Accuracy of Stereovision-Updated Versus Preoperative CT-Based Image Guidance in Multilevel Lumbar Pedicle Screw Placement

Abstract

Background: Change in vertebral position between preoperative imaging and the surgical procedure reduces the accuracy of image-guided spinal surgery, requiring repeated imaging and surgical field registration, a process that takes time and exposes patients to additional radiation. We developed a handheld, camera-based, deformable registration system (intraoperative stereovision, iSV) to register the surgical field automatically and compensate for spinal motion during surgery without further radiation exposure.Methods: We measured motion-induced errors in image-guided lumbar pedicle screw placement in 6 whole-pig cadavers using state-of-the-art commercial spine navigation (StealthStation; Medtronic) and iSV registration that compensates for intraoperative vertebral motion. We induced spinal motion by using preoperative computed tomography (pCT) of the lumbar spine performed in the supine position with accentuated lordosis and performing surgery with the animal in the prone position. StealthStation registration of pCT occurred using metallic fiducial markers implanted in each vertebra, and iSV data were acquired to perform a deformable registration between pCT and the surgical field. Sixty-eight pedicle screws were placed in 6 whole-pig cadavers using iSV and StealthStation registrations in random order of vertebral level, relying only on image guidance without invoking the surgeon's judgment. The position of each pedicle screw was assessed with post-procedure CT and confirmed via anatomical dissection. Registration errors were assessed on the basis of implanted fiducials. Results:The frequency and severity of pedicle screw perforation were lower for iSV registration compared with StealthStation (97% versus 68% with Grade 0 medial perforation for iSV and StealthStation, respectively). Severe perforation occurred only with StealthStation (18% versus 0% for iSV). The overall time required for iSV registration (computational efficiency) was ;10 to 15 minutes and was comparable with StealthStation registration (;10 min). The mean target registration error was smaller for iSV relative to StealthStation (2.81 ± 0.91 versus 8.37 ± 1.76 mm).Conclusions: Pedicle screw placement was more accurate with iSV registration compared with state-of-the-art commercial navigation based on preoperative CT when alignment of the spine changed during surgery.Clinical Relevance: The iSV system compensated for intervertebral motion, which obviated the need for repeated vertebral registration while providing efficient, accurate, radiation-free navigation during open spinal surgery.Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJSOA/A365).

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

“…It has also been demonstrated that this iSV system can drive the creation of an updated CT that accounts for the pre-operative-to-intraoperative shift of the spine pose (7)(8)(9)(10). To date, we have published studies investigating the effects of performing this updating on pre-operative imaging to match the pose of the spine from intraoperative patient positioning (7)(8)(9)(10)(11)(12). These studies account for any pre-operative to intraoperative motion that might occur; however, investigations into accounting for any motion that could occur as the surgery continues to proceed have not been conducted.…”

Simulation study of minimally invasive surgical scenes and their effect on hand-held stereovision driven level-wise registration techniques

“…[3][4][5] Modern methods of image registration have emerged within the area of image guided spine procedures. [6][7][8][9][10] One commercially available system exists. FLASH TM (7D Surgical, Toronto, On, Canada) This system uses a stereovision system mounted in the overhead light source.…”

“…Recently, a modern multi-level deformable registration technique has been developed. 7,8 This method utilizes a low-cost Hand-Held Stereovision system. 6 This system can be easily calibrated, and has shown a high degree of registration accuracy (< 3mm) in a cadaver pig model.…”

“…6 This system can be easily calibrated, and has shown a high degree of registration accuracy (< 3mm) in a cadaver pig model. [6][7][8]11 This method can be utilized on any number of vertebral levels due to its level-wise registration technique. One major drawback of this method is that previous studies only collected data from large surgical exposures.…”

“…These studies exposed almost the entire posterior surface of the vertebral body, including most of the transverse process. 7,8 Modern surgical techniques do not require an exposure this large. Most procedures only expose out to the lamina or facet joint.…”