Design and Integration of an Optical Frequency Domain Reflectometry (OFDR) Sensor with a Flexible Pedicle Screw for Biomechanical Evaluation

Abstract

Spinal fixation procedures rely on pedicle screws to stabilize the vertebral column, but conventional rigid pedicle screws (RPS) face challenges such as misplacement, pullout, and loosening, particularly in patients with low bone mineral density (BMD). To overcome these limitations, we recently proposed a flexible pedicle screw (FPS) inserted inside a J-shape trajectory drilled by a steerable drilling robot. Towards biomechanical evaluation of our proposed FPS for spinal fixation procedures, in this paper, we introduce the design, integration, calibration, and evaluation of an optical frequency domain reflectometry (OFDR) strain sensor into an FPS. This sensor-integrated FPS (Si-FPS) provides real-time strain and shape-sensing information, facilitating improved implant functionality assessment and optimization. To thoroughly evaluate the Si-FPS, we first additively manufacture a special FPS and integrate a OFDR shape sensing assembly within its structure. We then assess shape sensing performance of this sensorized FPS using static and dynamic FPS insertion experiments.