Monitoring reduced scattering coefficient in pedicle screw insertion trajectory using near-infrared spectroscopy

Pedicle screw (PS) implantation is an ideal treatment for severe multilevel vertebra instabilities. The accuracy of fixating PS is a key factor of spinal surgery. We developed a near-infrared spectroscopy device with a needlelike optical fiber probe to monitor optical parameters (reduced scattering coefficient) of vertebra models in real time. The fresh-frozen cadaver, cats and porcine vertebras were first studied in the experiments. Moreover, the reduced scattering coefficient (mu' (s)) along the different trajectories of PS insertion was obtained. In the fresh-frozen cadavera experiment, mu' (s) values could be used to distinguish the different compositions of the thoracic vertebra. In cat vertebra experiment, mu' (s) values of vertebrae bones, including cortical bone (15.30 +/- 0.18 cm(-1)), cancellous bone (7.84 +/- 1.11 cm(-1)) and spinal cord (19.46 +/- 0.21 cm(-1)), were different in vivo. In the pig vertebrae experiment, there were obvious differences between the normal and abnormal PS puncture curves based on mu' (s) values. Thus, mu' (s) values measured by using the proposed device could be used as the pattern factor in spinal fusion surgery. Our studies demonstrate that near-infrared spectroscopy method may be potentially used for assisting the PS insertion.