Fig. 1

Study protocol, patient selection and data collection. All patients suffering from a uni- or bilateral transalar fagility fracture of the sacrum were treated primarily conservatively with physical therapy (full weight bearing) and painkillers in accordance to the World Health Organization (WHO) analgesic ladder step 2. If adequate mobilization was achieved, conservative treatment was continued. In cases of persistent immobilization the surgical treatment was indicated. Patients treated posteriorly solely by a PMMA augmented SI screw without additional posterior stabilization and independent of the anterior stabilization were asked preoperatively to participate in the present study. Data were collected at the indicated time points prospectively and reviewed retrospectively