AANS: Spine surgeons face chronic radiation dangers
By not wearing appropriate radiation protection, spine surgeons performing high volumes of cases could approach the annual cumulative exposure limit of 5 Rem to the thyroid or torso, according to research to be presented during the America Association of Neurological Surgeons (AANS) annual conference, May 1-5 in Philadelphia. 

Shane Burch, MD, an orthopedic surgeon at the University of California, San Francisco, and colleagues said that in comparing surgeon exposure to radiation during thoracic and lumbar pedicle screw placement using the O-arm Imaging System with Stealthstation S7 computer assisted spinal navigation (O-arm Navigation) as opposed to standard C-arm fluoroscopy, spine surgeons can reduce their radiation exposure during these procedures.

The researchers utilized eight cadavers for their study, paired according to body mass index. The specimen pairs were divided into two groups, four for the O-arm Navigation station and four in the C-arm station. A total of 160 pedicle screws were placed, with bilateral pedicle screw placement of 80 screws being performed in four cadavers using fluoroscopic imaging, and the remaining 80 screws being replaced by using the O-arm intra-operative imaging system and StealthStation spinal navigation in four cadavers.

The authors wrote that the spine of each cadaver was exposed from T1-T6 prior to the study and in the lumbar region, typically, the percutaneous screws at L3-L4 were placed before the open L5-S1 screws and surgeons performed all L5-S1 exposures. The pedicle screws were placed based on the preferred techniques of the four surgeons for open and minimally invasive spine surgery (MIS) screw placement. In addition, the surgeons placed an equal amount of screws in pre-defined section of the spine including thoracic, open lumbar L5-S1 and MIS Lumbar L3- L4 using both O-arm and C-arm technologies.

Dosimeter badges were changed after each of the three separate procedures was carried out by each surgeon, the researchers explained, stating that the badges measured radiation dose rates to the surgeon’s neck, torso and dominant hand. Moreover, radiation levels were quantified at various distances from the dorsal lumbar surface using an ion chamber radiation survey meter.

“Surgeon dosimeter badge readings for radiation exposure using the O-arm System and Navigation was negligible across all screw placements. Surgeons stepped behind lead shields or left the room for the 13 second O-arm System navigation scan,” explained the researchers.

In terms of radiation exposure, the authors found that the average surgeon hand exposure was less than 1mrem with the O-arm Navigation and 4.08 mrem for the C-arm. Average surgeon torso exposure was also found to be less than 1 mrem with the O-arm Navigation and 36.75 mrem with C-arm. Like hand and torso, neck exposure was also less than 1 mrem with the O-arm Navigation and 5.75 mrem with C-arm.

The researchers also noted that surgeon radiation exposure per thoracic, open lumbar and MIS lumbar was lower with O-arm Navigation compared to C-arm, with the average surgeon exposure quantified at less than one 1mrem for each procedure and average exposure of 23.33, 10.33 and 12.92 mrem for each anatomical section, respectively.

Burch and colleagues said that if a surgeon performed 389 of these cases, they would exceed the 5 Rem limit. Noting that exposure is cumulative, they wrote that if a surgeon completes four of these cases a week without protection, they would approach the 5 Rem limit in just over eight years.

“By utilizing the O-arm System with StealthStation Navigation, spine surgeons can reduce their radiation exposure during pedicle screw placement,” the authors concluded.

Minneapolis-based Medtronic sponsored the trial, and Burch has received research support from the company.