Radiologic Analysis and Clinical Study of the Upper One-third Joint Technique for Fluoroscopically Guided Sacroiliac Joint Injection

Background: Sacroiliac intraarticular injection by the traditional technique can be challenging to perform when the joint is covered with osteophytes or is extremely narrow. Objective: To examine whether there is enough space for the needle to be advanced from the L5-S1 interspinous space to the upper one-third sacroiliac joint (SIJ) by magnetic resonance image (MRI) analysis as an alternative to fluoroscopically guided SIJ injection with the lower one-third joint technique, and to determine the feasibility of this novel technique in clinical practice. Study Design: MRI analysis and observational study. Setting: An interventional pain management practice at a university hospital. Methods: We analyzed 200 axial T2-weighted MRIs between the L5 and S1 vertebrae of 100 consecutive patients. The following measurements were obtained on both sides: 1) the thickness of fat in the midline; 2) the distance between the midline (Point C) and the junction (Point A) of the skin and the imaginary line that connects the SIJ and the most medial cortex of the ilium; 3) the distance between the midline (Point C) and the junction (Point B) of the skin and the imaginary line that connects the SIJ and the L5 spinous process; 4) the distance between the SIJ and midline (Point C) on the skin, or between the SIJ and the midpoint (Point C') of the line from Point A to Point B; and 5) the angle between the sagittal line and the imaginary line that connects the SIJ and the midline on the skin. The upper one-third joint technique was performed to establish the feasibility of the alternative technique in 20 patients who had unsuccessful sacroiliac intraarticular injections using the lower one-third joint technique. Results: The mean distances from the midline to Point A and to Point B were 21.9 +/- 13.7 mm and 27.8 +/- 13.6 mm, respectively. The mean distance between the SIJ and Point C (or Point C') was 81.0 +/- 13.3 mm. The angle between the sagittal line and the imaginary line that connects the SIJ and the midline on the skin was 42.8 +/- 5.1 degrees. The success rate of sacroiliac intraarticular injections with the upper one-third joint technique was 90% (18/20). Limitations: This was an observational study and lacked a control group. Conclusions: Sacroiliac intraarticular injections with the upper one-third joint technique are advisable when it is hard to perform them with the lower one-third joint technique.