Intraoperative Feedback System to Predict Long-Term Pedicle Screw Fixation using Modal Analysis

Abstract

This thesis presents a novel intraoperative feedback system designed to predict long-term pedicle screw fixation in spinal fusion surgeries by leveraging modal (vibrational) analysis. Spinal fusion is a prevalent procedure aimed at stabilizing vertebrae in cases of degenerative disease, trauma, or deformity; however, current intraoperative methods for assessing pedicle screw stability largely rely on subjective tactile feedback. To address this gap, we developed a compact, single-handed device that excites the screw–bone construct with a controlled vibrational input and measures the response via an embedded sensor. Through fast Fourier transforms and resonance frequency detection, the system quantitatively gauges screw anchorage quality in real time. Finite element analysis (FEA) of pedicle screws in bone analogs demonstrated that resonance frequency shifts reflect changes in bone–screw interface stiffness. Bench-top experiments with polyurethane foam blocks of varying densities confirmed strong correlations between resonant frequency and mechanical pull-out strength, validating the approach in a controlled environment. Further testing on cadaveric vertebrae reinforced the device’s clinical relevance, showing it can differentiate securely anchored screws from those at higher risk of loosening. Designed for seamless integration into the surgical workflow, the tool displays a simple color-coded readout (green/yellow/red) to guide intraoperative decision-making. User feedback from orthopedic surgeons highlights the system’s potential to reduce revision rates and hardware failures by enabling immediate identification of suboptimal fixation. Future work will focus on extending compatibility to polyaxial screws, refining signal processing algorithms for greater robustness, and undertaking large-scale clinical studies to establish the device as a standard instrument for spinal fusion procedures.