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 challengingto 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 fromthe L5-S1 interspinous space to the upper one-third sacroiliac joint (SIJ) by magnetic resonanceimage (MRI) analysis as an alternative to fluoroscopically guided SIJ injection with the lowerone-third joint technique, and to determine the feasibility of this novel technique in clinicalpractice.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 of100 consecutive patients. The following measurements were obtained on both sides: 1) thethickness 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 cortexof the ilium; 3) the distance between the midline (Point C) and the junction (Point B) of theskin and the imaginary line that connects the SIJ and the L5 spinous process; 4) the distancebetween 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 andthe imaginary line that connects the SIJ and the midline on the skin. The upper one-thirdjoint technique was performed to establish the feasibility of the alternative technique in 20patients who had unsuccessful sacroiliac intraarticular injections using the lower one-thirdjoint technique.Results: The mean distances from the midline to Point A and to Point B were 21.9 ± 13.7 mmand 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 connectsthe SIJ and the midline on the skin was 42.8 ± 5.1°. The success rate of sacroiliac intraarticularinjections 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 areadvisable when it is hard to perform them with the lower one-third joint technique.