Fiber-Optic Bragg Grating Sensors for Biomechanical Analysis of Fracture Healing

Despite the complexity of bone callus formation, the evaluation of fracture healing is usually performed based on x-ray visual inspection, a subjective and imprecise method. The main objective of this study is to access the evolution of bone callus. Tests were performed using a synthetic femur and an
in vivo
subject (preliminary results). Fiber Bragg Grating (FBG) sensors were glued to the Schanz pins of a circular external fixator for the analysis of static and dynamic strain. Three materials of different densities were inserted in the fracture site (synthetic femur) to simulate the formation of bone callus. The results from the static tests with the synthetic femur show that the strain measured on the Schanz pins presented an expected deformation pattern, according to a previous simulation. It was possible to differentiate bone callus stiffness through strain detected in the Schanz pins. The results from the dynamic tests allowed to find the first resonant frequency of each bone callus, with a difference of 4 Hz between them, measured by the FBG sensor. In the preliminary
in vivo
tests, the FBG sensor results demonstrated its technical viability to detect the bone callus healing stage. Nonetheless, a comprehensive study using a higher number of subjects is necessary. Being a noninvasive technology, it has the potential to become an important tool to assist medical staff in bone healing analysis.