Image Guided Spine Surgery: Available Technology and Future Potential

Review Article

Austin Neurosurg Open Access. 2016; 3(1): 1043.

Image Guided Spine Surgery: Available Technology and Future Potential

Karhade AV, Vasudeva VS, Pompeu YA, Lu Y*

Department of Neurosurgery, Brigham and Women’s Hospital, Harvard Medical School, USA

*Corresponding author: Yi Lu, Department of Neurosurgery, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, USA

Received: October 26, 2015; Accepted: January 18,2016; Published: January 19, 2016


Image-guided navigation systems for spinal surgery have evolved tremendously since they first became available in the 1990s. This technology, borrowed from cranial navigation systems, was initially difficult to use during spinal surgery due to intraoperative shift of spinal anatomy and of the inability to use skin and surface landmarks for registration. Spinal imaging systems include C-arm fluoroscopy, preoperative Computed Tomography (CT) based navigation, 2D fluoroscopy based navigation, and more recently, cone beam CT based navigation and intraoperative CT based navigation. Although the more primitive intraoperative imaging systems are relatively inexpensive and widely available, they require additional pre-operative preparation time and re-registration at each level for multiple level surgeries. Furthermore, they cannot produce axial reconstructions and expose the surgeon and operating room personnel to radiation. Newer imaging techniques such as cone beam CT based navigation and intraoperative CT based navigation allow for automatic registration, three-dimensional, multi-planar reconstructions, extended scan volume, and eliminate the need to obtain specialized pre-operative imaging for registration. Intraoperative image-guided spinal navigation has been shown to be a useful adjunct for spinal surgeons especially during the placement of spinal implants. This technology is particularly useful during minimally invasive spine procedures where direct visualization of the spinal anatomy is often not possible. We believe that ongoing advances in intraoperative image acquisition and navigation will lead to decreased complication rates and improved outcomes in the future.

Keywords: Image guidance; Neuronavigation; Spine; Spinal surgery; C-arm fluoroscopy; Preoperative CT; 2D fluoroscopy; Cone beam CT; Intraoperative CT


The past three decades of image-guided spine surgery have witnessed the development of multiple modalities for intraoperative imaging and navigation. The ultimate utility of these technologies depends on a critical appraisal of the unique advantages and disadvantages of each system. New generation tools such as cone beam CT and intraoperative CT have made tremendous improvements over initial technologies. For example, Barsa et al. placed 571 spinal implants with 99.13% accuracy [1,2] and Tormenti et al. placed 164 thoracolumbar pedicle screws using intraoperative CT with 1.2% pedicle breach compared to 5.2% with standard fluoroscopy [2,3]. Going forward, novel systems that optimize neuronavigation for minimally invasive spine surgery will lead to, in the short term, decreased complication rates and improved outcomes, and, in the long term, more innovative surgical procedures for existing problems.

Intraoperative image-guided navigation was first introduced to spine surgery in the mid-1990s [2,4]. The technology behind this advancement was initially developed for intracranial neurosurgery [2,5,6]. However, the application of this technology was more challenging for spinal neurosurgeons due to the inherent complexity of the anatomy of the spinal column. For example, the position of the brain within the skull is relatively constant, so cranial neurosurgeons were able to perform registration for intraoperative navigation based on high resolution imaging studies that were obtained preoperatively. For spinal neurosurgeons this proved difficult since the configuration of the spinal column could shift when the patient was positioned for surgery [7-10]. Additionally, skin surface landmarks were reliable for point and surface matching registration techniques during cranial neurosurgery. Conversely, in the spine, the skin and underlying soft tissue are mobile relative to the spinal column and it was therefore necessary to use bony landmarks for registration that required an extensive and meticulous surgical exposure [2,7-10].

Although the use of intraoperative navigation was not initially compatible with spinal anatomy, there was great demand for this technology amongst spine surgeons who felt that navigation would be especially useful in situations where spinal implants were placed without direct visualization. For example, the placement of pedicle screws is a common surgical procedure during which the surgeon must place an implant based on anatomical landmarks with minimal feedback to truly know that the trajectory of the screw will lie entirely within the confines of the pedicle [11]. This has led to rates of pedicle screw misplacement that have been reported as high as 40% in the lumbar spine and 55% in the thoracic spine [12,13]. Although these numbers are clearly overestimates by today’s standards, they illustrate that the misplacement of hardware can occur even in good hands and has been a longstanding concern for spine surgeons. In addition, with the introduction of minimally invasive surgical techniques for spine surgery, surgeons were trying to perform larger operations through smaller skin incisions and with less bony exposure. Intraoperative navigation had obvious utility in these procedures and motivated spine surgeons to modify and adopt navigation technology.

At our institution, we do not routinely use advanced intraoperative image navigation for all spinal surgeries. Rather, we consider using this technology when it is available in cases where there is unusual anatomy or when a difficult surgical approach is used.

Systems Used for Image-Guided Navigation

The technology used to acquire imaging for intraoperative navigation has evolved from the discovery of X-rays in the late 19th century to the highly sophisticated intraoperative Computed Tomography (CT) based navigation tools used today [14]. The range of available technologies includes C-arm fluoroscopy, preoperative CT based navigation, 2D fluoroscopy based navigation, cone beam CT based navigation, and intraoperative CT based navigation. Aside from fluoroscopy, these imaging modalities implement the basic steps of image acquisition, registration to patient anatomy, processing, and navigation [2,14,15].

C-Arm Fluoroscopy

C-arm fluoroscopy is the most widely available mode of intraoperative image acquisition and allows for the rapid and serial visualization of 2-dimensional images in real time. This imaging modality is a quick and effective way to determine the correct level of surgery. During minimally invasive procedures requiring biplanar fluoroscopy, two c-arms must be positioned into true Anteroposterior (AP) and lateral projections. True AP calibrations require visualization of the superior endplate as a single line, the pedicle shadows caudal to the superior endplate, and the spinous process shadow at the midpoint of the pedicle shadows. Lateral calibrations require visualization of both the superior endplate as a single line and the superimposition of the left and right pedicle shadows onto the posterior cortex of the vertebral body as a single line. Three-dimensional anatomy must be indirectly inferred from the 2-D images.

The major advantages of C-arm fluoroscopy are its low cost and widespread availability (Table 1). C-arm fluoroscopy also provides imaging in real time. The major disadvantages of C-arm fluoroscopy are that it exposes the surgeon and Operating Room (OR) personnel to radiation, it is cumber some to obtain images in multiple planes simultaneously, there are ergonomic challenges associated with the C-arm’s positioning, and the inability to visualize images in the axial plane [2,10,16,17].