Exploring Humerus Bone’s Fracture Patterns and Fixation Systems Via Laser Vibrometry

Background: The mechanical performance assessment of orthopedic fixation systems is computationally and experimentally challenging due to the complex geometrical and mechanical features of bones. Non-contact experimental techniques, widely adopted in several engineering fields, is shown to overcome these issues. Objective: 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 referred to as the gold standard surgery. The new surgery consists in the installation of an external fixation mechanism that constrains, according to different spatial patterns, a certain number of titanium slender bars inserted and clamped into the fractured bones. Methods: The mechanical properties of artificial bones are characterized through compressive tests, while the morphology of the fracture surface is analyzed using a scanning electron microscope. A three-dimensional laser vibrometer is used to measure the resonance frequencies, mode shapes, damping ratios, and mechanical waves propagating from the actuators across the surface of the bones. Results: The results provide insights into which configuration of the fixator performs better for a fast recovery. Based on the observed dynamic behaviors, the optimal configuration of the fixator offers performance that is comparable to, or potentially better than, the gold standard surgical procedure. Conclusions: The novelty and feasibility of the adopted experimental approach paves the way towards the adoption of advanced non-contact techniques for the mechanical characterization of complex, non-homegenous and anisotropic materials and structures in biomedical applications enabling also data-driven models of the systems.