Clarifying the origin of the interpubic cavity using a biomechanical model and the finite element method.

The interpubic cavity is a narrow, slit-like, oval-shaped cavity which has frequently been described within the fibrocartilaginous interpubic disc. The aim of the study was to clarify the origin of the primary interpubic cavity. Knowledge of the physiological load of the pubic symphysis while standing and walking is important when deciding on the load after pelvic fractures and when developing implants to fix injuries in the pubic region, and therefore this knowledge could clarify the origin of the interpubic cavity. It is not possible to measure the load on the pubic symphysis in clinical practice, therefore the authors simulated the load on the pelvis during walking using the finite element analysis. Analyses were performed on a physiological pelvis model loaded with a force corresponding to the reaction force in the hip joint. The pubic symphysis was more heavily loaded with forces from muscle groups, the maximum deformation on the pubic symphysis was localised to two places that are permanently loaded during physiological walking. The area associated with the distribution of reduced stress, the middle and caudal parts of the interpubic disc, correlates very well with the frequency of occurrence of the interpubic cavity. It can therefore be assumed that the cavity helps the joint with load bearing during the transition to bipedal walking, i.e., at the time of high biomechanical load. This study will help us clarify the origin of the interpubic cavity.