Image-Guided Spine Surgery

By Todd B. Francis, MD, PhD

The modality of image guidance as applied to spine surgery has been growing exponentially in the past several years. Prior to the development of neuronavigation in spine surgery, most spine procedures required large exposures, potentially increased blood loss, increased postoperative pain and high doses of radiation by way of intraoperative fluoroscopy.

Minimally invasive approaches to the spine, combined with image-guided neuronavigation, provide the spine surgeon a valuable tool to approach common problems while potentially limiting complications.

In this review, we will discuss the current state of image-guided spine surgery and how it has impacted the field of minimally invasive spine surgery (MIS). We will discuss in particular two MIS modalities that show a great deal of promise:

1. Percutaneous navigated pedicle screw instrumentation
2. Navigated direct lateral interbody fusion

Development of modern image-guided systems

Image-guided systems were primarily developed for use in cranial neurosurgery. These systems were first adapted for spine surgery applications in the 1990s. Foley and Glossop et al described their laboratory evaluations of neuronavigational systems for pedicle screw placement. These early systems used a preoperative spinal CT scan correlated to operator-selected fixed spinal points in real time (for example, transverse processes and spinous processes). Nolte et al described the use of a dynamic reference frame attached to the vertebral body of the level to be instrumented, obviating the need to specify bony landmarks intraoperatively. This early research formed the basis for most of the modern image guidance techniques used today.

With the advent of intraoperative CT imaging, surgeons are now able to acquire spinal CT images in the operating room and immediately upload these onto a neuronavigational unit, eliminating the need to obtain a preoperative CT scan. Intraoperative LED-based or reflective tools are used to plan trajectories in space, and the neuronavigational unit can correlate the position of the tool to the uploaded CT scan by way of the reference frame. The technology provides highly accurate intraoperative information, including screw trajectories. This makes it possible to place screws into the pedicles of even a severely deformed spine with a high degree of accuracy that is simply not achievable using traditional freehand techniques.

Advantages of percutaneous navigated pedicle screw instrumentation

Percutaneous navigated pedicle screw instrumentation has revolutionized the treatment of many spinal fractures and degenerative conditions. With the arrival of more advanced neuronavigational systems, it is possible to place a pedicle screw at any level in the thoracolumbar spine through a 1-inch skin incision, without any intraoperative radiation exposure to OR staff and without the use of a guidewire.

This technique is very powerful in two specific applications: fixation of a lumbar fracture (e.g., a burst fracture) and posterior instrumentation after anterior interbody fusion. In both cases, pedicle screws need to be placed with minimal to no bone work required (i.e., no laminectomy or posterior fusion). Percutaneous neuronavigation allows the surgeon to avoid having to go through a large midline incision, which involves stripping muscle off several levels of the spine and increasing blood loss, operative time and postoperative pain (Figures 1 and 2).

Figure 1: Intraoperative neuronavigational images on workstation demonstrating in near real time the planned pedicle screw trajectory in the sagittal plane (top left) and the axial plane (bottom left) correlated to real-time images of the pedicle screw in three dimensions. The surgeon is able to cannulate the pedicle with a tap and save the trajectory of the tap. Head-on view of instrumentation as it passes through the pedicle (top right). Global image of where the instrumentation is relative to reconstructed 3-D CT view of the spine (bottom right).

Figure 2: Intraoperative neuronavigational images on workstation demonstrating in near real time transpedicular pedicle screw placement in the sagittal plane (top left) and axial plane (bottom left). Head-on view of instrumentation as it passes through the pedicle (top right) as well as global image of instrumentation relative to reconstructed 3-D CT image (bottom right).

A major limiting factor in traditional (fluoroscopic) intraoperative imaging is its two dimensionality. Intraoperative neuronavigation allows the surgeon to visualize the spine in three dimensions in near real time.

Another major drawback of traditional intraoperative fluoroscopy is the radiation dose to the patient and operating room staff. Radiation exposure to the surgical team during a straightforward lumbar pedicle screw instrumentation using traditional fluoroscopy can be almost 10 times higher than that given during a navigated case. Total cumulative radiation dose to the patient is also higher in traditional fluoroscopy.

Advancements in navigated direct lateral interbody fusion

The lateral transpsoas approach is a very powerful tool in the treatment of multilevel lumbar spondylosis and degenerative scoliosis. Through an MIS approach utilizing a relatively small flank incision (potentially 3-4 inches long), it is possible to place large interbody grafts at potentially five lumbar levels (T12/L1, L1/2, L2/3, L3/4, L4/5) when anatomy is favorable.

Prior to the advent of navigational techniques, this procedure required biplane intraoperative fluoroscopy, which exposed both the patient and the surgical team to large intraoperative radiation doses. In addition, the patient’s positioning and the bulkiness of the C-arm unit were hard to work around.

Neuronavigation now provides near real-time images of both the working tools of the approach and the graft itself, allowing for a three-dimensional image of the interspace in question without the use of intraoperative fluoroscopy (Figure 3).

Figure 3: Navigated lateral transpsoas approach for lumbar interbody fusion. The navigational system renders a 3-D image of the spine and the implants. The working tools are visible in real time as are the grafts as they are placed in the axial plane (left image) and the coronal plane (right image). The surgeon is able to use the system to accurately identify the targeted lumbar disk, remove it safely and place the implant — all without the use of intraoperative fluoroscopy. (Images courtesy of Medtronic, Inc.)

The neuronavigational system has reduced the surgical time for this procedure so much that we are now able to complete large multilevel interbody fusion cases with posterior instrumentation in one operation. Previously, interbody fusion almost always needed to be staged, with a second operation for the posterior portion of the procedure.

Cleveland Clinic helped pioneer this surgical technique, and we are now one of the national leaders in this surgical approach in terms of volume and applications.

Adding power to minimally invasive techniques

Neuronavigational techniques have added significant power to MIS techniques in modern spine surgery. In properly selected patients, we can now place pedicle screws and interbody grafts through much smaller incisions with less blood loss, lower operative time, reduced postoperative pain and decreased length of stay. In addition, neuronavigation allows the surgeon to increase accuracy in pedicle screw placement when compared with more traditional freehand techniques.

MIS is an important tool for the surgeon to have in his/her arsenal because it allows alternative, potentially safer approaches to surgical problems in properly selected patients. However, MIS is not intended to be a replacement for traditional open techniques, which still hold a central place in the spine surgeon’s repertoire. Advances in neuronavigation are helping MIS quickly become commonplace in modern spine surgery.

Dr. Francis is a spine surgeon in the Center for Spine Health. He can be reached at francit@ccf.org or 440.312.6100.

Suggested Reading

Foley KT, Smith MM. Image-guided spine surgery. Neurosurg Clin N Am. 1996;7:171-186.

Glossop ND, Hu RW, Randle JA. Computer-aided pedicle screw placement using frameless stereotaxis. Spine. 1996;21:2026-2034.

Kim TT, Drazin D, Shweikeh F, Pashman R, Johnson JP. Clinical and radiographic outcomes of minimally invasive percutaneous pedicle screw placement with intraoperative CT (O-arm) image guidance navigation. Neurosurg Focus. 2014;36(3):E1.

Nolte LP, Zamorano LJ, Jiang Z, Wang Q, Langlotz F, Berlemann U. Image-guided insertion of transpedicular screws: A laboratory set-up. Spine. 1995;20:497-500.

Vanek P, Bradac O, Konopkova R, de Lacy P, Lacman J, Benes V. Treatment of thoracolumbar trauma by short-segment percutaneous transpedicular screw instrumentation: Prospective comparative study with a minimum 2-year follow-up. J Neurosurg Spine. 2014;20(2):150-156.

Villard J, Ryang YM, Demetriades AK, et al. Radiation exposure to the surgeon and the patient during posterior lumbar spinal instrumentation: A prospective randomized comparison of navigated versus non-navigated freehand techniques. Spine. 2014;39(13):1004-1009.