Experimental characterization of humerus bones with complex fracture patterns and fixation systems via laser vibrometry

Abstract This work discusses a comparative experimental investigation into specimens mimicking healthy humerus bones and fractured bones subject to an innovative surgery procedure and to a classical technique defined as the gold standard surgery. The new surgery technique consists in the installation of an external fixation mechanism (fixator) that constrains in defined positions a certain number of titanium slender bars inserted and clamped to the fractured bones according to different spatial patterns. The mechanical properties of the material constituting the artificial bones are obtained by means of compressive tests while a SEM imaging is employed to characterize the morphology of the fracture surface. A 3D laser vibrometer is employed to acquire the resonance frequencies and the associated operational deflection shapes of the specimens subject to piezoelectric actuation. The same experimental configurations are employed to acquire the mechanical waves propagating from the actuators across the surface of the bones. The analysis of the results provides insights into which configuration of the fixator performs better for a fast recovery using as references the healthy bones and the gold standard surgery. The experimental campaign paves also the way towards the adoption of advanced techniques employed for the mechanical characterization of materials and structures in biomedical applications with the additional aim of extracting data-driven models of the systems.