The relationship between histopathological and imaging features of sacroiliitis

This study aimed to investigate the histopathological feature of sacroiliitis and to examine its relationship with imaging features using various imaging techniques. Computed-tomography (CT)-guided needle biopsy of the sacroiliac (SI) joints was performed in 36 patients with spondyloarthritis. Histopathological examination was performed on the samples and subjects were divided as with or without sacroiliitis according histopathology. Magnetic resonance imaging (MRI), Single-photon emission CT (SPECT), CT scans and plain X-rays of the SI joints were conducted. Histopathological changes indicative of sacroiliitis were found in 29 (81%) of the 36 patients, with changes in cartilage (72.4%) and subchondral bone (72.4%) being the most common features. Histopathological sacroiliitis was not found in seven (19.4%) patients. Using MRI, sacroiliitis was found in 29 (80.5%) patients. Increased SI index (> 1.34) by SPECT scans indicative of sacroiliitis was found in 29 (80.5%) patients. Sacroiliitis was detected by CT and plain X-rays in 23 (63.8%) and 19 (52.7%) patients, respectively. Using the histopathological sacroiliitis as the gold standard, sensitivity for SPECT, MRI, CT and plain X-rays was 92.8%, 96.4%, 73.3%, respectively, and 64.2% and the corresponding specificity was 62.5%, 75%, 87.5% and 87.5%, respectively. Needle biopsy is an important method for the diagnosis of sacroiliitis. MRI and SPECT have comparable diagnostic value as CT and plain X-rays and can quantify the inflammatory activity. A combination of these two techniques could increase the sensitivity and specificity and serve as a valuable tool for the diagnosis, assessment and monitoring of sacroiliitis.