Strategies to Reduce Radiation Exposure During Spine Surgery

During the past 2 decades, spine surgery has become increasingly reliant on intraoperative imaging.[1] This trend has been driven by an evolution in minimally invasive techniques that preserve muscular attachments to the spine. Less invasive surgical techniques do not allow for visualization of the traditional topographic landmarks used to place instrumentation and instead rely on real-time images to guide surgical instruments. Despite recent advances in computerized navigation and robotics, fluoroscopy continues to be a widely used intraoperative imaging modality and imparts radiation exposure to the surgeon and operating room staff.

Health hazards related to radiation exposure during spine surgery have been well studied and include carcinogenesis, cataract formation, and mutagenesis within gonadal/hematopoietic tissue.[2] Hematopoietic, colon, lung, breast, and thyroid tissue are among the most radiosensitive tissue types.[3] Multiple studies have demonstrated the increased risk of malignancy in surgeons who utilize fluoroscopy.[4–6] To date, no large scale epidemiological study focused on cancer risk in spine surgeons has been performed. However, a widely quoted study conducted at an orthopaedic hospital in 2005 found a 29% incidence of cancer among orthopaedic surgeons at the facility over a 24-year period, compared with 4% in other employees at the facility.[7] Although the hospital was known to have substandard radiation protection practices in place during the study period, the incidence is alarming.

The International Commission on Radiological Protection sets radiation safety standards and recommends a maximum occupational radiation exposure of 20 millisievert (mSv) per year to both the body and the eye.[8] Cumulative exposure of 1 Sievert (Sv) is thought to correspond to an absolute lifetime risk of 5% mortality from malignancy.[9] The precise exposure corresponding to increased risk of cataract formation is controversial, with most studies suggesting a threshold lifetime dose of 0.5 Sv.[10] Multiple strategies can reduce radiation exposure to the spine surgeon. At a minimum, surgeons who utilize fluoroscopy during instrumentation should wear circumferential lead aprons with properly fit thyroid shields and leaded eyewear. Surgeons should avoid folding aprons as this can create defects in the shielding material. Protective aprons should be inspected on a yearly basis at a minimum. Because ionizing radiation follows an inverse square law, surgeons should always attempt to position themselves as far from the patient as possible during fluoroscopy. Standing at a distance of just 2 feet from the beam source can lower exposure by a factor of 8.

Specific settings on the C-arm can also be modified to improve radiation safety. Using “low dose” settings as well as pulsed rather than continuous fluoroscopy further reduces exposure. A 2013 study of minimally invasive transforaminal interbody fusion demonstrated an 80% reduction in fluoroscopy time per case compared with other published series by using a low-dose, pulsed technique.[11] Collimation involves the use of lead shielding to narrow the radiation beam to only the area of interest. By doing this, the amount of scatter radiation that reaches the surgical team is significantly reduced. Scatter radiation is the secondary radiation that is produced when the primary radiation beam interacts with the object being imaged (ie, the patient). Scatter accounts for the majority of radiation exposure to the surgeon in the operating room. A recent prospective study of spinal endoscopy demonstrated greater than 50% reduction in radiation exposure with the use of collimation.[12]

The type of C-arm used also impacts radiation exposure. Fluoroscopy machines can be categorized into two types: analog and digital. Analog fluoroscopy machines use a high-intensity x-ray beam to produce an image, which is then amplified by an image intensifier and captured by a camera. Digital fluoroscopy machines use a flat-panel detector to capture the radiographic image, which is then converted into a digital signal and displayed on a monitor. Due to the nature of the technology, digital machines use far less exposure to generate a high-quality image. While digital fluoroscopy became commercially available in the early 2000s, analog machines still remain in use today at many facilities due to cost considerations and lack of awareness regarding benefit. Digital fluoroscopy machines can lower radiation exposure by as much as 90%.[13,14]

Maintenance of protective equipment is also essential to limit radiation exposure to the surgeon. Lead aprons and thyroid shields should be inspected regularly for signs of wear and tear, such as cracks or holes. Lead aprons should be hung on a specially designed rack to prevent creasing or folding, which can cause the lead lining to break down over time. The aprons should be stored in a dry, cool location away from direct sunlight, as heat and moisture can also damage the lead lining. Lead aprons should be replaced periodically, even if they appear to be in good condition. The American Society of Radiologic Technologists recommends replacing lead aprons every 2 to 3 years, or sooner if they are damaged or show signs of wear.

Spine surgeons should be aware of the risks of ionizing radiation related to intraoperative imaging and take steps to minimize their exposure. Multiple strategies for exposure reduction exist, including wearing and appropriately maintaining protective equipment, maximizing distance from the imaging device and patient, limiting unnecessary image acquisition, and using modern fluoroscopy technology and settings to minimize scatter radiation. Dosimeters should be used by all spine surgeons and readings should be reviewed regularly. Further adoption of navigation technology and robotics that does not require the surgeon to be within range of the patient during image acquisition is certain to lower radiation-related risks for spine surgeons in the future. As this technology becomes more commonplace, future study will need to consider its impact on radiation risks imparted to the patient.

References

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2. Hadelsberg UP, Harel R. Hazards of ionizing radiation and its impact on spine surgery. World Neurosurg. 2016;92:353-359.

3. Hayda RA, Hsu RY, DePasse JM, Gil JA. Radiation exposure and health risks for orthopaedic surgeons. J Am Acad Orthop Surg. 2018;26(8):268-277.

4. Srinivasan D, Than KD, Wang AC, et al. Radiation safety and spine surgery: systematic review of exposure limits and methods to minimize radiation exposure. World Neurosurg. 2014;82(6):1337-1343.

5. Mastrangelo G, Fedeli U, Fadda E, Giovanazzi A, Scoizzato L, Saia B. Increased cancer risk among surgeons in an orthopaedic hospital. Occup Med (Lond). 2005;55(6):498-500.

6. Chou LB, Lerner LB, Harris AHS, Brandon AJ, Girod S, Butler LM. Cancer prevalence among a cross-sectional survey of female orthopedic, urology, and plastic surgeons in the United States. Womens Health Issues. 2015;25(5):476-481.

7. Mastrangelo G, Fedeli U, Fadda E, Giovanazzi A, Scoizzato L, Saia B. Increased cancer risk among surgeons in an orthopaedic hospital. Occup Med (Lond). 2005;55(6):498-500.

8. Clement CH, Stewart FA, Akleyev A V., et al. ICRP publication 118: ICRP statement on tissue reactions and early and late effects of radiation in normal tissues and organs—threshold doses for tissue reactions in a radiation protection context. Ann ICRP. 2012;42(1-2)1-322.

9. Pierce DA, Preston DL. Radiation-related cancer risks at low doses among atomic bomb survivors. Radiat Res. 2000;154(2):178-186.

10. Vano E, Kleiman NJ, Duran A, et al. Radiation cataract risk in interventional cardiology personnel. Radiat Res. 2010;174(4):490-495.

11. Clark JC, Jasmer G, Marciano FF, et al. Minimally invasive transforaminal lumbar interbody fusions and fluoroscopy: a low-dose protocol to minimize ionizing radiation. Neurosurg Focus. 2013;35:E8.

12. Erken HY, Yilmaz O. Collimation reduces radiation exposure to the surgeon in endoscopic spine surgery: a prospective study. J Neurol Surg A Cent Eur Neurosurg. 2022;83:6-12.

13. Lee JJ, Venna AM, McCarthy I, et al. Flat panel detector C-arms are associated with dramatically reduced radiation exposure during ureteroscopy and produce superior images. J Endourol. 2021;35:789-794.

14. Tzanis E, Raissaki M, Konstantinos A, et al. Radiation exposure to infants undergoing voiding cystourethrography: The importance of the digital imaging technology. Phys Med. 2021;85:123-128.

Brandon P. Hirsch, MD