A summary of ECRI Institute’s Emerging Technology Evidence Report
Editor’s Note: Managed care leaders are striving to make evidence-based decisions about new and emerging health technology. Managed Care and ECRI Institute have collaborated to publish bimonthly summaries of the Institute’s Emerging Technology Evidence Reports. ECRI Institute is an independent not-for-profit organization that researches the best approaches to improving patient care. It does its work by analyzing the research literature and data on clinical procedures, medical devices, and drug therapies. This summary provides a review of the literature through June 2011.
Intraoperative imaging during spinal surgery in most hospitals involves standard fluoroscopic guidance (C-arm fluoroscopy) with two-dimensional (2-D) imaging. This technology is limited in that it does not provide an image of the true three-dimensional (3-D) anatomy of the patient and cannot be used to treat complicated cases or deformities or to perform minimally invasive surgery.
As an alternative to 2-D fluoroscopy imaging, some hospitals use 3-D fluoroscopy and intraoperative computed tomography (CT) or 3-D fluoroscopy in combination with surgical navigation to provide 3-D imaging during spinal procedures. Repeated use of fluoroscopy during spinal surgery may result in significant radiation exposure to the patient and surgical staff. CT images obtained preoperatively for comparison with real-time patient anatomy or postoperatively to confirm implant positioning result in additional radiation exposure.
Developers of new intraoperative imaging systems aim to provide high-resolution, multiplanar views while minimizing the amount of radiation exposure.
Full-rotation 3-D intraoperative imaging using the O-arm Imaging System (Medtronic Navigation, Louisville, Colo.) during spinal surgery is most often used with a computer-assisted navigation system. Navigation systems convert the 3-D image from the imaging system into a computerized image, which is projected onto a monitor to provide real-time updates of instrument location and trajectory in reference to the operative images.
Surgeons can also use the system in a stand-alone mode as a CT scanner to confirm screw placement, spine decompression, and alignment.
Full-rotation 3-D intraoperative imaging using the O-arm Imaging System may offer the following benefits over intraoperative imaging using conventional C-arm fluoroscopy in 3-D mode:
Faster rotation time, resulting in shorter image acquisition time
Improved resolution and higher-quality images
Larger field of view, allowing the generation of multiplanar images
These combined features potentially offer enhanced visualization, improved precision, shorter operative times, and reduced radiation exposure for the surgeon and the patient. Improving precision may result in decreased risk of misplaced instrumentation, fewer adverse events (AEs), and reduced need for repeat surgery.
Key questions and findings
1. Does using full-rotation 3-D intraoperative imaging improve the accuracy of pedicle screw placement during spinal fusion compared to standard 2-D or 3-D C-arm fluoroscopy?
Forming a conclusion about accuracy is not possible because only one comparative study assessed this outcome. Silbermann et al. (2011) reported a higher accuracy rate by 5 percentage points for pedicle screw placement in an O-arm navigation group than in a 2-D fluoroscopy/CT group (99% versus 94.1%; p= 0.012). Researchers based comparative accuracy outcomes on radiographic metrics. Since the significance of cortical breaches in the absence of clinical symptoms remains uncertain, applicability of the findings to clinical practice is unclear.
2. Does using full-rotation 3-D intraoperative imaging during spinal surgery reduce total radiation exposure time, operative time, and number of revision surgeries compared to standard 2-D or 3-D C-arm fluoroscopy?
Forming a conclusion about these outcomes is not possible because only one comparative study reported on differences in operative time and AE rates, and no comparative study reported on radiation exposure times or revision surgery rates. Silbermann et al. (2011) reported that the mean patient positioning time was about 20 minutes longer in an O-arm navigation group than in a 2-D fluoroscopy/CT group and this was statistically significant (p <0.05). However, the between-group difference in the mean operative time did not reach statistical significance in this study.
3. What AEs are associated with using this technology?
The studies we assessed reported no AEs directly associated with full-rotation 3-D intraoperative imaging during spinal procedures. Pedicle screw misplacement rates ranged from 0% to 15.6%. No study assessing the full-rotation 3-D intraoperative imaging system reported need for reintervention because of pedicle screw misplacement.
Facilities considering purchasing a full-rotation 3-D intraoperative imaging system will need to consider:
The system’s higher cost compared to competing technologies that also provide 3-D volumetric imaging.
The system’s limited use for orthopedic, neurosurgical, and otolaryngologic applications compared to standard C-arms that may have broader use.
The need for multidisciplinary coordination between orthopedics, neurosurgery, and otolaryngology to avoid scheduling conflicts.
The need for training for new and existing staff.
The space required to accommodate the system in the operating room.
State of Evidence Base
Quantity of evidence base — low
The evidence base consists of a single controlled study of spinal fusion that compared the accuracy of pedicle screw placement in a patient group that had two-dimensional (2-D) and 3-D intraoperative imaging using the O-arm System (187 screws in 37 patients) and a patient group that had 2-D intraoperative fluoroscopy with postoperative computed tomography (152 screws in 30 patients).
Quality of evidence base — low
The included studies have several limitations. Protocols for evaluating pedicle screw placement vary. Studies assessed use of O-arm in conjunction with image guidance. Determining how integration with a surgical navigation system affects imaging and procedure time was not possible. No comparative study reported on important outcomes of interest (i.e., total radiation exposure times and revision surgery rates). Researchers based comparative accuracy outcomes on radiographic metrics. Since the significance of cortical breaches in the absence of clinical symptoms remains uncertain, applicability of the findings to clinical practice is unclear.
Consistency of evidence base — low
Assessment of consistency for most outcomes was not possible because only one study met our inclusion criteria for efficacy. All case series we assessed reported no adverse events directly associated with full-rotation three-dimensional intraoperative imaging during spinal procedures. Pedicle misplacement rates in studies varied ranging from 0% to 15.6%.
Excerpted with permission from ECRI Institute’s database of Emerging Technology Evidence Reports. For inquiries about this report or membership in ECRI Institute’s Health Technology Assessment Information Service, send e-mail to firstname.lastname@example.org