February 01, 2017
3 min read

Navigation aids accuracy of implant placement, mitigates bone damage

Navigation may reduce surgical time and radiation exposure in spine surgery, according to a presenter.

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Navigation used during spine surgery can help surgeons accurately place pedicle screws and insert the screws in the most optimal position to avoid damage to the bone and adjacent structures. According to a presenter, not only does this allow surgeons to accurately and precisely place pedicle screws, but it allows them to use O-arm navigation to place iliac bolts, perform precise three planar osteotomies and even perform precision tumor resections and simplify revision spinal surgery.

“[Navigation] has been shown that it reduces the number of pedicle screws breaching, it reduces the screw pull-out [and] it reduces our complication rate,” Andrew O’Brien, MD, MBBS, FRCS, said at the British Orthopaedic Association Annual Congress. “I think that navigation should be as essential a part of our armamentarium as the pedicle finder.”

He added, “Navigation has enhanced our ability to visualize the anatomy. It allows us to find pedicles that we cannot see with other techniques; it allows us to define both normal and abnormal anatomy; it allows us to compensate for missing pedicles or for bone loss; it allows us to work around existing metal work; and it allows us to take a bone scalpel and make precise cuts within the bone and take out bone in exactly the location and size we need it for precise facetectomies, decompressions or multiplanar osteotomies. Navigation is extending our range of abilities as surgeons.”

bypassing broken screws
Navigation can be effective for bypassing broken screws, as shown here, where the surgeon bypasses a broken screw to place a screw just past it.

Images: Molloy S

Navigation provides clearer image

O’Brien said patients may have difficult or abnormal anatomy, especially in deformity, with the possibility of distorted or absent traditional landmarks. In these cases, even intensified images are limited in what they can show.

“Navigation allows us to have a clearer image of the abnormal anatomy, that plain radiographs or image-intensifier [scans] allow, but it also enables us to explore the anatomy on a screen in real-time and on the operating table with the patient in front of us and to use a computer simulation to plan and deliver our surgery,” O’Brien said.

Scoliosis procedures
Scoliosis procedures can be performed entirely using navigation, which surgeons say helps optimize screw position and hold.

Navigation not only helps with the identification of bony structures, but it can also help surgeons preserve or protect the soft tissue, he said.

Navigation allows spine surgeons to “recover and retrieve” situations in which using conventional techniques would be extremely difficult or product a suboptimal result, O’Brien said.

“Navigation gives us another extension to our reality. Instead of losing the pedicle anchorage at that level and finding some alternative fix with a wire, hook or bypassing the level, we can utilize that difficult pedicle optimally by being able to put a pedicle screw with the optimum hold into the area,” he said.

Less radiation exposure for team

“[Looking] at the literature and looking at our experience, navigation reduces the surgical time in many cases. In some studies, that says equivalent,” O’Brien said. “It reduces the radiation exposure to the surgeon and the team, and it did significantly in our experience.”

He said there is conflicting evidence regarding the dose for the patient; however, the navigation dose is less than that of when fluoroscopy is used in larger procedures. Navigation also can compensate for lost landmarks and can allow surgeons to keep their incisions small and avoid stripping tissues, O’Brien said.

Other advantages of navigation he discussed were that surgeons can extend their range of surgical techniques when they use navigation-specific bone scalpels, drills and other devices. In addition, navigation may reduce stress during the surgery because the surgeon will know where the pedicle screw is ultimately going and that it will successfully hold. Navigation also gives surgeons the ability to work around existing metalwork and implants in a way that would be difficult using image intensifiers alone, he noted.

“It is brilliant for teaching. Trainees can look and see and get real-time feedback on what they are doing,” O’Brien said. – by Monica Jaramillo

Disclosure: O’Brien is a paid consultant to Medtronic.