Ventral sacroiliac ligament: Anatomic and pathologic considerations

Abstract

RATIONALE AND OBJECTIVES. The ventral sacroiliac ligament (VSL), which bridges the sacroiliac (SI) joint anteriorly, has been described as an important stabilizing structure of the joint, but no data exist regarding its assessment with routine and advanced imaging methods. The authors determine the imaging appearance of the normal and abnormal VSL using close anatomic- histologic-imaging correlation. METHODS. Eight and 10 cadaveric SI joints were examined with magnetic resonance imaging in axial and coronal planes, respectively; and in four computed tomography scanning in both planes was obtained. Anatomic sectioning with histologic correlation at levels corresponding to those of imaging planes was performed. Representative examples of diseases that produce abnormalities of the VSL and connective tissue about the SI joint were reviewed. RESULTS. Magnetic resonance images showed the VSL-anterior capsular complex as a hypointense, linear, or minimally curved structure of approximately 2 mm thickness traversing the SI joint anteriorly. The VSL could not be separated from the anterior joint capsule by imaging studies, but such differentiation by histology could be determined based upon the orientation of its collagen fibers. Any disease process that affects the ligament or the site of ligamentous attachment to bone produces characteristic imaging alterations. CONCLUSIONS. The VSL is a thin structure traversing the SI joint anteriorly. It blends with the anterior capsule of the SI joint and can be identified as a separate structure only by histology. It can be affected by any disease process that causes alterations in the joint capsule, ligament, or soft tissues. Knowledge of the anatomy of the VSL potentially is important in the evaluation of a number of abnormalities, as well as in establishing a specific and accurate diagnosis.