RESPONSE OF HUMAN FEMUR TO MECHANICAL VIBRATION

The effect of mechanical vibration in the frequency range 0-500 Hz on the cadaveric human femur was assessed. It was found that when the bone was fixed at both ends, its resonant frequency was markedly affected by end loading and damping. If the conditions of the experiment were designed to simulate the condition of the femur when prepared for a total hip replacement, it was found that the bone did not resonate but behaved in a mass-like mode. The significance of this observation is that in the event of vibration being applied to enhance the penetration of bone cement, the movement induced in the bone will be proportional to the force applied regardless of frequency. This also demonstrates that the concept of designing a prosthesis so that it is isoelastic with the femur is complex and potentially flawed, since th stiffness of the femur will vary during the walking cycle.