#448 Quantifying Radiation Exposure during Minimally Invasive Lateral Interbody Fusion

General Session: Lateral Interbody Fusion

Presented by: J. Bagley

Author(s):

J.H. Bagley (1)
S. Brigeman (1)
A. Marky (1)
J. Xi (1)
C. Brown (1)
R.E. Isaacs (1)

(1) Duke University Medical Center, Durham, NC, USA

Abstract

Background: Minimally invasive Extreme Lateral Interbody Fusion (XLIF) is an increasingly popular procedure for the treatment of isthmic and degenerative thoracolumbar spondylolisthesis. During this procedure, intraoperative fluoroscopy is used to visualize the vertebral anatomy and ensure the proper placement of the radiopaque construct. Patients and surgeons may be exposed to significant levels of radiation during their surgery. In sufficient doses, such ionizing radiation can cause skin burns, nausea, and cataracts as well as increase the lifetime risk of cancer. While several studies have demonstrated that the XLIF procedure is well-tolerated and produces a high rate of arthrodesis, the procedure requires more intraoperative fluoroscopy than open approaches. However, no study has yet quantified the amount of radiation to which the patient is exposed during XLIF.

Methods: Radiation dosage data was prospectively collected from 80 consecutive patients who underwent XLIF between April, 2010 and January, 2012. All surgeries were performed by two fellowship-trained spine surgeons, each with over 5 years of experience with the procedure. An OEC 9900 Elite C-arm that measured total absorbed dose and exposure time was used to provide fluoroscopic imaging in both the AP and lateral planes. When necessary, surgeons used magnification to improve image quality. In smaller patients, pulsed imaging could be used to reduce radiation exposure at the expense of image resolution. Cases involving heavy use (>30% total fluoroscopy time) of magnification (“Mag group”) and those utilizing pulsed imaging (“Pulse group”) were compared using one-way ANOVA to those cases performed under normal imaging (“NoMag group”).

Results: A total of 228 vertebral levels were treated with minimally invasive XLIF, ranging from T9-T10 to L4-L5. 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 statistically similar in age (62.3 Mag, 67.5 NoMag, 65.8 Pulse, 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). 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) were statistically significant.

Conclusions: Patients undergoing the XLIF procedure absorb a moderate amount of ionizing radiation during fluoroscopy. The amount of radiation exposure in our sample was more than the typical amount reported for open thoracolumbar fusions, but is well within the reported range of radiation exposure for minimally invasive spine procedures. Pulsed imaging, which can only be used in patients with a thin body habitus, was associated with an almost 50% reduction in radiation exposure per level compared to normal fluoroscopy. The use of magnification during intraoperative fluoroscopy was associated with a 300% increase in the amount of radiation used per level over normal fluoroscopy.