Putative proprioceptive function of the pelvic ligaments: biomechanical and histological studies

The sacrospinous (SS) and sacrotuberous (ST) ligaments of the pelvic ring are known as mechanical stabilisers of the pelvic girdle, primarily against rotational forces in the sagittal and horizontal planes. Earlier studies, however, raised the possibility that ST/SS ligaments possess significant proprioceptive function, while the mechanical role of these ligaments in maintaining the structural integrity of the pelvis is of less importance. The aim of this study is to determine whether the function of these ligaments is strictly to provide mechanical stability or if they have any additional functional properties, i.e., proprioception. In order to reveal the function of the SS/ST ligaments, biomechanical studies of cadaver pelvis were used along with the histological analysis of the ligaments. Following measurements to determine the accurate mechanical role of the pelvic ligaments, the strength of these ligaments was significantly less than we earlier expected. For this reason other functions of the SS/ST ligaments were considered, including the proprioceptive role. Indeed, histological studies revealed ramifying nerve terminals in the SS/ST ligaments. These terminals may represent the morphological substrate of the proprioceptive function associated with the ligaments. Our studies revealed that SS/ST ligaments might have a significant proprioceptive function providing information of the position of the pelvis. Consequently, the mechanical role of the ligaments in maintaining the structural integrity of the pelvis may be significantly less than previously assumed. Understanding the function of the SS/ST ligaments is crucial for providing more precise guidelines for patient management with injuries to the posterior pelvic region.