Computer-assisted navigation (CAN) may guide spinal surgeries, reliably reducing screw breach rates. Definitions of
screw breach, if reported, vary widely across studies. Absolute quantitative error is theoretically a more precise and
generalizable metric of navigation accuracy, but has been computed variably and reported in fewer than 25% of clinical
studies of CAN-guided pedicle screw accuracy. We reviewed a prospectively-collected series of 209 pedicle screws
placed with CAN guidance to characterize the correlation between clinical pedicle screw accuracy, based on postoperative
imaging, and absolute quantitative navigation accuracy. We found that acceptable screw accuracy was
achieved for significantly fewer screws based on 2mm grade vs. Heary grade, particularly in the lumbar spine. Inter-rater
agreement was good for the Heary classification and moderate for the 2mm grade, significantly greater among
radiologists than surgeon raters. Mean absolute translational/angular accuracies were 1.75mm/3.13° and 1.20mm/3.64°
in the axial and sagittal planes, respectively. There was no correlation between clinical and absolute navigation accuracy,
in part because surgeons appear to compensate for perceived translational navigation error by adjusting screw
medialization angle. Future studies of navigation accuracy should therefore report absolute translational and angular
errors. Clinical screw grades based on post-operative imaging, if reported, may be more reliable if performed in multiple
by radiologist raters.
Daipayan Guha, Raphael Jakubovic, Shaurya Gupta, and Victor X. D. Yang, "Spinal intra-operative three-dimensional navigation with infra-red tool tracking: correlation between clinical and absolute engineering accuracy," Proc. SPIE 10050, Clinical and Translational Neurophotonics, 100500I (Presented at SPIE BiOS: January 29, 2017; Published: 8 February 2017); https://doi.org/10.1117/12.2255050.
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