Measurement of Sacroiliac Joint Volume Using Live Fluoroscopy

Background: The sacroiliac joint (SIJ) is one source of mechanical low back pain. According to previous reports, volumes of 1.26-1.5 ml of contrast were required to SIJ until a firm endpoint resistance was reached or subjects reported discomfort. By contrast, up to 5 ml of injectate volume is recommended for SIJ block in some text books. We used live fluoroscopy to investigate the precise volume of injectate for IA SIJ. Methods: IA SIJ injection under live fluoroscopic guidance was performed using a mixture of contrast and local anesthetic as an injectate to patients with suspected symptomatic mechanical SIJ pain. The solution was injected until a firm endpoint resistance was produced and the operator confirmed that there was no further expansion of the injectate out of SIJ space. The volume of the solution injected was recorded. Results: Data from 55 SIJ injections in 40 patients were analyzed. The volume of injectate necessary for IA SIJ filling was 1.45 ± 0.44 ml. The minimum volume used was 0.7 ml and the maximum was 2.5 ml. The volume of the injectate had no clinically significant correlation with gender, age, weight, height, BMI, affected side and duration of symptom. Conclusions: Our result revealed that similar volume is needed to fill the SIJ compared to previous reports. The volume of the injectate had no clinically significant correlation with patients’ demographics, making it difficult to predict an adequate volume of injectate in advance for IA SIJ block.ope