Imaging for SIJ Injection Therapy

There are no published research studies comparing the injection success rates, procedure duration, radiation exposure, and patient comfort between the two standard imaging systems. The investigators hypothesize that the newer 3-D Cone-beam Based Computer Tomography (CBCT) image system will result in higher success rates, shorter procedure times, fewer image snapshots during the procedure, and less patient discomfort than conventional 2-D fluoroscopy imaging. Although the radiation exposure from one-time low-dose 3-D CT reconstruction with CBCT image system at the beginning of the procedure is higher, the number of later snapshots with the 3-D system is likely to be significantly lower. Therefore the 3-D system may result in overall equivalent radiation exposure to the 2-D system. A statistical power analysis was conducted and determined that a sample size of 100 (50 per group) will give 80% power for detecting a difference if the true rates are 65% (2-D Fluoroscopy guidance) and 90% (3-D CBCT guidance). For this study, patients undergoing SIJ injection will be randomized to either Fluoroscopy guidance or CBCT guidance. The primary outcome measure is injection success within 3 attempts of needle placement. Statistical analysis will use the Chi-square test to test whether the rate of injection success differs between the two methods of guidance. In order to provide appropriate clinical care, whenever success is not achieved with the initial guidance method then injection using the other guidance method will be attempted. However, the analysis will only consider whether or not injection success was achieved with the initial guidance method to which the subject was randomized. Whether or not injection success was achieved after crossing over to the other guidance method is not relevant to the primary analysis. In summary, the investigators would like to formally analyze the differences in these two standard image guidance options in SIJ injection therapy. The investigators propose to randomly select the first imaging system that will be utilized during standard medical care in patients scheduled to undergo an SIJ injection. Presumed that there is a difference in success rate between these two standard images, the imaging procedures are considered to be a part of the research.