The Stress-Strain State in the Pelvis During Sit-to-Stand Transfer

To achieve early mobilization of patients with unstable pelvic fractures, the osteosynthesis methods used must withstand the loads in the pelvis during everyday movements. There is currently no predictive tool to assess how suitable these methods are for this purpose. The development of such a tool requires an understanding of the effects of joint and muscle loads on the structural behavior of the pelvis during movement. To further this cause, the stress-strain state of the pelvis during a sit-to-stand transfer of a healthy adult male was analyzed. Muscle and joint reaction forces during the motion were predicted using a rigid-body musculoskeletal model. These loads were then utilized in the first-ever dynamic structural analysis of the pelvis during a sit-to-stand transfer using the finite element method. Several similarities in stress distributions during sit-to-stand transfer, gait, and standing were identified by comparing the finite element analysis results with literature. The common areas of increased stress between the three motions are the acetabular notch, the superior edge of the obturator foramen, the attachments of the gluteus maximus on the ilium, and the lesser sciatic notch. The results also provide important insights into global behavior of the pelvic ring and indicate the locations of concentrated stress during sit-to-stand transfer.