[Sacrum fractures and lumbopelvic instabilities in pelvic ring injuries: classification and biomechanical aspects].

Multiplanar posterior pelvic ring instabilities are severe injuries and typically occur in the os ilium, the sacroiliac joint, the sacrum and/or in a combination of these sites. They pose challenges to the orthopedic trauma surgeon during reconstruction, particularly when these injuries are associated with multiplanar sacral fractures and involvement of the lumbosacral junction. Due to the multidirectional forces affecting the pelvic ring, one has to have basic knowledge about the mechanism of injury, its biomechanics, and the various treatment options. In the following we give an overview on injury classifications, biomechanical aspects of the injuries and various types of operative treatments and osteosynthesis techniques.