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Role of intraoperative imaging in spine surgery continues to expand

Fluoroscopy vs. newer technology

Fluoroscopy is the most common intraoperative imaging technique and, according to Charles A. Sansur, MD, director of spine surgery at the University of Maryland School of Medicine, it remains the gold standard.

Charles A Sansur

Charles A. Sansur

“I don’t think fluoroscopy is ever going to die,” Sansur said. “You can get instant images without any concern about a lack of correlation between the image and the reference point. The only way these newer intraoperative imaging techniques work is by having an appropriate reference point, and your imaging is only as good as the stability of your reference point.”

Fessler also uses routine fluoroscopy. “Fluoroscopy is fast and one can do one’s surgery without any additional anesthesia time to the patient,” he said. “The disadvantage is exposure to radiation to the surgeon over the course of years, especially when young and learning.”

Khanna and his colleagues now use the Brainlab image guidance system, which is an intraoperative 3-D guidance system. Other systems available for intraoperative spine imaging include CT-guided systems like the O-Arm from Medtronic, the Brainlab Airo system, the Artis zeego system from Siemens and robotic systems like the Mazor Robotics Renaissance Guidance System for placement of pedicle screws.

Polly uses intraoperative 3-D imaging CT, the O-Arm and the Stealth image-guided technology for pedicle screw placement.

“The O-Arm gives you the ability to scan the patient prior to your incision and use that information during the surgery without the need to have the unit in the room,” Sansur said. “Even though the advance is there, I don’t think it is available at a lot of institutions, but I do think that ultimately, it will be a common thing.”

The Brainlab technology provides a sharp, clear image and has satisfactory accuracy beyond four or five levels.

“The only limitation to this technology is you have to have a separate dedicated OR table,” according to Sansur. “The O-Arm can be applied to any standard spine operating table.”

At Cedars-Sinai Medical Center, surgeons also use 3-D intraoperative imaging for spine surgery, in particular intraoperative CT scans — the O-Arm and the Brainlab Airo — to visualize the deep bony tissue, Kim said.

Increased precision

Intraoperative imaging systems help ensure precision, according to sources for this article.

“One of the big issues of spine surgery is we are trying to place screws into narrow corridors in the vertebrae. If we go too far medial, we hit the spinal cord and the nerve roots; if we go too far anterior, we could hit major blood vessels,” Khanna said. “We have to get the screw in the exact right place. The other cases are upper cervical spine cases, where we are doing instrumentation at C1 and C2 and those areas for the screws are also small. The stakes are high.”

Polly and his colleagues recently completed a preliminary study, which evaluated their per-screw placement time.

“We have been as fast as less than a minute per screw and our average time is about 5 minutes per screw,” Polly said. “That includes the acquisition of the intraoperative CT scan to do the navigation and then an intraoperative-check CT to make sure the screws are OK after we have placed them.”

Reporting on their first 2,500 screws using a mobile intraoperative CT imaging system, Polly and colleagues noted a 0% return-to-OR rate for implant malposition.

“The literature would suggest that between 1% and 4% of patients who have screws placed have a need to return to the OR for implant malposition,” Polly said.

He and his colleagues also have evaluated the technology’s use in more challenging cases such as congenital scoliosis.