Noninvasive Optical Instrumentation for Bone Healing Process Analysis

Abstract

In clinical practice, the evaluation of bone healing is based on radiographs and manual examination of fracture mobility. In these analyses, the patients are often exposed to high radiation levels, and the evaluation of the results is mostly dependent on the medical experience. Therefore, it is necessary to develop quantitative techniques to monitor the healing process. This article presents noninvasive optical instrumentation for bone healing analysis. This analysis presents the measurement of the static and dynamic strain of the external fixation device used in patients who have suffered fractures in the lower limb(s). The analysis was made through the numerical finite element method and validated with the experimental results. The experimental instrumentation verified the feasibility of using the fiber Bragg grating (FBG) sensors for measuring static and dynamic strain in an external fixation device. In order to validate the response of the FBG sensors, the results were compared to a piezoelectric accelerometer. The results showed that the forces are initially (after fracture fixation) supported exclusively by the external fixator; however, during healing, the support is divided with the femur. In the experimental analysis, it was observed that the four pins of the external fixator above the fracture showed an average deformation decrease of 95%, and the four pins below the fracture showed an average increase of 112.8%. From the response frequency analysis of the FBG sensor, it was possible to differentiate the system with fractured bone from the system with an intact one. Because of their high sensitivity, FBG sensors can be used as an auxiliary technique in the diagnosis and follow-up of the fracture healing process.