[[Image guidance]] in open [[spinal surgery]] is compromised by changes in [[spinal alignment]] between [[preoperative]] images and surgical [[position]]ing. Fan et al. evaluated the registration of stereo-views of the surgical field to compensate for vertebral alignment changes.

To assess the accuracy and efficiency of an optically tracked hand-held [[stereovision]] (HHS) system to acquire images of the exposed spine during surgery.

The standard midline posterior approach exposed L1 to L6 in 6 cadaver porcine spines. [[Fiducial]] markers were placed on each vertebra as "ground truth" locations. [[Spine]]s were positioned [[supine]] with accentuated [[lordosis]], and preoperative [[computed tomography]] (pCT) was acquired. Spines were re-positioned in a neutral [[prone]] posture, and locations of [[fiducial]]s were acquired with a tracked stylus. Intraoperative [[stereovision]] (iSV) images were acquired and 3-dimensional (3D) surfaces of the exposed spine were reconstructed. HHS accuracy was assessed in terms of distances between reconstructed fiducial marker locations and their tracked counterparts. Level-wise registrations aligned pCT with iSV to account for changes in spine posture. Accuracy of updated [[computed tomography]] (uCT) was assessed using fiducial markers and other [[landmark]]s.

The acquisition time for each image pair was <1 s. Mean reconstruction time was <1 s for each image pair using batch processing, and mean accuracy was 1.2 ± 0.6 mm across 6 cases. Mean errors of uCT were 3.1 ± 0.7 and 2.0 ± 0.5 mm on the dorsal and ventral sides, respectively.

Results suggest that a portable HHS system offers the potential to acquire accurate image data from the surgical field to facilitate surgical navigation during open spine surgery
((Fan X, Durtschi MS, Li C, Evans LT, Ji S, Mirza SK, Paulsen KD. Hand-Held
Stereovision System for Image Updating in Open Spine Surgery. Oper Neurosurg
(Hagerstown). 2020 May 4. pii: opaa057. doi: 10.1093/ons/opaa057. [Epub ahead of 
print] PubMed PMID: 32365204.
)).