The sacroiliac joint: anatomical study in the coronal plane and MR correlation.

The current clinical imaging technique applied to the sacroiliac joint (SIJ) is coronal Computed Tomography (CT). The aims of this study were: 1) to section the cartilage, the ligaments of the SIJ, and their relations to adjacent organs, in a coronal plane; 2) to correlate anatomical and magnetic resonance (MR) sections; 3) to extend these data in vivo. A topographic dissection of a 52 year-old female specimen was performed to identify the various components, and spatial relationships of the SIJ. Another fresh frozen 50 year-old female cadaver was chosen on CT criteria of normality, and examined with a high resolution (HR) T1-weighted spin echo sequence, in a plane parallel to the ventral limit of the first two sacral vertebrae. This cadaver was then sliced with a sliding gauge device (slice thickness: 5 mm, and device thickness: 1 mm). The SIJ of a 28 year-old nulliparous volunteer, were examined in HR MR imaging, and with a faster sequence, for comparison with the post mortem data. The slice study was correlated with conventional dissection. The continuity and thickness of the auricular cartilage, the complex fascicles of proximal ventral and dorsal sacroiliac ligaments, and distant sacrotuberous and sacrospinous ligaments, were studied. In each plane, coronal HR MR imaging studies were correlated with anatomical sections. The clinical relevance of this comparison was to extend these data in vivo. The auricular cartilage and the ligaments of the SIJ are clearly analyzed by MR imaging, which could contribute to the study of sacroiliitis.