Determination of detection depth of optical probe in pedicle screw measurement device

BACKGROUND: There is a high probability of accidental perforation of the vertebral pedicle wall in pedicle screw insertion surgery. A pedicle screw (PS) measurement device with an optical probe has been reported to send out a warning signal before the PS tip breaking the vertebral pedicle wall. METHODS: In this study, we explored the detection depth of optical probe in this measurement device, which was closely related to the effective alarm distance. In the boundary, the vertebrae tissues could be treated as 2-layer models including spongy bones and compact bones. The Monte Carlo simulation and phantom models were performed to analyse and define the detection depth. Then the porcine vertebrae models were performed to obtain optical spectrum and reduced scattering coefficient, based on which the detection depths were deduced. Moreover, a comparison was made to explore the most significant pattern factor from the experiment results. RESULTS: According to the pattern factor, an alarm threshold was successfully deduced to define the alarm distance during pedicle screw monitoring. CONCLUSIONS: Thus, the proposed alarm standard based on detection depth provides a potential for guiding pedicle screw in surgery.