstract 007480) is modified to include the resistance to lateral vibration which is provided by the surrounding musculature. The musculature is represented as a continuous series of damped oscillators attached to the ulna and characterized by mass, spring and damping coefficients m//D, k//D and c//D, respectively, per unit length of ulna. Using physically plausible values for the musculature parameters, the theoretical impedance response curves show close agreement with the experimental results of G. A. Thompson over a much wider range of forcing frequencies than is possible with the earlier model of Orne. Additional theoretical curves based on the modified model are generated to evaluate the sensitivity of ulnar impedance to changes in its modulus of elasticity, density and cross-sectional dimensions. A series of animal experiments is suggested which will provide a means of separately identifying and evaluating the various mechanisms which contribute to ulnar impedance. Recommendations are given for further improvements in modeling ulnar impedance. Some applications are suggested.