Introduction: Minimally invasive lateral interbody fusion is a common procedure for the treatment for thoracolumbar spondylolisthesis. Fluoroscopy, which is used in this procedure, produces ionizing radiation. In sufficient doses this radiation can cause burns, cataracts, and increase the lifetime risk of cancer. While this procedure is efficacious, it requires more fluoroscopy than open approaches. We sought to quantify the amount of patient radiation exposure during minimally invasive lateral fusion.
Methods: Data was prospectively collected from 80 consecutive patients who underwent minimally invasive lateral fusion. All surgeries were performed by two surgeons. An OEC 9900 Elite C-arm that measured total absorbed dose and exposure time provided fluoroscopic imaging. When necessary, surgeons used magnification to improve image quality. In smaller patients, pulsed imaging could be used to reduce radiation exposure. Cases involving heavy use (>30% total fluoroscopy time) of magnification (“Mag group”), those utilizing pulsed imaging (“Pulse group”), and those performed under normal imaging (“NoMag”) were compared using one-way ANOVA.
Results: A total of 228 vertebral levels were treated. Mean fluoroscopy time was 2.96 minutes (1.04 min/level) and mean absorbed dose was 107.9 mGy (37.9 mGy/level). The Mag group (N=44), NoMag group (N=28), and Pulse group (N=8) were similar in age (62.3, 67.5, 65.8, p=0.16), male-to-female ratio (0.36, 0.39, 0.25, p=0.76), BMI (30.2, 28.7, 24.9, p=0.08), and levels treated (2.7, 2.9, 3.5, p=0.56). There were significant differences between the total fluoroscopy time per level (1.64 min/level Mag, 0.75 min/level NoMag, 0.34 min/level Pulse, p<0.001) and absorbed dose per level (64.5 mGy/level, 20.7 mGy/level, 12.2 mGy/level, p<0.001).
Conclusions: Patients undergoing the minimally invasive lateral fusion absorb a moderate amount of radiation, which is within the range of exposure reported for minimally invasive spine procedures. Compared to normal imaging, pulsed imaging reduced radiation exposure by 50% while magnification increased exposure 300%.
Patient Care: Minimally invasive spine procedures are increasingly common. They have been shown to produce high rates of arthrodesis, and the minimally invasive approach reduces some of the complications associated with traditional approaches. However, minimally invasive procedures are known to require much more radiation than open approaches because the surgeon relies on fluoroscopy to visualize the vertebral anatomy and ensure proper placement of the construct. While the amount of radiation absorbed by the patient during minimally invasive lateral interbody fusion is significantly higher than the typical amount for an open approach, we demonstrated that the radiation exposure is well within the range normally reported for minimally invasive spine cases. Surgeons will benefit from this finding because it will help inform their selection of approach when considering fusion for thoracolumbar spondylolisthesis.
Additionally, we provide two methods that the surgeon can use to minimize radiation exposure: use of pulse imaging and avoidance of image magnification. If followed, these suggestions will improve patient care by reducing the amount of patient radiation exposure during minimally invasive spine procedures.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the relative amount of patient radiation exposure during a minimally invasive lateral interbody fusion, 2) Describe the effect that pulsed imaging and magnification have on the amount of radiation exposure per level, 3) Identify potential methods to reduce radiation exposure during minimally invasive spine procedures.