Towards accounting for intraoperative spine motion: a simulation study of registration between stereovision surfaces

Abstract

Registration of preoperative or intraoperative imaging is necessary to facilitate surgical navigation in spine surgery. After image acquisition, intervertebral motion and spine pose changes can occur during surgery from instrumentation, decompression, physician manipulation or correction. This causes deviations from the reference imaging reducing the navigation accuracy. To evaluate the ability to use the registration between stereovision surfaces in order to account for this intraoperative spine motion through a simulation study. Co-registered CT and stereovision surface data were obtained of a swine cadaver’s exposed lumbar spine in the prone position. Data was segmented and labeled by vertebral level. A simulation of biomechanically bounded motion was applied to each vertebral level to move the prone spine to a new position. A reduced surface data set was then registered level-wise back to the prone spines original position. The average surface to surface distance was recorded between simulated and prone positions. Localized targets on these surfaces were used for a calculation of target registration error. Target registration error increases with distance between surfaces. Movement exceeding 2.43 cm between stereovision acquisitions exceeds registration accuracy of 2mm. Lateral bending of the spine contributes most to this effect compared to axial rotation and flexion-extension. In conclusion, the viability of using stereovision-to-stereovision registration to account for interoperative motion of the spine is shown through this simulation. It is suggested the distance of spine movement between corresponding points does not surpass 2.43 cm between stereovision acquisitions.